WorldWideScience

Sample records for air wall ionization chambers

  1. Characterization of a free air ionization chamber for low energies

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Natalia F.; Xavier, Marcos; Vivolo, Vitor; Caldas, Linda V.E., E-mail: nsilva@ipen.br, E-mail: mxavier@ipen.br, E-mail: vivolo@ipen.br, E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleres (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Free air ionization chambers are used by most primary metrology laboratories as primary standards of the quantities air kerma and exposure in X-ray beams. The free air ionization chamber for low energies of the Calibration Laboratory (LCI) of IPEN showed in a characterization test a problem in the set responsible for the variation of its sensitive volume. After a modification in the support of the micrometers used for the movement of the internal cylinder and the establishment of a new alignment system protocol, the tests were redone. The objective of this work was to present the results obtained in the new condition. (author)

  2. Experimental and calculated calibration of ionization chambers with air circulation

    CERN Document Server

    Peetermans, A

    1972-01-01

    The reports describes the method followed in order to calibrate the different ionization chambers with air circulation, used by the 'Health Physics Group'. The calculations agree more precisely with isotopes cited previously (/sup 11/C, /sup 13/N, /sup 15/O, /sup 41 /Ar, /sup 14/O, /sup 38/Cl) as well as for /sup 85/Kr, /sup 133/Xe, /sup 14/C and tritium which are used for the experimental standardisation of different chambers.

  3. The wall correction factor for a spherical ionization chamber used in brachytherapy source calibration

    Energy Technology Data Exchange (ETDEWEB)

    Piermattei, A [Istituto di Fisica, Universita Cattolica S Cuore, Rome (Italy); Azario, L [Istituto di Fisica, Universita Cattolica S Cuore, Rome (Italy); Fidanzio, A [Istituto di Fisica, Universita Cattolica S Cuore, Rome (Italy); Viola, P [Istituto di Fisica, Universita Cattolica S Cuore, Rome (Italy); Dell' Omo, C [Istituto di Fisica, Universita Cattolica S Cuore, Rome (Italy); Iadanza, L [Centro di Riferimento Oncologico della Basilicata-Rionero in Vulture, Pz (Italy); Fusco, V [Centro di Riferimento Oncologico della Basilicata-Rionero in Vulture, Pz (Italy); Lagares, J I [Universidad de Sevilla, Facultad de Medicina, Dpto Fisiologia Medica y Biofisica, Sevilla (Spain); Capote, R [Universidad de Sevilla, Facultad de Medicina, Dpto Fisiologia Medica y Biofisica, Sevilla (Spain)

    2003-12-21

    The effect of wall chamber attenuation and scattering is one of the most important corrections that must be determined when the linear interpolation method between two calibration factors of an ionization chamber is used. For spherical ionization chambers the corresponding correction factors A{sub w} have to be determined by a non-linear trend of the response as a function of the wall thickness. The Monte Carlo and experimental data here reported show that the A{sub w} factors obtained for an Exradin A4 chamber, used in the brachytherapy source calibration, in terms of reference air kerma rate, are up to 1.2% greater than the values obtained by the linear extrapolation method for the studied beam qualities. Using the A{sub w} factors derived from Monte Carlo calculations, the accuracy of the calibration factor N{sub K,Ir} for the Exradin A4, obtained by the interpolation between two calibration factors, improves about 0.6%. The discrepancy between the new calculated factor and that obtained using the complete calibration curve of the ion-chamber and the {sup 192}Ir spectrum is only 0.1%.

  4. Experimental determination of wall correction factors. Pt. 2; NACP and Markus plane-parallel ionization chambers

    Energy Technology Data Exchange (ETDEWEB)

    Wittkaemper, F.W.; Mijnheer, B.J. (Nederlands Kanker Inst. ' Antoni van Leeuwenhoekhuis' , Amsterdam (Netherlands)); Aalbers, A.H.L. (Netherlands Measurements Inst., Bilthoven (Netherlands))

    1992-04-01

    The formalism to derive the absorbed dose to water from ionization chamber measurements in a phantom includes several wall correction factors depending on shape, size and composition of the chamber. Wall correction factors have been measured for a number of NACP and PTW/Markers Chambers. Significant deviations from calculated values occur due to uncertainties in the contribution to the total ionization from the different materials of these inhomogeneous ionization chambers. The discrepancies illustrate the need for the development of a homogeneous plane-parallel chamber. In addition, detailed Monte Carlo calculations, taking the different wall materials into account, are required to quantitatively predict the response of heterogeneous plane-parallel chambers in photon beams. (UK).

  5. Development and characterization of a graphite-walled ionization chamber as a reference dosimeter for 60Co beams

    Science.gov (United States)

    Perini, Ana P.; Neves, Lucio P.; Caldas, Linda V. E.

    2014-11-01

    A graphite-walled ionization chamber with a sensitive volume of 6.4 cm3 was developed at the Calibration Laboratory of IPEN (LCI) to determine the air kerma rate of a 60Co source. This new prototype was developed to be a simple chamber, without significant nongraphite components and with a simple set-up, which allows the determination of its various required correction factors by Monte Carlo simulations. This new ionization chamber was characterized according to the IEC 60731 standard, and all results were obtained within its limits. Furthermore, Monte Carlo simulations were undertaken to obtain the correction factors involved with the air kerma determination. The air kerma rate obtained with the graphite-walled ionization chamber was compared with that from the reference dosimeter at the LCI, a PTW ionization chamber (model TN30002). The results obtained showed good agreement within the statistical uncertainties. A graphite ionization chamber was assembled and characterized as a reference dosimeter. The characterization test results were within recommended limits. Monte Carlo simulations were undertaken to obtain the correction factors. The air kerma rate of a 60Co source was obtained with satisfactory results.

  6. Polarity and ion recombination corrections in continuous and pulsed beams for ionization chambers with high Z chamber walls.

    Science.gov (United States)

    Aldosary, Ghada; Safigholi, Habib; Song, William; Seuntjens, Jan; Sarfehnia, Arman

    2017-03-01

    In this work, the response of Farmer-type ionization chambers fitted with high atomic number (Z) walls is studied, and results of the effects of such walls on polarity and ion recombination correction factors in both continuous and pulsed beams are presented. Measurements were made in a continuous Co-60 beam and a pulsed 6MV linac beam using an Exradin-A12 ionization chamber fitted with the manufacturer's C-552 plastic wall, as well as geometrically identical walls made from aluminum, copper and molybdenum. The bias voltage was changed between 10values (range: +50 to +560V). Ion recombination was determined from Jaffé plots and by using the "two-voltage technique". The saturation charge measured with each chamber wall was extrapolated from Jaffé plots. Additionally, the effect of different wall materials on chamber response was studied using MCNP simulations. Results showed that the polarity correction factor is not significantly affected by changes in chamber wall material (within 0.1%). Furthermore, although the saturation charges greatly vary with each chamber wall material, and charge multiplication increases for higher atomic number wall materials, the standard methods of calculating ion recombination yielded results that differed by only 0.2%. Therefore, polarity and ion recombination correction factors are not greatly affected by the chamber wall material. The experimental saturation charges for all the different wall materials agreed well within the uncertainty with MCNP simulations. The breakdown of the linear relationship in Jaffé plots that was previously reported to exist for conventional chamber walls was also observed with the different wall materials.

  7. Air-kerma determination using a variable-volume cavity ionization chamber standard.

    Science.gov (United States)

    Burns, D T; Kessler, C; Roger, P

    2007-12-01

    A graphite-walled cavity ionization chamber of modular design and variable volume has been used to determine the air-kerma rate in the reference 60Co field at the BIPM. The chamber can be configured in five sizes. High-accuracy mechanical measurements of the volume of the air cavity were made for each configuration using a co-ordinate measuring machine. Ionization current measurements were made for each configuration and corrected for the effects of ion recombination and diffusion, stem scatter and chamber orientation. Monte Carlo calculations of cavity dose were made to evaluate the correction factors kwall and kan. A reproducibility of the ionization current per mass of 1.5 parts in 10(4) was achieved on the repeated assembly of each configuration. The results show an air-kerma rate determination that increases with volume, the total change being around 8 parts in 10(4). When analysed differentially, the air-kerma rate relative to the BIPM standard is Kdiff/KBIPM = 1.0026(6). A detailed uncertainty budget is presented. Possible reasons for the observed behaviour are discussed that might have consequences for all existing standards for air-kerma.

  8. An open-walled ionization chamber appropriate to tritium monitoring for glovebox.

    Science.gov (United States)

    Chen, Zhilin; Chang, Ruiming; Mu, Long; Song, Guoyang; Wang, Heyi; Wu, Guanyin; Wei, Xiye

    2010-07-01

    An open-walled ionization chamber is developed to monitor the tritium concentration in gloveboxes in tritium processing systems. Two open walls are used to replace the sealed wall in common ionization chambers, through which the tritium gas can diffuse into the chamber without the aid of pumps and pipelines. Some basic properties of the chamber are examined to evaluate its performance. Results turn out that an open-walled chamber of 1 l in volume shows a considerably flat plateau over 700 V for a range of tritium concentration. The chamber also gives a good linear response to gamma fields over 4 decades under a pressure condition of 1 atm. The pressure dependence characteristics show that the ionization current is only sensitive at low pressures. The pressure influence becomes weaker as the pressure increases mainly due to the decrease in the mean free path of beta particles produced by tritium decay. The minimum detection limit of the chamber is 3.7x10(5) Bq/m(3).

  9. A new standard cylindrical graphite-walled ionization chamber for dosimetry in 60Co beams at calibration laboratories

    Science.gov (United States)

    Neves, Lucio P.; Perini, Ana P.; Caldas, Linda V. E.

    2014-11-01

    60Co sources are used mostly at dosimetry laboratories for calibration of ionization chambers utilized for radiotherapy dosimetry, mainly in those laboratories where there is no linear accelerator available. In this work, a new cylindrical ionization chamber was developed and characterized to be used as a reference dosimeter at the Calibration Laboratory of the IPEN. The characterization tests were performed according to the IEC 60731 standard, and all tests presented results within its recommended limits. Furthermore, the correction factors for the wall, stem, central collecting electrode, nonaxial uniformity and the mass-energy absorption coefficient were determined using the EGSnrc Monte Carlo code. The air kerma rate determined with this new dosimeter was compared to the one obtained with the IPEN standard, presenting a difference of 1.5%. Therefore, the new ionization chamber prototype developed and characterized in this work presents potential use as a primary standard dosimeter at radiation metrology laboratories.

  10. Stability results of a free air ionization chamber in standard mammography beams

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Natalia F.; Xavier, Marcos; Vivolo, Vitor; Caldas, Linda V.E., E-mail: nsilva@ipen.br, E-mail: mxavier@ipen.br, E-mail: vivolo@ipen.br, E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Free air ionization chambers are absolute dosimeters, because they can measure basic physical quantities directly without the need of their calibration in a standard radiation beam. They are used for measuring exposure and air kerma in X and gamma radiation beams. The Calibration Laboratory (LCI) of IPEN has a free air ionization chamber of the cylindrical type for low energies. The characterization of this ionization chamber was already performed and reported in a previous study. After a modification in the support of the micrometers used for the movement of the internal cylinder devices, the tests were redone. The objective of this work was to present the new alignment protocol of the free air ionization chamber in low energies of X-ray beams of standard mammography qualities, assuring the positioning reproducibility, and new results of stability tests performed with the application of this protocol will be presented. (author)

  11. Characterization of a free air ionization chamber for low energy X-rays

    Science.gov (United States)

    Silva, N. F.; Xavier, M.; Vivolo, V.; Caldas, L. V. E.

    2016-07-01

    Free air ionization chambers are used by most primary metrology laboratories as primary standards of the quantities air kerma and exposure in X-ray beams. The free air ionization chamber for low energies of the Calibration Laboratory (LCI) of IPEN showed in a characterization test a problem in the set responsible for the variation of its sensitive volume. After a modification in the support of the micrometers used for the movement of the internal cylinder and the establishment of a new alignment system protocol, the tests were redone. The objective of this work was to present the results obtained in the new condition.

  12. Measurement of ion and electron drift velocity and electronic attachment in air for ionization chambers

    CERN Document Server

    Boissonnat, Guillaume; Colin, Jean; Remadi, Aurelien; Salvador, Samuel

    2016-01-01

    Air-ionization chambers have been used in radiotherapy and particle therapy for decades. However, fundamental parameters in action in the detector responses are sparsely studied. In this work we aimed to measure the electronic attachment, electrons and ions mobilities of an ionization chamber (IC) in air. The main idea is to extract these from the actual response of the IC to a single ionizing particle in order to insure that they were measured in the same condition they are to be used while neglecting undesired phenomena: recombination and space charge effect. The non-standard signal shape analysis performed here were also confronted to a more standard drift chamber measurements using time-of-flight. It was found that both detectors displayed compatible results concerning positive and negative ions drift velocities where literature data is well spread out. In the same time, electron attachment measurements sit in the middle of known measurements while electron drift velocities seemed to show an offset compar...

  13. Design and preliminary test of a free-air ionization chamber for low-energy X-ray

    Institute of Scientific and Technical Information of China (English)

    WU Jin-Jie; YANG Yuan-Di; WANG Pei-Wei; CHEN Jing; LIU Jia-Cheng

    2011-01-01

    A free-air ionization chamber in low-energy X-ray has been designed and manufactured at theNational Institute of Metrology (NIM, China) according to the defination of alr-kerma. The results of a preliminary test show that the leakage current of ionization chamber is around 2×10A, and the correction factor of ion recombination for the ionization chamber is also obtained. The free-air ionization chamber is suitable for the primary standard in low-energy X-rays.

  14. PTRAC File Utilization for Calculation of Free-Air Ionization Chamber Correction Factors by MCNPX

    Science.gov (United States)

    Šolc, Jaroslav; Sochor, Vladimír

    2014-06-01

    A free-air ionization chamber is used as a standard of photon air-kerma. Several correction factors are applied to the air-kerma value. Correction factors for electron loss (kloss) and for additional ionization current caused by photon scatter (ksc), photon fluorescence (kfl), photon transmission through diaphragm edge (kdtr), and photon scatter from the surface of the diaphragm aperture (kdsc) were determined by the MCNPX code utilizing information stored in Particle Track (PTRAC) output files. Individual steps of the procedure are described and the calculated values of the correction factors are presented. The values are in agreement with the correction factors published in a literature for similar free-air chambers.

  15. A free-air ionization chamber with a large aperture diaphragm

    Energy Technology Data Exchange (ETDEWEB)

    Takata, N., E-mail: n.takata@aist.go.j [Ionizing Radiation Section, NMIJ, AIST, Tsukuba, Ibaraki 305-8568 (Japan)

    2010-07-21

    Calculations of the electric field distributions in free-air ionization chambers reveal that the distortion of the charge collection volume is small even for wide X-ray beam passage if the diaphragm and the X-ray shielding box are kept at a potential equal to half that applied to the high-voltage electrode. Applying this potential to the diaphragm and the shielding box permits a larger aperture diaphragm to be used. This will allow a wider X-ray beam to enter the chamber, thus generating a larger signal. In addition, the distance between the diaphragm and the charge collection volume can be shortened to reduce the amount of X-ray attenuation. It is also possible to calibrate a dosimeter against a free-air ionization chamber that has a diaphragm whose aperture size is equal to the size of the dosimeter in an X-ray field that is collimated to the same size. This is important since free-air ionization chambers are not sensitive to X-rays that are incident at large angles, such as those scattered by the collimator, filters and air.

  16. Free-air ionization chamber, FAC-IR-300, designed for medium energy X-ray dosimetry

    Science.gov (United States)

    Mohammadi, S. M.; Tavakoli-Anbaran, H.; Zeinali, H. Z.

    2017-01-01

    The primary standard for X-ray photons is based on parallel-plate free-air ionization chamber (FAC). Therefore, the Atomic Energy Organization of Iran (AEOI) is tried to design and build the free-air ionization chamber, FAC-IR-300, for low and medium energy X-ray dosimetry. The main aim of the present work is to investigate specification of the FAC-IR-300 ionization chamber and design it. FAC-IR-300 dosimeter is composed of two parallel plates, a high voltage (HV) plate and a collector plate, along with a guard electrode that surrounds the collector plate. The guard plate and the collector were separated by an air gap. For obtaining uniformity in the electric field distribution, a group of guard strips was used around the ionization chamber. These characterizations involve determining the exact dimensions of the ionization chamber by using Monte Carlo simulation and introducing correction factors.

  17. High-resolution ion pulse ionization chamber with air filling for the Rn-222 decays detection

    CERN Document Server

    Gavrilyuk, Yu M; Gezhaev, A M; Etezov, R A; Kazalov, V V; Kuzminov, V V; Panasenko, S I; Ratkevich, S S; Tekueva, D A; Yakimenko, S P

    2015-01-01

    The construction and characteristics of the cylindrical ion pulse ionization chamber (CIPIC) with a working volume of 3.2 L are described. The chamber is intended to register alpha-particles from the $^{222}$Rn and its daughter's decays in the filled air sample. The detector is less sensitive to electromagnetic pick-ups and mechanical noises. The digital pulse processing method is proposed to improve the energy resolution of the ion pulse ionization chamber. An energy resolution of 1.6% has been achieved for the 5.49 MeV alpha-line. The dependence of the energy resolution on high voltage and working media pressure has been investigated and the results are presented.

  18. High-resolution ion pulse ionization chamber with air filling for the 222Rn decays detection

    Science.gov (United States)

    Gavrilyuk, Yu. M.; Gangapshev, A. M.; Gezhaev, A. M.; Etezov, R. A.; Kazalov, V. V.; Kuzminov, V. V.; Panasenko, S. I.; Ratkevich, S. S.; Tekueva, D. A.; Yakimenko, S. P.

    2015-11-01

    The construction and characteristics of the cylindrical ion pulse ionization chamber (CIPIC) with a working volume of 3.2 L are described. The chamber is intended to register α-particles from the 222Rn and its daughter's decays in the filled air sample. The detector is less sensitive to electromagnetic pick-ups and mechanical noises. The digital pulse processing method is proposed to improve the energy resolution of the ion pulse ionization chamber. An energy resolution of 1.6% has been achieved for the 5.49 MeV α-line. The dependence of the energy resolution on high voltage and working media pressure has been investigated and the results are presented.

  19. Beam-loss monitoring system with free-air ionization chambers

    Science.gov (United States)

    Nakagawa, H.; Shibata, S.; Hiramatsu, S.; Uchino, K.; Takashima, T.

    1980-08-01

    A monitoring system for proton beam losses was installed in the proton synchrotron at the National Laboratory for High Energy Physics in Japan (KEK). The system consists of 56 air ionization chambers (AIC) for radiation detectors, 56 integrators, 56 variable gain amplifiers, two multiplexers, a computer interface circuit, a manual controller and a high tension power supply. The characteristics of the AIC, time resolution, radiation measurement upper limit saturation, kinetic energy dependence of the sensitivity, chamber activation effect, the beam loss detection system and the results of observations with the monitoring system are described.

  20. Air filled ionization chambers and their response to high LET radiation

    DEFF Research Database (Denmark)

    Kaiser, Franz-Joachim; Bassler, Niels; Tölli, Heikki

    Background Air filled ionization chambers (ICs) are widely used for absolute dosimetry, not only in photon beams but also in beams of heavy charged particles. Within the IC, electron hole pairs are generated by the energy deposition originating from incoming radiation. High-LET particles create...... structure theory. More specifically, we solved the equation for the geometrical setup of the Bragg-peak IC, which is a plane parallel IC with a 2 mm spacing between the electrodes. The sensitive volume of the IC is located in a thermoplastic housing of several mm thickness. Results We compare...

  1. Wall Attenuation and Scatter Characteristics of Ionization Chambers at Armed Forces Radiobiology Research Institute

    Science.gov (United States)

    1986-12-01

    0.5 0.10 TE 155 Exradin Cylindrical 0.05 0.10 TE, tissue-equivalent plastic type A-150; GR, graphite; MG, magnesium For each wall thickness, the...11 to be used in AAPM protocol (reference 16) tExtrapolated from Table III in reference 16 DISCUSSION The results shown in Table 2 and Appendix B...Physicists in Medicine ( AAPM ) Task Group 21 protocol for High Energy Photon and Electron Dosimetry (16). In this protocol, the chamber wall correction

  2. Design and preliminary test of a free-air ionization chamber for low-energy X-ray

    Institute of Scientific and Technical Information of China (English)

    吴金杰; 杨元第; 王培玮; 陈靖; 柳加成

    2011-01-01

    A free-air ionization chamber in low-energy X-ray has been designed and manufactured at the National Institute of Metrology (NIM, China) according to the defination of air-kerma. The results of a preliminary test show that the leakage current of ionizatio

  3. Initial recombination in the track of heavy charged particles: Numerical solution for air filled ionization chambers

    DEFF Research Database (Denmark)

    Kaiser, Franz-Joachim; Bassler, Niels; Tölli, Heikki

    2012-01-01

    Introduction Modern particle therapy facilities enable sub-millimeter precision in dose deposition. Here, also ionization chambers (ICs) are used, which requires knowledge of the recombination effects. Up to now, recombination is corrected using phenomenological approaches for practical reasons...

  4. Air-turbulence and temperature gradients reduced in plant growth chambers by small-hole diffuser-walls

    Energy Technology Data Exchange (ETDEWEB)

    Browne, L. E.; Noey, J. L.; Kerr, Pat C.; Haber, A. H.

    1967-01-01

    A new, simple, and relatively inexpensive method is described for smoothly introducing into plant growth chambers the large volumes of preconditioned air necessary to maintain great uniformity of temperature and humidity. Preconditioned air from a plenum is introduced into the chamber through diffuser-walls containing numerous evenly spaced holes.

  5. Consequences of air around an ionization chamber : Are existing solid phantoms suitable for reference dosimetry on an MR-linac?

    NARCIS (Netherlands)

    Hackett, S. L.; Van Asselen, B.; Wolthaus, J. W H; Kok, J. G M; Woodings, S. J.; Lagendijk, J. J W; Raaymakers, B. W.

    2016-01-01

    Purpose: A protocol for reference dosimetry for the MR-linac is under development. The 1.5 T magnetic field changes the mean path length of electrons in an air-filled ionization chamber but has little effect on the electron trajectories in a surrounding phantom. It is therefore necessary to correct

  6. Dependence with air density of the response of the PTW SourceCheck ionization chamber for low energy brachytherapy sources

    Energy Technology Data Exchange (ETDEWEB)

    Tornero-López, Ana M.; Guirado, Damián; Ruiz-Arrebola, Samuel [Servicio de Radiofísica y Protección Radiológica, Hospital Universitario San Cecilio, E-18012 Granada (Spain); Perez-Calatayud, Jose [Servicio de Radioterapia, Unidad de Radiofísica, Hospital Universitario y Politécnico La Fe, E-46026 Valencia (Spain); Simancas, Fernando; Lallena, Antonio M. [Departamento de Física Atómica, Molecular y Nuclear, Universidad de Granada, E-18071 Granada (Spain); Gazdic-Santic, Maja [Department of Medical Physics and Radiation Safety, Clinical Centre of Sarajevo University, 71000 Sarajevo (Bosnia and Herzegovina)

    2013-12-15

    Purpose: Air-communicating well ionization chambers are commonly used to assess air kerma strength of sources used in brachytherapy. The signal produced is supposed to be proportional to the air density within the chamber and, therefore, a density-independent air kerma strength is obtained when the measurement is corrected to standard atmospheric conditions using the usual temperature and pressure correction factor. Nevertheless, when assessing low energy sources, the ionization chambers may not fulfill that condition and a residual density dependence still remains after correction. In this work, the authors examined the behavior of the PTW 34051 SourceCheck ionization chamber when measuring the air kerma strength of {sup 125}I seeds.Methods: Four different SourceCheck chambers were analyzed. With each one of them, two series of measurements of the air kerma strength for {sup 125}I selectSeed{sup TM} brachytherapy sources were performed inside a pressure chamber and varying the pressure in a range from 747 to 1040 hPa (560 to 780 mm Hg). The temperature and relative humidity were kept basically constant. An analogous experiment was performed by taking measurements at different altitudes above sea level.Results: Contrary to other well-known ionization chambers, like the HDR1000 PLUS, in which the temperature-pressure correction factor overcorrects the measurements, in the SourceCheck ionization chamber they are undercorrected. At a typical atmospheric situation of 933 hPa (700 mm Hg) and 20 °C, this undercorrection turns out to be 1.5%. Corrected measurements show a residual linear dependence on the density and, as a consequence, an additional density dependent correction must be applied. The slope of this residual linear density dependence is different for each SourceCheck chamber investigated. The results obtained by taking measurements at different altitudes are compatible with those obtained with the pressure chamber.Conclusions: Variations of the altitude and

  7. High-resolution ion pulse ionization chamber with air filling for the {sup 222}Rn decays detection

    Energy Technology Data Exchange (ETDEWEB)

    Gavrilyuk, Yu.M.; Gangapshev, A.M.; Gezhaev, A.M.; Etezov, R.A.; Kazalov, V.V.; Kuzminov, V.V. [Baksan Neutrino Observatory,Institute for Nuclear Research RAS, 361609 Neutrino (Russian Federation); Panasenko, S.I. [V.N.Karazin Kharkiv National University, 61022 Kharkiv (Ukraine); Ratkevich, S.S., E-mail: ssratk@gmail.com [V.N.Karazin Kharkiv National University, 61022 Kharkiv (Ukraine); Tekueva, D.A.; Yakimenko, S.P. [Baksan Neutrino Observatory,Institute for Nuclear Research RAS, 361609 Neutrino (Russian Federation)

    2015-11-21

    The construction and characteristics of the cylindrical ion pulse ionization chamber (CIPIC) with a working volume of 3.2 L are described. The chamber is intended to register α-particles from the {sup 222}Rn and its daughter's decays in the filled air sample. The detector is less sensitive to electromagnetic pick-ups and mechanical noises. The digital pulse processing method is proposed to improve the energy resolution of the ion pulse ionization chamber. An energy resolution of 1.6% has been achieved for the 5.49 MeV α-line. The dependence of the energy resolution on high voltage and working media pressure has been investigated and the results are presented. - Highlights: • The construction and characteristics of the cylindrical ion pulse ionization chamber (CIPIC) with a working volume of 3.2 L are described. • The chamber is intended to register alpha-particles from {sup 222}Rn and its daughter's decays in the filled air sample. • The detector is less sensitive to electromagnetic pick-ups and mechanical noises. • An energy resolution of 1.6% has been achieved for the 5.49 MeV alpha-line. The dependence of the energy resolution on high voltage and working media pressure have been investigated and the results are presented.

  8. Liquid Wall Chambers

    Energy Technology Data Exchange (ETDEWEB)

    Meier, W R

    2011-02-24

    The key feature of liquid wall chambers is the use of a renewable liquid layer to protect chamber structures from target emissions. Two primary options have been proposed and studied: wetted wall chambers and thick liquid wall (TLW) chambers. With wetted wall designs, a thin layer of liquid shields the structural first wall from short ranged target emissions (x-rays, ions and debris) but not neutrons. Various schemes have been proposed to establish and renew the liquid layer between shots including flow-guiding porous fabrics (e.g., Osiris, HIBALL), porous rigid structures (Prometheus) and thin film flows (KOYO). The thin liquid layer can be the tritium breeding material (e.g., flibe, PbLi, or Li) or another liquid metal such as Pb. TLWs use liquid jets injected by stationary or oscillating nozzles to form a neutronically thick layer (typically with an effective thickness of {approx}50 cm) of liquid between the target and first structural wall. In addition to absorbing short ranged emissions, the thick liquid layer degrades the neutron flux and energy reaching the first wall, typically by {approx}10 x x, so that steel walls can survive for the life of the plant ({approx}30-60 yrs). The thick liquid serves as the primary coolant and tritium breeding material (most recent designs use flibe, but the earliest concepts used Li). In essence, the TLW places the fusion blanket inside the first wall instead of behind the first wall.

  9. Smart ionization chamber for gamma-ray monitoring

    OpenAIRE

    Drndarević Vujo R.; Jevtić Nenad J.; Rajović Vladimir M.; Stanković Srboljub J.

    2014-01-01

    A design and implementation of a smart ionization chamber suitable for connection into gamma radiation monitoring networks is presented in this paper. The smart ionization chamber consists of air-equivalent one liter ionization chamber with associated electronics and a built-in memory for storage of electronic data specifications. Generally, operating and measurement characteristics of the used ionization chamber are written into the memory chip attached to...

  10. Liquid ionization chambers for LET determination

    DEFF Research Database (Denmark)

    Kaiser, Franz-Joachim; Bassler, Niels; Tölli, Heikki

    Liquid ionization chambers [1] (LICs) have have been used in the last decades as background dosemeters. Since a few years LICs are also commercially available for dosimetry and are used for measurements of dose distributions where a high spatial distribution is necessary. Also in the last decades...... a differential equation applying several simplifications and approximations leading to discrepancies between theory and experiments [3]. The theory predicts the collection efficiency as a function of the electrical field and was applied for both air filled ionization chambers and liquid filled ionization...... chambers. For liquids the LET can be roughly deduced from the collection efficiency dependency on the electrical field inside a liquid ionization chambers [4] using an extrapolation method. We solved the fundamental differential equation again presented by Jaffe numerically, but now taking into account...

  11. Scattering study at free air ionization chamber diaphragm; Estudo do espalhamento no diafragma da camara de ionizacao de ar livre

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Alexandre Lo Bianco dos

    2011-07-01

    The maim of this work consisted in the assessment of the correction factor for air kerma, due to scattered radiation in the diaphragm of the free-air ionization chamber model 481. LNMRl measurements were made to acquire x-ray spectra corresponding to the Qualities RQR-M, described in IEC 61627 standards (2005). These spectra were used as input data in the MC simulations. The operational range of energy spectra provide up to 35 keV. This energy range is typically used in diagnostic radiology, although there is not primary standard for air kerma. The determination of this factor is a fundamental process in the primary standardization of the air kerma. These factors were obtained by computer simulation using the Penelope code. The results are k{sub RQR-M1}=0,9946, k{sub RQR} {sub -M2}=0,9932, k{sub RQR-M3}=0,9978 and k{sub RQR-M4}=0,9885; with uncertainties of 0,007 and coverage factor equal to 2. lt can be concluded that, with respect to the diaphragm, the chamber can be used in the primary standard of air kerma. (author)

  12. Ionization Chamber Measures Extreme Ultraviolet

    Science.gov (United States)

    Carlson, Robert W.

    1987-01-01

    Ionization chamber operates in nearly total photon absorption as stable, self-calibrating detector of ionizing extreme ultraviolet radiation. Working gas of instrument is neon; photoionization properties well known and readily applicable to absolute measurements. Designed for measurements of solar ultraviolet flux aboard sounding rocket, instrument used on Earth to measure ultraviolet radiation in vacuum systems. Ionization chamber collects positive neon ions and electrons produced by irradiation of neon gas by ultraviolet photons. Approximately one ion produced by each photon; consequently, photoionization current nearly proportional to photon flux.

  13. Ionization chambers for LET determination

    DEFF Research Database (Denmark)

    Kaiser, Franz-Joachim; Bassler, Niels; Tölli, Heikki

    2010-01-01

    resolution and high sensitivity are necessary. For exact dosimetry which is done using ionization chambers (ICs), the recombination taking place in the IC has to be known. Up to now, recombination is corrected phenomenologically and more practical approaches are currently used. Nevertheless, Jaff´e's theory...... of columnar recombination was designed to model the detector efficiency of an ionization chamber. Here, we have shown that despite the approximations and simplification made, the theory is correct for the LETs typically found in clinical radiotherapy employing particles from protons to carbon ions...

  14. Fabrication of Free Air Well Type Ionization Chamber and Calculational Assessment and Measurement of Its Operational Characteristics

    Directory of Open Access Journals (Sweden)

    Koroush Arbabi

    2007-12-01

    Full Text Available Introduction: Well type ionization chamber is a measuring device which is used to determine the activity of brachytherapy sources. The chamber has a cylindrical volume in which a cylindrical tube is mounted in the middle of the chamber. For the measurements, the brachytherapy sources are transferred to the middle of the tube. Materials and Methods: For designing the well type chamber, the measurement principals of well type chambers were considered and MCNP-4C code as a calculation tool was used. The designed chamber was simulated and the response of the chamber was evaluated. In this investigation, the chamber operational parameters such as operating voltage, leakage current, reproducibility, reference measuring point, recombination and polarization factors as well as response stability for 137Cs, 57Co and 241Am sources were studied. Results: The chamber leakage currents at the operating voltage in comparison to the chamber response for the measurement of the above mentioned sources were negligible. The responses of the fabricated chamber for these sources are reproducible and its reference measurement position for these sources was obtained at 6 cm from the bottom of the chamber. The recombination factor for the well type chamber was negligible and the polarization factor is close to 1. Therefore, these two factors were not considered in the measurements. The reproducibility of the measurements in different intervals shows the stability of the chamber response for each source. Also the results of the chamber current measurement in term of source strength were compared to the response of the simulated chamber for different source positions and energy ranges of the used sources. Discussion and Conclusion: The results show that the measurement of the reference positions for each source in the simulated and fabricated chamber is quite in a good agreement. Regarding the reliable operational properties of the fabricated chamber, this chamber can be

  15. Smart ionization chamber for gamma-ray monitoring

    Directory of Open Access Journals (Sweden)

    Drndarević Vujo R.

    2014-01-01

    Full Text Available A design and implementation of a smart ionization chamber suitable for connection into gamma radiation monitoring networks is presented in this paper. The smart ionization chamber consists of air-equivalent one liter ionization chamber with associated electronics and a built-in memory for storage of electronic data specifications. Generally, operating and measurement characteristics of the used ionization chamber are written into the memory chip attached to the chamber. A microcontroller-based data acquisition system with a mixed-mode interface has been implemented for the purpose of reading electronic data specifications from the memory chip, and for configuration and interfacing of the ionization chamber to the monitoring network using plug-and-play concept. The details of smart ionization chamber implementation and test results are included in the paper. [Projekat Ministarstva nauke Republike Srbije, br. TR36047 i br. TR32043

  16. Loss of ions in cavity ionization chambers

    Energy Technology Data Exchange (ETDEWEB)

    Takata, N. [Ionizing Radiation Section, NMIJ/AIST, Tsukuba 305-8568 (Japan)]. E-mail: n.takata@aist.go.jp; Tran, N.T. [Institute for Nuclear Science and Technique, VAEC, Hanoi (Viet Nam); Kim, E. [Radiation Safety Section, NIRS, Inageku, Chiba-city 263-8555 (Japan); Marsoem, P. [P3KRBiN-BATAN, JL Cinere-Pasar Jum' at, Jakarta 12070 (Indonesia); Kurosawa, T. [Ionizing Radiation Section, NMIJ/AIST, Tsukuba 305-8568 (Japan); Koyama, Y. [Ionizing Radiation Section, NMIJ/AIST, Tsukuba 305-8568 (Japan)

    2005-12-01

    Ion losses due to initial recombination, volume recombination, and back diffusion were each determined by measurements and calculations for different size cylindrical ionization chambers and spherical ionization chambers. By measuring signal currents from these ionization chambers irradiated with {sup 60}Co gamma rays, two groups of ion losses were obtained. (Group 1) Ion loss due to initial recombination and diffusion, which changes proportionally to the inverse of the voltage applied to the ionization chambers; (and group 2) ion loss due to volume recombination, which changes proportionally to the inverse of the square of the applied voltage. The diffusion loss was obtained separately by computing electric field distributions in the ionization chambers. It was found that diffusion loss is larger than initial recombination loss for the cylindrical ionization chambers and vise versa for the spherical ionization chambers.

  17. LET measurements with a liquid ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Tegami, Sara

    2013-02-08

    Deep-seated tumors can be efficiently treated with heavy charged particles. The characteristic depth dose profile inside the tissue (Bragg peak) allows to deliver a high dose inside the tumor, while sparing the neighboring healthy tissue. As compared to protons, heavy ions like carbon or oxygen produce a higher amount of ionization events along their track (and in particular at the end of the ion beam path), resulting in an irreparable damage to the DNA of the tumor cells. The density of such ionization events is described in terms of Linear Energy Transfer (LET), an important physical quantity, but difficult to be measured directly. The aim of this work is to determine LET of hadrontherapy beams by using Liquid Ionization Chambers (LIC). The ionization signal in LICs is affected by recombination effects that depend on the LET of the incident radiation. Differences in recombination effects in LICs and air-filled ionization chambers can be exploited to obtain the recombination index, which can be related to the LET, calculated by Monte Carlo methods. We thus developed a method to construct a calibration curve, which relates the recombination index with the LET at each depth in water. The result of this work can be used for online monitoring of the ion beam quality.

  18. Design of sensor of air pulse ionization chamber%空气脉冲电离室传感器的设计

    Institute of Scientific and Technical Information of China (English)

    张国华; 方方; 耿波

    2011-01-01

    基于氡及其子体衰变放出的α射线能使空气分子电离的现象,设计新型空气脉冲电离室传感器,主要由电离室、中心电极和保护环组成.采用前置放大器和RC-CR带通滤波器把来自电离室的微弱信号进行放大,再经过脉冲甄别器与给定的阙值电压比较,最终转换成数字量信号.现场应用结果表明:该传感器具有广泛的应用价值.%A new type of sensor of air pulse ionization chamber is designed,based on the phenomenon that a-rays decayed by radon and its progeny can ionize the air molecules,consists of ionization chamber,central electrode and guard ring. Using the preamplifier and RC-CR bandpass filter, the weak signals from ionization chamber are amplified, and compared with the threshold voltage. These signals have been processed into digital signals. Practical applications show that the sensor has wide.application.

  19. Dosimetric Performance of Newly Developed Farmer-Type Ionization Chamber in Radiotherapy Practice.

    Science.gov (United States)

    Saminathan, Sathiyan; Godson, Henry Finlay; Ponmalar, Retna; Manickam, Ravikumar; Mazarello, James; Fernandes, Rahul

    2016-12-01

    Dose measurement with ionization chamber is essential to deliver accurate dose to the tumor in radiotherapy. The cylindrical Farmer-type ionization chamber is recommended by various dosimetry protocols for dose measurement of radiotherapy beams. The air-equivalent graphite wall Farmer-type ionization chamber (FAR 65 GB) of active volume 0.65 cm(3) with aluminum as the central electrode material was fabricated. Various dosimetric parameters were studied for the newly developed ionization chamber in cobalt-60, 6 and 18 MV photon beams. The preirradiation and postirradiation leakage of the chamber was within 0.08%. The long-term stability and the stem effect of the chamber were within 0.07% and 0.3%, respectively. The sensitivity of the ionization chamber was found to be 22.15 nC/Gy. The chamber shows linear response with dose for cobalt-60, 6 and 18 MV photon beams. The ion recombination correction factor increases with increase in bias voltage. For all energies and field sizes, the polarity correction factor is almost closer to unity. The ion recombination and polarity correction measurements show that the polarizing potential and polarity recommended during the calibration of ionization chamber should be used for routine measurement to avoid the uncertainty. The chamber response is independent of dose rate and energy. The chamber is cost-effective and shows precise and reproducible response. The study carried out confirms that the newly fabricated ion chamber can be used in the measurement of absolute dose for high-energy photon beams.

  20. An ionization chamber with magnetic levitated electrodes

    CERN Document Server

    Kawaguchi, T

    1999-01-01

    A new type of ionization chamber which has magnetically levitated electrodes has been developed. The electrodes are supplied voltages for the repelling of ions by a battery which is also levitated with the electrodes. The characteristics of this ionization chamber are investigated in this paper.

  1. Determination of the air attenuation and electronic loss for the free air concentric cylinders ionization chamber; Determinacao da atenuacao do ar e perda eletronica para a camara de ionizacao de ar livre de cilindros concentricos

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Hebert Pinto Silveira de

    2010-07-01

    Along the latest years, the LNMRI has been proceeding a continuous research work with a concentric cylinders type free air ionizing chamber (VICTOREEN, model 481), aiming to establish it as a new national standard, and, as a consequence, replace the worldwide accepted secondary standard, calibrated by PTB. Taking into account that the absolute determination of kerma in air with a free air ionizing chamber implies the acquirement of a number of correction factors. The main objective of the present work comprises the determination of the two factors, specifically, electronic loss (k{sub e}) and air attenuation (k{sub a}). The correction factors were obtained through mammography qualities reference spectrum, using Monte Carlo simulation method. The Penelope code was used in the simulation procedures. Simulations took place in two stages, the acquirement of specters related to the qualities of interest (mammography) with the x ray tube (Pantak, model HF160 e Panalytical, model XRF window), and the free-air ionization chamber. The data were compared to those related to the BIPM chamber, to electronic loss were not detected. The comparison between air attenuation factors was obtained data bellow 0.13%. (author)

  2. Multi-concentric-ring open-air ionization chamber for high-intensity X-ray beams

    Science.gov (United States)

    Nariyama, Nobuteru

    2014-11-01

    An ionization chamber with four concentric ring electrodes was used to measure doses of white, 10, 15 and 20 keV synchrotron X-ray beams. The ring-shaped electrodes, which had diameters less than 11.8 mm, collected charges independently only around the beam, excluding strong in-beam charges when the beams passed through a small hole in the electrode centers. As a result, under low saturation voltages, the measured dose rates were confirmed to correlate with the beam intensity when conversion factors calculated with a Monte Carlo code were employed. The influence of the assumed beam sizes and incident positions on the current was almost negligible, with the exception of the incident position dependence at 10 keV.

  3. Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam.

    Science.gov (United States)

    Groetz, J-E; Ounoughi, N; Mavon, C; Belafrites, A; Fromm, M

    2014-08-01

    We report the design of a millimeter-sized parallel plate free-air ionization chamber (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors necessary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL™ and FLUKA). Measurements of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte Carlo calculations. We show that the developed ionization chamber makes it possible to determine accurate photon fluence rates in routine work and will constitute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays.

  4. Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam

    Energy Technology Data Exchange (ETDEWEB)

    Groetz, J.-E., E-mail: jegroetz@univ-fcomte.fr; Mavon, C.; Fromm, M. [Laboratoire Chrono-Environnement, UMR CNRS 6249, Université de Franche-Comté, 16 route de Gray, 25030 Besançon Cedex (France); Ounoughi, N. [Laboratoire Chrono-Environnement, UMR CNRS 6249, Université de Franche-Comté, 16 route de Gray, 25030 Besançon Cedex (France); Laboratoire de Physique des Rayonnements et Applications, Université de Jijel, B.P. 98 Ouled Aissa, Jijel 18000 (Algeria); Belafrites, A. [Laboratoire de Physique des Rayonnements et Applications, Université de Jijel, B.P. 98 Ouled Aissa, Jijel 18000 (Algeria)

    2014-08-15

    We report the design of a millimeter-sized parallel plate free-air ionization chamber (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors necessary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL™and FLUKA). Measurements of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte Carlo calculations. We show that the developed ionization chamber makes it possible to determine accurate photon fluence rates in routine work and will constitute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays.

  5. Conception and realization of a parallel-plate free-air ionization chamber for the absolute dosimetry of an ultrasoft X-ray beam

    Science.gov (United States)

    Groetz, J.-E.; Ounoughi, N.; Mavon, C.; Belafrites, A.; Fromm, M.

    2014-08-01

    We report the design of a millimeter-sized parallel plate free-air ionization chamber (IC) aimed at determining the absolute air kerma rate of an ultra-soft X-ray beam (E = 1.5 keV). The size of the IC was determined so that the measurement volume satisfies the condition of charged-particle equilibrium. The correction factors necessary to properly measure the absolute kerma using the IC have been established. Particular attention was given to the determination of the effective mean energy for the 1.5 keV photons using the PENELOPE code. Other correction factors were determined by means of computer simulation (COMSOL™and FLUKA). Measurements of air kerma rates under specific operating parameters of the lab-bench X-ray source have been performed at various distances from that source and compared to Monte Carlo calculations. We show that the developed ionization chamber makes it possible to determine accurate photon fluence rates in routine work and will constitute substantial time-savings for future radiobiological experiments based on the use of ultra-soft X-rays.

  6. Multi-anode ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Bolotnikov, Aleksey E. (South Setauket, NY); Smith, Graham (Port Jefferson, NY); Mahler, George J. (Rocky Point, NY); Vanier, Peter E. (Setauket, NY)

    2010-12-28

    The present invention includes a high-energy detector having a cathode chamber, a support member, and anode segments. The cathode chamber extends along a longitudinal axis. The support member is fixed within the cathode chamber and extends from the first end of the cathode chamber to the second end of the cathode chamber. The anode segments are supported by the support member and are spaced along the longitudinal surface of the support member. The anode segments are configured to generate at least a first electrical signal in response to electrons impinging thereon.

  7. Quantification of static magnetic field effects on radiotherapy ionization chambers

    Science.gov (United States)

    Agnew, J.; O’Grady, F.; Young, R.; Duane, S.; Budgell, G. J.

    2017-03-01

    Integrated magnetic resonance (MR) imaging and radiotherapy (RT) delivery machines are currently being developed, with some already in clinical use. It is anticipated that the strong magnetic field used in some MR-RT designs will have a significant impact on routine measurements of dose in the MR-linac performed using ionization chambers, which provide traceability back to a primary standard definition of dose. In particular, the presence of small air gaps around ionization chambers may introduce unacceptably high uncertainty into these measurements. In this study, we investigate and quantify the variation attributable to air gaps for several routinely-used cylindrical ionization chambers in a magnetic field, as well as the effect of the magnetic field alone on the response of the chambers. The measurements were performed in a Co-60 beam, while the ionization chambers were positioned in custom-made Perspex phantoms between the poles of an electromagnet, which was capable of generating magnetic fields of up to 2 T field strength, although measurements were focused around 1.5 T. When an asymmetric air gap was rotated at cardinal angles around the ionization chambers investigated here, variation of up to 8.5  ±  0.2 percentage points (PTW 31006 chamber) was observed in an applied magnetic field of 1.5 T. The minimum peak-to-peak variation was 1.1  ±  0.1% (Exradin A1SL). When the same experiment was performed with a well-defined air gap of known position using the PTW 30013 chamber, a variation of 3.8  ±  0.2% was observed. When water was added to the phantom cavity to eliminate all air gaps, the variation for the PTW 30013 was reduced to 0.2  ±  0.01%.

  8. Classification of the LHC BLM Ionization Chamber

    CERN Document Server

    Stockner, M; Fabjan, Christian Wolfgang; Holzer, E B; Kramer, Daniel

    2008-01-01

    The LHC beam loss monitoring (BLM) system must prevent the super conducting magnets from quenching and protect the machine components from damage. The main monitor type is an ionization chamber. About 4000 of them will be installed around the ring. The lost beam particles initiate hadronic showers through the magnets and other machine components. These shower particles are measured by the monitors installed on the outside of the accelerator equipment. For the calibration of the BLM system the signal response of the ionization chamber is simulated in GEANT4 for all relevant particle types and energies (keV to TeV range). For validation, the simulations are compared to measurements using protons, neutrons, photons and mixed radiation fields at various energies and intensities. This paper will focus on the signal response of the ionization chamber to various particle types and energies including space charge effects at high ionization densities.

  9. Evaluation of wall correction factor of INER's air-kerma primary standard chamber and dose variation by source displacement for HDR ¹⁹²Ir brachytherapy.

    Science.gov (United States)

    Lee, J H; Wang, J N; Huang, T T; Su, S H; Chang, B J; Su, C H; Hsu, S M

    2013-01-01

    The aim of the present study was to estimate the wall effect of the self-made spherical graphite-walled cavity chamber with the Monte Carlo method for establishing the air-kerma primary standard of high-dose-rate (HDR) ¹⁹²Ir brachytherapy sources at the Institute of Nuclear Energy Research (INER, Taiwan). The Monte Carlo method established in this paper was also employed to respectively simulate wall correction factors of the ¹⁹²Ir air-kerma standard chambers used at the National Institute of Standards and Technology (NIST, USA) and the National Physical Laboratory (NPL, UK) for comparisons and verification. The chamber wall correction calculation results will be incorporated into INER's HDR ¹⁹²Ir primary standard in the future. For the brachytherapy treatment in the esophagus or in the bronchi, the position of the isotope may have displacement in the cavity. Thus the delivered dose would differ from the prescribed dose in the treatment plan. We also tried assessing dose distribution due to the position displacement of HDR ¹⁹²Ir brachytherapy source in a phantom with a central cavity by the Monte Carlo method. The calculated results could offer a clinical reference for the brachytherapy within the human organs with cavity.

  10. Characteristics of a miniature parallel-plate free-air ionization chamber for measuring the intensity of synchrotron radiation from an undulator

    Science.gov (United States)

    Nariyama, Nobuteru

    2004-09-01

    In order to develop an absolute intensity monitor for synchrotron radiation from an undulator, the characteristics of a parallel-plate free-air ionization chamber with a plate separation of 4.2 mm, which was considered to be as narrow as possible, were investigated using 8-30 keV monoenergetic photons at SPring-8. Using a Si-PIN photodiode as the reference monitor, saturation was confirmed at 8-30 keV at a photon intensity of an order of 1013 photons/s. The collection efficiency became almost unity at 8 and 10 keV within 3.8% and 1.1%, respectively, which gradually decreased with increasing energy and attained 0.52 at 30 keV because some of the high-energy electrons escaped from the sensitive volume. When the pair of electrodes was transferred from the upper and lower sides to the left and right sides of the beam axis in order to investigate the influence of linear polarization of synchrotron radiation, a decrease in the collection efficiency was observed. Monte Carlo simulations considering linear polarization showed that the plate separation required for no electron loss was 26, 14, and 8 mm for 30, 20, and 15 keV photons, respectively. For 20 keV photons, saturation characteristics were investigated using an ionization chamber with 14 mm plate separation.

  11. The GODDESS ionization chamber: developing robust windows

    Science.gov (United States)

    Blanchard, Rose; Baugher, Travis; Cizewski, Jolie; Pain, Steven; Ratkiewicz, Andrew; Goddess Collaboration

    2015-10-01

    Reaction studies of nuclei far from stability require high-efficiency arrays of detectors and the ability to identify beam-like particles, especially when the beam is a cocktail beam. The Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies (GODDESS) is made up of the Oak Ridge-Rutgers University Barrel Array (ORRUBA) of silicon detectors for charged particles inside of the gamma-ray detector array Gammasphere. A high-rate ionization chamber is being developed to identify beam-like particles. Consisting of twenty-one alternating anode and cathode grids, the ionization chamber sits downstream of the target chamber and is used to measure the energy loss of recoiling ions. A critical component of the system is a thin and robust mylar window which serves to separate the gas-filled ionization chamber from the vacuum of the target chamber with minimal energy loss. After construction, windows were tested to assure that they would not break below the required pressure, causing harm to the wire grids. This presentation will summarize the status of the ionization chamber and the results of the first tests with beams. This work is supported in part by the U.S. Department of Energy and National Science Foundation.

  12. Making MUSIC: A multiple sampling ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Shumard, B. [Argonne National Laboratory, Building 203 H-113, Argonne, IL 60439 (United States)]. E-mail: shumard@phy.anl.gov; Henderson, D.J. [Argonne National Laboratory, Building 203 H-113, Argonne, IL 60439 (United States); Rehm, K.E. [Argonne National Laboratory, Building 203 H-113, Argonne, IL 60439 (United States); Tang, X.D. [Argonne National Laboratory, Building 203 H-113, Argonne, IL 60439 (United States)

    2007-08-15

    A multiple sampling ionization chamber (MUSIC) was developed for use in conjunction with the Atlas scattering chamber (ATSCAT). This chamber was developed to study the ({alpha}, p) reaction in stable and radioactive beams. The gas filled ionization chamber is used as a target and detector for both particles in the outgoing channel (p + beam particles for elastic scattering or p + residual nucleus for ({alpha}, p) reactions). The MUSIC detector is followed by a Si array to provide a trigger for anode events. The anode events are gated by a gating grid so that only ({alpha}, p) reactions where the proton reaches the Si detector result in an anode event. The MUSIC detector is a segmented ionization chamber. The active length of the chamber is 11.95 in. and is divided into 16 equal anode segments (3.5 in. x 0.70 in. with 0.3 in. spacing between pads). The dead area of the chamber was reduced by the addition of a Delrin snout that extends 0.875 in. into the chamber from the front face, to which a mylar window is affixed. 0.5 in. above the anode is a Frisch grid that is held at ground potential. 0.5 in. above the Frisch grid is a gating grid. The gating grid functions as a drift electron barrier, effectively halting the gathering of signals. Setting two sets of alternating wires at differing potentials creates a lateral electric field which traps the drift electrons, stopping the collection of anode signals. The chamber also has a reinforced mylar exit window separating the Si array from the target gas. This allows protons from the ({alpha}, p) reaction to be detected. The detection of these protons opens the gating grid to allow the drift electrons released from the ionizing gas during the ({alpha}, p) reaction to reach the anode segment below the reaction.

  13. SU-E-T-552: Monte Carlo Calculation of Correction Factors for a Free-Air Ionization Chamber in Support of a National Air-Kerma Standard for Electronic Brachytherapy

    Energy Technology Data Exchange (ETDEWEB)

    Mille, M; Bergstrom, P [National Institute of Standards and Technology, Gaithersburg, MD (United States)

    2015-06-15

    Purpose: To use Monte Carlo radiation transport methods to calculate correction factors for a free-air ionization chamber in support of a national air-kerma standard for low-energy, miniature x-ray sources used for electronic brachytherapy (eBx). Methods: The NIST is establishing a calibration service for well-type ionization chambers used to characterize the strength of eBx sources prior to clinical use. The calibration approach involves establishing the well-chamber’s response to an eBx source whose air-kerma rate at a 50 cm distance is determined through a primary measurement performed using the Lamperti free-air ionization chamber. However, the free-air chamber measurements of charge or current can only be related to the reference air-kerma standard after applying several corrections, some of which are best determined via Monte Carlo simulation. To this end, a detailed geometric model of the Lamperti chamber was developed in the EGSnrc code based on the engineering drawings of the instrument. The egs-fac user code in EGSnrc was then used to calculate energy-dependent correction factors which account for missing or undesired ionization arising from effects such as: (1) attenuation and scatter of the x-rays in air; (2) primary electrons escaping the charge collection region; (3) lack of charged particle equilibrium; (4) atomic fluorescence and bremsstrahlung radiation. Results: Energy-dependent correction factors were calculated assuming a monoenergetic point source with the photon energy ranging from 2 keV to 60 keV in 2 keV increments. Sufficient photon histories were simulated so that the Monte Carlo statistical uncertainty of the correction factors was less than 0.01%. The correction factors for a specific eBx source will be determined by integrating these tabulated results over its measured x-ray spectrum. Conclusion: The correction factors calculated in this work are important for establishing a national standard for eBx which will help ensure that dose

  14. Development and characterization of a new graphite ionization chamber for dosimetry of {sup 60}Co beams

    Energy Technology Data Exchange (ETDEWEB)

    Neves, Lucio Pereira; Perini, Ana Paula; Santos, William de Souza; Caldas, Linda V.E., E-mail: lpneves@ipen.br, E-mail: aperini@ipen.br, E-mail: wssantos@ipen.br, E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2014-07-01

    Ionization chambers are the most employed dosimeters for precise measurements, as those required in radiotherapy. In this work, a new graphite ionization chamber was developed and characterized in order to compose a primary standard system for the beam dosimetry of the {sup 60}Co sources. This dosimeter is a cylindrical type ionization chamber, with walls and collecting electrode made of high-purity graphite, and the insulators and stem made of Teflon®. The walls are 3.0 mm thick, and it has a sensitive volume of 1.40 cm{sup 3}. The characterization was divided in two steps: experimental and Monte Carlo evaluations. This new dosimeter was evaluated in relation to its saturation curve, ion collection efficiency, polarity effect, short- and medium-term stabilities, leakage current, stabilization time, linearity of response and angular dependence. All results presented values within the established limits. The second part of the characterization process involved the determination of the correction factors, obtained by Monte Carlo simulations. Comparing these correction factors values with those from other primary standard laboratories, the highest differences were those for the wall and stem correction factors. The air-kerma rate of the {sup 60}Co source was determined with this new dosimeter and with the IPEN standard system, presenting a difference of 1.7%. These results indicate that this new dosimeter may be used as a primary standard system for {sup 60}Co gamma beams. (author)

  15. IKAR, a ionization chamber for WA9

    CERN Document Server

    1976-01-01

    This ionization chamber arrived at CERN from Leningrad for a high precision study of hadron elastic scattering by a CERN-Clermont-Ferrand-Leningrad-Lyon-Uppsala Collaboration in the H3 beam (WA9). G.A. Korolev (third from right) looks at the drawings.

  16. Precision electronics for ionization chamber measurements

    Energy Technology Data Exchange (ETDEWEB)

    Santry, D.C.; Bowes, G.C.; Munzenmayer, K.

    1987-01-01

    By using commercially available units, an electrometer and an IBM personal computer, it was relatively inexpensive and simple to assemble a system which permits ..gamma..-ray-emitting radionuclide activities to be measured in an ionization chamber with an uncertainty of + - 0.5% and a reproducibility of + - 0.05%.

  17. Calibration of a pencil ionization chamber with and without preamplifier

    OpenAIRE

    Maia, Ana Figueiredo

    2004-01-01

    The pencil ionization chamber is a cylindrical dosimeter developed for computed tomography beams. Many kinds of ionization chambers have a preamplifier connected to the chamber to make it electrically more stable, specially for field instruments. In this study, the performance of a Victoreen pencil ionization chamber with the original preamplifier and after its removal was compared. The objective of the preamplifier removal was to enable connecting the chamber to other kinds of electromete...

  18. Improvement of a New Gas Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    In order to identify heavier elements, we have developed a new longitudinal field gas ionization chamber (IC)with an angle of 30° of plate (as shown in Fig.1). The IC is operated in flowing iso-butane gas at a pressure of 10kPa. After testing by using a 3- component α particle source and comparing with the old longitudinal field

  19. Cosmic Rays Response of High-pressure Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    GAO; Fei; XIAO; Xue-fu; NI; Ning; ZHANG; Xi; HOU; Jin-bing; SONG; Ming-zhe; WANG; Hong-yu

    2013-01-01

    In order to study cosmic rays response characteristics of self-designed HPIC(high pressure ionization chamber),model JLZ-Ⅲ,the JLZ-Ⅲwas placed on a boat which is 3 meters much deeper and at least 1 kilometer away from land to measure air kerma rate in the open water in Miyun Reservoir(geomagnetic latitude 29°N,altitude 160 m),Beijing.The result was compared with the measurement

  20. Nuclear Fission Investigation with Twin Ionization Chamber

    Science.gov (United States)

    Zeynalova, O.; Zeynalov, Sh.; Nazarenko, M.; Hambsch, F.-J.; Oberstedt, S.

    2011-11-01

    The purpose of the present paper was to report the recent results, obtained in development of digital pulse processing mathematics for prompt fission neutron (PFN) investigation using twin ionization chamber (TIC) along with fast neutron time-of-flight detector (ND). Due to well known ambiguities in literature (see refs. [4, 6, 9 and 11]), concerning a pulse induction on TIC electrodes by FF ionization, we first presented detailed mathematical analysis of fission fragment (FF) signal formation on TIC anode. The analysis was done using Ramo-Shockley theorem, which gives relation between charged particle motion between TIC electrodes and so called weighting potential. Weighting potential was calculated by direct numerical solution of Laplace equation (neglecting space charge) for the TIC geometry and ionization, caused by FF. Formulae for grid inefficiency (GI) correction and digital pulse processing algorithms for PFN time-of-flight measurements and pulse shape analysis are presented and discussed.

  1. LARGE VOLUME IONIZATION CHAMBER USED AS LABORATORY REFERENCE FOR LOW ENERGY X—RAY MEASUREMENT

    Institute of Scientific and Technical Information of China (English)

    杨国山; 薛永库; 等

    1994-01-01

    A large volume spherical ionization chamber of 195mm diameter and 0.36mg/cm2 wall thickness made from conducting carbon-fibre epoxy composite material has been developed.The mechanical intensity of the chamber is satisfactory for a good longterm volume stability.Owing to its large volume and thin wall,the chamber is sensitive to low energy photon beams and has excellent energy-response characteristics.This ionization chamber is suitable not only for a laboratory reference but also for measurement of low energy photon beam exposure rates at protection-level.

  2. Saturation curves of parallel-plate ionization chambers

    Energy Technology Data Exchange (ETDEWEB)

    Fallone, B.G.; Podgorsak, E.B.

    A new analytical expression is presented to describe the full saturation curve of parallel-plate ionization chambers. In contrast to the presently known expressions, which hold only for the near saturation region, this empirically determined expression is in excellent agreement with measurements in the whole collection efficiency range from 0 to 1 for x-ray sources with effective energies from 20 to 150 keV and cobalt-60 gamma rays. The dependence of the ion collection efficiency and the extrapolated electric field, which is a parameter in the new saturation curve expression, on electric field, dose, dose rate, beam quality, and chamber volume, is discussed. The effect of photoemission from the chamber polarizing electrode for low-energy x-ray beams on the saturation current is demonstrated. A universal ionization chamber constant is derived experimentally. It is shown that all parameters of the saturation curve equation and thus the saturation curve itself, can be calculated from one single measurement of ionization current at a given electric field and air gap thickness.

  3. SU-E-T-525: Ionization Chamber Perturbation in Flattening Filter Free Beams

    Energy Technology Data Exchange (ETDEWEB)

    Czarnecki, D; Voigts-Rhetz, P von [Technische Hochschule Mittelhessen - University of Applied Sciences, Giessen, DE (Germany); Zink, K [Technische Hochschule Mittelhessen - University of Applied Sciences, Giessen, DE (Germany); Germany and Department of Radiotherapy and Radiooncology, University Medical Center Giessen-Marburg, Marburg, DE (Germany)

    2015-06-15

    Purpose: Changing the characteristic of a photon beam by mechanically removing the flattening filter may impact the dose response of ionization chambers. Thus, perturbation factors of cylindrical ionization chambers in conventional and flattening filter free photon beams were calculated by Monte Carlo simulations. Methods: The EGSnrc/BEAMnrc code system was used for all Monte Carlo calculations. BEAMnrc models of nine different linear accelerators with and without flattening filter were used to create realistic photon sources. Monte Carlo based calculations to determine the fluence perturbations due to the presens of the chambers components, the different material of the sensitive volume (air instead of water) as well as the volume effect were performed by the user code egs-chamber. Results: Stem, central electrode, wall, density and volume perturbation factors for linear accelerators with and without flattening filter were calculated as a function of the beam quality specifier TPR{sub 20/10}. A bias between the perturbation factors as a function of TPR{sub 20/10} for flattening filter free beams and conventional linear accelerators could not be observed for the perturbations caused by the components of the ionization chamber and the sensitive volume. Conclusion: The results indicate that the well-known small bias between the beam quality correction factor as a function of TPR20/10 for the flattening filter free and conventional linear accelerators is not caused by the geometry of the detector but rather by the material of the sensitive volume. This suggest that the bias for flattening filter free photon fields is only caused by the different material of the sensitive volume (air instead of water)

  4. Ionization Chamber for Prompt Fission Neutron Investigations

    OpenAIRE

    ZEYNALOV Sh.; ZEYNALOVA O. V.; Hambsch, Franz-Josef; Sedyshev, P.; SHVETSOV V.

    2014-01-01

    In this work we report recent achievements in design of twin back-to-back ionization chamber (TIC) for fission fragment (FF) mass and kinetic energy measurement. Correlated FF kinetic energies, their masses and the angle of FF in respect to the axes in 3D Cartesian coordinates can be determined from analysis of the heights and shapes of the pulses induced by the fission fragments on the anodes of TIC. Anodes of TIC were designed as consisting of isolated strips each having independent electro...

  5. Reference dosimetry at the Australian Synchrotron's imaging and medical beamline using free-air ionization chamber measurements and theoretical predictions of air kerma rate and half value layer

    Energy Technology Data Exchange (ETDEWEB)

    Crosbie, Jeffrey C.; Rogers, Peter A. W. [Department of Obstetrics and Gynaecology, University of Melbourne, The Royal Women' s Hospital, Parkville, Victoria 3052 (Australia); Stevenson, Andrew W. [CSIRO Materials Science and Engineering, Clayton, Victoria 3169 (Australia); Hall, Christopher J. [Imaging and Medical Beamline, Australian Synchrotron, Clayton, Victoria 3168 (Australia); Lye, Jessica E. [Australian Radiation Protection and Nuclear Safety Agency, Yallambie, Victoria 3085 (Australia); Nordstroem, Terese [KTH Royal Institute of Technology, Stockholm SE-100 44 (Sweden); Midgley, Stewart M. [School of Physics, Monash University, Clayton, Victoria 3800 (Australia); Lewis, Robert A. [Department of Medical Imaging and Radiation Sciences, Monash University, Clayton, Victoria 3800 (Australia)

    2013-06-15

    Purpose: Novel, preclinical radiotherapy modalities are being developed at synchrotrons around the world, most notably stereotactic synchrotron radiation therapy and microbeam radiotherapy at the European Synchrotron Radiation Facility in Grenoble, France. The imaging and medical beamline (IMBL) at the Australian Synchrotron has recently become available for preclinical radiotherapy and imaging research with clinical trials, a distinct possibility in the coming years. The aim of this present study was to accurately characterize the synchrotron-generated x-ray beam for the purposes of air kerma-based absolute dosimetry. Methods: The authors used a theoretical model of the energy spectrum from the wiggler source and validated this model by comparing the transmission through copper absorbers (0.1-3.0 mm) against real measurements conducted at the beamline. The authors used a low energy free air ionization chamber (LEFAC) from the Australian Radiation Protection and Nuclear Safety Agency and a commercially available free air chamber (ADC-105) for the measurements. The dimensions of these two chambers are different from one another requiring careful consideration of correction factors. Results: Measured and calculated half value layer (HVL) and air kerma rates differed by less than 3% for the LEFAC when the ion chamber readings were corrected for electron energy loss and ion recombination. The agreement between measured and predicted air kerma rates was less satisfactory for the ADC-105 chamber, however. The LEFAC and ADC measurements produced a first half value layer of 0.405 {+-} 0.015 and 0.412 {+-} 0.016 mm Cu, respectively, compared to the theoretical prediction of 0.427 {+-} 0.012 mm Cu. The theoretical model based upon a spectrum calculator derived a mean beam energy of 61.4 keV with a first half value layer of approximately 30 mm in water. Conclusions: The authors showed in this study their ability to verify the predicted air kerma rate and x-ray attenuation

  6. Characterization of a homemade ionization chamber for radiotherapy beams.

    Science.gov (United States)

    Neves, Lucio P; Perini, Ana P; dos Santos, Gelson P; Xavier, Marcos; Khoury, Helen J; Caldas, Linda V E

    2012-07-01

    A homemade cylindrical ionization chamber was studied for routine use in therapy beams of (60)Co and X-rays. Several characterization tests were performed: leakage current, saturation, ion collection efficiency, polarity effect, stability, stabilization time, chamber orientation and energy dependence. All results obtained were within international recommendations. Therefore the homemade ionization chamber presents usefulness for routine dosimetric procedures in radiotherapy beams.

  7. Effect of the calibration in water and the build-up cap on the Mg(Ar) ionization chamber measurements.

    Science.gov (United States)

    Koivunoro, H; Hyvönen, H; Uusi-Simola, J; Jokelainen, I; Kosunen, A; Kortesniemi, M; Seppälä, T; Auterinen, I; Savolainen, S

    2011-12-01

    Magnesium-walled argon gas flow ionization chamber (Mg(Ar)) is used for photon dose measurements in the epithermal neutron beam of FiR 1 reactor in Finland. In this study, the photon dose measurements were re-evaluated against calculations applying a new chamber calibration factor defined in water instead of in air. Also, effect of the build-up cap on the measurements was investigated. The new calibration factor provides improved agreement between measured and calculated photon dose. Use of the build-up cap does not affect the measured signal in water in neutron beam.

  8. Effect of the calibration in water and the build-up cap on the Mg(Ar) ionization chamber measurements

    Energy Technology Data Exchange (ETDEWEB)

    Koivunoro, H., E-mail: hanna.koivunoro@helsinki.fi [Boneca Corporation, FI-00290 Helsinki (Finland)] [Department of Physics, P.O.B. 64, FI-00014 University of Helsinki (Finland)] [Department of Oncology, Helsinki University Central Hospital, P.O.B. 180, 00029 HUS (Finland); Hyvoenen, H. [Boneca Corporation, FI-00290 Helsinki (Finland); Uusi-Simola, J. [HUS Helsinki Medical Imaging Center, University of Helsinki (Finland); Jokelainen, I.; Kosunen, A. [Radiation Metrology Laboratory, Radiation and Nuclear Safety Authority-STUK, FI-00881 (Finland); Kortesniemi, M. [HUS Helsinki Medical Imaging Center, University of Helsinki (Finland); Seppaelae, T. [Department of Oncology, Helsinki University Central Hospital, P.O.B. 180, 00029 HUS (Finland); Auterinen, I. [VTT Technical Research Centre of Finland, Espoo (Finland); Savolainen, S. [Department of Physics, P.O.B. 64, FI-00014 University of Helsinki (Finland)] [HUS Helsinki Medical Imaging Center, University of Helsinki (Finland)

    2011-12-15

    Magnesium-walled argon gas flow ionization chamber (Mg(Ar)) is used for photon dose measurements in the epithermal neutron beam of FiR 1 reactor in Finland. In this study, the photon dose measurements were re-evaluated against calculations applying a new chamber calibration factor defined in water instead of in air. Also, effect of the build-up cap on the measurements was investigated. The new calibration factor provides improved agreement between measured and calculated photon dose. Use of the build-up cap does not affect the measured signal in water in neutron beam.

  9. Characterization of a free-air ionization chamber in direct X-ray beams as used in mammography; Caracterizacao de uma camara de ionizacao de ar-livre em feixes diretos de raios X utilizados em mamografia

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Mateus Hilario de

    2014-08-01

    At this work stability and characterization tests were undertaken on a Victoreen free-air ionization chamber, model 481. The tests were realized using direct X-ray beams as a contribution for its establishment as a primary standard system of the quantity air kerma. The characterization tests were: saturation curve, ion collection efficiency, polarity effect, response linearity with the air kerma rate and response linearity with the chamber volume variation. The ion collection efficiency allowed the determination of the ion recombination factor. Most of the test results showed agreement with the limits established by international standards. Furthermore, the air attenuation factors for the mammography beams with aluminum and molybdenum filters were obtained. The factors for photon transmission and scattering at the diaphragm edges were also determined for mammography beams with aluminum filter and for the standard beam with molybdenum filter. (author)

  10. Current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization

    CERN Document Server

    Stoyanov, Dimitar G

    2007-01-01

    The balances of particles and charges in the volume of parallel-plane ionization chamber are considered. Differential equations describing the distribution of current densities in the chamber volume are obtained. As a result of the differential equations solution an analytical form of the current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization in the volume is got.

  11. Current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization

    Energy Technology Data Exchange (ETDEWEB)

    Stoyanov, D G [Faculty of Engineering and Pedagogy in Sliven, Technical University of Sofia, 59, Bourgasko Shaussee Blvd, 8800 Sliven (Bulgaria)

    2007-08-15

    The balances of particles and charges in the volume of parallel-plane ionization chamber are considered. Differential equations describing the distribution of current densities in the chamber volume are obtained. As a result of the differential equations solution an analytical form of the current-voltage characteristic of parallel-plane ionization chamber with inhomogeneous ionization in the volume is obtained.

  12. Investigation of electric field distribution on FAC-IR-300 ionization chamber

    Science.gov (United States)

    Mohammadi, S. M.; Tavakoli-Anbaran, H.; Zeinali, H. Z.

    2016-07-01

    One of the important parameters for establishing charge particle equilibrium (CPE) conditions of free-air ionization chamber is an electric field distribution. In this paper, electric field distribution inside the ionization chamber was investigated by finite element method. For this purpose, the effects of adding guard plate and guard strips on the electric field distribution in the ionization chamber were studied. it is necessary to apply a lead box around the ionization chamber body to avoid of scattered radiation effects on the ionization chamber operation, but the lead box changes the electric field distribution. In the following, the effect of lead box on the electric field distribution was studied. Finally, electric field distribution factor (kfield) was calculated by the simulation. The results of the simulation showed that presence of the guard plate and guard strips, and applying a suitable potential to lead box, a convergence of kfield to 1 was achieved.

  13. High spatial resolution dosimetric response maps for radiotherapy ionization chambers measured using kilovoltage synchrotron radiation

    Science.gov (United States)

    Butler, D. J.; Stevenson, A. W.; Wright, T. E.; Harty, P. D.; Lehmann, J.; Livingstone, J.; Crosbie, J. C.

    2015-11-01

    Small circular beams of synchrotron radiation (0.1 mm and 0.4 mm in diameter) were used to irradiate ionization chambers of the types commonly used in radiotherapy. By scanning the chamber through the beam and measuring the ionization current, a spatial map of the dosimetric response of the chamber was recorded. The technique is able to distinguish contributions to the large-field ionization current from the chamber walls, central electrode and chamber stem. Scans were recorded for the NE 2571 Farmer chamber, the PTW 30013, IBA FC65-G Farmer-type chambers, the NE 2611A and IBA CC13 thimble chambers, the PTW 31006 and 31014 pinpoint chambers, the PTW Roos and Advanced Markus plane-parallel chambers, and the PTW 23342 thin-window soft x-ray chamber. In all cases, large contributions to the response arise from areas where the incident beam grazes the cavity surfaces. Quantitative as well as qualitative information about the relative chamber response was extracted from the maps, including the relative contribution of the central electrode. Line scans using monochromatic beams show the effect of the photon energy on the chamber response. For Farmer-type chambers, a simple Monte Carlo model was in good agreement with the measured response.

  14. Monte Carlo calculation of energy deposition in ionization chambers for tritium measurements

    Science.gov (United States)

    Zhilin, Chen; Shuming, Peng; Dan, Meng; Yuehong, He; Heyi, Wang

    2014-10-01

    Energy deposition in ionization chambers for tritium measurements has been theoretically studied using Monte Carlo code MCNP 5. The influence of many factors, including carrier gas, chamber size, wall materials and gas pressure, has been evaluated in the simulations. It is found that β rays emitted by tritium deposit much more energy into chambers flowing through with argon than with deuterium in them, as much as 2.7 times higher at pressure 100 Pa. As chamber size gets smaller, energy deposition decreases sharply. For an ionization chamber of 1 mL, β rays deposit less than 1% of their energy at pressure 100 Pa and only 84% even if gas pressure is as high as 100 kPa. It also indicates that gold plated ionization chamber results in the highest deposition ratio while aluminum one leads to the lowest. In addition, simulations were validated by comparison with experimental data. Results show that simulations agree well with experimental data.

  15. Response of ionization chamber based pocket dosimeter to beta radiation.

    Science.gov (United States)

    Kumar, Munish; Gupta, Anil; Pradhan, S M; Bakshi, A K; Chougaonkar, M P; Babu, D A R

    2013-12-01

    Quantitative estimate of the response of ionization chamber based pocket dosimeters (DRDs) to various beta sources was performed. It has been established that the ionization chamber based pocket dosimeters do not respond to beta particles having energy (Emax)1 MeV, the DRDs exhibit measureable response and the values are ~8%, ~14% and ~27% per mSv for natural uranium, (90)Sr/(90)Y and (106)Ru/(106)Rh beta sources respectively. As the energy of the beta particles increases, the response also increases. The response of DRDs to beta particles having energy>1 MeV arises due to the fact that the thickness of the chamber walls is less than the maximum range of beta particles. This may also be one of the reasons for disparity between doses measured with passive/legal dosimeters (TLDs) and DRDs in those situations in which radiation workers are exposed to mixed field of gamma photons and beta particles especially at uranium processing plants, nuclear (power and research) reactors, waste management facilities and fuel reprocessing plants etc. The paper provides the reason (technical) for disparity between the doses recorded by TLDs and DRDs in mixed field of photons and beta particles.

  16. A new ring-shaped graphite monitor ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Yoshizumi, M.T., E-mail: mairaty@ipen.b [Instituto de Pesquisas Energeticas e Nucleares IPEN - CNEN/SP, Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo-SP (Brazil); Caldas, L.V.E., E-mail: lcaldas@ipen.b [Instituto de Pesquisas Energeticas e Nucleares IPEN - CNEN/SP, Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo-SP (Brazil)

    2010-07-21

    A ring-shaped monitor ionization chamber was developed at the Instituto de Pesquisas Energeticas e Nucleares. This ionization chamber presents an entrance window of aluminized polyester foil. The guard ring and collecting electrode are made of graphite coated Lucite plates. The main difference between this new ionization chamber and commercial monitor chambers is its ring-shaped design. The new monitor chamber has a central hole, allowing the passage of the direct radiation beam without attenuation; only the penumbra radiation is measured by the sensitive volume. This kind of ionization chamber design has already been tested, but using aluminium electrodes. By changing the electrode material from aluminium to a graphite coating, an improvement in the chamber response stability was expected. The pre-operational tests, as saturation curve, recombination loss and polarity effect showed satisfactory results. The repeatability and the long-term stability tests were also evaluated, showing good agreement with international recommendations.

  17. Monte Carlo Simulation Optimizing Design of Grid Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    ZHENG; Yu-lai; WANG; Qiang; YANG; Lu

    2013-01-01

    The grid ionization chamber detector is often used for measuring charged particles.Based on Monte Carlo simulation method,the energy loss distribution and electron ion pairs of alpha particle with different energy have been calculated to determine suitable filling gas in the ionization chamber filled with

  18. Practical method for determination of air kerma by use of an ionization chamber toward construction of a secondary X-ray field to be used in clinical examination rooms.

    Science.gov (United States)

    Maehata, Itsumi; Hayashi, Hiroaki; Kimoto, Natsumi; Takegami, Kazuki; Okino, Hiroki; Kanazawa, Yuki; Tominaga, Masahide

    2016-07-01

    We propose a new practical method for the construction of an accurate secondary X-ray field using medical diagnostic X-ray equipment. For accurate measurement of the air kerma of an X-ray field, it is important to reduce and evaluate the contamination rate of scattered X-rays. To determine the rate quantitatively, we performed the following studies. First, we developed a shield box in which an ionization chamber could be set at an inner of the box to prevent detection of the X-rays scattered from the air. In addition, we made collimator plates which were placed near the X-ray source for estimation of the contamination rate by scattered X-rays from the movable diaphragm which is a component of the X-ray equipment. Then, we measured the exposure dose while changing the collimator plates, which had diameters of 25-90 mm(ϕ). The ideal value of the exposure dose was derived mathematically by extrapolation to 0 mm(ϕ). Tube voltages ranged from 40 to 130 kV. Under these irradiation conditions, we analyzed the contamination rate by the scattered X-rays. We found that the contamination rates were less than 1.7 and 2.3 %, caused by air and the movable diaphragm, respectively. The extrapolated value of the exposure dose has been determined to have an uncertainty of 0.7 %. The ionization chamber used in this study was calibrated with an accuracy of 5 %. Using this kind of ionization chamber, we can construct a secondary X-ray field with an uncertainty of 5 %.

  19. A Fast Ionization Chamber for GODDESS

    Science.gov (United States)

    Lumb, R. T.; Lipman, A. S.; Baugher, T.; Cizewski, J. A.; Ratkiewicz, A.; Pain, S. D.; Kozub, R. L.

    2014-09-01

    Transfer reactions are among the main methods used in nuclear physics to probe the structure of nuclei. Such information is needed to constrain nuclear models and to understand various nucleosynthesis processes. In many cases, the nuclear level densities are too high to be resolved in transfer reactions via charged particle detection alone. This problem and issues arising from contaminants in radioactive beams can be addressed by using particle- γ coincidence techniques along with heavy recoil identification in inverse kinematics. A device to accomplish these tasks is Gammasphere ORRUBA: Dual Detectors for Experimental Structure Studies (GODDESS), currently being commissioned for the ATLAS facility at ANL. We are currently building a compact, tilted grid ionization chamber for GODDESS to detect and identify beam-like recoils near zero degrees in the lab. The tilt (30 degrees off normal to the beam) helps the ion pairs to be detected quickly, after drifting only a short distance away from the beam axis. This reduces the response time, allowing counting rates of ~500,000/s. The design and current status of the project will be presented. Research supported by the U. S. DOE.

  20. The FiR 1 photon beam model adjustment according to in-air spectrum measurements with the Mg(Ar) ionization chamber.

    Science.gov (United States)

    Koivunoro, H; Schmitz, T; Hippeläinen, E; Liu, Y-H; Serén, T; Kotiluoto, P; Auterinen, I; Savolainen, S

    2014-06-01

    The mixed neutron-photon beam of FiR 1 reactor is used for boron-neutron capture therapy (BNCT) in Finland. A beam model has been defined for patient treatment planning and dosimetric calculations. The neutron beam model has been validated with an activation foil measurements. The photon beam model has not been thoroughly validated against measurements, due to the fact that the beam photon dose rate is low, at most only 2% of the total weighted patient dose at FiR 1. However, improvement of the photon dose detection accuracy is worthwhile, since the beam photon dose is of concern in the beam dosimetry. In this study, we have performed ionization chamber measurements with multiple build-up caps of different thickness to adjust the calculated photon spectrum of a FiR 1 beam model.

  1. Establishment of a primary standard system for low energy X-rays using a free air ionization chamber; Estabelecimento de um sistema padrao primario para raios-X de energias baixas com uma camara de ionizacao de ar livre

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Natalia Fiorini da

    2016-08-01

    In this work a primary standard system was established for low energy X-rays (10 kV to 50 kV), using a free air ionization chamber with concentric cylinders, Victoreen (Model 481-5), at the Calibration Laboratory of Instruments (LCI) of the Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP). For this, a new ionization chamber alignment protocol was developed for the radiation system and a modification on the micrometer housing used for the movement of the internal cylinders was ma de. The results obtained for the stability and characterization tests showed to be within the limits established by the standards IEC 61674 and IEC 60731. The correction factors for photon attenuation in the air, transmission and scattering in the diaphragm, scattering and fluorescence and ion recombination were also determined. These values were compared with those obtained by the German primary standard laboratory, Physikalisch-Technische Bundesanstalt (PTB), showing good agreement. Finally, the absolute values of the quantity air kerma rate for the standard qualities direct beams MWV28 and WMV35 and the attenuated beams WMH28 and WMH35 were determined; the results are in agreement, with a maximum difference of 3,8% with the values obtained using the secondary standard system of LCI. (author)

  2. On the wall perturbation correction for a parallel-plate NACP-02 chamber in clinical electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Zink, K.; Wulff, J. [University Hospital Marburg, Philipps-University, D-35043 Marburg, Germany and Institut fuer Medizinische Physik und Strahlenschutz - IMPS, University of Applied Sciences Giessen-Friedberg, D-35390 Giessen (Germany); Institut fuer Medizinische Physik und Strahlenschutz - IMPS, University of Applied Sciences Giessen-Friedberg, D-35390 Giessen (Germany)

    2011-02-15

    Purpose: In recent years, several Monte Carlo studies have been published concerning the perturbation corrections of a parallel-plate chamber in clinical electron beams. In these studies, a strong depth dependence of the relevant correction factors (p{sub wall} and p{sub cav}) for depth beyond the reference depth is recognized and it has been shown that the variation with depth is sensitive to the choice of the chamber's effective point of measurement. Recommendations concerning the positioning of parallel-plate ionization chambers in clinical electron beams are not the same for all current dosimetry protocols. The IAEA TRS-398 as well as the IPEM protocol and the German protocol DIN 6800-2 interpret the depth of measurement within the phantom as the water equivalent depth, i.e., the nonwater equivalence of the entrance window has to be accounted for by shifting the chamber by an amount {Delta}z. This positioning should ensure that the primary electrons traveling from the surface of the water phantom through the entrance window to the chamber's reference point sustain the same energy loss as the primary electrons in the undisturbed phantom. The objective of the present study is the determination of the shift {Delta}z for a NACP-02 chamber and the calculation of the resulting wall perturbation correction as a function of depth. Moreover, the contributions of the different chamber walls to the wall perturbation correction are identified. Methods: The dose and fluence within the NACP-02 chamber and a wall-less air cavity is calculated using the Monte Carlo code EGSnrc in a water phantom at different depths for different clinical electron beams. In order to determine the necessary shift to account for the nonwater equivalence of the entrance window, the chamber is shifted in steps {Delta}z around the depth of measurement. The optimal shift {Delta}z is determined from a comparison of the spectral fluence within the chamber and the bare cavity. The wall

  3. Characterization of a homemade ionization chamber for radiotherapy beams

    Energy Technology Data Exchange (ETDEWEB)

    Neves, Lucio P., E-mail: lpneves@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000 Sao Paulo (Brazil); Perini, Ana P., E-mail: aperini@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000 Sao Paulo (Brazil); Santos, Gelson P. dos, E-mail: gpsantos@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000 Sao Paulo (Brazil); Xavier, Marcos, E-mail: mxavier@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000 Sao Paulo (Brazil); Khoury, Helen J., E-mail: khoury@ufpe.br [Universidade Federal de Pernambuco, Departamento de Energia Nuclear, Av. Prof. Luiz Freire 1000, 50740-540 Recife (Brazil); Caldas, Linda V.E., E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000 Sao Paulo (Brazil)

    2012-07-15

    A homemade cylindrical ionization chamber was studied for routine use in therapy beams of {sup 60}Co and X-rays. Several characterization tests were performed: leakage current, saturation, ion collection efficiency, polarity effect, stability, stabilization time, chamber orientation and energy dependence. All results obtained were within international recommendations. Therefore the homemade ionization chamber presents usefulness for routine dosimetric procedures in radiotherapy beams. - Highlights: Black-Right-Pointing-Pointer A homemade ionization chamber was studied for routine use in radiotherapy. Black-Right-Pointing-Pointer Several characterization tests were performed and the results were satisfactory. Black-Right-Pointing-Pointer This chamber was compared to commercial ones and the results were similar. Black-Right-Pointing-Pointer This chamber is suitable for calibration procedures in {sup 60}Co beams.

  4. Preliminary studies of a new monitor ionization chamber.

    Science.gov (United States)

    Yoshizumi, Maíra T; Vivolo, Vitor; Caldas, Linda V E

    2010-01-01

    A new monitor ionization chamber was developed at Instituto de Pesquisas Energéticas e Nucleares (IPEN) in order to monitor X-ray beams. The main difference of this monitor ionization chamber in relation to other monitor chambers is its geometry, which consists of a ring-shaped sensitive volume. Because of this geometry, the monitor chamber has a central hole through which the direct radiation beam passes. The operational characteristics of the monitor chamber were evaluated: saturation, ion collection efficiency and polarity effect. Besides these tests, the short- and medium-term stabilities of its response were also evaluated. During the tests the leakage current was always negligible. All results showed values within those recommended internationally (IEC, 1997. Medical electrical equipment-dosimeters with ionization chambers and/or semi-conductor detectors as used in X-ray diagnostic imaging. IEC 61674. International Electrotechnical Commission, Genève).

  5. Dosimetric evaluation of newly developed well-type ionization chamber for use in the calibration of brachytherapy sources

    Directory of Open Access Journals (Sweden)

    Sathiyan Saminathan

    2016-01-01

    Full Text Available The well-type ionization chamber has been designed for convenient use in brachytherapy source strength calibration. The chamber has a volume of 240 cm 3 , weight of 2.5 kg, and is open to atmospheric conditions. The well-type ionization chamber dosimetric characteristics such as leakage current, stability, scattering effect, ion collection efficiency, and nominal response with energy were studied. The evaluated dosimetric characteristics of well-type ionization chamber were compared with two other commercially available well-type ionization chambers. The study shows that the newly developed well-type ionization chamber is reliable for air-kerma strength calibration. The results obtained confirm that this chamber can be used for the calibrations of high-dose rate brachytherapy sources.

  6. Dosimetric evaluation of newly developed well-type ionization chamber for use in the calibration of brachytherapy sources.

    Science.gov (United States)

    Saminathan, Sathiyan; Godson, Henry Finlay; Ponmalar, Retna; Manickam, Ravikumar; Mazarello, James

    2016-01-01

    The well-type ionization chamber has been designed for convenient use in brachytherapy source strength calibration. The chamber has a volume of 240 cm(3), weight of 2.5 kg, and is open to atmospheric conditions. The well-type ionization chamber dosimetric characteristics such as leakage current, stability, scattering effect, ion collection efficiency, and nominal response with energy were studied. The evaluated dosimetric characteristics of well-type ionization chamber were compared with two other commercially available well-type ionization chambers. The study shows that the newly developed well-type ionization chamber is reliable for air-kerma strength calibration. The results obtained confirm that this chamber can be used for the calibrations of high-dose rate brachytherapy sources.

  7. Determination of the correction factor for attenuation, dispersion and production of electrons (K{sub wall}) in the wall of graphite of a ionization chamber Pattern National Type CC01 in fields of gamma radiation of {sup 60}Co; Determinacion del factor de correccion por atenuacion, dispersion y produccion de electrones (K{sub wall}) en la pared de grafito de una Camara de Ionizacion Patron Nacional Tipo CC01 en campos de radiacion gamma de {sup 60} Co

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez R, J.T.; Morales P, J.; Cruz E, P. [ININ, 52045 Ocoyoacac, Estado de Mexico (Mexico)

    2001-12-15

    It was determined the Kwall correction factor for the wall of graphite of the chamber of the pattern national type CC01 series 133 for a radiation field Gamma of {sup 60}Co. With this end to measured the currents of ionization l(x) as function of the thickness of the wall of the chamber: X=4,8,12,16 and 20 mm.The mensurations for each thickness consisting of three groups, of sizes n = 30 or 60 data for each group; obtaining 8 complete groups of mensurations independent in eight different dates.The determinate the factor carried out using three regression models: lineal, logarithmic and quadratic, models that were tried to validate with the tests of : i) Shapiro-Wilk and {chi}{sup 2} for the normality of the entrance data ii) Tests of Bartlett for variances homogeneity among groups for each thickness iii) The tests of Duncan for the stockings among groups of each thickness, and iv) The tests of adjustment lack (LOF) for the models used. Nevertheless, alone the models of the group of corresponding mensurations at 01-03-2000 17-08-2001 they can be validated by LOF, but not for tests of normality and homogeneity of variances. Among other assignable causes of variation we have: i) The values captured by the system of mensuration of the variables of it influences: pressure, temperature and relative humidity don{sup t} belong together with the existent ones to the moment to capture the l(x). ii) The mensuration room presents flows of air, for what was suited o diminish their volume and to eliminate the flows of air. iii) A protocol settled down of taking of measures that it consisted in: - Pre-irradiation 5 minutes the chamber after the change of polarity and hood change, with a period of stabilization of 5 minutes after the pre-irradiation. - Pre-irradiation for 5 minutes before the taking of the readings, with the object of eliminating variation sources assigned to currents of escapes or due variations to transitory. iv) To realize corrections for relative humidity of

  8. A comparative study of three ionizing chambers for measurements of personal dose equivalent, Hp(10)

    Science.gov (United States)

    Oliveira, C.; Cardoso, J.; Silva, H.

    2015-11-01

    A comparative study of three ionization chambers which directly measure the quantity personal dose equivalent Hp(10), was performed. Results show that the ratio between the response (air kerma) determined by Monte Carlo and the experimental response (collected charge) normalized by the monitor unit is the same whatever is the chamber and that this ratio is proportional to the conversion coefficients for air kerma from photon fluence.

  9. X-ray detector for automatic exposure control using ionization chamber filled with xenon gas

    CERN Document Server

    Nakagawa, A; Yoshida, T

    2003-01-01

    This report refers to our newly developed X-ray detector for reliable automatic X-ray exposure control, which is to be widely used for X-ray diagnoses in various clinical fields. This new detector utilizes an ionization chamber filled with xenon gas, in contrast to conventional X-ray detectors which use ionization chambers filled with air. Use of xenon gas ensures higher sensitivity and thinner design of the detector. The xenon gas is completely sealed in the chamber, so that the influence of the changes in ambient environments is minimized. (author)

  10. Development of standard ionization chamber counting system for activity measurements

    CERN Document Server

    Pyun, W B; Lee, H Y; Park, T S

    1998-01-01

    This study is to set up the activity measuring system using a 4 pi gamma ionization chamber as used mainly in national standards laboratories that are responsible for radionuclide metrology. The software for automatic control between the electrometer and personal computer is developed using Microsoft visual basic 4.0 and IEEE488 Interface. The reproducibility of this 4 pi gamma ionization chamber is about 0.02% and the background current is 0.054+-0.024 pA. this 4 pi gamma ionization chamber is calibrated by 6 standard gamma emitting radionuclides from KRISS. According to the result of this study, it is revealed that this 4 pi gamma ionization chamber counting system can be used as a secondary standard instrument for radioactivity measurement.

  11. A comparison of different experimental methods for general recombination correction for liquid ionization chambers

    DEFF Research Database (Denmark)

    Andersson, Jonas; Kaiser, Franz-Joachim; Gomez, Faustino

    2012-01-01

    Radiation dosimetry of highly modulated dose distributions requires a detector with a high spatial resolution. Liquid filled ionization chambers (LICs) have the potential to become a valuable tool for the characterization of such radiation fields. However, the effect of an increased recombination...... of the charge carriers, as compared to using air as the sensitive medium has to be corrected for. Due to the presence of initial recombination in LICs, the correction for general recombination losses is more complicated than for air-filled ionization chambers. In the present work, recently published...

  12. Development of Master Chamber Software for Data Acquisition of Ionization Chamber for Indus 2 RRCAT

    OpenAIRE

    Priyesh Soni; Mrs. B. Harita; Nawaz Ali Sayed

    2013-01-01

    The main goal of this paper was to Develop Master control software for DAQ of ionization chamber for INDUS-2 beam lines for detection of X-ray flux by an Ionization chamber that will remotely control and monitor the ultra low current signal detection analog module precisely. This application will be useful to measure the intensity of X-ray flux through ionization chamber in a beam line of synchrotron radiation source which is mounted in INDUS-2. It is one of new technique of detection. Beam l...

  13. Uncertainty evaluation of the kerma in the air, related to the active volume in the ionization chamber of concentric cylinders, by Monte Carlo simulation; Avaliacao de incerteza no kerma no ar, em relacao ao volume ativo da camara de ionizacao de cilindros concentricos, por simulacao de Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Lo Bianco, A.S.; Oliveira, H.P.S.; Peixoto, J.G.P., E-mail: abianco@ird.gov.b [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil). Lab. Nacional de Metrologia das Radiacoes Ionizantes (LNMRI)

    2009-07-01

    To implant the primary standard of the magnitude kerma in the air for X-ray between 10 - 50 keV, the National Metrology Laboratory of Ionizing Radiations (LNMRI) must evaluate all the uncertainties of measurement related with Victtoren chamber. So, it was evaluated the uncertainty of the kerma in the air consequent of the inaccuracy in the active volume of the chamber using the calculation of Monte Carlo as a tool through the Penelope software

  14. Absolute dosimetry on a dynamically scanned sample for synchrotron radiotherapy using graphite calorimetry and ionization chambers

    Science.gov (United States)

    Lye, J. E.; Harty, P. D.; Butler, D. J.; Crosbie, J. C.; Livingstone, J.; Poole, C. M.; Ramanathan, G.; Wright, T.; Stevenson, A. W.

    2016-06-01

    The absolute dose delivered to a dynamically scanned sample in the Imaging and Medical Beamline (IMBL) on the Australian Synchrotron was measured with a graphite calorimeter anticipated to be established as a primary standard for synchrotron dosimetry. The calorimetry was compared to measurements using a free-air chamber (FAC), a PTW 31 014 Pinpoint ionization chamber, and a PTW 34 001 Roos ionization chamber. The IMBL beam height is limited to approximately 2 mm. To produce clinically useful beams of a few centimetres the beam must be scanned in the vertical direction. In practice it is the patient/detector that is scanned and the scanning velocity defines the dose that is delivered. The calorimeter, FAC, and Roos chamber measure the dose area product which is then converted to central axis dose with the scanned beam area derived from Monte Carlo (MC) simulations and film measurements. The Pinpoint chamber measures the central axis dose directly and does not require beam area measurements. The calorimeter and FAC measure dose from first principles. The calorimetry requires conversion of the measured absorbed dose to graphite to absorbed dose to water using MC calculations with the EGSnrc code. Air kerma measurements from the free air chamber were converted to absorbed dose to water using the AAPM TG-61 protocol. The two ionization chambers are secondary standards requiring calibration with kilovoltage x-ray tubes. The Roos and Pinpoint chambers were calibrated against the Australian primary standard for air kerma at the Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Agreement of order 2% or better was obtained between the calorimetry and ionization chambers. The FAC measured a dose 3-5% higher than the calorimetry, within the stated uncertainties.

  15. Response and Monte Carlo evaluation of a reference ionization chamber for radioprotection level at calibration laboratories

    Science.gov (United States)

    Neves, Lucio P.; Vivolo, Vitor; Perini, Ana P.; Caldas, Linda V. E.

    2015-07-01

    A special parallel plate ionization chamber, inserted in a slab phantom for the personal dose equivalent Hp(10) determination, was developed and characterized in this work. This ionization chamber has collecting electrodes and window made of graphite, and the walls and phantom made of PMMA. The tests comprise experimental evaluation following international standards and Monte Carlo simulations, employing the PENELOPE code to evaluate the design of this new dosimeter. The experimental tests were conducted employing the radioprotection level quality N-60 established at the IPEN, and all results were within the recommended standards.

  16. Electrostatic fields in an ionization chamber electret

    Science.gov (United States)

    Fallone, B. G.; Podgorsak, E. B.

    1983-09-01

    The theory of linear systems is used to derive the potential and electric field in distance space in a cylindrical polarization/depolarization electret chamber. General solutions for the near, intermediate, and far regions are given and their domains of convergence discussed. On the axis of the chamber the solutions for the electret surface are equal to those obtained from Gauss's and Kirchoff's laws, and at large distances from the surface to those obtained from the introduction of a dipole layer model.

  17. Design of ionization chambers for use in teaching x-ray dosimetry

    Science.gov (United States)

    Ross, Joseph

    Ionization chambers are one of the most commonly used radiation detectors in radiation dosimetry. In this project, nine ionization chambers were constructed for use in teaching radiation dosimetry to students of health physics, medical physics, nuclear engineering, and related disciplines. The components of these detectors such as detector wall composition, type of electrode, type of leakage current guard ring, fill gas pressure, and interior conducting material differ in a systematic way to show that various parameters of ionization chamber design can affect the response of the detectors. Each of these variables was investigated using an 80 keV x-ray machine to determine detector response in terms of absorbed dose, HVL, polarity, and operating voltage. Of the components studied, wall thickness and composition was found to be the most sensitive variable. The pressure inside the chamber did have a significant effect on the amount of charge collected and the absorbed dose. The leakage current guard ring was not a critical component for this ionization chamber design.

  18. Performance of vintage direct reading pocket ionization chambers.

    Science.gov (United States)

    Bergen, Robert J; Harvey, John A; Kearfott, Kimberlee J

    2010-05-01

    The linearity, accuracy, and precision of each of two groups of vintage 51.6 microC-kg-1 maximum scale passive direct reading pocket ionization chambers, each from a different manufacturer and all aged at least 50 years since manufacture, were tested. The pocket ionization chambers were suspended on a phantom and exposed using a 137Cs source. Variations from trial to trial were smaller than variations from chamber to chamber. The average percent standard deviations ranged from 5.7% to 14% across all exposures. The accuracy of the dosimeter readings increased as the exposure level increased. Percent error from known exposure values decreased as exposure increased. An independent samples t test indicated there was a statistically significant difference between the two groups only at a delivered exposure of 6.45 microC-kg-1. Testing was performed in a 222Rn drum to determine the effect of Rn on the pocket ionization chambers. Exposure of five chambers to an average Rn level of 4.70 kBq m-3 and thirty chambers to 3.86 kBq m-3 over a 7-d period produced abnormally high readings at least three times background in eight of the 35 chambers tested.

  19. Characterization of a CT ionization chamber for radiation field mapping

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana P., E-mail: aperini@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo, SP (Brazil); Neves, Lucio P., E-mail: lpneves@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo, SP (Brazil); Vivolo, Vitor, E-mail: vivolo@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo, SP (Brazil); Xavier, Marcos, E-mail: mxavier@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo, SP (Brazil); Khoury, Helen J., E-mail: hjkhoury@gmail.com [Universidade Federal de Pernambuco, Departamento de Energia Nuclear, Av. Prof. Luiz Freire 1000, 50740-540, Recife, PE (Brazil); Caldas, Linda V.E., E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000, Sao Paulo, SP (Brazil)

    2012-07-15

    A pencil-type ionization chamber, developed at Instituto de Pesquisas Energeticas e Nucleares (IPEN), was characterized with the objective to verify the possibility of its application in radiation field mapping procedures. The characterization tests were evaluated, and the results were satisfactory. The results obtained for the X radiation field mapping with the homemade chamber were compared with those of a PTW Farmer-type chamber (TN 30011-1). The maximum difference observed in this comparison was only 1.25%, showing good agreement. - Highlights: Black-Right-Pointing-Pointer A new ionization chamber was made and tested for radiation field mapping. Black-Right-Pointing-Pointer This ionization chamber was made using only accessible low cost materials. Black-Right-Pointing-Pointer The operational tests were made and the results were within the recommended limits. Black-Right-Pointing-Pointer The field map was compared with a commercial chamber presenting a 1.25% difference. Black-Right-Pointing-Pointer Our chamber presents potential for assurance reliability in calibration procedures.

  20. Positioning of a plane-parallel ionization chamber in clinical electron beams and the impact on perturbation factors.

    Science.gov (United States)

    Zink, K; Wulff, J

    2009-04-21

    Current dosimetry protocols recommend the use of plane-parallel ionization chambers for the dosimetry of clinical electron beams. The necessary perturbation corrections p(wall) and p(cav) are assumed to be unity, independent of the depth of measurement and the energy of the primary electrons. To verify these assumptions detailed Monte Carlo studies of a Roos chamber in clinical electron beams with energies in the range of 6-21 MeV are performed at different depths in water and analyzed in terms of Spencer-Attix cavity theory. Separate simulations for the perturbation corrections p(wall) and p(cav) indicate quite different properties of both correction factors with depth. Dose as well as fluence calculations show a nearly depth-independent wall correction factor for a shift of the Roos chamber Deltaz = -0.017 cm toward the focus. This value is in good agreement with the positioning recommendation given in all dosimetry protocols. Regarding the fluence perturbation p(cav) the simulation of the electron fluence inside the air cavity in comparison to water unambiguously reveals an in-scattering of low energy electrons, despite the fact, that the cavity is 'well guarded'. For depths beyond the reference depth z(ref) this effect is superimposed by an increased loss of primary electrons from the beam resulting in p(cav) > 1. This effect is largest for low electron energies but present for all electron energies involved in this study. Based on the different depth dependences of p(wall) and p(cav) it is possible to choose a chamber shift Deltaz in a way to minimize the depth dependence of the overall perturbation factor p. For the Roos chamber this shift is Deltaz = -0.04 cm independent of electron energy.

  1. Positioning of a plane-parallel ionization chamber in clinical electron beams and the impact on perturbation factors

    Energy Technology Data Exchange (ETDEWEB)

    Zink, K; Wulff, J [Institut fuer Medizinische Physik und Strahlenschutz-IMPS, University of Applied Sciences Giessen-Friedberg, Wiesenstr. 14, D-35390 Giessen (Germany)], E-mail: klemens.zink@tg.fh-giessen.de

    2009-04-21

    Current dosimetry protocols recommend the use of plane-parallel ionization chambers for the dosimetry of clinical electron beams. The necessary perturbation corrections p{sub wall} and p{sub cav} are assumed to be unity, independent of the depth of measurement and the energy of the primary electrons. To verify these assumptions detailed Monte Carlo studies of a Roos chamber in clinical electron beams with energies in the range of 6-21 MeV are performed at different depths in water and analyzed in terms of Spencer-Attix cavity theory. Separate simulations for the perturbation corrections p{sub wall} and p{sub cav} indicate quite different properties of both correction factors with depth. Dose as well as fluence calculations show a nearly depth-independent wall correction factor for a shift of the Roos chamber {delta}z = -0.017 cm toward the focus. This value is in good agreement with the positioning recommendation given in all dosimetry protocols. Regarding the fluence perturbation p{sub cav} the simulation of the electron fluence inside the air cavity in comparison to water unambiguously reveals an in-scattering of low energy electrons, despite the fact, that the cavity is 'well guarded'. For depths beyond the reference depth z{sub ref} this effect is superimposed by an increased loss of primary electrons from the beam resulting in p{sub cav} > 1. This effect is largest for low electron energies but present for all electron energies involved in this study. Based on the different depth dependences of p{sub wall} and p{sub cav} it is possible to choose a chamber shift {delta}z in a way to minimize the depth dependence of the overall perturbation factor p. For the Roos chamber this shift is {delta}z = -0.04 cm independent of electron energy.

  2. LET measurements with a Liquid Ionization Chamber

    OpenAIRE

    Tegami, S.

    2013-01-01

    Deep-seated tumors can be efficiently treated with heavy charged particles. The characteristic depth dose profile inside the tissue (Bragg peak) allows to deliver a high dose inside the tumor, while sparing the neighboring healthy tissue. As compared to protons, heavy ions like carbon or oxygen produce a higher amount of ionization events along their track (and in particular at the end of the ion beam path), resulting in an irreparable damage to the DNA of the tumor cells. T...

  3. Construction and commissioning of a position-sensitive ionization chamber

    Science.gov (United States)

    Kwag, M. S.; Chae, K. Y.; Cha, S. M.; Kim, A.; Kim, M. J.; Lee, E. J.; Lee, J. H.

    2016-05-01

    A position-sensitive ionization chamber has been constructed and commissioned at the Physics Department of Sungkyunkwan University to extract position information on incident charged particles for future nuclear reaction measurements. By utilizing the newly-designed position-sensitive anodes and the previously-commissioned portable gas-filled ionization chamber by Chae et al., position information on incident particles could be obtained. The device was tested with an 241Am α-emitting source, and the standard deviation of the fitted Gaussian distribution was measured to be 1.76 mm when a collimator with a 2 mm hole was used.

  4. The response of ionization chambers to relativistic heavy nuclei

    Science.gov (United States)

    Newport, B. J.; Stone, E. C.; Waddington, C. J.; Binns, W. R.; Fixsen, D. J.; Garrard, T. L.; Grimm, G.; Israel, M. H.; Klarmann, J.

    1985-01-01

    The LBL Bevalac for the Heavy Nuclei Experiment on HEAO-3, compared the response of a set of laboratory ionization chambers to beams of 26Fe, 36Kr, 54Xe, 67 Ho, and 79Au nuclei at maximum energies ranging from 1666 MeV/amu for Fe to 1049 MeV/amu for Au. The response of these chambers shows a significant deviation from the expected energy dependence, but only a slight deviation from Z sq scaling.

  5. Gridded Ionization Chamber; Camara de ionizacion con reja

    Energy Technology Data Exchange (ETDEWEB)

    Manero Amoros, F.

    1962-07-01

    In the present paper the working principles of a gridded ionization chamber are given, and all the different factors that determine its resolution power are analyzed in detail. One of these devices, built in the Physics Division of the JEN and designed specially for use in measurements of alpha spectroscopy, is described. finally the main applications, in which the chamber can be used, are shown. (Author) 17 refs.

  6. Ionization Chambers for Monitoring in High-Intensity Neutrino Beams

    CERN Document Server

    McDonald, J; Velissaris, C; Erwin, A R; Ping, H; Viren, B M; Diwan, M V

    2002-01-01

    Radiation-hard ionization chambers were tested using an intense electron beam from the accelerator test facility (ATF) at the Brookhaven National Laboratory (BNL). The detectors were designed to be used as the basic element for monitoring muons in the Main Injector Neutrino beamline (NuMI) at the Fermi National Accelerator Laboratory (FNAL). Measurements of linearity of response, voltage dependence, and the onset of ionization saturation as a function of gap voltage were performed.

  7. LET measurements with a Liquid Ionization Chamber

    OpenAIRE

    Tegami, S.

    2013-01-01

    Deep-seated tumors can be efficiently treated with heavy charged particles. The characteristic depth dose profile inside the tissue (Bragg peak) allows to deliver a high dose inside the tumor, while sparing the neighboring healthy tissue. As compared to protons, heavy ions like carbon or oxygen produce a higher amount of ionization events along their track (and in particular at the end of the ion beam path), resulting in an irreparable damage to the DNA of the tumor cells. The density of such...

  8. Characterization of a CT ionization chamber for radiation field mapping.

    Science.gov (United States)

    Perini, Ana P; Neves, Lucio P; Vivolo, Vitor; Xavier, Marcos; Khoury, Helen J; Caldas, Linda V E

    2012-07-01

    A pencil-type ionization chamber, developed at Instituto de Pesquisas Energéticas e Nucleares (IPEN), was characterized with the objective to verify the possibility of its application in radiation field mapping procedures. The characterization tests were evaluated, and the results were satisfactory. The results obtained for the X radiation field mapping with the homemade chamber were compared with those of a PTW Farmer-type chamber (TN 30011-1). The maximum difference observed in this comparison was only 1.25%, showing good agreement.

  9. Segmented ionization chambers for beam monitoring in hadrontherapy

    Science.gov (United States)

    Braccini, Saverio; Cirio, Roberto; Donetti, Marco; Marchetto, Flavio; Pittà, Giuseppe; Lavagno, Marco; La Rosa, Vanessa

    2015-06-01

    Segmented ionization chambers represent a good solution to monitor the position, the intensity and the shape of ion beams in hadrontherapy. Pixel and strip chambers have been developed for both passive scattering and active scanning dose delivery systems. In particular, strip chambers are optimal for pencil beam scanning, allowing for spatial and time resolutions below 0.1 mm and 1 ms, respectively. The MATRIX pixel and the Strip Accurate Monitor for Beam Applications (SAMBA) detectors are described in this paper together with the results of several beam tests and industrial developments based on these prototypes.

  10. Evaluation of a plane-parallel ionization chamber for low-energy radiotherapy beams

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana Paula; Neves, Lucio Pereira; Santos, William de Souza; Caldas, Linda V.E., E-mail: aperini@ipen.br, E-mail: lpneves@ipen.br, E-mail: wssantos@ipen.br, E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2014-07-01

    A plane-parallel ionization chamber, with a sensitive volume of 6.3 cm{sup 3}, developed at the Calibration Laboratory of IPEN (LCI), was utilized to verify the possibility of its application in low-energy X-ray beam qualities for radiotherapy (T-qualities). This homemade ion chamber was manufactured using polymethyl methacrylate (PMMA) coated with graphite, and co-axial cables. In order to evaluate the performance of this ionization chamber, some characterization tests were performed: short- and medium-term stability, leakage current, saturation, ion collection efficiency, polarity effect and linearity of response. The maximum value obtained in the short-term stability test was 0.2%, in accordance with the limit value of 0.3% provided by the IEC 60731 standard. The saturation curve was obtained varying the applied voltage from -400 V to +400 V, in steps of 50 V, using the charge collecting time of 20 s. From the saturation curve two other characteristics were analyzed: the polarity effect and the ion collection efficiency, with results within the international recommendations. The leakage current of the ionization chamber was measured in time intervals of 20 minutes, before and after its irradiations, and all the results obtained were in agreement with the IEC 60731 standard. The linearity of response was verified utilizing the T-50(b) radiation quality, and the ionization chamber was exposed to different air kerma rates. The response of the ionization chamber presented a linear behavior. Therefore, all results were considered satisfactory, within international recommendations, indicating that this homemade ionization chamber presents potential routine use in dosimetry of low-energy radiotherapy beams. (author)

  11. Pencil beam proton radiography using a multilayer ionization chamber

    NARCIS (Netherlands)

    Farace, Paolo; Righetto, Roberto; Meijers, Arturs

    2016-01-01

    A pencil beam proton radiography (PR) method, using a commercial multilayer ionization chamber (MLIC) integrated with a treatment planning system (TPS) was developed. A Giraffe (IBA Dosimetry) MLIC (+/- 0.5 mm accuracy) was used to obtain pencil beam PR by delivering spots uniformly positioned at a

  12. A multiple sampling ionization chamber for the External Target Facility

    Science.gov (United States)

    Zhang, X. H.; Tang, S. W.; Ma, P.; Lu, C. G.; Yang, H. R.; Wang, S. T.; Yu, Y. H.; Yue, K.; Fang, F.; Yan, D.; Zhou, Y.; Wang, Z. M.; Sun, Y.; Sun, Z. Y.; Duan, L. M.; Sun, B. H.

    2015-09-01

    A multiple sampling ionization chamber used as a particle identification device for high energy heavy ions has been developed for the External Target Facility. The performance of this detector was tested with a 239Pu α source and RI beams. A Z resolution (FWHM) of 0.4-0.6 was achieved for nuclear fragments of 18O at 400 AMeV.

  13. Space-charge effects in liquid argon ionization chambers

    Science.gov (United States)

    Rutherfoord, J. P.; Walker, R. B.

    2015-03-01

    We have uniformly irradiated liquid argon ionization chambers with betas from high-activity 90Sr sources. The radiation environment is similar to that in the liquid argon calorimeters which are part of the ATLAS detector installed at CERN's Large Hadron Collider (LHC). We measured the resulting ionization current over a wide range of applied potential for two different source activities and for three different chamber gaps. These studies provide operating experience at exceptionally high ionization rates. In particular they indicate a stability at the 0.1% level for these calorimeters over years of operation at the full LHC luminosity when operated in the normal mode at an electric field E = 1.0 kV / mm. We can operate these chambers in the normal mode or in the space-charge limited regime and thereby determine the transition point between the two. This transition point is parameterized by a positive argon ion mobility of μ+ = 0.08 ± 0.02mm2 / V s at a temperature of 88.0±0.5 K and at a pressure of 1.02±0.02 bar. In the space-charge limited regime the ionization currents are degraded and show signs of instability. At the highest electric fields in our study (6.7 kV/mm) the ionization current is still slowly rising with increasing electric field.

  14. Source geometry factors for HDR 192Ir brachytherapy secondary standard well-type ionization chamber calibrations

    Science.gov (United States)

    Shipley, D. R.; Sander, T.; Nutbrown, R. F.

    2015-03-01

    Well-type ionization chambers are used for measuring the source strength of radioactive brachytherapy sources before clinical use. Initially, the well chambers are calibrated against a suitable national standard. For high dose rate (HDR) 192Ir, this calibration is usually a two-step process. Firstly, the calibration source is traceably calibrated against an air kerma primary standard in terms of either reference air kerma rate or air kerma strength. The calibrated 192Ir source is then used to calibrate the secondary standard well-type ionization chamber. Calibration laboratories are usually only equipped with one type of HDR 192Ir source. If the clinical source type is different from that used for the calibration of the well chamber at the standards laboratory, a source geometry factor, ksg, is required to correct the calibration coefficient for any change of the well chamber response due to geometric differences between the sources. In this work we present source geometry factors for six different HDR 192Ir brachytherapy sources which have been determined using Monte Carlo techniques for a specific ionization chamber, the Standard Imaging HDR 1000 Plus well chamber with a type 70010 HDR iridium source holder. The calculated correction factors were normalized to the old and new type of calibration source used at the National Physical Laboratory. With the old Nucletron microSelectron-v1 (classic) HDR 192Ir calibration source, ksg was found to be in the range 0.983 to 0.999 and with the new Isodose Control HDR 192Ir Flexisource ksg was found to be in the range 0.987 to 1.004 with a relative uncertainty of 0.4% (k = 2). Source geometry factors for different combinations of calibration sources, clinical sources, well chambers and associated source holders, can be calculated with the formalism discussed in this paper.

  15. Production of foil electrets by ionizing radiation in air

    Science.gov (United States)

    Fallone, B. G.; Podgorsak, E. B.

    1983-02-01

    Isothermal charge deposition on polymers to form stable foil electrets by using apparatuses resembling parallel-plate ionization chambers is reported. Charge carriers produced by irradiation of the sensitive chamber air volume drift in an externally applied electric field and get trapped on the polymer surface to form electrets with maximum charge densities close to 10-6 C/cm2. Charge density as a function of applied voltage follows the form typical of a Schottky or Poole-Frenkel process.

  16. Calibration coefficient of reference brachytherapy ionization chamber using analytical and Monte Carlo methods.

    Science.gov (United States)

    Kumar, Sudhir; Srinivasan, P; Sharma, S D

    2010-06-01

    A cylindrical graphite ionization chamber of sensitive volume 1002.4 cm(3) was designed and fabricated at Bhabha Atomic Research Centre (BARC) for use as a reference dosimeter to measure the strength of high dose rate (HDR) (192)Ir brachytherapy sources. The air kerma calibration coefficient (N(K)) of this ionization chamber was estimated analytically using Burlin general cavity theory and by the Monte Carlo method. In the analytical method, calibration coefficients were calculated for each spectral line of an HDR (192)Ir source and the weighted mean was taken as N(K). In the Monte Carlo method, the geometry of the measurement setup and physics related input data of the HDR (192)Ir source and the surrounding material were simulated using the Monte Carlo N-particle code. The total photon energy fluence was used to arrive at the reference air kerma rate (RAKR) using mass energy absorption coefficients. The energy deposition rates were used to simulate the value of charge rate in the ionization chamber and N(K) was determined. The Monte Carlo calculated N(K) agreed within 1.77 % of that obtained using the analytical method. The experimentally determined RAKR of HDR (192)Ir sources, using this reference ionization chamber by applying the analytically estimated N(K), was found to be in agreement with the vendor quoted RAKR within 1.43%.

  17. A magnetically levitated electrode ionization chamber of the noncontact measurement type

    CERN Document Server

    Kawaguchi, T

    2002-01-01

    A new type of ionization chamber with levitated electrode has been developed. In this ionization chamber, an ion-collection electrode levitates in the air without getting any physical support from the insulator. The electrode is charged by an electrostatic charger without physical contact. The charge of the electrode is read out at a Faraday cage periodically at a given time interval without physical contact. Because its electrode levitates, the ionization chamber produces no background current caused by leaks or piezo current. In addition, as the charging of its electrode and the read-out of its charge are carried out without physical contact, no irregular charge or contact potential difference due to the chattering between electrode and contact point occurs. Through experiments, it was found that this ionization chamber was able to measure the gamma-ray dose such as the environmental radiation with a high degree of sensitivity. The minimum detectable value of ionization current when accumulated for 1 h is a...

  18. Application of the two-dose-rate method for general recombination correction for liquid ionization chambers in continuous beams

    Science.gov (United States)

    Andersson, Jonas; Tölli, Heikki

    2011-01-01

    A method to correct for the general recombination losses for liquid ionization chambers in continuous beams has been developed. The proposed method has been derived from Greening's theory for continuous beams and is based on measuring the signal from a liquid ionization chamber and an air filled monitor ionization chamber at two different dose rates. The method has been tested with two plane parallel liquid ionization chambers in a continuous radiation x-ray beam with a tube voltage of 120 kV and with dose rates between 2 and 13 Gy min-1. The liquids used as sensitive media in the chambers were isooctane (C8H18) and tetramethylsilane (Si(CH3)4). The general recombination effect was studied using chamber polarizing voltages of 100, 300, 500, 700 and 900 V for both liquids. The relative standard deviation of the results for the collection efficiency with respect to general recombination was found to be a maximum of 0.7% for isooctane and 2.4% for tetramethylsilane. The results are in excellent agreement with Greening's theory for collection efficiencies over 90%. The measured and corrected signals from the liquid ionization chambers used in this work are in very good agreement with the air filled monitor chamber with respect to signal to dose linearity.

  19. Application of the two-dose-rate method for general recombination correction for liquid ionization chambers in continuous beams

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Jonas; Toelli, Heikki, E-mail: jonas.andersson@radfys.umu.se [Department of Radiation Sciences, Radiation Physics, Umeaa University, SE-901 85 Umeaa (Sweden)

    2011-01-21

    A method to correct for the general recombination losses for liquid ionization chambers in continuous beams has been developed. The proposed method has been derived from Greening's theory for continuous beams and is based on measuring the signal from a liquid ionization chamber and an air filled monitor ionization chamber at two different dose rates. The method has been tested with two plane parallel liquid ionization chambers in a continuous radiation x-ray beam with a tube voltage of 120 kV and with dose rates between 2 and 13 Gy min{sup -1}. The liquids used as sensitive media in the chambers were isooctane (C{sub 8}H{sub 18}) and tetramethylsilane (Si(CH{sub 3}){sub 4}). The general recombination effect was studied using chamber polarizing voltages of 100, 300, 500, 700 and 900 V for both liquids. The relative standard deviation of the results for the collection efficiency with respect to general recombination was found to be a maximum of 0.7% for isooctane and 2.4% for tetramethylsilane. The results are in excellent agreement with Greening's theory for collection efficiencies over 90%. The measured and corrected signals from the liquid ionization chambers used in this work are in very good agreement with the air filled monitor chamber with respect to signal to dose linearity.

  20. Development of special ionization chambers for a quality control program in mammography; Desenvolvimento de camaras de ionizacao especiais para controle de qualidade em mamografia

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Jonas Oliveira da

    2013-07-01

    Mammography is an imaging method that uses X-rays. The use of ionization chambers in mammography quality control programs presents an essential role which is to verify whether the parameters of the patient exposure are correct. However, the commercial ionization chambers for dosimetry in mammography represent a high cost for small and medium size clinics that wish to have this equipment or for professionals that work with quality control programs. The innovative feature of this work was to develop ionization chambers for this purpose. In this work ionization chambers for X radiation beams in the mammography energy range were designed, constructed and characterized. The ionization chambers were tested in standard X radiation beams at the LCI/IPEN. The main characterization tests performed with the ionization chambers were: saturation curve, linearity of response, angular and energy dependence. The response stability tests of the ionization chambers were also conducted at the LCI, presenting results within 2.0 % for long-term stability. The results of the remaining tests are in accordance with international standards. These ionization chambers were also submitted to quality control tests of mammography equipment: linearity of the air kerma rates, determination of half-value layers and mean glandular doses. The results for air kerma rate linearity were less than 10 %, as recommended in international standards. The mean glandular dose obtained with the developed chambers presented values comparable to those of commercial ionization chambers tested, with an estimated variation within international standards. (author)

  1. NIST Ionization Chamber “A” Sample-Height Corrections

    OpenAIRE

    Fitzgerald, Ryan

    2012-01-01

    For over 30 years scientists in the NIST radioactivity group have been using their pressurized ionization chamber “A” (PIC “A”) to make measurements of radioactivity and radioactive half-lives. We now have evidence that some of those reported measurements were incorrect due to slippage of the source positioning ring over time. The temporal change in the holder caused an error in the source-height within the chamber, which was thought to be invariant. This unaccounted-for height change caused ...

  2. Neutron Dosimetry Using a Tissue-Equivalent Ionization Chamber.

    Science.gov (United States)

    1980-05-01

    procedures are described, and correction factors discussed. /’ On a montg et v~rifiA un systtme de niesure d’oZz la dose ou le kerma tissulaire neutronique ...tube 3.8 cm in diameter. At the same time, it is advantageous to keep the active volume as large as possible in order to maximize sensitivity. The...CHAMBER The construction of the FWT TE Ionization chamber is Illustrated in figure 1. The active volume lies between the central electrode and the

  3. Study of the response of low pressure ionization chambers

    CERN Document Server

    Nebot Del Busto, E; Effinger, E; Grishin, V; Herranz Alvarez, J

    2012-01-01

    The Beam Loss Monitoring System (BLM) of the Large Hadron Collider (LHC) is based on parallel plate Ionization Chambers (IC) with active volume 1.5l and a nitrogen filling gas at 0.1 bar overpressure. At the largest loss locations, the ICs generate signals large enough to saturate the read-out electronics. A reduction of the active volume and filling pressure in the ICs would decrease the amount of charge collected in the electrodes, and so provide a higher saturation limit using the same electronics. This makes Little Ionization Chambers (LIC) with both reduced pressure and small active volume a good candidate for these high radiation areas. In this contribution we present measurements performed with several LIC monitors with reduced active volume and various filling pressures. These detectors were tested under various conditions with different beam setups, with standard LHC ICs used for calibration purposes

  4. Imaging with high Dynamic using an Ionization Chamber

    OpenAIRE

    Menk, Ralf-Hendrik; Amenitsch, Heinz; Arfelli, Fulvia; Bernstorff, Sigrid; Besch, Hans Juergen; Voltolina, Francesco

    2010-01-01

    In this work a combination of an ionization chamber with one-dimensional spatial resolution and a MicroCAT structure will be presented. The combination between gas gain operations and integrating front-end electronics yields a dynamic range as high as eight to nine orders of magnitude. Therefore this device is well suitable for medical imaging or applications such as small angle x-ray scattering, where the requirements on the dynamic of the detector are exceptional high. Basically the describ...

  5. A multiple sampling ionization chamber for the External Target Facility

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, X.H., E-mail: zhxh@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Tang, S.W.; Ma, P.; Lu, C.G.; Yang, H.R.; Wang, S.T.; Yu, Y.H.; Yue, K.; Fang, F. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Yan, D.; Zhou, Y.; Wang, Z.M.; Sun, Y. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Sun, Z.Y.; Duan, L.M. [Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Sun, B.H. [School of Physics and Nuclear Energy Engineering, Beihang University, Beijing 100191 (China)

    2015-09-21

    A multiple sampling ionization chamber used as a particle identification device for high energy heavy ions has been developed for the External Target Facility. The performance of this detector was tested with a {sup 239}Pu α source and RI beams. A Z resolution (FWHM) of 0.4–0.6 was achieved for nuclear fragments of {sup 18}O at 400 AMeV.

  6. Project, construction and characterization of ionization chambers for use as standard systems in X and gamma radiation beams; Projeto, construcao e caracterizacao de camaras de ionizacao para utilizacao como sistemas padroes em feixes de radiacao X e gama

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana Paula

    2013-07-01

    Ionization chambers present some advantages in relation to other dosimeters: easiness of handling, low energy dependence and high precision. The advantages associated to ionization chambers and the large number of diagnostic radiology exams and therapeutic treatments motivated the development of this PhD program. In this project ionization chambers were developed and characterized to be applied in diagnostic radiology and therapy beam dosimetry, with high precision and performance, in compliance with international recommendations. They were assembled in a simple way, utilizing low-cost national materials, so they can be reproduced and applied at calibration laboratories. The project of these ionization chambers presents some differences in relation to commercial ionization chambers, as the materials utilized and geometrical arrangements. Besides the development of the ionization chambers to be utilized in standard X-ray beam dosimetry as work standard systems, two graphite parallel-plate ionization chambers were developed and characterized to be applied as reference standard systems for determining the air kerma rates of gamma radiation sources. Comparing the air kerma rates determined with the reference standard of the Calibration Laboratory of IPEN, a Farmer ionization chamber, with the values of the air kerma rates obtained with the graphite ionization chambers, the maximum differences obtained were only 1.7% and 1.2% for the G1 and G2 graphite ionization chambers, respectively. Moreover, these ionization chambers presented correction factors close to 1.000, which is ideal for an ionization chamber be characterized as a reference standard system. (author)

  7. Two-dimensional position sensitive ionization chamber with GEM

    Science.gov (United States)

    Kitamura, Noritaka; Noro, Tetsuo; Sakaguchi, Satoshi; Takao, Hideaki; Nishio, Yasutaka

    2014-09-01

    We have been developing a multi-anode ionization chamber for Accelerator Mass Spectrometry (AMS) at Kyushu University. Furthermore, we are planning to construct a neutron detector with high position resolution by combining the chamber with Gas Electron Multiplier (GEM) and a neutron converter. One of purposes is the measurement of p-> , pn knockout reaction from unstable nuclei. The multi-anode ionization chamber is composed of subdivided multiple anodes, a cathode to produce an uniform electric field, and a Frisch grid. The chamber must have position sensitivity because obtaining a beam profile is required for AMS measurements, where counting loss should be avoided. Also in the case of the neutron detector, it is necessary to measure the position to deduce the scattering angles. We have recently established a two-dimensional position readout system by the following methods: the measurement of horizontal position is enabled by trimming some anodes into wedge-like shape, and vertical position can be determined by the ratio of induced charge on the grid to the total charge on anodes. In addition, improvement of S/N ratio is important for isotope separation and position resolution. We installed a rectangular-shaped GEM and tried improving S/N ratio by electron amplification.

  8. Poster — Thur Eve — 24: Commissioning and preliminary measurements using an Attix-style free air ionization chamber for air kerma measurements on the BioMedical Imaging and Therapy beamlines at the Canadian Light Source

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, D [Department of Oncology, University of Alberta, Edmonton, AB (Canada); McEwen, M; Shen, H [Ionizing Radiation Standards, National Research Council of Canada, Ottawa, ON (Canada); Siegbahn, EA [Department of Medical Physics, Stockholm University, Stockholm (Sweden); Fallone, BG; Warkentin, B [Department of Oncology, University of Alberta, Edmonton, AB (Canada); Department of Medical Physics, Cross Cancer Institute, Edmonton, AB (Canada)

    2014-08-15

    Synchrotron facilities, including the Canadian Light Source (CLS), provide opportunities for the development of novel imaging and therapy applications. A vital step progressing these applications toward clinical trials is the availability of accurate dosimetry. In this study, a refurbished Attix-style (cylindrical) free air chamber (FAC) is tested and used for preliminary air kerma measurements on the two BioMedical Imaging and Therapy (BMIT) beamlines at the CLS. The FAC consists of a telescoping chamber that relies on a difference measurement of collected charge in expanded and collapsed configurations. At the National Research Council's X-ray facility, a Victoreen Model 480 FAC was benchmarked against two primary standard FACs. The results indicated an absolute accuracy at the 0.5% level for energies between 60 and 150 kVp. A series of measurements were conducted on the small, non-uniform X-ray beams of the 05B1-1 (∼8 – 100 keV) and 05ID-2 (∼20 – 200 keV) beamlines for a variety of energies, filtrations and beam sizes. For the 05B1-1 beam with 1.1 mm of Cu filtration, recombination corrections of less than 5 % could only be achieved for field sizes no greater than 0.5 mm × 0.6 mm (corresponding to an air kerma rate of ∼ 57 Gy/min). Ionic recombination thus presents a significant challenge to obtaining accurate air kerma rate measurements using this FAC in these high intensity beams. Future work includes measurements using a smaller aperture to sample a smaller and thus more uniform beam area, as well as experimental and Monte Carlo-based investigation of correction factors.

  9. Beta-efficiency of a typical gas-flow ionization chamber using GEANT4 Monte Carlo simulations

    Directory of Open Access Journals (Sweden)

    Hussain Abid

    2011-01-01

    Full Text Available GEANT4 based Monte Carlo simulations have been carried out for the determination of efficiency and conversion factors of a gas-flow ionization chamber for beta particles emitted by 86 different radioisotopes covering the average-b energy range of 5.69 keV-2.061 MeV. Good agreements were found between the GEANT4 predicted values and corresponding experimental data, as well as with EGS4 based calculations. For the reported set of b-emitters, the values of the conversion factor have been established in the range of 0.5×1013-2.5×1013 Bqcm-3/A. The computed xenon-to-air conversion factor ratios have attained the minimum value of 0.2 in the range of 0.1-1 MeV. As the radius and/or volume of the ion chamber increases, conversion factors approach a flat energy response. These simulations show a small, but significant dependence of ionization efficiency on the type of wall material.

  10. kQ factors for ionization chamber dosimetry in clinical proton beams.

    Science.gov (United States)

    Vatnitsky, S M; Siebers, J V; Miller, D W

    1996-01-01

    We discuss a formalism for clinical proton beam dosimetry based on the use of ionization chamber absorbed dose-to-water calibration and beam quality correction factors. A quantity kQ, the beam quality correction factor, is defined which corrects the absorbed dose-to-water calibration factor ND,w in a reference beam of quality Q0 to that in a user's beam of quality Q1. This study of proton beam quality correction factors used 60Co (kQ gamma) and proton (kQp) reference beams. The kQ gamma factors were measured using combined water calorimetry and ionometry for PTW and Capintec-Farmer-type ionization chambers, and were computed from standard dosimetry protocols. Agreement between measured and calculated kQ gamma values for both chambers was found within 1.2% in the plateau region for a monoenergetic 250-MeV beam and within 1.8% at the spread-out Bragg peak for a 155-MeV range-modulated beam. Comparison of absorbed doses to water determined in the range-modulated 155-MeV beam was performed with the PTW chamber using three calibration methods: Ngas calibration (AAPM Report 16), ND,w,gamma calibration in a 60Co beam in conjunction with a kQ gamma factor, and ND,w,p calibration in a proton beam in conjunction with a kQp factor. Absorbed doses to water obtained with the three methods agreed within 2% when ionization chamber dosimetry data were analyzed using the proton W-value for air from the AAPM Report 16 and the ICRU 49 proton stopping powers. The use of the proton-calibrated reference ionization chamber, in conjunction with the beam quality correction factor kQp, significantly reduced the systematic uncertainty of the absorbed dose determination.

  11. Characterization tests of a new parallel plate ionization chamber for use in electron beams

    Science.gov (United States)

    Nonato, Fernanda B. C.; Sakuraba, Roberto K.; da Cruz, José Carlos; Caldas, Linda V. E.

    2014-11-01

    Linear accelerators with electron beams are used in several Brazilian hospitals. Consequently, there is an increasing demand for parallel-plate ionization chambers, to be utilized for dosimetry of electron beams. In Brazil, the commercial ionization chambers utilized are imported. The ionization chambers have usually a simple construction, using different materials and geometries. A homemade ionization chamber was developed to be used in electron beams of linear accelerator. The ionization chamber body is made of acrylic and the collecting electrode is painted with graphite powder mixed with nail polish. Several tests were applied, and the results showed values better than the limits established by the international recommendations, except for the polarity effect test, but the response of the developed ionization chamber, for this test, is similar in relation to the response of other commercial ionization chambers from the literature.

  12. Establishment of a tandem ionization chamber system in standard mammography beams

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Jonas O. da; Caldas, L.V.E., E-mail: jonas.silva@ipen.b, E-mail: lcaldas@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    A double-faced tandem ionization chamber system was developed at the Calibration Laboratory of IPEN. It has different collecting electrode materials: aluminium and graphite. The response repeatability and reproducibility and the energy dependence test of this tandem ionization chamber were evaluated. The chamber response stability is within the {+-}3% limit recommended in international standards. The energy dependence test of the ionization chamber system using the tandem curve obtained, presented agreement with literature results. (author)

  13. Analytical form of current-voltage characteristic of cylindrical and spherical ionization chambers

    CERN Document Server

    Stoyanov, Dimitar G

    2007-01-01

    The basic processes of ionization and recombination of gas-filled ionization chamber are presented in this article. A differential equation describing the distribution of current densities in the volume of the ionization chamber is obtained from the balance of the particles and charges densities. As a result of the differential equation solving an analytical form of the current-voltage characteristic of cylindrical and spherical ionization chambers is got.

  14. Development of Master Chamber Software for Data Acquisition of Ionization Chamber for Indus 2 RRCAT

    Directory of Open Access Journals (Sweden)

    Priyesh Soni

    2013-02-01

    Full Text Available The main goal of this paper was to Develop Master control software for DAQ of ionization chamber for INDUS-2 beam lines for detection of X-ray flux by an Ionization chamber that will remotely control and monitor the ultra low current signal detection analog module precisely. This application will be useful to measure the intensity of X-ray flux through ionization chamber in a beam line of synchrotron radiation source which is mounted in INDUS-2. It is one of new technique of detection. Beam line area is highly restricted because of hazardous radiation, so through this application remote interfacing is provided for the ultra low current signal detection card that can be controlled by Master software. The development of such type arrangement we used software in C#.NET there are many issues like develop code, Design forms, to achieve the specified response from the CPU card, code developed in C# .NET. Initially, I explored and gained the knowledge of C#.NET. I practices some small modular projects as part to learn how the system works. I used programming language C#.NET architecture version 3.5 in Visual Studio 2008

  15. Long term response stability of a well-type ionization chamber used in calibration of high dose rate brachytherapy sources

    Directory of Open Access Journals (Sweden)

    Vandana S

    2010-01-01

    Full Text Available Well-type ionization chamber is often used to measure strength of brachytherapy sources. This study aims to check long term response stability of High Dose Rate (HDR -1000 Plus well-type ionization chamber in terms of reference air kerma rate (RAKR of a reference 137 Cs brachytherapy source and recommend an optimum frequency of recalibration. An HDR-1000 Plus well-type ionization chamber, a reference 137 Cs brachytherapy source (CDCSJ5, and a MAX-4000 electrometer were used in this study. The HDR-1000 Plus well-type chamber was calibrated in terms of reference air kerma rate by the Standards Laboratory of the International Atomic Energy Agency (IAEA, Vienna. The response of the chamber was verified at regular intervals over a period of eight years using the reference 137 Cs source. All required correction factors were applied in the calculation of the RAKR of the 137 Cs source. This study reveals that the response of the HDR-1000 Plus well-type chamber was well within ±0.5% for about three years after calibration/recalibration. However, it shows deviations larger than ±0.5% after three years of calibration/recalibration and the maximum variation in response of the chamber during an eight year period was 1.71%. The optimum frequency of recalibration of a high dose rate well-type chamber should be three years.

  16. Long term response stability of a well-type ionization chamber used in calibration of high dose rate brachytherapy sources.

    Science.gov (United States)

    Vandana, S; Sharma, S D

    2010-04-01

    Well-type ionization chamber is often used to measure strength of brachytherapy sources. This study aims to check long term response stability of High Dose Rate (HDR)-1000 Plus well-type ionization chamber in terms of reference air kerma rate (RAKR) of a reference (137)Cs brachytherapy source and recommend an optimum frequency of recalibration. An HDR-1000 Plus well-type ionization chamber, a reference (137)Cs brachytherapy source (CDCSJ5), and a MAX-4000 electrometer were used in this study. The HDR-1000 Plus well-type chamber was calibrated in terms of reference air kerma rate by the Standards Laboratory of the International Atomic Energy Agency (IAEA), Vienna. The response of the chamber was verified at regular intervals over a period of eight years using the reference (137)Cs source. All required correction factors were applied in the calculation of the RAKR of the (137)Cs source. This study reveals that the response of the HDR-1000 Plus well-type chamber was well within +/-0.5% for about three years after calibration/recalibration. However, it shows deviations larger than +/-0.5% after three years of calibration/recalibration and the maximum variation in response of the chamber during an eight year period was 1.71%. The optimum frequency of recalibration of a high dose rate well-type chamber should be three years.

  17. Use of a liquid ionization chamber for stereotactic radiotherapy dosimetry.

    Science.gov (United States)

    Wagner, A; Crop, F; Lacornerie, T; Vandevelde, F; Reynaert, N

    2013-04-21

    Liquid ionization chambers (LICs) offer an interesting tool in the field of small beam dosimetry, allowing better spatial resolution and reduced perturbation effects. However, some aspects remain to be addressed, such as the higher recombination and the effects from the materials of the detector. Our aim was to investigate these issues and their impact. The first step was the evaluation of the recombination effects. Measurements were performed at different SSDs to vary the dose per pulse, and the collection efficiency was obtained. The BEAMnrc code was then used to model the Cyberknife head. Finally, the liquid ionization chamber itself was modelled using the EGSnrc-based code Cavity allowing the evaluation of the influence of the volume and the chamber materials. The liquid ionization charge collection efficiency is approximately 0.98 at 1.5 mGy pulse(-1), the highest dose per pulse that we have measured. Its impact on the accuracy of output factors is less than half a per cent. The detector modelling showed a significant contribution from the graphite electrode, up to 6% for the 5 mm collimator. The dependence of the average electronic mass collision stopping power of iso-octane with beam collimation is negligible and thus has no influence on output factor measurements. Finally, the volume effect reaches 5% for the small 5 mm collimator and becomes much smaller (<0.5%) for diameters above 10 mm. LICs can effectively be used for small beam relative dosimetry as long as adequate correction factors are applied, especially for the electrode and volume effects.

  18. Modeling of Fuel Film Cooling on Chamber Hot Wall

    Science.gov (United States)

    2014-07-01

    wall-normal Cartesian coordinate y+ = dimensionless y-spacing at wall CEA = Chemical Equilibrium with Applications (computer program) CFD ...Introduction The walls of liquid rocket engine chambers and nozzles must contain large pressures while being exposed to very high temperature gases, and...The physical and chemical phenomena involved in hydrocarbon FFC is notionally represented in Fig. 1. Hydrocarbon fuel at the fuel tank temperature

  19. Characterization of Tandem systems of commercial ionization chambers for radiation dosimetry (radiotherapy level)

    CERN Document Server

    Galhardo, E P

    1998-01-01

    The use of X rays for radiotherapy purposes is of great importance for Medicine, and it is necessary to control periodically the performance of the ionization chambers and the radiation beams in order to obtain the best results. The verification of the beam characteristics is made by using standard dosimetry procedures which include the determination of the half-value layers and the exposure rates or the absorbed dose rates in air. Several Tandem systems were set up and tested, using commercial ionization chambers in the energy interval from 14 up to 130 KeV at the Instrumentation Calibration Laboratory of IPEN and at other three institutions, in substitution to the routine conventional procedure of determination of half-value layers using absorbers. The obtained results show the usefulness of these Tandem system for the routine dosimetric procedures of radiotherapy X radiation beams.

  20. An online monitor ionization chamber used in particle therapy

    Institute of Scientific and Technical Information of China (English)

    TANG Bin; HU Zhengguo; MAO Ruishi; XU Zhiguo; WANG Jiansong; YUE Ke; TU Xiaolin; WU Dapeng; CHEN Jinda; ZHANG Jie; WANG Meng; SUN Zhiyu; ZHANG Xueheng; LI Qiang; XU Hushan; XIOA Guoqing

    2009-01-01

    The clinical trials of tumor therapy using heavy ions beam 12C are now in progress at Institute of Modern Physics in Lanzhou. In order to achieve the precise radiotherapy with the high energy 12C beam in active pencil beam scanning mode, we have developed an ionization chamber(IC) as an online monitor for beam intensity and also a do-simeter after calibration. Through the choosing of working gas and voltage, optimizing of the electrics and the read-out system, calibrating the linearity, the detector system provide us one of the simple and highly reliable way to monitoring the beam during the active pencil beam scanning treatments. The measurement results of this detector sys-tem show that it could work well under the condition of high energy 12C beam in active pencil beam scanning mode.

  1. Laboratory implantation for well type ionization chambers calibration; Implantacao de um laboratorio para calibracao de camaras de ionizacao tipo poco

    Energy Technology Data Exchange (ETDEWEB)

    Vianello, E.A.; Dias, D.J.; Almeida, C.E. de [Laboratorio de Ciencias Radiologicas- LCR- DBB (UERJ). R. Sao Francisco Xavier, 524- Pav. HLC, sala 136 terreo- CEP 20.550-013. Rio de Janeiro (Brazil)

    1998-12-31

    The Radiological Science Laboratory is implanting a service for calibration of well type chambers by IAEA training program. The kerma rate in the air (mu Gy/h) of the linear Cs-137 reference source CDCS-J4 have been determined using a well type chamber Standard Imaging HDR-1000 model, which have been calibrated at Secondary Standard Laboratory Calibration of IAEA, whereas two HDR-1000 Plus chambers were calibrated too, following the same standards. The results were compared with Wisconsin University calibration certification and has demonstrated that well type ionization chamber calibration can be used in brachytherapy for several kinds of radionuclides. (Author)

  2. Amplitude distribution of ionization jerks in ionization-chamber ASK-1 according long-term measurements

    Science.gov (United States)

    Timofeev, Vladislav

    2016-07-01

    As part of the Yakut complex systems by measuring the intensity of cosmic rays has a unique device spherical - ionization chamber ASK-1 with a lead screen thickness of 12 cm. The camera allows you to explore the physical characteristics of the so-called "ionization jerks " - sharp increases ionization current caused by the passage through the device much ionizing particles of cosmic origin. Due to a large increase in current nuclear cascade "showers", formed mainly by particles of cosmic rays in the camera screen. Over the entire period of observation (50 years old) camera ASK-1 was registered 59125 aftershocks. Their nature and properties still does not sufficiently studied, especially in medium and large amplitudes.

  3. Physical fundamentals for the functional simulation of the ionization transmission chamber in X-ray diagnostics; Physikalische Grundlagen fuer die Funktionssimulation der Ionisations-Durchstrahlkammer in der Roentgendiagnostik

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, Horst

    2012-11-01

    The presentation of the physical fundamentals for the functional simulation of the ionization transmission chamber in X-ray diagnostics covers the mathematical description of the interaction of photons with solid materials in Mote Carlo compliable way, including Rayleigh and Compton scattering and photoabsorption. The energy dependence of the emitted secondary electrons is described according the Coulomb and Moeller scattering theory. The simulation is aimed to determine the spectral electron flux density in the air-filled measuring space of the ionization chamber for the defined X-ray energy spectrum dependent on the voltage at the X-ray tube. The influence of geometry and materials on the spectral energy flux density provides hints for the construction of the ionization transmission chamber. The differential energy loss of the secondary electrons in air is determined allowing the calculation of the ionization rate. The ionization of air is described, providing the conditions for a linear relation between ionization rate and ionic current.

  4. Performance parameters of a liquid filled ionization chamber array

    Energy Technology Data Exchange (ETDEWEB)

    Poppe, B.; Stelljes, T. S.; Looe, H. K.; Chofor, N. [Clinic for Radiation Therapy, Pius-Hospital, Oldenburg 26121, Germany and WG Medical Radiation Physics, Carl von Ossietzky University, Oldenburg 26121 (Germany); Harder, D. [Prof. em., Medical Physics and Biophysics, Georg August University, Göttingen 37073 (Germany); Willborn, K. [Clinic for Radiation Therapy, Pius-Hospital, Oldenburg 26121 (Germany)

    2013-08-15

    Purpose: In this work, the properties of the two-dimensional liquid filled ionization chamber array Octavius 1000SRS (PTW-Freiburg, Germany) for use in clinical photon-beam dosimetry are investigated.Methods: Measurements were carried out at an Elekta Synergy and Siemens Primus accelerator. For measurements of stability, linearity, and saturation effects of the 1000SRS array a Semiflex 31013 ionization chamber (PTW-Freiburg, Germany) was used as a reference. The effective point of measurement was determined by TPR measurements of the array in comparison with a Roos chamber (type 31004, PTW-Freiburg, Germany). The response of the array with varying field size and depth of measurement was evaluated using a Semiflex 31010 ionization chamber as a reference. Output factor measurements were carried out with a Semiflex 31010 ionization chamber, a diode (type 60012, PTW-Freiburg, Germany), and the detector array under investigation. The dose response function for a single detector of the array was determined by measuring 1 cm wide slit-beam dose profiles and comparing them against diode-measured profiles. Theoretical aspects of the low pass properties and of the sampling frequency of the detector array were evaluated. Dose profiles measured with the array and the diode detector were compared, and an intensity modulated radiation therapy (IMRT) field was verified using the Gamma-Index method and the visualization of line dose profiles.Results: The array showed a short and long term stability better than 0.1% and 0.2%, respectively. Fluctuations in linearity were found to be within ±0.2% for the vendor specified dose range. Saturation effects were found to be similar to those reported in other studies for liquid-filled ionization chambers. The detector's relative response varied with field size and depth of measurement, showing a small energy dependence accounting for maximum signal deviations of ±2.6% from the reference condition for the setup used. The σ-values of

  5. Analysis of dose perturbation factors of a NACP-02 ionization chamber in clinical electron beams.

    Science.gov (United States)

    Chin, E; Palmans, H; Shipley, D; Bailey, M; Verhaegen, F

    2009-01-21

    For well-guarded plane-parallel ionization chambers, international dosimetry protocols recommend a value of unity for electron perturbation factors in water. However, recent data published by various groups have challenged this. Specifically for the NACP-02 chamber, non-unity electron perturbation factors have already been published by Verhaegen et al (2006 Phys. Med. Biol. 51 1221-35) and Buckley and Rogers (2006 Med. Phys. 33 1788-96). Recently it was found that the mass thickness of the front chamber window can be 35% greater than is listed in the IAEA's TRS-398 absorbed dose protocol (Chin et al 2008 Phys. Med. Biol. 53 N119-26). This study therefore recalculated NACP-02 electron perturbation correction factors for energies 4-18 MeV at depths z(ref) and R(50) to determine the effect of the chamber model change. Results showed that perturbation factors at z(ref) are fairly stable for similar chamber models but become highly sensitive to small changes at deeper depths. The results also showed some dependence on using 1 keV versus 10 keV for the transport cut-off. Additional investigations revealed that the wall perturbation factor, p(wall), is strongly influenced by the chamber back wall at z(ref) and at larger depths small changes in the positioning of the effective point of measurement cause large fluctuations in the final value. Finally, the cavity perturbation factor, p(cav), was found to be primarily influenced by electron backscatter.

  6. Analytical form of current-voltage characteristic of parallel-plane, cylindrical and spherical ionization chambers with homogeneous ionization

    CERN Document Server

    Stoyanov, Dimitar G

    2007-01-01

    The elementary processes taking place in the formation of charged particles and their flow in the ionization chamber are considered. On the basic of particles and charges balance a differential equation describing the distribution of current densities in the ionization chamber volume is obtained. As a result of the differential equation solution an analytical form of the current-voltage.

  7. Imaging with high Dynamic using an Ionization Chamber

    CERN Document Server

    Menk, Ralf-Hendrik; Arfelli, Fulvia; Bernstorff, Sigrid; Besch, Hans Juergen; Voltolina, Francesco

    2010-01-01

    In this work a combination of an ionization chamber with one-dimensional spatial resolution and a MicroCAT structure will be presented. The combination between gas gain operations and integrating front-end electronics yields a dynamic range as high as eight to nine orders of magnitude. Therefore this device is well suitable for medical imaging or applications such as small angle x-ray scattering, where the requirements on the dynamic of the detector are exceptional high. Basically the described detector is an ionization chamber adapted to fan beam geometry with an active area of 192 cm and a pitch of the anode strips of 150 micrometer. In the vertical direction beams as high as 10 mm can be accepted. Every read-out strip is connected to an analogue integrating electronics channel realized in a custom made VLSI chip. A MicroCAT structure utilized as a shielding grid enables frame rates as high as 10kHz. The high dynamic range observed stems from the fact that the MicroCAT enables active electron amplification ...

  8. Development of a portable gas-filled ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Chae, K. Y.; Cha, S. M.; Gwak, M. S. [Sungkyunkwan University, Suwon (Korea, Republic of)

    2014-02-15

    A new portable gas-filled ionization chamber has been designed and constructed at the Physics Department of Sung Kyun Kwan University. To overcome the maximum count rate of ∼ 10{sup 5} particles per second of a conventional ionization chamber, which utilizes a Frisch grid, and to enhance the portability of a detector, we adopted the design of multiple electrodes and modified it from the original designs by Kimura et al. and Chae et al. The new design utilizes a stack of multiple electrodes installed perpendicular to the optical beam axis. This configuration provides a fast response time for the detector, which is essential for high-rate counting. The device has been tested with a {sup 241}Am (t{sub 1/2} = 432.2 years) radioactive α source, which mainly emits 5.486-MeV (branching ratio of 85%) and 5.443-MeV (branching ratio of 13%) α particles. An energy resolution of 6.3% was achieved.

  9. An ionization chamber shower detector for the LHC luminosity monitor

    CERN Document Server

    Beche, J F; Datte, P S; Haguenauer, Maurice; Manfredi, P F; Millaud, J E; Placidi, Massimo; Ratti, L; Re, V; Riot, V J; Schmickler, Hermann; Speziali, V; Turner, W C

    2000-01-01

    The front IR quadrupole absorbers (TAS) and the IR neutral particle absorbers (TAN) in the high luminosity insertions of the Large Hadron Collider (LHC) each absorb approximately 1.8 TeV of forward collision products on average per pp interaction (~235 W at design luminosity 10/sup 34/ cm/sup -2/ s/sup -1/). This secondary particle flux can be exploited to provide a useful storage ring operations tool for optimization of luminosity. A novel segmented, multi-gap, pressurized gas ionization chamber is being developed for sampling the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The system design choices have been strongly influenced by optimization of signal to noise ratio and by the very high radiation environment. The ionization chambers are instrumented with low noise, fast, pulse shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. Data on each bunch are to be separately accumulated over multiple bunch crossings until the desire...

  10. Analytical form of current-voltage characteristic of parallel-plane, cylindrical and spherical ionization chambers with homogeneous ionization

    Energy Technology Data Exchange (ETDEWEB)

    Stoyanov, D G [Faculty of Engineering and Pedagogy in Sliven, Technical University of Sofia, 59, Bourgasko Shaussee Blvd, 8800 Sliven (Bulgaria)

    2007-11-15

    The elementary processes taking place in the formation of charged particles and their flow in parallel-plane, cylindrical and spherical geometry cases of ionization chamber are considered. On the basis of particles and charges balance a differential equation describing the distribution of current densities in the ionization chamber volume is obtained. As a result of the differential equation solution an analytical form of the current-voltage characteristic of an ionization chamber with homogeneous ionization is obtained. For the parallel-plane case comparision with experimental data is performed.

  11. Comparison between a commercial and homemade ionization chamber for dosimetry of {sup 60}Co beams

    Energy Technology Data Exchange (ETDEWEB)

    Neves, Lucio P.; Perini, Ana P.; Caldas, Linda V.E., E-mail: lpneves@ipen.b, E-mail: aperini@ipen.b, E-mail: lcaldas@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    The Calibration Laboratory at IPEN/CNEN (LCI) has developed several ionization detectors for dosimetry in diagnostic radiology, radiation protection and radiotherapy. Recently, a cylindrical ionization chamber, with a sensitive volume of 1.06cm{sup 3}, was developed, and several tests were performed to characterize this ionization chamber for radiotherapy level. The results showed that its performance was within the recommended international limits. In order to complement the studies regarding the response of this ionization chamber, in this work, the chamber response was compared with that of a commercial ionization chamber Farmer PTW, model TN30011-1. The ionization chamber produced at LCI is made of PVC and PMMA. A special build-up cap for {sup 60}Co beams was made of acrylic, with 4.00 mm thickness. All tests of both ionization chambers were performed under the same conditions, allowing good geometrical reproducibility. The performed tests were: saturation, ion collection efficiency, polarity effect and chamber tilt. The results obtained in this comparison program were all within the international recommendations, and demonstrate a good agreement of the performance of the commercial and the homemade ionization chambers. From this comparison results and from previous data, it is possible to conclude that the ionization chamber produced at IPEN presents usefulness for dosimetric applications at radiotherapy level in {sup 60}Co beams.(author)

  12. Saturation current and collection efficiency for ionization chambers in pulsed beams.

    Science.gov (United States)

    DeBlois, F; Zankowski, C; Podgorsak, E B

    2000-05-01

    Saturation currents and collection efficiencies in ionization chambers exposed to pulsed megavoltage photon and electron beams are determined assuming a linear relationship between 1/I and 1/V in the extreme near-saturation region, with I and V the chamber current and polarizing voltage, respectively. Careful measurements of chamber current against polarizing voltage in the extreme near-saturation region reveal a current rising faster than that predicted by the linear relationship. This excess current combined with conventional "two-voltage" technique for determination of collection efficiency may result in an up to 0.7% overestimate of the saturation current for standard radiation field sizes of 10X10 cm2. The measured excess current is attributed to charge multiplication in the chamber air volume and to radiation-induced conductivity in the stem of the chamber (stem effect). These effects may be accounted for by an exponential term used in conjunction with Boag's equation for collection efficiency in pulsed beams. The semiempirical model follows the experimental data well and accounts for both the charge recombination as well as for the charge multiplication effects and the chamber stem effect.

  13. Gridded Ionization Chambers for Time Resolved X-Ray Absorption Spectroscopy

    Science.gov (United States)

    Müller, O.; Stötzel, J.; Lützenkirchen-Hecht, D.; Frahm, R.

    2013-03-01

    Common parallel plate ionization chambers are bandwidth limited by the ion drift velocity. Therefore they can severely decrease the effective energy resolution of time resolved EXAFS or XANES spectra. We therefore developed gridded ionization chambers which suppress the ionic component of the ionization current, which results in a substantial improvement of its bandwidth of typically two orders of magnitude. The rise time of these chambers is measured to be less than 5.5 μs. We have investigated the step response of parallel plate and gridded ionization chambers and discuss their influence on QEXAFS spectra.

  14. Two-Phase Air/Oil Flow in Aero-Engine Bearing Chambers – Assessment of an Analytical Prediction Method for the Internal Wall Heat Transfer

    Directory of Open Access Journals (Sweden)

    A. Glahn

    1999-01-01

    Full Text Available The present paper gives a theoretical outline on liquid film flows driven by superimposed effects of interfacial shear and gravity forces and discusses related heat transfer processes which are relevant for lubrication oil systems of aero engines. It is shown that a simple analytical approach is able to predict measured heat transfer data fairly well. Therefore, it offers scope for improvements within the analysis of bearing chamber heat transfer characteristics as well as for appropriate studies with respect to other components of the lubrication oil system such as vent pipeline elements.

  15. An automated ionization chamber for secondary radioactivity standards.

    Science.gov (United States)

    Fitzgerald, R

    2010-01-01

    I report on the operation and characterization of a new ionization chamber system, "AUTOIC", featuring a commercial digital electrometer and a commercial robotic sample changer. The relative accuracy of the electrometer was improved significantly beyond the manufacturer's specifications through an in-house calibration of the various ranges, applied via software. The measurement precision and repeatability of the system have been determined by measuring multiple samples of the same radionuclide over the span of two or three years. The linearity of the system was examined by following the decay of (99m)Tc, (99)Mo and (133)Xe sources for up to 19 half-lives and determining half-life values. All of these values agree with the accepted literature values, within their combined uncertainties.

  16. An automated ionization chamber for secondary radioactivity standards

    Energy Technology Data Exchange (ETDEWEB)

    Fitzgerald, R., E-mail: ryan.fitzgerald@nist.go [Physics Laboratory, National Institute of Standards and Technology, 100 Bureau Drive, Gaithersburg, MD 20899 (United States)

    2010-07-15

    I report on the operation and characterization of a new ionization chamber system, 'AUTOIC', featuring a commercial digital electrometer and a commercial robotic sample changer. The relative accuracy of the electrometer was improved significantly beyond the manufacturer's specifications through an in-house calibration of the various ranges, applied via software. The measurement precision and repeatability of the system have been determined by measuring multiple samples of the same radionuclide over the span of two or three years. The linearity of the system was examined by following the decay of {sup 99m}Tc, {sup 99}Mo and {sup 133}Xe sources for up to 19 half-lives and determining half-life values. All of these values agree with the accepted literature values, within their combined uncertainties.

  17. Assessment of ionization chamber correction factors in photon beams using a time saving strategy with PENELOPE code.

    Science.gov (United States)

    Reis, C Q M; Nicolucci, P

    2016-02-01

    The purpose of this study was to investigate Monte Carlo-based perturbation and beam quality correction factors for ionization chambers in photon beams using a saving time strategy with PENELOPE code. Simulations for calculating absorbed doses to water using full spectra of photon beams impinging the whole water phantom and those using a phase-space file previously stored around the point of interest were performed and compared. The widely used NE2571 ionization chamber was modeled with PENELOPE using data from the literature in order to calculate absorbed doses to the air cavity of the chamber. Absorbed doses to water at reference depth were also calculated for providing the perturbation and beam quality correction factors for that chamber in high energy photon beams. Results obtained in this study show that simulations with phase-space files appropriately stored can be up to ten times shorter than using a full spectrum of photon beams in the input-file. Values of kQ and its components for the NE2571 ionization chamber showed good agreement with published values in the literature and are provided with typical statistical uncertainties of 0.2%. Comparisons to kQ values published in current dosimetry protocols such as the AAPM TG-51 and IAEA TRS-398 showed maximum percentage differences of 0.1% and 0.6% respectively. The proposed strategy presented a significant efficiency gain and can be applied for a variety of ionization chambers and clinical photon beams.

  18. Characterization tests and application of special ionization chambers in standard mammography beams

    Energy Technology Data Exchange (ETDEWEB)

    Honda, Cristiane J.C.; Caldas, Linda V.E., E-mail: cristianehonda@usp.br, E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Silva, Jonas O., E-mail: jonas.silva@ufg.br [Universidade Federal de Goias (UFG), Goiania, GO (Brazil). Instituto de Fisica

    2015-07-01

    The most used instrument for quality assurance programs in mammography beams is the ionization chamber. At the Calibration Laboratory of IPEN three different ionization chambers were recently designed and assembled for dosimetry in standard mammography beams. These ionization chambers are parallel plate chambers, with different geometries. The objective of this work was to study the performance of all three ionization chambers in relation to a commercial one. The established standard beams at an industrial X-ray system Pantak-Seifert were used for the characterization tests of the ionization chambers as short- and medium-term stability, saturation curves, polarity effect, ion collection efficiency, response linearity and angular dependence. All of the results obtained were within the limits recommended by the international standards IEC 61674 and IEC 60731. (author)

  19. A two-dose-rate method for general recombination correction for liquid ionization chambers in pulsed beams

    Energy Technology Data Exchange (ETDEWEB)

    Toelli, Heikki; Sjoegren, Rickard; Wendelsten, Mikael, E-mail: heikki.tolli@radfys.umu.s [Department of Radiation Sciences, Radiation Physics, Umeaa University, SE-901 85 Umeaa (Sweden)

    2010-08-07

    The correction for general recombination losses in liquid ionization chambers (LICs) is more complex than that in air-filled ionization chambers. The reason for this is that the saturation charge in LICs, i.e. the charge that escapes initial recombination, depends on the applied voltage. This paper presents a method, based on measurements at two different dose rates in a pulsed beam, for general recombination correction in LICs. The Boag theory for pulsed beams is used and the collection efficiency is determined by numerical methods which are equivalent to the two-voltage method used in dosimetry with air-filled ionization chambers. The method has been tested in experiments in water in a 20 MeV electron beam using two LICs filled with isooctane and tetramethylsilane. The dose per pulse in the electron beam was varied between 0.1 mGy/pulse and 8 mGy/pulse. The relative standard deviations of the collection efficiencies determined with the two-dose-rate method ranged between 0.1% and 1.5%. The dose-rate variations of the general recombination corrected charge measured with the LICs are in excellent agreement with the corresponding values obtained with an air-filled plane parallel ionization chamber.

  20. NIST Ionization Chamber “A” Sample-Height Corrections

    Science.gov (United States)

    Fitzgerald, Ryan

    2012-01-01

    For over 30 years scientists in the NIST radioactivity group have been using their pressurized ionization chamber “A” (PIC “A”) to make measurements of radioactivity and radioactive half-lives. We now have evidence that some of those reported measurements were incorrect due to slippage of the source positioning ring over time. The temporal change in the holder caused an error in the source-height within the chamber, which was thought to be invariant. This unaccounted-for height change caused a change in the detector response and thus a relative error in measured activity on the order of 10−5 to 10−3 per year, depending on the radionuclide. The drifting detector response affected calibration factors and half-life determinations. After discovering the problem, we carried out historic research and new sensitivity tests. As a result, we have created a quantitative model of the effect and have used that model to estimate corrections to some of the past measurement results from PIC “A”. In this paper we report the details and results of that model. Meanwhile, we have fixed the positioning ring and are recalibrating the detector using primary measurement methods and enhanced quality control measures. PMID:26900515

  1. NIST Ionization Chamber "A" Sample-Height Corrections.

    Science.gov (United States)

    Fitzgerald, Ryan

    2012-01-01

    For over 30 years scientists in the NIST radioactivity group have been using their pressurized ionization chamber "A" (PIC "A") to make measurements of radioactivity and radioactive half-lives. We now have evidence that some of those reported measurements were incorrect due to slippage of the source positioning ring over time. The temporal change in the holder caused an error in the source-height within the chamber, which was thought to be invariant. This unaccounted-for height change caused a change in the detector response and thus a relative error in measured activity on the order of 10(-5) to 10(-3) per year, depending on the radionuclide. The drifting detector response affected calibration factors and half-life determinations. After discovering the problem, we carried out historic research and new sensitivity tests. As a result, we have created a quantitative model of the effect and have used that model to estimate corrections to some of the past measurement results from PIC "A". In this paper we report the details and results of that model. Meanwhile, we have fixed the positioning ring and are recalibrating the detector using primary measurement methods and enhanced quality control measures.

  2. Performance of the ETH gas ionization chamber at low energy

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, A.M., E-mail: arnold.mueller@phys.ethz.ch [Laboratory of Ion Beam Physics, ETH-Zurich, Schafmattstrasse 20, CH-8093 Zurich (Switzerland); Doebeli, M.; Suter, M.; Synal, H.-A. [Laboratory of Ion Beam Physics, ETH-Zurich, Schafmattstrasse 20, CH-8093 Zurich (Switzerland)

    2012-09-15

    The performance of gas ionization chambers (GIC) for the detection of low energy ions has been considerably improved in the past years by the use of silicon nitride entrance windows and low noise preamplifiers. This has led to an increased use of high resolution GICs in the fields of accelerator mass spectrometry and ion beam analysis. This development and the underlying physical principles are reviewed and the latest technical status of such devices is summarized. A detailed study on energy resolution and pulse height defect is presented with projectiles covering a wide particle mass range (H, {sup 9}Be, {sup 13}C, {sup 27}Al, {sup 35}Cl, {sup 127}I, {sup 232}Th) with energies between 0.1 and 2.2 MeV. The dependence of energy resolution and charge output per unit particle energy on the nuclear charge of the projectile is investigated and parametrized. SRIM calculations of ionizing energy loss considerably differ from these experimental findings. For 1 MeV particles discrepancies up to 50% are observed. The performance of GICs and their practical use is compared to that of solid state detectors. The potential for further improvement of the technology and its fields of application are assessed.

  3. Investigation of electron-loss and photon scattering correction factors for FAC-IR-300 ionization chamber

    Science.gov (United States)

    Mohammadi, S. M.; Tavakoli-Anbaran, H.; Zeinali, H. Z.

    2017-02-01

    The parallel-plate free-air ionization chamber termed FAC-IR-300 was designed at the Atomic Energy Organization of Iran, AEOI. This chamber is used for low and medium X-ray dosimetry on the primary standard level. In order to evaluate the air-kerma, some correction factors such as electron-loss correction factor (ke) and photon scattering correction factor (ksc) are needed. ke factor corrects the charge loss from the collecting volume and ksc factor corrects the scattering of photons into collecting volume. In this work ke and ksc were estimated by Monte Carlo simulation. These correction factors are calculated for mono-energy photon. As a result of the simulation data, the ke and ksc values for FAC-IR-300 ionization chamber are 1.0704 and 0.9982, respectively.

  4. Dosimetric characteristics of the novel 2D ionization chamber array OCTAVIUS Detector 1500

    Energy Technology Data Exchange (ETDEWEB)

    Stelljes, T. S., E-mail: tenzin.s.stelljes@uni-oldenburg.de; Looe, H. K.; Chofor, N.; Poppe, B. [Clinic for Radiation Therapy, Pius-Hospital, Oldenburg 26121, Germany and WG Medical Radiation Physics, Carl von Ossietzky University, Oldenburg 26129 (Germany); Harmeyer, A.; Reuter, J. [WG Medical Radiation Physics, Carl von Ossietzky University, Oldenburg 26129 (Germany); Harder, D. [Prof. em., Medical Physics and Biophysics, Georg August University, Göttingen 37073 (Germany)

    2015-04-15

    Purpose: The dosimetric properties of the OCTAVIUS Detector 1500 (OD1500) ionization chamber array (PTW-Freiburg, Freiburg, Germany) have been investigated. A comparative study was carried out with the OCTAVIUS Detector 729 and OCTAVIUS Detector 1000 SRS arrays. Methods: The OD1500 array is an air vented ionization chamber array with 1405 detectors in a 27 × 27 cm{sup 2} measurement area arranged in a checkerboard pattern with a chamber-to-chamber distance of 10 mm in each row. A sampling step width of 5 mm can be achieved by merging two measurements shifted by 5 mm, thus fulfilling the Nyquist theorem for intensity modulated dose distributions. The stability, linearity, and dose per pulse dependence were investigated using a Semiflex 31013 chamber (PTW-Freiburg, Freiburg, Germany) as a reference detector. The effective depth of measurement was determined by measuring TPR curves with the array and a Roos chamber type 31004 (PTW-Freiburg, Freiburg, Germany). Comparative output factor measurements were performed with the array, the Semiflex 31010 ionization chamber and the Diode 60012 (both PTW-Freiburg, Freiburg, Germany). The energy dependence of the OD1500 was measured by comparing the array’s readings to those of a Semiflex 31010 ionization chamber for varying mean photon energies at the depth of measurement, applying to the Semiflex chamber readings the correction factor k{sub NR} for nonreference conditions. The Gaussian lateral dose response function of a single array detector was determined by searching the convolution kernel suitable to convert the slit beam profiles measured with a Diode 60012 into those measured with the array’s central chamber. An intensity modulated dose distribution measured with the array was verified by comparing a OD1500 measurement to TPS calculations and film measurements. Results: The stability and interchamber sensitivity variation of the OD1500 array were within ±0.2% and ±0.58%, respectively. Dose linearity was within 1

  5. Numerical studies of wall-plasma interactions and ionization phenomena in an ablative pulsed plasma thruster

    Science.gov (United States)

    Yang, Lei; Zeng, Guangshang; Tang, Haibin; Huang, Yuping; Liu, Xiangyang

    2016-07-01

    Wall-plasma interactions excited by ablation controlled arcs are very critical physical processes in pulsed plasma thrusters (PPTs). Their effects on the ionization processes of ablated vapor into discharge plasma directly determine PPT performances. To reveal the physics governing the ionization phenomena in PPT discharge, a modified model taking into account the pyrolysis effect of heated polytetrafluoroethylene propellant on the wall-plasma interactions was developed. The feasibility of the modified model was analyzed by creating a one-dimensional simulation of a rectangular ablative PPT. The wall-plasma interaction results based on this modified model were found to be more realistic than for the unmodified model; this reflects the dynamic changes of the inflow parameters during discharge in our model. Furthermore, the temporal and spatial variations of the different plasma species in the discharge chamber were numerically studied. The numerical studies showed that polytetrafluoroethylene plasma was mainly composed of monovalent ions; carbon and fluorine ions were concentrated in the upstream and downstream discharge chamber, respectively. The results based on this modified model were in good agreement with the experimental formation times of the various plasma species. A large number of short-lived and highly ionized carbon and fluorine species (divalent and trivalent ions) were created during initial discharge. These highly ionized species reached their peak density earlier than the singly ionized species.

  6. Polarity correction factor for flattening filter free photon beams in several cylindrical ionization chambers.

    Science.gov (United States)

    Ogata, Toshiyuki; Uehara, Kazuyuki; Nakayama, Masao; Tsudou, Shinji; Masutani, Takashi; Okayama, Takanobu

    2016-07-01

    In this study, we aimed to compare the polarity correction factor in ionization chambers for flattening filter free (FFF) photon beams and flattening filter (FF) beams. Measurements were performed with both 6 and 10 MV FFF and FF beams. Five commercial ionization chambers were evaluated: PTW TN30013; IBA Dosimetry CC01, CC04, and CC13; and Exradin A12S. Except for the CC01 ionization chamber, the other four chambers showed less than a 0.3 % difference in the polarity effect between the FFF and the FF beams. The CC01 chamber showed a strong field-size-dependence, unlike the other chambers. The polarity effect for all chambers with FFF beams did not change with the dose rate. Except in the case of the CC01 chamber, the difference in the polarity effect between FFF and FF beams was not significant.

  7. A measure method of the time respond function for gas ionization chamber

    CERN Document Server

    Wang Li; Qing Shang Yu

    2002-01-01

    In quick scanning radiography system, the time respond speed of array gas ionization chamber effects the image clarity directly. The author presents a measure method of the time respond function for gas ionization chamber. The image clarity will be improved by inverse convoluting the image data

  8. Theoretical Calculation and Monte Carlo Simulation of Photon Energy Response of Large Size Cavity Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    SONG; Ming-zhe; WEI; Ke-xin; HOU; Jin-bing; WANG; Hong-yu; GAO; Fei; NI; Ning

    2015-01-01

    The Bragg-Gray cavity theory(B-G theory)provided a theoretical basis for the analytical calculation of the energy response for ionization chamber.It was widely used in the theoretical calculation of the ionization chamber detector and the tissue equivalent detector.However,the B-G

  9. A time dependent solution for the operation of ion chambers in a high ionization background

    CERN Document Server

    Velissaris, C

    2005-01-01

    We have derived a time dependent solution describing the development of space charge inside an ion chamber subjected to an externally caused ionization rate N. The solution enables the derivation of a formula that the operational parameters of the chamber must satisfy for saturation free operation. This formula contains a correction factor to account for the finite duration of the ionization rate N.

  10. Source geometry factors for HDR ¹⁹²Ir brachytherapy secondary standard well-type ionization chamber calibrations.

    Science.gov (United States)

    Shipley, D R; Sander, T; Nutbrown, R F

    2015-03-21

    Well-type ionization chambers are used for measuring the source strength of radioactive brachytherapy sources before clinical use. Initially, the well chambers are calibrated against a suitable national standard. For high dose rate (HDR) (192)Ir, this calibration is usually a two-step process. Firstly, the calibration source is traceably calibrated against an air kerma primary standard in terms of either reference air kerma rate or air kerma strength. The calibrated (192)Ir source is then used to calibrate the secondary standard well-type ionization chamber. Calibration laboratories are usually only equipped with one type of HDR (192)Ir source. If the clinical source type is different from that used for the calibration of the well chamber at the standards laboratory, a source geometry factor, k(sg), is required to correct the calibration coefficient for any change of the well chamber response due to geometric differences between the sources. In this work we present source geometry factors for six different HDR (192)Ir brachytherapy sources which have been determined using Monte Carlo techniques for a specific ionization chamber, the Standard Imaging HDR 1000 Plus well chamber with a type 70010 HDR iridium source holder. The calculated correction factors were normalized to the old and new type of calibration source used at the National Physical Laboratory. With the old Nucletron microSelectron-v1 (classic) HDR (192)Ir calibration source, ksg was found to be in the range 0.983 to 0.999 and with the new Isodose Control HDR (192)Ir Flexisource k(sg) was found to be in the range 0.987 to 1.004 with a relative uncertainty of 0.4% (k = 2). Source geometry factors for different combinations of calibration sources, clinical sources, well chambers and associated source holders, can be calculated with the formalism discussed in this paper.

  11. A new method for measuring the response time of the high pressure ionization chamber.

    Science.gov (United States)

    Wang, Zhentao; Shen, Yixiong; An, Jigang

    2012-08-01

    Time response is an important performance characteristic for gas-pressurized ionization chambers. To study the time response, it is especially crucial to measure the ion drift time in high pressure ionization chambers. In this paper, a new approach is proposed to study the ion drift time in high pressure ionization chambers. It is carried out with a short-pulsed X-ray source and a high-speed digitizer. The ion drift time in the chamber is then determined from the digitized data. By measuring the ion drift time of a 15 atm xenon testing chamber, the method has been proven to be effective in the time response studies of ionization chambers.

  12. A double faced ionization chamber for quality control in diagnostic radiology beams.

    Science.gov (United States)

    Silva, Jonas O; Caldas, Linda V E

    2012-07-01

    The development of new radiation detectors of low cost but with adequate materials is a very important task for countries that have to import ionization chambers such as Brazil. A special double faced ionization chamber was developed for use in conventional diagnostic radiology beams and computed tomography energy ranges. The results show that this new chamber present applicability in conventional diagnostic radiology and computed tomography quality control programs.

  13. Research on the application of 2-D air vented ionization chamber array MatriXX system%二维空气电离室矩阵MatriXX系统的应用研究

    Institute of Scientific and Technical Information of China (English)

    张书旭; 周凌宏; 陈光杰; 林生趣; 沈国辉; 王余峰

    2009-01-01

    Objective To investigate the features of 2-D air vented ionization chamber array MatriXX system to use the QA procedures of radiotherapy. Methods Some important QA procedure of clinical radiotherapy practice were investigated by using a MatriXX system and a phantom made in house, mainly including the calibration of MatriXX, the off-axis rate (OAR) of virtual wedge fields, the connection between two half-fields or two asymmetry-fields, the skillful adjustment of the clinac flat filter, the 2-D dose distribution verification of radiotherapy planning, the influence of scatter screen to a large area electron beam field, the effect and best thickness and shielding position of block for a large area electron beam fields with scatter screen. Results The OAR of any virtual wedge field can be measured by a MatriXX system in a single irradiation. The conjunction accuracy of two half-fields or two asymmetry-fields may be less than 1 ram. The difference between the calculated and measured dose of any point or any isodose or any OAR of a field can be determined by using a MatriXX system. After the adjustment of the elinae flat filter with the help of MatriXX system, the flatness and symmetry of the field are 1. 85 % and 0.98 %, respectively. The dose characteristic of a large area electron beam field may be distinctively influenced by a scatter screen, and under this condition, the block faraway from the shielded target can hardly protect the organ at risk, and directe block which is put on or near the organ at risk is perfect. Conclusion Compared with conventional ionization chamber (Farmer type) or film dose measuring, the MatriXX combined with the OmniPre I'mRT software is much more convenient and effective in QA practice of clinical radiotherapy, and it's a perfect tool for the QA procedure of radiation therapy.%目的 探讨二维空气电离室矩阵MatriXX系统应用于放疗质量控制中的特点.方法 用MatriXX系统和自制的剂量测量体模,对临床放疗

  14. A new mini gas ionization chamber for IBA applications

    Energy Technology Data Exchange (ETDEWEB)

    Mueller, A.M., E-mail: arnold.mueller@phys.ethz.ch [Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich (Switzerland); Cassimi, A., E-mail: cassimi@ganil.fr [CIMAP/CIRIL, CEA/CNRS/ENSICAEN, BP5133, F-14070 Caen cedex 5 (France); Doebeli, M., E-mail: doebeli@phys.ethz.ch [Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich (Switzerland); Mallepell, M., E-mail: mallepell@phys.ethz.ch [Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich (Switzerland); Monnet, I., E-mail: monnet@ganil.fr [CIMAP/CIRIL, CEA/CNRS/ENSICAEN, BP5133, F-14070 Caen cedex 5 (France); Simon, M.J. [Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich (Switzerland); Suter, M., E-mail: martin.suter@phys.ethz.ch [Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich (Switzerland); Synal, H.-A., E-mail: synal@phys.ethz.ch [Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich (Switzerland)

    2011-12-15

    Novel prototypes of high resolution gas ionization chambers (GIC) were designed with increased compactness and simplicity of the setup. They have no Frisch-grid and a simple anode wire. Under certain operating conditions these mini detectors have an energy resolution comparable with that of state-of-the-art GICs of much higher complexity. They can be operated both under vacuum and atmospheric pressure. First measurements were made with protons in the energy range of 0.3-1.0 MeV. For protons at 0.3 MeV an energy resolution of about 12 keV was achieved. With a 72 MeV {sup 129}Xe beam a relative resolution of 1.4% was obtained. Due to their versatility and reduced size the detectors can easily be applied in the field of ion beam analysis (IBA) and accelerator mass spectrometry (AMS). Since they are almost completely insensitive to radiation damage they are especially suited for use in high fluence applications such as scanning transmission ion microscopy (STIM). A comparison of the radiation hardness of the mini GIC with a Si PIN diode was therefore performed. The GIC showed no peak shift or change in energy resolution at all after collecting 10{sup 15} protons per cm{sup 2} while the performance of the Si detector clearly started to degrade at 10{sup 12} particles per cm{sup 2}.

  15. A correction to Birks' Law in liquid argon ionization chamber simulations for highly ionizing particles

    Energy Technology Data Exchange (ETDEWEB)

    Burdin, Sergey [Department of Physics, University of Liverpool, Liverpool L69 7ZE (United Kingdom); Horbatsch, Marko [Department of Physics and Astronomy, York University, Toronto, ON, M3J 1P3 (Canada); Taylor, Wendy, E-mail: taylorw@yorku.ca [Department of Physics and Astronomy, York University, Toronto, ON, M3J 1P3 (Canada)

    2012-02-01

    We present a study of the performance of Birks' Law in liquid argon ionization chamber simulations as applied to highly ionizing particles, such as particles with multiple electric charges or with magnetic charge. We used Birks' Law to model recombination effects in a GEANT4 simulation of heavy ions in a liquid argon calorimeter. We then compared the simulation to published heavy-ion data to extract a highly ionizing particle correction to Birks' Law.

  16. Determination of small-field correction factors for cylindrical ionization chambers using a semiempirical method.

    Science.gov (United States)

    Park, Kwangwoo; Bak, Jino; Park, Sungho; Choi, Wonhoon; Park, Suk Won

    2016-02-07

    A semiempirical method based on the averaging effect of the sensitive volumes of different air-filled ionization chambers (ICs) was employed to approximate the correction factors for beam quality produced from the difference in the sizes of the reference field and small fields.We measured the output factors using several cylindrical ICs and calculated the correction factors using a mathematical method similar to deconvolution; in the method, we modeled the variable and inhomogeneous energy fluence function within the chamber cavity. The parameters of the modeled function and the correction factors were determined by solving a developed system of equations as well as on the basis of the measurement data and the geometry of the chambers. Further, Monte Carlo (MC) computations were performed using the Monaco® treatment planning system to validate the proposed method.The determined correction factors () were comparable to the values derived from the MC computations performed using Monaco®. For example, for a 6 MV photon beam and a field size of 1  ×  1 cm2, was calculated to be for a PTW 31010 chamber and for a PTW 31016 chamber. On the other hand, the values determined from the MC computations were 1.121 and 1.031, respectively; the difference between the proposed method and the MC computation is less than 2%. In addition, we determined the values for PTW 30013, PTW 31010, PTW 31016, IBA FC23-C, and IBA CC13 chambers as well.We devised a method for determining from both the measurement of the output factors and model-based mathematical computation. The proposed method can be useful in case the MC simulation would not be applicable for the clinical settings.

  17. Comparison of pencil-type ionization chamber calibration results and methods between dosimetry laboratories.

    Science.gov (United States)

    Hourdakis, Costas J; Büermann, Ludwig; Ciraj-Bjelac, Olivera; Csete, Istvan; Delis, Harry; Gomola, Igor; Persson, Linda; Novak, Leos; Petkov, Ivailo; Toroi, Paula

    2016-01-01

    A comparison of calibration results and procedures in terms of air kerma length product, PKL, and air kerma, K, was conducted between eight dosimetry laboratories. A pencil-type ionization chamber (IC), generally used for computed tomography dose measurements, was calibrated according to three calibration methods, while its residual signal and other characteristics (sensitivity profile, active length) were assessed. The results showed that the "partial irradiation method" is the preferred method for the pencil-type IC calibration in terms of PKL and it could be applied by the calibration laboratories successfully. Most of the participating laboratories achieved high level of agreement (>99%) for both dosimetry quantities (PKL and K). Estimated relative standard uncertainties of comparison results vary among laboratories from 0.34% to 2.32% depending on the quantity, beam quality and calibration method applied. Detailed analysis of the assigned uncertainties have been presented and discussed.

  18. Low-level measurements of Ra-226/Rn-222 by pulse ionization chambers

    Science.gov (United States)

    El-Daoushy, Fand; Garcia-Tenorio, Rafael

    1988-10-01

    Characteristics of two ionization chambers have been studied and the chambers utilized for 226Ra/ 222Rn measurements for more than ten years. The results obtained show that coating of internal surfaces with a pure and thin Ag-layer enhances the background of ionization chambers in spite of some improvements at the early stages of operation. In addition to previously known parameters influencing the accuracy in routine measurements, new correction factors are suggested. 226Ra impurities in the body of ionization chambers are found to act not only as a permanent, but also as a temperature-dependent source of background. Earlier accuracies of 226Ra/ 222Rn measurements have been considerably improved by assuring long-term mechanical and thermal stability of the ionization chambers.

  19. A double faced ionization chamber for quality control in diagnostic radiology beams

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Jonas O., E-mail: josofisico@yahoo.com.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Av. Prof. Lineu Prestes, 2242, 05508-000, Sao Paulo (Brazil); Caldas, Linda V.E. [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Av. Prof. Lineu Prestes, 2242, 05508-000, Sao Paulo (Brazil)

    2012-07-15

    The development of new radiation detectors of low cost but with adequate materials is a very important task for countries that have to import ionization chambers such as Brazil. A special double faced ionization chamber was developed for use in conventional diagnostic radiology beams and computed tomography energy ranges. The results show that this new chamber present applicability in conventional diagnostic radiology and computed tomography quality control programs. - Highlights: Black-Right-Pointing-Pointer We constructed a double faced ionization chamber. Black-Right-Pointing-Pointer It was submitted to conventional diagnostic and computed tomography X-rays beams. Black-Right-Pointing-Pointer The results obtained showed good agreement with international standards. Black-Right-Pointing-Pointer This ionization chamber can be used in clinic quality control program.

  20. Evaluation of ozone generation and indoor organic compounds removal by air cleaners based on chamber tests

    Science.gov (United States)

    Yu, Kuo-Pin; Lee, Grace Whei-May; Hsieh, Ching-Pei; Lin, Chi-Chi

    2011-01-01

    Ozone can cause many health problems, including exacerbation of asthma, throat irritation, cough, chest ache, shortness of breath, and respiratory infections. Air cleaners are one of the sources of indoor ozone, and thus the evaluation of ozone generated by air cleaners is desired significant issue. Most evaluation methods proposed are based on chamber tests. However, the adsorption and desorption of ozone on the wall of test chamber and the deposition of ozone resulted from the surface reaction can influence the evaluation results. In this study, we developed a mass balance model that took the adsorption, desorption and deposition of ozone into consideration to evaluate the effective ozone emission rates of six selected air cleaners. The experiments were conducted in a stainless steel chamber with a volume of 11.3 m 3 at 25 °C and 60% relative humidity. The adsorption, desorption and deposition rate constants of ozone obtained by fitting the model to the experimental data were k a = 0.149 ± 0.052 m h -1, k d = 0.013 ± 0.007 h -1, and k r = 0.050 ± 0.020 h -1, respectively. The effective ozone emission rates of Air Cleaners No. 1, 2, and 3 ranged between 13,400-24,500 μg h -1, 7190-10,400 μg h -1, and 4880-6560 μg h -1, respectively, which were more stable than those of No.4, 5, and 6. The effective ozone emission rates of Air Cleaners No. 4, 5, and 6 increased with the time of operation which might be relevant to the decrease of ozone removal by the "aging" filter installed in these cleaners. The removal of toluene and formaldehyde by these six air cleaners were also evaluated and the clean air delivery rates (CADRs) of these two pollutants ranged from non-detectable to 0.42 ± 0.08 m 3 h -1, and from non-detectable to 0.75 ± 0.07 m 3 h -1, respectively. The CADRs showed an insignificant relationship with the effective ozone emission rates. Thus, the removal of toluene and formaldehyde might be resulted from the adsorption on the filters and the

  1. Calibration of ionization chamber for ¹⁸F and ⁶⁸Ga.

    Science.gov (United States)

    da Silva, Carlos J; de Oliveira, Estela M; Iwahara, A; Delgado, José U; Poledna, R; de Oliveira, Antônio E; Moreira, Denise S; da Silva, Ronaldo L; Gomes, Regio dos Santos; de Veras, Eduardo V

    2014-05-01

    In order to maintain the results of primary activity standardizations carried out in 2011 the LNMRI has determined the calibration factors for a pressurized 4π-ionization chamber for the nuclides (18)F and (68)Ga. This ionization chamber is coupled to a 6517A Keithley electrometer which is controlled by a homemade LabVIEW program. This paper will describe the main issues related to the calibration of an ionization chamber system for positron emitters and short half-life radionuclides such as timing, current measurement, background, decay, and (226)Ra check source measurements.

  2. a High Resolution Ionization Chamber for the SPIDER Fission Fragment Detector

    Science.gov (United States)

    Meierbachtol, K.; Tovesson, F.; Arnold, C. W.; Laptev, A. B.; Bredeweg, T. A.; Jandel, M.; Nelson, R. O.; White, M. C.; Hecht, A. A.; Mader, D.

    2014-09-01

    An ionization chamber for measuring the energy loss and kinetic energy of fragments produced through neutron-induced fission at the Los Alamos Neutron Science Center (LANSCE) has been designed as a component of the the new SPIDER detector. Design criteria included energy resolutions of <1% for high energy resolution and increased charge resolution. The ionization chamber will be combined with a high resolution time-of-flight detector to achieve fragment yield measurements with mass and nuclear charge resolutions of 1 amu and Z=1. The present status of the ionization chamber will be presented.

  3. Traceability of the ionization chambers calibrated at Kyushu regional center (I) for standard doses in medicine

    Energy Technology Data Exchange (ETDEWEB)

    Araki, Fujio; Noda, Hiroji; Higashida, Yoshiharu; Matsumoto, Masanori [Kumamoto Univ. (Japan). Coll. of Medical Science

    1997-12-01

    We investigated the traceability of the ionization chambers calibrated by the standard dosimeter with Kyushu regional center (I) for standard doses in medicine. Accuracy management of the ionization chambers of Kyushu regional center (I) has been maintained within 0.5% by intercomparison with that of the National Institute of Radiological Sciences (NIRS). The number of hospitals and the number of intercomparisons were 17 and 33 on an average per year, respectively. Accuracy of the ionization chambers of each hospital in recent years was less than 0.5% to the hospitals of 65-80% and less than 1.0% to those of 80-90%. (author)

  4. Determinations of the correction factors for small fields in cylindrical ionization chambers based on measurement and numerical calculation

    Science.gov (United States)

    Park, Kwangwoo; Choi, Wonhoon; Park, Sungho; Choi, Jin Hwa; Park, Suk Won; Bak, Jino

    2015-07-01

    We investigated the volume averaging effect for air-filled cylindrical ionization chambers to determine the correction factors in a small photon field for a given chamber. We measured output factors with several cylindrical ionization chambers, and by using a mathematical method similar to deconvolution, we modeled the non-constant and inhomogeneous exposure function in the cavity of the chamber. The parameters in the exposure function and the correction factors were determined by solving a system of equations that we had developed by using the measured data and the geometry of the given chamber. The correction factors (CFs) were very similar to those obtained from Monte Carlo (MC) simulations. For example, the CFs in this study were found to be 1.116 for PTW31010 and 1.0225 for PTW31016 while the CFs obtained from MC simulations were reported as being approximately between 1.17 and 1.20 for PTW31010 and between 1.02 and 1.06 for PTW31016 in a 6-MV photon beam of 1 × 1 cm2. Furthermore, the method of deconvolution combined with the MC result for the chamber's response function showed a similar CF for PTW 30013, which was reported as 2.29 and 1.54 for a 1 × 1 cm2 and a 1.5 × 1.5 cm2 field size, respectively. The CFs from our method were similar, 2.42 and 1.54. In addition, we report CFs for PTW30013, PTW31010, PTW31016, IBA FC23-C, and IBA CC13. As a consequence, we suggest the use of our method to measure the correct output factor by using the fact that an inhomogeneous exposure causes a volume averaging effect in the cavity of air-filled cylindrical ionization chamber. The result obtained by using our method is very similar to that obtained from MC simulations. The method we developed can easily be applied in clinics.

  5. On the Frisch-Grid signal in ionization chambers

    Energy Technology Data Exchange (ETDEWEB)

    Al-Adili, A. [EC-JRC - Institute for Reference Materials and Measurements, B-2440 Geel (Belgium); Division of Applied Nuclear Physics, Uppsala University, S-751 20 Uppsala (Sweden); Hambsch, F.-J., E-mail: Franz-Josef.HAMBSCH@ec.europa.eu [EC-JRC - Institute for Reference Materials and Measurements, B-2440 Geel (Belgium); Bencardino, R. [EC-JRC - Institute for Reference Materials and Measurements, B-2440 Geel (Belgium); Pomp, S. [Division of Applied Nuclear Physics, Uppsala University, S-751 20 Uppsala (Sweden); Oberstedt, S. [EC-JRC - Institute for Reference Materials and Measurements, B-2440 Geel (Belgium); Zeynalov, Sh. [JINR - Joint Institute for Nuclear Research, Dubna, R-141980 (Russian Federation)

    2012-04-11

    A recent theoretical approach concerning the grid-inefficiency (GI) problem in Twin Frisch-Grid Ionization Chambers was validated experimentally. The experimental verification focused on the induced signal on the anode plate. In this work the investigation was extended by studying the grid signal. The aim was to verify the grid-signal dependency on the grid inefficiency {sigma}. The measurements were made with fission fragments from {sup 252}Cf(sf), using two different grids, with 1 and 2 mm wire distances, leading to the GI values: {sigma}=0.031 and {sigma}=0.083, respectively. The theoretical grid signal was confirmed because the detected grid pulse-height distribution was smaller for the larger {sigma}. By applying the additive GI correction approach, the two grid pulse heights were consistent. In the second part of the work, the corrected grid signal was used to deduce emission angles of the fission fragments. It is inconvenient to treat the grid signal by means of conventional analogue electronics, because of its bipolarity. Therefore, the anode and grid signals were summed to create a unipolar, angle-dependent pulse height. Until now the so-called summing method has been the well-established approach to deduce the angle from the grid signal. However, this operation relies strongly on an accurate and stable calibration between the two summed signals. By application of digital-signal processing, the grid signal's bipolarity is no longer an issue. Hence one can bypass the intermediate summation step of the two different pre-amplifier signals, which leads to higher stability. In this work the grid approach was compared to the summing method in three cases: {sup 252}Cf(sf), {sup 235}U(n,f) and {sup 234}U(n,f). By using the grid directly, the angular resolution was found equally good in the first case but gave 7% and 20% improvements, respectively, in the latter cases.

  6. Study of the energy response of high pressure ionization chamber for high energy gamma-ray

    Institute of Scientific and Technical Information of China (English)

    HUA Zheng-Dong; XU Xun-Jiang; WANG Jian-Hua; LIU Shu-Dong; LI Jian-Ping

    2008-01-01

    The energy response calibration of the commonly used high pressure ionization chamber is very difficult to obtain when the gamma-ray energy is more than 3 MeV.In order to get the calibration of the higher part of the high pressure ionization chamber,we use the Fluka Monte Carlo program to perfclrm the energy response in both the spherical and the cylindrical high pressure ionization chamber which are full of argon gas.The results compared with prior study when the gamma-ray energy is less than 1.25 MeV.Our result of Monte Carlo calculation shows agreement with those obtained by measurement within the uncertainty of the respective methods.The calculation of this study is significant for the high pressure ionization chamber to measure the high energy gamma-ray.

  7. Monte CarIo SimuIation of PhysicaI Parameters for Air Kerma Measurement by Graphite Pancake Ionization Chamber%圆饼电离室空气比释动能物理参量的蒙特卡洛模拟

    Institute of Scientific and Technical Information of China (English)

    王坤; 李涛; 金孙均; 杨小元; 樊铁栓

    2016-01-01

    为建立基于圆饼电离室系统的60 Coγ射线空气比释动能基准装置,对辐射场及场中电离室的相关物理参量进行了蒙特卡洛模拟研究。通过BEAMnrc程序建立辐照器模型计算测量点处能谱和注量分布,使用EGSnrc计算圆饼电离室在辐射场中各物理参量。60 Coγ射线空气比释动能绝对测量装置通过蒙特卡洛模拟得到的相关物理参数合成不确定度为0.20豫,该结果与澳大利亚计量院同结构电离室的结果在不确定度范围内一致,与国家基准球-圆柱形电离室及球形电离室相比在不确定范围内符合。%In order to establish the air kerma primary standard based on a graphite pancake ionization chamber for 60 Co gamma rays,the radiation field and related physical parameters of the chamber are calculated by the Monte Carlo simulation method. The γ-ray energy spectra and fluence distributions are calculated by the model built by BEAMnrc code,the parameters of the graphite pancake ionization chamber in 60 Co γ-ray radiation filed are calculated by EGSnrc code. The combined standard uncertainty of the parameters of the chamber calculated by Monte Carlo method is 0. 20%,the results of simulation are accord with results of the same structural chamber from the ARPANSA in the region of the uncertainty. And the change of the values with the primary standard based on a sphere-cylindrical graphite ionization chamber is under expected.

  8. Matrix:. AN Innovative Pixel Ionization Chamber for On-Line Beam Monitoring in Hadrontherapy

    Science.gov (United States)

    Braccini, S.; Pitta', G.; Donetti, M.; Cirio, R.; La Rosa, A.; Garella, M. A.; Giordanengo, S.; Marchetto, F.; Peroni, C.

    2006-04-01

    The control of intensity, position and shape of clinical beams are key issues in the treatment of tumours using hadron beams, especially in the case of active dose distribution systems. For this purpose an innovative pixel ionization chamber, named MATRIX, has been designed, constructed and tested. The chamber is conceived to be located very near the patient to precisely monitor the beam parameters used to verify the treatment planning specifications. MATRIX operates in air and is characterized by a 21 × 21 cm2 sensitive area subdivided in 1024 pixels of 6.5 × 6.5 mm2. To minimize the amount of material crossed by the beam, the anode is made of a 50 μm kapton foil, with a deposit of 17 μm copper on each side. A very sensitive electronics is used for the readout, based on a dedicated chip. In this paper the construction of the chamber and the very positive results of the first beam tests are described.

  9. On line high dose static position monitoring by ionization chamber detector for industrial gamma irradiators

    Energy Technology Data Exchange (ETDEWEB)

    Rodrigues, Ary A. [Universidade Estadual de Londrina-Depto de Fisica, Rodovia Celso Garcia Cid, km 38, 086051-990 Londrina (Brazil); Vieira, Jose M. [Instituto de Pesquisas Energeticas e Nucleares-IPEN/CNEN-SP, Prof. Lineu Prestes, 2242-Cidade Universitaria, 05508-900 Sao Paulo (Brazil); Hamada, Margarida M. [Instituto de Pesquisas Energeticas e Nucleares-IPEN/CNEN-SP, Prof. Lineu Prestes, 2242-Cidade Universitaria, 05508-900 Sao Paulo (Brazil)], E-mail: mmhamada@ipen.br

    2010-04-15

    A 1 cm{sup 3} cylindrical ionization chamber was developed to measure high doses on line during the sample irradiation in static position, in a {sup 60}Co industrial plant. The developed ionization chamber showed to be suitable for use as a dosimeter on line. A good linearity of the detector was found between the dose and the accumulated charge, independently of the different dose rates caused by absorbing materials.

  10. Experimental and Monte Carlo evaluation of an ionization chamber in a {sup 60}Co beam

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana P.; Neves, Lucio Pereira, E-mail: anapaula.perini@ufu.br [Universidade Federal de Uberlandia (INFIS/UFU), MG (Brazil). Instituto de Fisica; Santos, William S.; Caldas, Linda V.E. [Instituto de Pesquisas Energeticas e Nucleres (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    Recently a special parallel-plate ionization chamber was developed and characterized at the Instituto de Pesquisas Energeticas e Nucleares. The operational tests presented results within the recommended limits. In order to determine the influence of some components of the ionization chamber on its response, Monte Carlo simulations were carried out. The experimental and simulation results pointed out that the dosimeter evaluated in the present work has favorable properties to be applied to {sup 60}Co dosimetry at calibration laboratories. (author)

  11. On line high dose static position monitoring by ionization chamber detector for industrial gamma irradiators.

    Science.gov (United States)

    Rodrigues, Ary A; Vieira, Jose M; Hamada, Margarida M

    2010-01-01

    A 1 cm(3) cylindrical ionization chamber was developed to measure high doses on line during the sample irradiation in static position, in a (60)Co industrial plant. The developed ionization chamber showed to be suitable for use as a dosimeter on line. A good linearity of the detector was found between the dose and the accumulated charge, independently of the different dose rates caused by absorbing materials.

  12. Experimental and Monte Carlo evaluation of an ionization chamber in a 60Co beam

    Science.gov (United States)

    Perini, A. P.; Neves, L. P.; Santos, W. S.; Caldas, L. V. E.

    2016-07-01

    Recently a special parallel-plate ionization chamber was developed and characterized at the Instituto de Pesquisas Energeticas e Nucleares. The operational tests presented results within the recommended limits. In order to determine the influence of some components of the ionization chamber on its response, Monte Carlo simulations were carried out. The experimental and simulation results pointed out that the dosimeter evaluated in the present work has favorable properties to be applied to 60Co dosimetry at calibration laboratories.

  13. Pencil beam proton radiography using a multilayer ionization chamber

    Science.gov (United States)

    Farace, Paolo; Righetto, Roberto; Meijers, Arturs

    2016-06-01

    A pencil beam proton radiography (PR) method, using a commercial multilayer ionization chamber (MLIC) integrated with a treatment planning system (TPS) was developed. A Giraffe (IBA Dosimetry) MLIC (±0.5 mm accuracy) was used to obtain pencil beam PR by delivering spots uniformly positioned at a 5.0 mm distance in a 9  ×  9 square of spots. PRs of an electron-density (with tissue-equivalent inserts) phantom and a head phantom were acquired. The integral depth dose (IDD) curves of the delivered spots were computed by the TPS in a volume of water simulating the MLIC, and virtually added to the CT at the exit side of the phantoms. For each spot, measured and calculated IDD were overlapped in order to compute a map of range errors. On the head-phantom, the maximum dose from PR acquisition was estimated. Additionally, on the head phantom the impact on the range errors map was estimated in case of a 1 mm position misalignment. In the electron-density phantom, range errors were within 1 mm in the soft-tissue rods, but greater in the dense-rod. In the head-phantom the range errors were  -0.9  ±  2.7 mm on the whole map and within 1 mm in the brain area. On both phantoms greater errors were observed at inhomogeneity interfaces, due to sensitivity to small misalignment, and inaccurate TPS dose computation. The effect of the 1 mm misalignment was clearly visible on the range error map and produced an increased spread of range errors (-1.0  ±  3.8 mm on the whole map). The dose to the patient for such PR acquisitions would be acceptable as the maximum dose to the head phantom was  <2cGyE. By the described 2D method, allowing to discriminate misalignments, range verification can be performed in selected areas to implement an in vivo quality assurance program.

  14. Beam Tests of Ionization Chambers for the NuMI Neutrino Beam

    CERN Document Server

    Zwaska, R M; Kopp, S E; Proga, M; Erwin, A R; Ping, H; Velissaris, C; Harris, D A; Naples, D; McDonald, J; Northacker, D; Diwan, M V; Viren, B M; Hall, James; Kopp, Sacha E.; Proga, Marek; Erwin, Albert R.; Ping, Huican; Velissaris, Christos; Harris, Deborah A.; Naples, Donna; Donald, Jeffrey Mc; Northacker, David; Diwan, Milind; Viren, Brett

    2003-01-01

    We have conducted tests at the Fermilab Booster of ionization chambers to be used as monitors of the NuMI neutrino beamline. The chambers were exposed to proton fluxes of up to 10$^{12}$ particles/cm$^2$/1.56$\\mu$s. We studied space charge effects which can reduce signal collection from the chambers at large charged particle beam intensities.

  15. Pre-evaluation of an ionization chamber for clinical radiotherapy dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Neves, Lucio P.; Perini, Ana P.; Xavier, Marcos; Caldas, Linda V.E., E-mail: mxavier@ipen.b, E-mail: lcaldas@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Khoury, Helen J., E-mail: khoury@ufpe.b [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear

    2011-07-01

    This work presents some pre-operational tests for characterization of a new homemade ionization chamber developed at the Calibration Laboratory of Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP). This chamber was designed for use in radiotherapy dosimetry. To study the utilization of this chamber in radiotherapy, some tests were undertaken: short- and medium-term stabilities, saturation curve, recombination loss, polarity effect and leakage current. All results obtained in these tests were within the international recommendations. (author)

  16. Fast-neutron spectrometry using a ³He ionization chamber and digital pulse shape analysis.

    Science.gov (United States)

    Chichester, D L; Johnson, J T; Seabury, E H

    2012-08-01

    Digital pulse shape analysis (dPSA) has been used with a Cuttler-Shalev type (3)He ionization chamber to measure the fast-neutron spectra of a deuterium-deuterium electronic neutron generator, a bare (252)Cf spontaneous fission neutron source, and of the transmitted fast neutron spectra of a (252)Cf source attenuated by water, graphite, liquid nitrogen, and magnesium. Rise-time dPSA has been employed using the common approach for analyzing n +(3)He→(1)H+(3)H ionization events and improved to account for wall-effect and pile-up events, increasing the fidelity of these measurements. Simulations have been performed of the different experimental arrangements and compared with the measurements, demonstrating general agreement between the dPSA-processed fast-neutron spectra and predictions. The fast-neutron resonance features of the attenuation cross sections of the attenuating materials are clearly visible within the resolution limits of the electronics used for the measurements, and the potential applications of high-resolution fast-neutron spectrometry for nuclear nonproliferation and safeguards measurements are discussed.

  17. A boron-coated ionization chamber for ultra-cold neutron detection

    Energy Technology Data Exchange (ETDEWEB)

    Salvat, D.J., E-mail: dsalvat@indiana.edu [Indiana University Center for Exploration of Energy and Matter, Bloomington, IN 47408 (United States); Morris, C.L.; Wang, Z. [Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Adamek, E.R. [Indiana University Center for Exploration of Energy and Matter, Bloomington, IN 47408 (United States); Bacon, J. [Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Hickerson, K.P. [California Institute of Technology, Pasadena, CA 91125 (United States); Hoagland, J.; Holley, A.T. [North Carolina State University, Raleigh, NC 27695 (United States); Liu, C.-Y. [Indiana University Center for Exploration of Energy and Matter, Bloomington, IN 47408 (United States); Makela, M.; Ramsey, J. [Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); Reid, A. [North Carolina State University, Raleigh, NC 27695 (United States); Rios, R. [Idaho State University, Pocatello, ID 83209 (United States); Saunders, A.; Sjue, S.K.L. [Los Alamos National Laboratory, Los Alamos, NM 87544 (United States); VornDick, B.; Young, A.R. [North Carolina State University, Raleigh, NC 27695 (United States)

    2012-11-01

    The design and performance of a boron-coated ionization chamber for the detection of ultra-cold neutrons (UCN) are presented. We detect UCN from the solid deuterium-based UCN source at the Los Alamos Neutron Science Center. Our results indicate comparable efficiency to {sup 3}He ionization chambers and proportional counters currently used at the UCN source. In addition, the ion chamber is used to detect thermal neutrons; a comparison of the thermal neutron and UCN pulse-height spectra indicates that UCN mostly capture near the layer surface.

  18. Performance of a parallel plate ionization chamber in beta radiation dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Antonio, Patricia L.; Caldas, Linda V.E., E-mail: patrilan@ipen.b, E-mail: lcaldas@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    A homemade parallel plate ionization chamber with graphite collecting electrode, and developed for use in mammography beams, was tested in relation to its usefulness in beta radiation dosimetry at the Calibration Laboratory of IPEN. Characterization tests of this ionization chamber were performed, using the Sr-90 + Y-90, Kr-85 and Pm-147 sources of a beta secondary standard system. The results of saturation, leakage current, stabilization time, response stability, linearity, angular dependence, and calibration coefficients are within the recommended limits of international recommendations that indicate that this chamber may be used for beta radiation dosimetry. (author)

  19. The non-uniformity correction factor for the cylindrical ionization chambers in dosimetry of an HDR 192Ir brachytherapy source

    Directory of Open Access Journals (Sweden)

    Majumdar Bishnu

    2006-01-01

    Full Text Available The aim of this study is to derive the non-uniformity correction factor for the two therapy ionization chambers for the dose measurement near the brachytherapy source. The two ionization chambers of 0.6 cc and 0.1 cc volume were used. The measurement in air was performed for distances between 0.8 cm and 20 cm from the source in specially designed measurement jig. The non-uniformity correction factors were derived from the measured values. The experimentally derived factors were compared with the theoretically calculated non-uniformity correction factors and a close agreement was found between these two studies. The experimentally derived non-uniformity correction factor supports the anisotropic theory.

  20. Determination of Correction Factors for Small Field Based on Measurement and Numerical Calculation using Cylindrical Ionization Chambers

    CERN Document Server

    Park, Kwangwoo; Park, Sungho; Choi, Jin Hwa; Park, Suk Won; Bak, Jino

    2015-01-01

    We studied the investigation of volume averaging effect for air-filled cylindrical ionization chambers to determine correction factors in small photon field for the given chamber. As a method, we measured output factors using several cylindrical ionization chambers and calculated with mathematical method similar to deconvolution in which we modeled non-constant and inhomogeneous exposure function in the cavity of chamber. The parameters in exposure function and correction factors were determined by solving a system of equations we developed with measurement data and geometry of the given chamber. Correction factors (CFs) we had found are very similar to that from Monte Carlo (MC) simulation. For example, CFs in this study were computed as 1.116 for PTW31010, and 1.0225 for PTW31016, while CFs from MC were reported as approximately between 1.17 and 1.20 for PTW31010, and between 1.02 and 1.06 for PTW31016 in of 6MV photon beam . Furthermore, the result from the method of deconvolution combined with MC for cham...

  1. Elements Discrimination in the Study of Super-Heavy Elements using an Ionization Chamber

    CERN Document Server

    Wieloch, A; Péter, J; Lojek, K; Alamanos, N; Amar, N; Anne, R; Angélique, J C; Auger, G; Dayras, R; Drouart, A; Fontbonne, J M; Gillibert, A; Grévy, S; Hanappe, F; Hannachi, F; Hue, R; Khouaja, A; Legou, T; López-Martens, A; Liénard, E; Manduci, L; De Oliveira-Santos, F; Politi, G; Saint-Laurent, M G; Stodel, C; Stuttgé, L; Tillier, J; De Tourreil, R; Villari, A C C; Wieleczko, J P

    2004-01-01

    Dedicated ionization chamber was built and installed to measure the energy loss of very heavy nuclei at 2.7 MeV/u produced in fusion reactions in inverse kinematics (beam of 208Pb). After going through the ionization chamber, products of reactions on 12C, 18O targets are implanted in a Si detector. Their identification through their alpha decay chain is ambiguous when their half-life is short. After calibration with Pb and Th nuclei, the ionization chamber signal allowed us to resolve these ambiguities. In the search for rare super-heavy nuclei produced in fusion reactions in inverse or symmetric kinematics, such a chamber will provide direct information on the nuclear charge of each implanted nucleus.

  2. A twin-type airflow pulse ionization chamber for continuous alpha-radioactivity monitoring in atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Kada, Wataru, E-mail: kada@nf.eie.eng.osaka-u.ac.j [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan); Dwaikat, Nidal; Datemichi, Jun; Sato, Fuminobu; Murata, Isao; Kato, Yushi; Iida, Toshiyuki [Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita, Osaka 565-0871 (Japan)

    2010-10-15

    A simple and inexpensive twin-type airflow pulse ionization chamber was developed for the continuous monitoring of alpha-radioactivity in atmosphere under high humidity condition. The symmetrical structure of the twin-type ionization chamber was effective in the improvement of the ratio of signal to noise in the measurement of pulses induced by alpha-rays. Outdoor alpha-ray measurement was well performed with this ionization chamber by applying sufficiently high bias voltage to the electrodes, except for at very high humidity conditions. It was confirmed that the declination of the counting efficiency due to wetting was easily recovered by the dry-up of the inside of the chamber. Alpha-radioactivity from radon and other alpha-emitting radionuclide in atmosphere was satisfactorily monitored by the detector.

  3. [Influence on measurements of pre-irradiation due to differences in ionization chamber shape or frequency in use].

    Science.gov (United States)

    Shimono, Tetsunori; Nambu, Hidekazu; Matsubara, Kosuke; Koshida, Kichiro; Gomi, Tsutomu

    2012-01-01

    Ionization chamber measurements in radiation therapy should be repeatedly performed until a stable reading is obtained. Ionization chambers exhibit a response which depends on time elapsed since the previous irradiation. In this study, we investigated the response of a set of two Farmer-style, one Plane parallel, and seven small ionization chambers, which are exposed to 4, 6, 10, and 14 MV. The results show that Farmer-style and Plane parallel ionization chambers settle quickly within 9-20 min. On the other hand, small ionization chambers exhibit settling times of 12-33 min for 6, 10, and 14 MV. It will take longer for a settling time of 4 MV. The settling time showed time dependent irradiation. The first reading was up to 0.76% lower in the Farmer-style and Plane parallel ionization chambers. The small ionization chambers had a 2.60% lower first reading and more gradual response in reaching a stable reading. In this study, individual ionization chambers can vary significantly in their settling behavior. Variation of the responses on ionization chambers were confirmed not only when radiation was not used for a week but also when it was halted for a month. Pre-irradiation of small ionization chambers is clearly warranted for eliminating inadvertent error in the calibration of radiation beams.

  4. Heat Transfer Model with Two Heat Transfer Coefficients Along a Multiperforated Plate--Application to Combustion Chamber Wall Cooling

    Institute of Scientific and Technical Information of China (English)

    Brice Pêtre; Eva Dorignac; Jean Jacques Vullierme

    2003-01-01

    Walls'cooling of aeronautic propeller combustion chamber is performed with the injection, through the combustion chamber wall, of a part of the air coming from compressors placed upstream. Measurements of the wall thermal fields are made by infrared thermography along the injection wall. This injection wall is pierced by 9 rows of 8 holes (α=90°) in staggered configuration (p/D=s/D=6). We propose a model using two heat transfer coefficients to represent the convective exchanges. The results are non-dimensioned and presented in comparison with the case without holes. The use of this model allows us to define 4 zones. Those 4 zones exist for the 5 blowing rates.

  5. Determination of small-field correction factors for cylindrical ionization chambers using a semiempirical method

    Science.gov (United States)

    Park, Kwangwoo; Bak, Jino; Park, Sungho; Choi, Wonhoon; Park, Suk Won

    2016-02-01

    A semiempirical method based on the averaging effect of the sensitive volumes of different air-filled ionization chambers (ICs) was employed to approximate the correction factors for beam quality produced from the difference in the sizes of the reference field and small fields. We measured the output factors using several cylindrical ICs and calculated the correction factors using a mathematical method similar to deconvolution; in the method, we modeled the variable and inhomogeneous energy fluence function within the chamber cavity. The parameters of the modeled function and the correction factors were determined by solving a developed system of equations as well as on the basis of the measurement data and the geometry of the chambers. Further, Monte Carlo (MC) computations were performed using the Monaco® treatment planning system to validate the proposed method. The determined correction factors (k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} ) were comparable to the values derived from the MC computations performed using Monaco®. For example, for a 6 MV photon beam and a field size of 1  ×  1 cm2, k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} was calculated to be 1.125 for a PTW 31010 chamber and 1.022 for a PTW 31016 chamber. On the other hand, the k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} values determined from the MC computations were 1.121 and 1.031, respectively; the difference between the proposed method and the MC computation is less than 2%. In addition, we determined the k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} values for PTW 30013, PTW 31010, PTW 31016, IBA FC23-C, and IBA CC13 chambers as well. We devised a method for determining k{{Q\\text{msr}},Q}{{f\\text{smf}}, {{f}\\text{ref}}} from both the measurement of the output factors and model-based mathematical computation. The proposed method can be useful in case the MC simulation would not be applicable for the clinical settings.

  6. Backscattered radiation into a transmission ionization chamber: measurement and Monte Carlo simulation.

    Science.gov (United States)

    Yoshizumi, Maíra T; Yoriyaz, Hélio; Caldas, Linda V E

    2010-01-01

    Backscattered radiation (BSR) from field-defining collimators can affect the response of a monitor chamber in X-radiation fields. This contribution must be considered since this kind of chamber is used to monitor the equipment response. In this work, the dependence of a transmission ionization chamber response on the aperture diameter of the collimators was studied experimentally and using a Monte Carlo (MC) technique. According to the results, the BSR increases the chamber response of over 4.0% in the case of a totally closed collimator and 50 kV energy beam, using both techniques. The results from Monte Carlo simulation confirm the validity of the simulated geometry.

  7. Characterization of Ion-Acoustic Wave Reflection Off A Plasma Chamber Wall

    Science.gov (United States)

    Berumen, Jorge; Chu, Feng; Hood, Ryan; Mattingly, Sean; Rogers, Anthony; Skiff, Fred

    2015-11-01

    We present an experimental characterization of the ion acoustic wave reflection coefficient off a plasma chamber wall. The experiment is performed in a cylindrical, magnetized, singly-ionized Argon inductively-coupled gas discharge plasma that is weakly collisional with typical conditions: n ~ 1010cm-3 Te ~ 3 eV and B ~ 1 kG. The main diagnostics are laser-induced fluorescence and Langmuir probe measurements. A survey of the ion velocity distribution function's zeroth and first order as well as density fluctuations at different wave excitation frequencies is obtained. Analysis of the reflection coefficient's dependence on the phase velocity and frequency of the wave is done through the characterization of waves utilizing Case-Van Kampen modes and the use of Morrison's G-transform. This research is supported by the Department of Energy under grant No. DOE DE-FG02-99ER54543.

  8. Evaluation of a tissue equivalent ionization chamber in X-ray beams

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana Paula; Neves, Lucio Pereira; Santos, William de Souza; Caldas, Linda V.E., E-mail: aperini@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Frimaio, Audrew [Seal Technology Ind. Com. Ltda, Sao Paulo, SP (Brazil); Costa, Paulo R. [Universidade de Sao Paulo (USP/IF), Sao Paulo, SP (Brazil). Inst. de Fisica

    2014-07-01

    Tissue equivalent materials present a variety of uses, including routine quality assurance and quality control programs in both diagnostic and therapeutic physics. They are frequently used in research facilities to measure doses delivered to patients undergoing various clinical procedures. This work presents the development and evaluation of a tissue equivalent ionization chamber, with a sensitive volume of 2.3 cm{sup 3}, for routine use in X-rays beams. This ionization chamber was developed at the Calibration Laboratory/IPEN. The new tissue equivalent material was developed at the Physics Institute of the University of Sao Paulo. In order to evaluate the dosimetric performance of the new ionization chamber, several tests described by international standards were undertaken, and all results were within the recommended limits. (author)

  9. Initial test results of an ionization chamber shower detector for a LHC luminosity monitor

    CERN Document Server

    Datte, P S; Haguenauer, Maurice; Manfredi, P F; Manghisoni, M; Millaud, J E; Placidi, Massimo; Ratti, L; Riot, V J; Schmickler, Hermann; Speziali, V; Traversi, G; Turner, W C

    2003-01-01

    A novel segmented multigap pressurized gas ionization chamber is being developed for optimization of the luminosity of the Large Hadron Collider (LHC). The ionization chambers are to be installed in the front quadrupole and 0 degrees neutral particle absorbers in the high luminosity interaction regions (IRs) and sample the energy deposited near the maxima of the hadronic/electromagnetic showers in these absorbers. The ionization chambers are instrumented with low noise, fast pulse-shaping electronics to be capable of resolving individual bunch crossings at 40 MHz. In this paper, we report the initial results of our second test of this instrumentation in a super proton synchrotron (SPS) external proton beam. Single 300 GeV protons are used to simulate the hadronic/electromagnetic showers produced by the forward collision products from the interaction regions of the LHC. The capability of instrumentation to measure the luminosity of individual bunches in a 40 MHz bunch train is demonstrated. (10 refs) .

  10. Calibration of KRISS reference ionization chamber for key comparison of (99m)Tc measurement.

    Science.gov (United States)

    Lee, Jong-Man; Lee, K B; Lee, S H; Park, Tae Soon

    2012-09-01

    KRISS, as the national metrology institute of Korea, has used a reference ionization chamber system to certify the activity of (99m)Tc aqueous sources, but could only recently participate in a comparison exercise by the BIPM (BIPM.RI(II)-K4.Tc-99m) to secure the international equivalence of (99m)Tc radioactivity measurement by way of the BIPM transfer instrument (SIRTI). The KRISS ionization chamber system was calibrated about 100 days before the comparison with a (99m)Tc solution source standardized by the 4πβ(LS)-γ(NaI(Tl)) coincidence counting method. During the comparison, beginning with a higher activity mother solution, the KRISS ionization chamber measured its specific activity without a dilution. The activity of a diluted-solution source was measured by the SIRTI at the same time.

  11. Development of an Ionization Chamber for the SPIDER Fission Fragment Detector

    Science.gov (United States)

    Meierbachtol, K.; Tovesson, F.; Arnold, C. W.; Laptev, A. B.; Bredeweg, T. A.; Jandel, M.; Nelson, R. O.; White, M. C.

    2014-05-01

    The ionization chamber component of the SPIDER detector has been designed to measure energy loss and kinetic energy of fragments produced through neutron-induced fission with energy resolutions of <1% and a time-dependent signal collection. Important design elements implemented are an axial configuration of the electrodes for improved energy loss and measurement and a thin silicon nitride entrance window to minimize both energy loss and energy straggling of the incoming fragments. High energy resolution and improved charge resolution from the ionization chamber are combined with the high precision of the upstream time-of-flight component of SPIDER to achieve resolutions in mass and nuclear charge of 1 AMU and Z=1. A discussion of the present resolution capabilities of the ionization chamber will be presented.

  12. Dosimetric characterization of a large area pixel-segmented ionization chamber.

    Science.gov (United States)

    Amerio, S; Boriano, A; Bourhaleb, F; Cirio, R; Donetti, M; Fidanzio, A; Garelli, E; Giordanengo, S; Madon, E; Marchetto, F; Nastasi, U; Peroni, C; Piermattei, A; Sanz Freire, C J; Sardo, A; Trevisiol, E

    2004-02-01

    A pixel-segmented ionization chamber has been designed and built by Torino University and INFN. The detector features a 24 x 24 cm2 active area divided in 1024 independent cylindrical ionization chambers and can be read out in 500 micros without introducing dead time; the digital charge quantum can be adjusted between 100 fC and 800 fC. The sensitive volume of each single ionization chamber is 0.07 cm3. The purpose of the detector is to ease the two-dimensional (2D) verifications of fields with complex shapes and large gradients. The detector was characterized in a PMMA phantom using 60Co and 6 MV x-ray photon beams. It has shown good signal linearity with respect to dose and dose rate to water. The average sensitivity of a single ionization chamber was 2.1 nC/Gy, constant within 0.5% over one month of daily measurements. Charge collection efficiency was 0.985 at the operating polarization voltage of 400 V and 3.5 Gy/min dose rate. Tissue maximum ratio and output factor have been compared with a Farmer ionization chamber and were found in good agreement. The dose profiles have been compared with the ones obtained with an ionization chamber in water phantom for the field sizes supplied by a 3D-Line dynamic multileaf collimator. These results show that this detector can be used for 2D dosimetry of x-ray photon beams, supplying a good spatial resolution and sensibly reducing the time spent in dosimetric verification of complex radiation fields.

  13. Influence of the radioactive source position inside the well-type ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Kuahara, L.T.; Correa, E.L.; Potiens, M.P.A., E-mail: liliankuahara@usp.br [Instituto de Pesquisas Energeticas e Nucleres (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    The activimeter, instrument used in radionuclide activity measurement, consists primarily of a well type ionization chamber coupled to a special electronic device. Its response, after calibration, is shown in activity units (Becquerel or Curie). The goal of this study is to verify radioactive source position influence over activity measured by this instrument. Radioactive sources measurements were made at different depths inside the ionization chamber well. Results showed maximum variation of -23 %, -28 % and -15 % for {sup 57}Co, {sup 133}Ba and {sup 137}Cs, respectively. (author)

  14. Update of NIST half-life results corrected for ionization chamber source-holder instability.

    Science.gov (United States)

    Unterweger, M P; Fitzgerald, R

    2014-05-01

    As reported at the ICRM 2011, it was discovered that the source holder used for calibrations in the NIST 4πγ ionization chamber (IC) was not stable. This has affected a large number of half-life measurement results previously reported and used in compilations of nuclear data. Corrections have been made on all of the half-life data based on the assumption that the changes to the ionization chamber response were gradual. The corrections are energy dependent and therefore radionuclide specific. This presentation will review our results and present the recommended changes in half-life values and/or uncertainties.

  15. Construction of a fast ionization chamber for high-rate particle identification

    Energy Technology Data Exchange (ETDEWEB)

    Chae, K.Y., E-mail: kchae@skku.edu [Department of Physics, Sungkyunkwan University, Suwon 440-746 (Korea, Republic of); Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Ahn, S. [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States); Bardayan, D.W. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Chipps, K.A. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States); Department of Physics, Colorado School of Mines, Golden, CO 80401 (United States); Manning, B. [Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States); Pain, S.D. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Peters, W.A. [Oak Ridge Associated Universities, Oak Ridge, TN 37831 (United States); Schmitt, K.T. [Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996 (United States); Smith, M.S. [Physics Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831 (United States); Strauss, S.Y. [Department of Physics, University of Notre Dame, Notre Dame, IN 46556 (United States); Department of Physics and Astronomy, Rutgers University, Piscataway, NJ 08854 (United States)

    2014-07-01

    A new gas-filled ionization chamber for high count rate particle identification has been constructed and commissioned at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). To enhance the response time of the ionization chamber, a design utilizing a tilted entrance window and tilted electrodes was adopted, which is modified from an original design by Kimura et al. [1]. A maximum counting rate of ∼700,000 particles per second has been achieved. The detector has been used for several radioactive beam measurements performed at the HRIBF.

  16. Performance of three pencil-type ionization chambers (10 cm) in computed tomography standard beams

    Science.gov (United States)

    de Castro, Maysa C.; Xavier, Marcos; Caldas, Linda V. E.

    2016-07-01

    The use of computed tomography (CT) has increased over the years, thus generating a concern about the doses received by patients undergoing this procedure. Therefore, it is necessary to perform routinely beam dosimetry with the use of a pencil-type ionization chamber. This detector is the most utilized in the procedures of quality control tests on this kind of equipment. The objective of this work was to perform some characterization tests in standard CT beams, as the saturation curve, polarity effect, ion collection efficiency and linearity of response, using three ionization chambers, one commercial and two developed at the IPEN.

  17. Determination of (137)Cs half-life with an ionization chamber.

    Science.gov (United States)

    Juget, Frédéric; Nedjadi, Youcef; Buchillier, Thierry; Bochud, François; Bailat, Claude

    2016-12-01

    The half-life of (137)Cs was measured with an ionization chamber by following the decay of 5 sources over a 30 years period between 1983 and 2013. The ratio between the ionization chamber current for the cesium sources and (226)Ra source was used for the half-life calculation. The value found for the (137)Cs half-life is 10,955.2±10.7 days, where the uncertainty evaluation combines type A and B for one standard deviation.

  18. Construction of a fast ionization chamber for high-rate particle identification

    Science.gov (United States)

    Chae, K. Y.; Ahn, S.; Bardayan, D. W.; Chipps, K. A.; Manning, B.; Pain, S. D.; Peters, W. A.; Schmitt, K. T.; Smith, M. S.; Strauss, S. Y.

    2014-07-01

    A new gas-filled ionization chamber for high count rate particle identification has been constructed and commissioned at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). To enhance the response time of the ionization chamber, a design utilizing a tilted entrance window and tilted electrodes was adopted, which is modified from an original design by Kimura et al. [1]. A maximum counting rate of ~700,000 particles per second has been achieved. The detector has been used for several radioactive beam measurements performed at the HRIBF.

  19. Performance of three pencil-type ionization chambers (10 cm) in computed tomography standard beams

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Maysa C. de; Xavier, Marcos; Caldas, Linda V.E., E-mail: mcastro@ipen.br, E-mail: mxavier@ipen.br, E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleres (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    The use of computed tomography (CT) has increased over the years, thus generating a concern about the doses received by patients undergoing this procedure. Therefore, it is necessary to perform routinely beam dosimetry with the use of a pencil-type ionization chamber. This detector is the most utilized in the procedures of quality control tests on this kind of equipment. The objective of this work was to perform some characterization tests in standard CT beams, as the saturation curve, polarity effect, ion collection efficiency and linearity of response, using three ionization chambers, one commercial and two developed at the IPEN. (author)

  20. A ΔE-E Telescope with Ionization Chamber Used in Excitation Function Measurement

    Institute of Scientific and Technical Information of China (English)

    LiSonglin; WangQi; DongYuchuan; XuHuagen; ChenRuofu

    2003-01-01

    A thorough study of excitation function in dissipative heavy ion collision requires the identification of the nuclear charge number Z of the reaction products. For this purpose, a special designed ΔE-E telescope is employed, which consists of a gas filled ionization chamber to detect the energy loss and a position sensitive semiconductor Si detector (300μm in thickness and 8 mm×45 mm in active area) as the residual energy detector. The ionization chamber with a sensitive length of about 60 mm, is divided into two parts of ΔE1 and ΔE2, each with length of 30 mm. The trajectory of the incident particles is parallel to the direction of the electric field in the ionization chamber. The anodes of ΔE1 and ΔE2 are realized through the rectangular empty metallic frames. In order to collect ionized charge produced by the incident particle inside the ionization chamber effectively, two equipotential frame-shape electrodes were placed on both sides of each anode, to form a strong electric focused field toward the anode. The advantages of this type of the detector arc as follows: (1)lower energy detection threshold; (2) wide dynamical range both for the light particles and the heavy fragments;(3) larger solid angle coverage with a relatively smaller detector size based on the position information from the Si detector.

  1. Comparison of experimental and calculated calibration coefficients for a high sensitivity ionization chamber.

    Science.gov (United States)

    Amiot, M N; Mesradi, M R; Chisté, V; Morin, M; Rigoulay, F

    2012-09-01

    The response of a Vacutec 70129 ionization chamber was calculated using the PENELOPE-2008 Monte Carlo code and compared to experimental data. The filling gas mixture composition and its pressure have been determined using IC simulated response adjustment to experimental results. The Monte Carlo simulation revealed a physical effect in the detector response to photons due to the presence of xenon in the chamber. A very good agreement is found between calculated and experimental calibration coefficients for 17 radionuclides.

  2. Ionization chambers for monitoring in high-intensity charged particle beams

    CERN Document Server

    McDonald, J; Viren, B; Diwan, M; Erwin, A R; Naples, D; Ping, H

    2003-01-01

    Radiation-hard ionization chambers were tested using an intense electron beam from the accelerator test facility at the Brookhaven National Laboratory. The detectors were designed to be used as the basic element for monitoring muons in the Main Injector Neutrino beamline at the Fermi National Accelerator Laboratory. Measurements of linearity of response, voltage dependence, and the onset of ionization saturation as a function of gap voltage were performed.

  3. A convolution model for obtaining the response of an ionization chamber in static non standard fields

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez-Castano, D. M.; Gonzalez, L. Brualla; Gago-Arias, M. A.; Pardo-Montero, J.; Gomez, F.; Luna-Vega, V.; Sanchez, M.; Lobato, R. [Radiation Physics Laboratory, Universidad de Santiago de Compostela, 15782 (Spain) and Dpto de Fisica de Particulas, Universidad de Santiago de Compostela, 15782 (Spain); Servicio de Radiofisica ERESA, Consorcio Hospital General Universitario de Valencia, 46014 (Spain); Dpto de Fisica de Particulas, Universidad de Santiago de Compostela, 15782 (Spain); Radiation Physics Laboratory, Universidad de Santiago de Compostela, 15782 Spain and Dpto de Fisica de Particulas, Universidad de Santiago de Compostela, 15782 (Spain); Servicio de Radiofisica y Proteccion Radiologica, Hospital Clinico Universitario de Santiago, Santiago de Compostela, 15782 (Spain)

    2012-01-15

    Purpose: This work contains an alternative methodology for obtaining correction factors for ionization chamber (IC) dosimetry of small fields and composite fields such as IMRT. The method is based on the convolution/superposition (C/S) of an IC response function (RF) with the dose distribution in a certain plane which includes chamber position. This method is an alternative to the full Monte Carlo (MC) approach that has been used previously by many authors for the same objective. Methods: The readout of an IC at a point inside a phantom irradiated by a certain beam can be obtained as the convolution of the dose spatial distribution caused by the beam and the IC two-dimensional RF. The proposed methodology has been applied successfully to predict the response of a PTW 30013 IC when measuring different nonreference fields, namely: output factors of 6 MV small fields, beam profiles of cobalt 60 narrow fields and 6 MV radiosurgery segments. The two-dimensional RF of a PTW 30013 IC was obtained by MC simulation of the absorbed dose to cavity air when the IC was scanned by a 0.6 x 0.6 mm{sup 2} cross section parallel pencil beam at low depth in a water phantom. For each of the cases studied, the results of the IC direct measurement were compared with the corresponding obtained by the C/S method. Results: For all of the cases studied, the agreement between the IC direct measurement and the IC calculated response was excellent (better than 1.5%). Conclusions: This method could be implemented in TPS in order to calculate dosimetry correction factors when an experimental IMRT treatment verification with in-phantom ionization chamber is performed. The miss-response of the IC due to the nonreference conditions could be quickly corrected by this method rather than employing MC derived correction factors. This method can be considered as an alternative to the plan-class associated correction factors proposed recently as part of an IAEA work group on nonstandard field dosimetry.

  4. Digital mammography with multi-electrode ionization chamber

    CERN Document Server

    Groshev, V R; Nifontov, V I; Pishenuok, S M; Samsonov, A A; Shekhtman, L I; Telnov, V I

    2000-01-01

    For viewing micro-calcifications smaller than 100 mu m investigation of image formation in mammography shows that a significant dose to the patient is imperative. We propose a novel one-dimensional Multi- electrode Ionisation Chamber (MIC), with high spatial resolution, and lowered doses. In this work, first results from a prototype are presented. High spatial resolution is demonstrated working with Xe mixture at high pressure. An addition of a Gas Electron Multiplier (GEM) allowed an improvement in sensitivity up to almost single- photon level. (8 refs).

  5. Development of a Grid Ionization Chamber for a Dram of α Ray

    Directory of Open Access Journals (Sweden)

    YANG Lu;WANG Qiang;ZHENG Yu-lai;WANG Guo-bao

    2016-11-01

    Full Text Available This article introduced the parallel grid ionization chamber that used to measure the α radioactivity, which had a independent vacuum system. The system was composed of main body of the chamber, gas-filled and electronics system. Energy resolution was 26 keV for 239Pu, background was 10 counts for one hour from 4 MeV to 6 MeV energy range, the stability of 24 hours was less than 0.5% . The chamber can measure the energy of nuclide and analyze the energy spectrum structure to identify nuclear.

  6. Ionization Chambers for the LHC Beam Loss Detection

    CERN Document Server

    Assmann, R W; Ferioli, G; Gschwendtner, E; Kain, V

    2003-01-01

    At the Large Hadron Collider (LHC) a beam loss system will be used to prevent and protect superconducting magnets against coil quenches and coil damages. Ionisation chambers will be mounted outside the cryostat to measure the secondary shower particles caused by lost beam particles. Since the stored particle beam intensity is eight orders of magnitude larger than the lowest quench level and the losses should be detected with a relative error of two, the design and the location of the detectors have to be optimised. For that purpose a two-fold simulation was carried out. The longitudinal loss locations of the tertiary halo is investigated by tracking the halo through several magnet elements. These loss distributions are combined with simulations of the particle fluence outside the cryostat, which is induced by lost protons at the vacuum pipe. The base-line ionisation chamber has been tested at the PS Booster in order to determine the detector response at the high end of the dynamic range.

  7. Determination of relative ion chamber calibration coefficients from depth-ionization measurements in clinical electron beams

    Science.gov (United States)

    Muir, B. R.; McEwen, M. R.; Rogers, D. W. O.

    2014-10-01

    A method is presented to obtain ion chamber calibration coefficients relative to secondary standard reference chambers in electron beams using depth-ionization measurements. Results are obtained as a function of depth and average electron energy at depth in 4, 8, 12 and 18 MeV electron beams from the NRC Elekta Precise linac. The PTW Roos, Scanditronix NACP-02, PTW Advanced Markus and NE 2571 ion chambers are investigated. The challenges and limitations of the method are discussed. The proposed method produces useful data at shallow depths. At depths past the reference depth, small shifts in positioning or drifts in the incident beam energy affect the results, thereby providing a built-in test of incident electron energy drifts and/or chamber set-up. Polarity corrections for ion chambers as a function of average electron energy at depth agree with literature data. The proposed method produces results consistent with those obtained using the conventional calibration procedure while gaining much more information about the behavior of the ion chamber with similar data acquisition time. Measurement uncertainties in calibration coefficients obtained with this method are estimated to be less than 0.5%. These results open up the possibility of using depth-ionization measurements to yield chamber ratios which may be suitable for primary standards-level dissemination.

  8. Determination of saturation charge and collection efficiency for ionization chambers in continuous beams.

    Science.gov (United States)

    Zankowski, C; Podgorsak, E B

    1998-06-01

    The procedure recommended by radiation dosimetry protocols for determining the collection efficiency f of an ionization chamber assumes the predominance of general recombination and ignores other charge loss mechanisms such as initial recombination and ionic diffusion. For continuous radiation beams, general recombination theory predicts that f can be determined from a linear relationship between 1/Q and 1/V2 in the near saturation region (f > 0.7), where Q is the measured charge and V the applied chamber potential. Measurements with Farmer-type cylindrical ionization chambers exposed to cobalt-60 gamma rays reveal that the assumed linear relationship between 1/Q and 1/V2 breaks down in the extreme near-saturation region (f > 0.99) where Q increases with V at a rate exceeding the predictions of general recombination theory. A comprehensive model is developed to describe the saturation characteristics of ionization chambers. The model accounts for dosimetric charge loss (initial recombination, ionic diffusion, and general recombination) and nondosimetric charge multiplication in an ionization chamber, and suggests that charge multiplication plays a significant role under typical chamber operating conditions (300 V) used in radiation dosimetry. Through exclusion of charge multiplication from the measured chamber signal Q, the model predicts the breakdown of the 1/Q vs 1/V2 relationship and shows that the final approach to saturation is governed by initial recombination and ionic diffusion which are characterized by a linear relationship between 1/Q and 1/V. Collection efficiencies calculated with this model differ by up to 0.4% from those determined through a rigorous application of general recombination theory alone.

  9. SU-E-T-415: An Ionization Chamber Array with High Spatial Resolution for External Beam Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Togno, M [Klinikum rechts der Isar, Technische Universitaet Muenchen, Muenchen (Germany); IBA Dosimetry, Schwarzenbruck (Germany); Wilkens, J [Klinikum rechts der Isar, Technische Universitaet Muenchen, Muenchen (Germany); Menichelli, D [IBA Dosimetry, Schwarzenbruck (Germany)

    2014-06-01

    Purpose: To characterize an ionization chamber array technology with high spatial resolution and high charge collection efficiency for external beam radiotherapy. Methods: The prototype under test is a linear array of air vented ionization chambers developed by IBA Dosimetry, consisting of 80 pixels with 3.5mm spatial resolution and 4mm{sup 3} sensitive volume. The detector was characterized in a plastic phantom with {sup 60} Co radiation and MV X-rays from an ELEKTA Agility LINAC (with flattened and unflattened beam qualities). Bias voltage was varied in order to evaluate charge collection efficiency. A commercial array of ionization chambers (MatriXX Evolution, IBA Dosimetry) and an amorphous silicon flat panel in direct conversion configuration were used as references. Results: Repeatability (0.4%) and stability under continuous gamma irradiation (0.3%) are very good, in spite of low active volume and sensitivity (∼200pC/Gy). Charge collection efficiency is higher than 99% already at 150V with ∼2mGy dose per pulse, leading to a ±1.1% sensitivity change with dose per pulse in the range 0.09-2mGy (covering all flattened and unflattened applications). Measured dose profiles are in agreement with MatriXX for fields larger than 2×2cm{sup 2}, in which case the linear array offers a much better characterization of the penumbra region. Down to 1×1cm{sup 2}, measured profiles are in very good agreement with the flat panel. Conclusion: The array represents a valuable tool for the characterization of treatment fields in which high spatial resolution is required, together with the dosimetric performance of air vented ionization chambers. Such a technology would be particularly valuable in association with advanced treatment modalities such as rotational radiotherapy, stereotactic treatments (even with unflattened beam qualities) and proton therapy, due to the insensitivity of the chambers on dose per pulse. In the future, a two dimensional prototype based on this

  10. Time-resolved dosimetry using a pinpoint ionization chamber as quality assurance for IMRT and VMAT

    NARCIS (Netherlands)

    Louwe, R.J.; Wendling, M.; Monshouwer, R.; Satherley, T.; Day, R.A.; Greig, L.

    2015-01-01

    PURPOSE: To develop a method to verify the dose delivery in relation to the individual control points of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) using an ionization chamber. In addition to more effective problem solving during patient-specific quality assu

  11. A VLSI analog pipeline read-out for electrode segmented ionization chambers

    CERN Document Server

    Bonazzola, G C; Cirio, R; Donetti, M; Figus, M; Marchetto, F; Peroni, C; Pernigotti, E; Thénard, J M; Zampieri, A

    1999-01-01

    We report on the design and test of a 32-channel VLSI chip based on the analog pipeline memory concept. The charge from a strip of a ionization chamber, is stored as a function of time in a switched capacitor array. The cell reading can be done in parallel with the writing.

  12. Development of a pixel ionization chamber for beam monitor in proton therapy

    Energy Technology Data Exchange (ETDEWEB)

    La Rosa, A. [Dipartimento di Fisica Sperimentale, Universita di Torino, Via P. Giuria 1, Turin 10125 (Italy) and INFN, Sezione di Torino, Via P. Giuria, Turin 10125 (Italy)]. E-mail: larosa@to.infn.it; Garella, M.A. [INFN, Sezione di Torino, Via P. Giuria, Turin 10125 (Italy); Attili, A. [Dipartimento di Fisica Sperimentale, Universita di Torino, Via P. Giuria 1, Turin 10125 (Italy); Bourhaleb, F. [Fondazione TERA, Via Puccini 11, Novara 28100 (Italy); Cirio, R. [INFN, Sezione di Torino, Via P. Giuria, Turin 10125 (Italy); Donetti, M. [INFN, Sezione di Torino, Via P. Giuria, Turin 10125 (Italy); Fondazione CNAO, Via Caminadella 16, Milan 20123 (Italy); Giordanengo, S. [INFN, Sezione di Torino, Via P. Giuria, Turin 10125 (Italy); Givehchi, N. [Dipartimento di Fisica Sperimentale, Universita di Torino, Via P. Giuria 1, Turin 10125 (Italy); INFN, Sezione di Torino, Via P. Giuria, Turin 10125 (Italy); Marchetto, F. [INFN, Sezione di Torino, Via P. Giuria, Turin 10125 (Italy); Mazza, G. [INFN, Sezione di Torino, Via P. Giuria, Turin 10125 (Italy); Meyroneinc, S. [Institut Curie-Centre de Protontherapie de Orsay, Bat. 101 Campus Universitaire, Orsay Cedex 91898 (France); Pecka, A. [Dipartimento di Fisica Sperimentale, Universita di Torino, Via P. Giuria 1, Turin 10125 (Italy); Peroni, C. [Dipartimento di Fisica Sperimentale, Universita di Torino, Via P. Giuria 1, Turin 10125 (Italy); INFN, Sezione di Torino, Via P. Giuria, Turin 10125 (Italy); Pitta, G. [Fondazione TERA, Via Puccini 11, Novara 28100 (Italy)

    2007-03-01

    We have developed a detector to be used as monitor for proton therapy beam lines. The detector is a 2-D parallel plate ionization chamber, with the anode segmented in 1024 square pixels arranged in a 32x32 matrix. The detector characterization is presented.

  13. Measurement of surface alpha-acrivity of different samples with ion pulse ionization chamber

    CERN Document Server

    Gavriljuk, Yu M; Gangapshev, A M; Kazalov, V V; Kuzminov, V V; Panasenko, S I; Ratkevich, S S

    2007-01-01

    The construction of an ion pulse ionization chamber aimed at measuring ultra-low levels of surface alpha-activity of different samples is described. The results of measurement carried out with alpha-source and copper samples and light-reflecting film VM2000 are presented.

  14. A VLSI analog pipeline read-out for electrode segmented ionization chambers

    Science.gov (United States)

    Bonazzola, G. C.; Bouvier, S.; Cirio, R.; Donetti, M.; Figus, M.; Marchetto, F.; Peroni, C.; Pernigotti, E.; Thenard, J. M.; Zampieri, A.

    1999-05-01

    We report on the design and test of a 32-channel VLSI chip based on the analog pipeline memory concept. The charge from a strip of a ionization chamber, is stored as a function of time in a switched capacitor array. The cell reading can be done in parallel with the writing.

  15. Development of a pixel ionization chamber for beam monitor in proton therapy

    Science.gov (United States)

    La Rosa, A.; Garella, M. A.; Attili, A.; Bourhaleb, F.; Cirio, R.; Donetti, M.; Giordanengo, S.; Givehchi, N.; Marchetto, F.; Mazza, G.; Meyroneinc, S.; Pecka, A.; Peroni, C.; Pittà, G.

    2007-03-01

    We have developed a detector to be used as monitor for proton therapy beam lines. The detector is a 2-D parallel plate ionization chamber, with the anode segmented in 1024 square pixels arranged in a 32×32 matrix. The detector characterization is presented.

  16. Performance of a Roos ionization chamber in gamma radiation beams ({sup 60}Co)

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana P.; Neves, Lucio P.; Caldas, Linda V.E., E-mail: lcaldas@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    Among the different types of dosimetry instruments, the ionization chambers are the most practical and and important radiation measurement devices due to their high sensitivity and relatively constant response within a wide range of energies. A commercial PTW ionization chamber (Roos electron chamber) usually utilized in X-ray beams, was tested to verify the possibility of its dosimetric application in {sup 60}Co beams. The main tests in this work were: short- and long-term stability, saturation, ion collection efficiency, polarity effect, leakage current and angular dependence. The characterization tests were performed using a Gammatron {sup 60}Co irradiator and a special goniometer made of PMMA. All results were within international recommendations. The reproducibility test presented results within the recommended limit of {+-}1%, and all coefficients of variation observed in the repeatability test were lower than {+-}0.07%. The ion collection efficiency was better than 99.9% for both polarities. For all pairs of polarity evaluated during the saturation test, the polarity effect was lower than the recommended limit. The maximum variation obtained for angular dependence test was only 0.5%. The chamber tested in this work achieved the expected results in the case of all pre-operational tests realized: stability, leakage current, angular dependence, saturation, ion collection and polarity effect. Evaluating the satisfactory results obtained, it is possible to indicate the usefulness of this ionization chamber for dosimetry in {sup 60}Co gamma radiation beams. (author)

  17. a Solution for Dosimetry and Quality Assurance in Imrt and Hadrontherapy:. the Pixel Ionization Chamber

    Science.gov (United States)

    Amerio, S.; Coda, S.; Nastasi, U.; Belletti, S.; Ghedi, B.; Boriano, A.; Cirio, R.; Luparia, A.; Marchetto, F.; Peroni, C.; Sanz Freire, C. J.; Donetti, M.; Madon, E.; Trevisiol, E.; Urgesi, A.

    2002-11-01

    The new radiotherapy techniques require new detectors to monitor and measure the clinical field. The Intensity Modulated Radiation Therapy (IMRT) techniques like step and shoot, sliding window, dynamic wedge or scanning beam add the time variable to the treatment field. In this case the water phantom with a single ionization chamber moving inside the field needs very long measurement time. Linear arrays of ionization chambers or diodes measure the field only along a line. 2D detectors like radiographic or gafchromic film are not suitable to be used as on line detectors. We have developed, built and tested an ionization chamber segmented in pixels that measure the dose in a plane at several points. Every channel has a dedicated electronic chain that digitizes the collected charge and data from all the channels are sent to the computer that performs the data acquisition. One read out cycle is very fast allowing to measure in real time the fluency and the shape of the field. The chamber can be used in two different ways, as monitor chamber and as relative dosemeter. A description of the detector, the electronics, and test results with both photon and hadron beams will be reported.

  18. Comparação entre fatores de calibração em termos de dose absorvida no ar para uma câmara de ionização de placas paralelas Comparison of absorbed dose to air calibration factors for a parallel plate ionization chamber

    Directory of Open Access Journals (Sweden)

    Roseli T. Bulla

    2006-06-01

    Full Text Available OBJETIVO: O objetivo deste trabalho foi realizar uma comparação entre os fatores de calibração em termos de dose absorvida no ar determinados em feixes gama (60Co e de elétrons. MATERIAIS E MÉTODOS: Foram utilizados um irradiador de 60Co e um acelerador linear Varian, modelo Clinac 2100C, com feixes de fótons e de elétrons. Foram testadas uma câmara de ionização cilíndrica e três de placas paralelas. RESULTADOS: Os sistemas de medidas foram submetidos aos testes preliminares (estabilidade de resposta e corrente de fuga, com resultados muito bons. Os fatores de calibração em termos de dose absorvida no ar foram determinados utilizando-se quatro sistemas de medidas e dois tipos de objetos simuladores, com a obtenção de resultados dentro das recomendações internacionais. CONCLUSÃO: Os resultados mostraram que os fatores de calibração em termos de dose absorvida no ar obtidos para câmaras de ionização de placas paralelas, determinados em feixes de 60Co, são no máximo 1,2% mais altos que os valores obtidos em feixes de elétrons de altas energias.OBJECTIVE: The objective of this study was to compare the absorbed dose to air calibration factors determined in gamma (60Co and electron beams. MATERIALS AND METHODS: An irradiator with a 60Co source and a Varian, Clinac 2100C linear accelerator with photon and electron beams were utilized. One thimble-type and three parallel-plate ionization chambers were tested. RESULTS: The measurement systems were submitted to preliminary tests (response stability and leakage current, with quite good results. The absorbed dose to air calibration factors were determined using four measurement systems and two types of phantoms. Results were obtained in compliance with the international recommendations. CONCLUSION: Absorbed dose to air calibration factors obtained for parallel plate ionization chambers, determined in 60Co beams, at maximum, are 1.2% higher than the values obtained in high energy

  19. The Time Response of Glass Resistive Plate Chambers to Heavily Ionizing Particles

    CERN Document Server

    Artamonov, A; Bogomilov, M; Booth, C; Borghi, S; Catanesi, M G; Chimenti, P; Gastaldi, Ugo; Giani, S; Graulich, J S; Grégoire, G; Grossheim, A; Guglielmi, A; Ivantchenko, V; Kolev, D; Meurer, C; Mezzetto, M; Panman, J; Popov, B; Radicioni, E; Schroeter, R; Temnikov, P; Chernyaev, E; Tsenov, R; Tsukerman, I; Wiebusch, C

    2007-01-01

    The HARP system of resistive plate chambers (RPCs) was designed to perform particle identification by the measurement of the difference in the time-of-flight of different particles. In previous papers an apparent discrepancy was shown between the response of the RPCs to minimum ionizing pions and heavily ionizing protons. Using the kinematics of elastic scattering off a hydrogen target a controlled beam of low momentum recoil protons was directed onto the chambers. With this method the trajectory and momentum, and hence the time-of-flight of the protons can be precisely predicted without need for a measurement of momentum of the protons. It is demonstrated that the measurement of the time-of-arrival of particles by the thin gas-gap glass RPC system of the HARP experiment depends on the primary ionization deposited by the particle in the detector.

  20. Characterization of recombination effects in a liquid ionization chamber used for the dosimetry of a radiosurgical accelerator.

    Science.gov (United States)

    Wagner, Antoine; Crop, Frederik; Lacornerie, Thomas; Reynaert, Nick

    2014-05-09

    Most modern radiation therapy devices allow the use of very small fields, either through beamlets in Intensity-Modulated Radiation Therapy (IMRT) or via stereotactic radiotherapy where positioning accuracy allows delivering very high doses per fraction in a small volume of the patient. Dosimetric measurements on medical accelerators are conventionally realized using air-filled ionization chambers. However, in small beams these are subject to nonnegligible perturbation effects. This study focuses on liquid ionization chambers, which offer advantages in terms of spatial resolution and low fluence perturbation. Ion recombination effects are investigated for the microLion detector (PTW) used with the Cyberknife system (Accuray). The method consists of performing a series of water tank measurements at different source-surface distances, and applying corrections to the liquid detector readings based on simultaneous gaseous detector measurements. This approach facilitates isolating the recombination effects arising from the high density of the liquid sensitive medium and obtaining correction factors to apply to the detector readings. The main difficulty resides in achieving a sufficient level of accuracy in the setup to be able to detect small changes in the chamber response.

  1. Development and production of the ionization chamber for the T2K muon monitor

    Energy Technology Data Exchange (ETDEWEB)

    Matsuoka, K., E-mail: matsuoka@scphys.kyoto-u.ac.j [Kyoto University, Kitashirakawa-Oiwake-cho Sakyo-ku, Kyoto 606-8502 (Japan); Ichikawa, A.; Kubo, H. [Kyoto University, Kitashirakawa-Oiwake-cho Sakyo-ku, Kyoto 606-8502 (Japan); Maruyama, T. [High Energy Accelerator Research Organization (KEK), Oho 1-1, Tsukuba 305-0801 (Japan); Murakami, A.; Nakaya, T.; Yokoyama, M. [Kyoto University, Kitashirakawa-Oiwake-cho Sakyo-ku, Kyoto 606-8502 (Japan)

    2010-11-01

    We report on the development of an ionization chamber for the muon monitor in the T2K (Tokai-to-Kamioka) long baseline neutrino oscillation experiment. In the T2K experiment, we generate a muon neutrino beam using the 50-GeV proton synchrotron in J-PARC and detect it in the Super-Kamiokande detector, which is 295 km away from J-PARC. We aim the neutrino beam off-axis by 2.5{sup o} from Super-Kamiokande in order to maximize the sensitivity to the neutrino oscillation measurement. Since the beam direction is required to be aimed within 1 mrad, we need to monitor it with a precision better than 1 mrad. The muon monitor is the only instrument that can monitor the neutrino beam direction in real time by measuring a profile of muons which are generated along with neutrinos. It is required to measure the intense muon beam precisely and stably in a high radiation area. Therefore, we use two independent systems for the muon monitor: an array of ionization chambers and another array of solid-state detectors. We developed the ionization chamber and performed beam tests with an electron beam at the Laboratory of Particle Beam Science in Kyoto University. We also had a long-term test in the NuMI beamline at Fermilab. Then we finalized the design of the ionization chamber and built it. We expect the ionization chambers as the muon monitor to monitor the beam direction with a precision of 0.2 mrad.

  2. Performance evaluation of multi sampling ionization chamber for heavy ion beams by comparison with GEANT4 simulation

    Science.gov (United States)

    Kanke, Yuki; Himac H093 Collaboration

    2014-09-01

    In high-energy heavy-ion accelerator facilities, multi sampling ionization chambers are often used for the identification of the atomic number Z by detecting the energy deposit in it. In the study at GSI, the picture of the escape of secondary electrons, δ rays, from the ionization chamber explains the experimental data of pulse-height resolution. If this picture is correct, the pulse-height resolution should depend on the effective area of the ionization chamber. The experiment have been performed at NIRS-HIMAC. The pulse-height resolutions of two ionization chambers with different effective area were compared by using a 400-MeV/u Ni beam and their fragments. The difference in the pulse-height resolutions was observed. By comparison with the GEANT4 simulation including the δ-rays emission, the performance of the ionization chamber have been evaluated.

  3. Determination of ion recombination correction factors for a liquid ionization chamber in megavoltage photon beams

    Science.gov (United States)

    Choi, Sang Hyoun; Kim, Kum-Bae; Ji, Young Hoon; Kim, Chan Hyeong; Kim, Seonghoon; Huh, Hyun Do

    2015-05-01

    The aim of this study is to determine the ion recombination correction factor for a liquid ionization chamber in a high energy photon beam by using our experimental method. The ion recombination correction factors were determined by using our experimental method and were compared with theoretical and experimental methods proposed by using the theoretical method (Greening, Johansson) and the two-dose rate method in a cobalt beam and a high energy photon beam. In order to apply the liquid ionization chamber in a reference and small field dosimetry, we acquired the absorbed dose to water correction coefficient, the beam quality correction factor, and the influence quantities for the microLion chamber according to the TRS-398 protocol and applied the results to a high energy photon beam used in clinical fields. As a result, our experimental method for ion recombination in a cobalt beam agreed with the results from the heoretical method (Greening theory) better than it did with the results from the two-dose rate method. For high energy photon beams, the two-dose rate and our experimental methods were in good agreement, less than 2% deviation, while the theoretical general collection efficiency (Johansson et al.) deviated greatly from the experimental values. When we applied the factors for the absorbed dose to water measurement, the absorbed dose to water for the microLion chamber was in good agreement, within 1%, compared with the values for the PTW 30013 chamber in 6 and 10 MV Clinac iX and 6 and 15 MV Oncor impression. With these results, not only can the microLion ionization chamber be used to measure the absorbed dose to water in a reference condition, it can also be used to a the chamber for small, non-standard field dosimetry.

  4. Evaluation of linearity of response and angular dependence of an ionization chamber for dosimetry in computed tomography

    Energy Technology Data Exchange (ETDEWEB)

    Perini, Ana P.; Neves, Lucio P.; Xavier, Marcos; Caldas, Linda V.E., E-mail: mxavier@ipen.b, E-mail: lcaldas@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Khoury, Helen J., E-mail: khoury@ufpe.b [Universidade Federal de Pernambuco (UFPE), Recife, PE (Brazil). Dept. de Energia Nuclear

    2011-07-01

    In this paper a pencil-type ionization chamber designed and manufactured at Instituto de Pesquisas Energeticas e Nucleares was evaluated for dosimetric applications in computed tomography beams. To evaluate the performance of this chamber two tests were undertaken: linearity of response and angular dependence. The results obtained in these tests showed good results, within the international recommendations. Moreover, this homemade ionization chamber is easy to manufacture, of low cost and efficient. (author)

  5. Characterization of the PTW SourceCheck ionization chamber with the Valencia lodgment for (125)I seed verification.

    Science.gov (United States)

    Tornero-López, Ana M; Torres Del Río, Julia; Ruiz, Carmen; Perez-Calatayud, Jose; Guirado, Damián; Lallena, Antonio M

    2015-12-01

    In brachytherapy using (125)I seed implants, a verification of the air kerma strength of the sources used is required. Typically, between 40 and 100 seeds are implanted. Checking all of them is unaffordable, especially when seeds are disposed in sterile cartridges. Recently, a new procedure allowing the accomplishment of the international recommendations has been proposed for the seedSelectron system of Elekta Brachytherapy. In this procedure, the SourceCheck ionization chamber is used with a special lodgment (Valencia lodgment) that allows to measure up to 10 seeds simultaneously. In this work we analyze this procedure, showing the feasibility of the approximations required for its application, as well as the effect of the additional dependence with the air density that shows the chamber model used. Uncertainty calculations and the verification of the approximation needed to obtain a calibration factor for the Valencia lodgment are carried out. The results of the present work show that the chamber dependence with the air density is the same whether the Valencia lodgment is used or not. On the contrary, the chamber response profile is influenced by the presence of the lodgment. The determination of this profile requires various measurements due to the nonnegligible variability found between different experiments. If it is considered, the uncertainty in the determination of the air-kerma strength increases from 0.5% to 1%. Otherwise, a systematic additional uncertainty of 1% would occur. This could be relevant for the comparison between user and manufacturer measurements that is mandatory in the case studied here.

  6. Microwave Triggered Laser Ionization of Air

    Science.gov (United States)

    Vadiee, Ehsan; Prasad, Sarita; Jerald Buchenauer, C.; Schamiloglu, Edl

    2012-10-01

    The goal of this work is to study the evolution and dynamics of plasma expansion when a high power microwave (HPM) pulse is overlapped in time and space on a very small, localized region of plasma formed by a high energy laser pulse. The pulsed Nd:YAG laser (8 ns, 600mJ, repetition rate 10 Hz) is focused to generate plasma filaments in air with electron density of 10^17/cm^3. When irradiated with a high power microwave pulse these electrons would gain enough kinetic energy and further escalate avalanche ionization of air due to elastic electron-neutral collisions thereby causing an increased volumetric discharge region. An X-band relativistic backward wave oscillator(RBWO) at the Pulsed Power,Beams and Microwaves laboratory at UNM is constructed as the microwave source. The RBWO produces a microwave pulse of maximum power 400 MW, frequency of 10.1 GHz, and energy of 6.8 Joules. Special care is being given to synchronize the RBWO and the pulsed laser system in order to achieve a high degree of spatial and temporal overlap. A photodiode and a microwave waveguide detector will be used to ensure the overlap. Also, a new shadowgraph technique with a nanosecond time resolution will be used to detect changes in the shock wave fronts when the HPM signal overlaps the laser pulse in time and space.

  7. An ionization chamber for (n,z) reaction cross section measurements on gaseous targets

    CERN Document Server

    Machrafi, R; Son, D; Gledenov, Yu M; Salatskii, V I; Sedyshev, P V; Andrzejewski, J; Szalanski, P; Gledenov, Yu.M.

    2002-01-01

    An ionization chamber with gaseous samples has been designed. It has been tested on the beam of the pulsed reactor IBR-30 of FLNP, JINR-Dubna. The experiment has been carried out with resonance neutrons. The exposed gas volume serves as a target for neutron beam. We have compared the chamber to samples on substrates, the background component due to Li and B microimpurities in this case is totally absent. It has been tested also the recovery capability of the chamber after the reactor power pulse using the protons from the 3He(n,p)3H reaction, alpha-particles from a U-source and a pulsed precision generator. Moreover the energy resolution of the chamber with its equipment has been carried out.

  8. Study of Neutron-Induced Ionization in Helium and Argon Chamber Gases

    CERN Document Server

    Indurthy, D; Harris, D; Kopp, S; Proga, M; Zwaska, R M

    2004-01-01

    Ion chambers used to monitor the secondary hadron and tertiary muon beam in the NuMI neutrino beamline will be exposed to background particles, including low energy neutrons produced in the beam dump. To understand these backgrounds, we have studied Helium- and Argon-filled ionization chambers exposed to intense neutron fluxes from PuBe neutron sources ($E_n=1-10$ MeV). The sources emit about 10$^8$ neutrons per second. The number of ion pairs in the chamber gas volume per incident neutron is derived. While limited in precision because of a large gamma ray background from the PuBe sources, our results are consistent with the expectation that the neutrons interact purely elastically in the chamber gas.

  9. Calculation of correction factors for ionization chamber measurements with small fields in low-density media.

    Science.gov (United States)

    Pisaturo, O; Pachoud, M; Bochud, F O; Moeckli, R

    2012-07-21

    The quantity of interest for high-energy photon beam therapy recommended by most dosimetric protocols is the absorbed dose to water. Thus, ionization chambers are calibrated in absorbed dose to water, which is the same quantity as what is calculated by most treatment planning systems (TPS). However, when measurements are performed in a low-density medium, the presence of the ionization chamber generates a perturbation at the level of the secondary particle range. Therefore, the measured quantity is close to the absorbed dose to a volume of water equivalent to the chamber volume. This quantity is not equivalent to the dose calculated by a TPS, which is the absorbed dose to an infinitesimally small volume of water. This phenomenon can lead to an overestimation of the absorbed dose measured with an ionization chamber of up to 40% in extreme cases. In this paper, we propose a method to calculate correction factors based on the Monte Carlo simulations. These correction factors are obtained by the ratio of the absorbed dose to water in a low-density medium □D(w,Q,V1)(low) averaged over a scoring volume V₁ for a geometry where V₁ is filled with the low-density medium and the absorbed dose to water □D(w,QV2)(low) averaged over a volume V₂ for a geometry where V₂ is filled with water. In the Monte Carlo simulations, □D(w,QV2)(low) is obtained by replacing the volume of the ionization chamber by an equivalent volume of water, according to the definition of the absorbed dose to water. The method is validated in two different configurations which allowed us to study the behavior of this correction factor as a function of depth in phantom, photon beam energy, phantom density and field size.

  10. Towards reference dosimetry for the MR-linac: magnetic field correction of the ionization chamber reading.

    Science.gov (United States)

    Smit, K; van Asselen, B; Kok, J G M; Aalbers, A H L; Lagendijk, J J W; Raaymakers, B W

    2013-09-07

    In the UMC Utrecht a prototype MR-linac has been installed. The system consists of a 6 MV Elekta (Crawley, UK) linear accelerator and a 1.5 T Philips (Best, The Netherlands) Achieva MRI system. This paper investigates the feasibility to correct the ionization chamber reading for the magnetic field within the dosimetry calibration method described by Almond et al (1999 Med. Phys. 26 1847-70). Firstly, the feasibility of using an ionization chamber in an MR-linac was assessed by investigating possible influences of the magnetic field on NE2571 Farmer-type ionization chamber characteristics: linearity, repeatability, orientation in the magnetic field; and AAPM TG51 correction factor for voltage polarity and ion recombination. We found that these AAPM correction factors for the NE2571 chamber were not influenced by the magnetic field. Secondly, the influence of the permanent 1.5 T magnetic field on the NE2571 chamber reading was quantified. The reading is influenced by the magnetic field; therefore, a correction factor has been added. For the standardized setup used in this paper, the NE2571 chamber reading increases by 4.9% (± 0.2%) due to the transverse 1.5 T magnetic field. Dosimetry measurements in an MR-linac are feasible, if a setup-specific magnetic field correction factor (P1.5 T) for the charge reading is introduced. For the setup investigated in this paper, the P1.5 T has a value of 0.953.

  11. Set-Up on the Basis of Multiwire Proportional and Ionization Chambers for Radioactive Beam Experiments

    CERN Document Server

    Astabatyan, R A; Kavalov, R L; Kugler, A; Kuznetsov, I V; Kushniruk, V F; Lobastov, S P; Lukyanov, S M; Markaryan, E R; Maslov, V A; Mikhailov, L; Penionzhkevich, Yu E; Poroshin, N O; Skobelev, N K; Smirnov, V I; Sobolev, Yu G; Ugryumov, V Yu

    2002-01-01

    A large-aperture set-up designed for nuclear physics experiments on beams of radioactive nuclei is described. The set-up includes Multiwire Proportional Chamber (MWPC) for measuring the beam profile, MWPC for measuring reaction product angular distributions, a CsI(Tl)-crystal detector and a longitudinal drift ionization chamber for identifying scattered particles and measuring their energy. The results of tests of coordinate MWPCs, particle identification on photon and ion beams, and preliminary measurements of the elastic scattering and the charge exchange reaction of 170 MeV ^{6}He on a CH_{2} target are presented.

  12. Total diesel exhaust particulate length measurements using a modified household smoke alarm ionization chamber.

    Science.gov (United States)

    Vojtisek-Lom, Michal

    2011-02-01

    To evaluate the effectiveness of various means to combat the negative health effects of ultrafine particles emitted by internal combustion engines, a reliable, low-cost instrument for dynamic measurements of the exhaust emissions of ultrafine particulate matter (PM) is needed. In this study, an ordinary ionization-type building smoke detector was modified to serve as a measuring ionization chamber and utilized for dynamic measurements of PM emissions from diesel engines. When used with diluted exhaust, the readings show an excellent correlation with total particulate length. The instrument worked well with raw and diluted exhaust and with varying emission levels and is well suitable for on-board use.

  13. Source self-attenuation in ionization chamber measurements of (57)Co solutions.

    Science.gov (United States)

    Cessna, Jeffrey T; Golas, Daniel B; Bergeron, Denis E

    2016-03-01

    Source self-attenuation for solutions of (57)Co of varying density and carrier concentration was measured in nine re-entrant ionization chambers maintained at NIST. The magnitude of the attenuation must be investigated to determine whether a correction is necessary in the determination of the activity of a source that differs in composition from the source used to calibrate the ionization chamber. At our institute, corrections are currently made in the measurement of (144)Ce, (109)Cd, (67)Ga, (195)Au, (166)Ho, (177)Lu, and (153)Sm. This work presents the methods used as recently applied to (57)Co. A range of corrections up to 1% were calculated for dilute to concentrated HCl at routinely used carrier concentrations.

  14. Measurements and Simulations of Ionization Chamber Signals in Mixed Radiation Fields for the LHC BLM System

    CERN Document Server

    Dehning, B; Ferioli, G; Holzer, EB; Stockner, M

    2006-01-01

    The LHC beam loss monitoring (BLM) system must prevent the super conducting magnets from quenching and protect the machine components from damage. The main monitor type is an ionization chamber. About 4000 of them will be installed around the ring. The lost beam particles initiate hadronic showers through the magnets, which are measured by the monitors installed outside of the cryostat around each quadrupole magnet. They probe the far transverse tail of the hadronic shower. The specification for the BLM system includes a factor of two absolute precision on the prediction of the quench levels. To reach this accuracy a number of simulations are being combined to calibrate the monitor signals. To validate the monitor calibration the simulations are compared with test measurements. This paper will focus on the simulated prediction of the development of the hadronic shower tails and the signal response of ionization chambers to various particle types and energies. Test measurements have been performed at CERN and ...

  15. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    Science.gov (United States)

    Müller, O.; Lützenkirchen-Hecht, D.; Frahm, R.

    2015-03-01

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper.

  16. Using a tandem ionization chamber for quality control of X-ray beams

    Energy Technology Data Exchange (ETDEWEB)

    Yoshizumi, Maira T.; Caldas, Linda V.E., E-mail: mairaty@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2011-07-01

    X-ray beam qualities are defined by both the mean energies and by the half-value layers (HVL). Many international protocols use the half-value layer and the beam voltage to characterize the X-ray beam quality. A quality control program for X-ray equipment includes the constancy check of beam qualities, i.e., the periodical verification of the half-value layer, which can be a time consumable procedure. A tandem ionization chamber, developed at Instituto de Pesquisas Energeticas e Nucleares, was used to determine the HVL and its constancy for five radiotherapy standard beam qualities. This ionization chamber is composed by two sensitive volumes with inner electrodes made of different materials: aluminum and graphite. The beam quality constancy check test was performed during two months and the maximum variation obtained was 1.24% for the radiation beam quality T-10. This result is very satisfactory according to national recommendations. (author)

  17. Neutron and gamma detector using an ionization chamber with an integrated body and moderator

    Science.gov (United States)

    Ianakiev, Kiril D.; Swinhoe, Martyn T.; Lestone, John Paul

    2006-07-18

    A detector for detecting neutrons and gamma radiation includes a cathode that defines an interior surface and an interior volume. A conductive neutron-capturing layer is disposed on the interior surface of the cathode and a plastic housing surrounds the cathode. A plastic lid is attached to the housing and encloses the interior volume of the cathode forming an ionization chamber, into the center of which an anode extends from the plastic lid. A working gas is disposed within the ionization chamber and a high biasing voltage is connected to the cathode. Processing electronics are coupled to the anode and process current pulses which are converted into Gaussian pulses, which are either counted as neutrons or integrated as gammas, in response to whether pulse amplitude crosses a neutron threshold. The detector according to the invention may be readily fabricated into single or multilayer detector arrays.

  18. Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes

    Energy Technology Data Exchange (ETDEWEB)

    Müller, O., E-mail: o.mueller@uni-wuppertal.de; Lützenkirchen-Hecht, D.; Frahm, R. [Bergische Universität Wuppertal, Gaußstraße 20, Wuppertal 42119 (Germany)

    2015-03-15

    A fast X-ray chopper capable of producing ms long X-ray pulses with a typical rise time of few μs was realized. It is ideally suited to investigate the temporal response of X-ray detectors with response times of the order of μs to ms, in particular, any kind of ionization chambers and large area photo diodes. The drive mechanism consists of a brushless DC motor and driver electronics from a common hard disk drive, keeping the cost at an absolute minimum. Due to its simple construction and small dimensions, this chopper operates at home lab based X-ray tubes and synchrotron radiation sources as well. The dynamics of the most important detectors used in time resolved X-ray absorption spectroscopy, namely, ionization chambers and Passivated Implanted Planar Silicon photodiodes, were investigated in detail. The results emphasize the applicability of this X-ray chopper.

  19. Some specific features of ionization chamber calibrations in linac x-ray beams at the LNE-LNHB.

    Science.gov (United States)

    Delaunay, F; Ostrowsky, A

    2007-05-07

    The purpose of this note is to give some details about the modus operandi employed today to calibrate ionization chambers in radiotherapy linac photon beams at the Laboratoire National Henri Becquerel (LNE-LNHB). Some specific features are described: first the equipment (including the external monitoring ionization chambers), second the calculations of the profile or radial non-uniformity correction factors (up to 0.5% effect for commonly used ionization chambers) and finally the calculations to get the calibration coefficients for customer beam qualities.

  20. Comparative study of ionization chamber detectors vis-a-vis a CCD detector for dispersive XAS measurement in transmission geometry

    Energy Technology Data Exchange (ETDEWEB)

    Poswal, A. K.; Agrawal, A.; Bhattachryya, D.; Jha, S. N.; Sahoo, N. K. [Applied Spectroscopy Division, Bhabha Atomic Research Centre, Mumbai -400 085 (India)

    2013-02-05

    We have designed and fabricated parallel plate ionization chamber detectors and voltage vs. current characteristics (V-I curve) of the detectors were recorded with synchrotron radiation to qualify for use in X-ray Absorption Spectroscopy (XAS) measurements. After qualifying the ionization chambers, the detectors were used in the dispersive EXAFS beamline (BL-08) at INDUS-2 SRS in Turbo-XAS geometry. Using the same setup and under the same setting, XAS spectra were also recorded with a CCD detector and the observation on relative performance of the ionization chamber vis-a-vis the CCD detector is presented in this paper.

  1. Detection of scintillation light in coincidence with ionizing tracks in a liquid argon time projection chamber

    CERN Document Server

    Cennini, P; Rubbia, Carlo; Sergiampietri, F; Bueno, A G; Campanelli, M; Goudsmit, P; Rubbia, André; Periale, L; Suzuki, S; Chen, C; Chen, Y; He, K; Huang, X; Li, Z; Lu, F; Ma, J; Xu, G; Xu, Z; Zhang, C; Zhang, Q; Zheng, S; Cavanna, F; Mazza, D; Piano Mortari, G; Petrera, S; Rossi, C; Mannocchi, G; Picchi, P; Arneodo, F; De Mitri, I; Palamara, O; Cavalli, D; Ferrari, A; Sala, P R; Borio di Tigliole, A A; Cesana, A; Terrani, M; Zavattari, C; Baibusinov, S; Bettini, A; Carpanese, C; Centro, Sandro; Favaretto, D; Pascoli, D; Pepato, Adriano; Pietropaolo, F; Ventura, Sandro; Benetti, P; Calligarich, E; Campo, S; Coco, S; Dolfini, R; Ghedi, B; Gigli-Berzolari, A; Mauri, F; Mazzone, L; Montanari, C; Piazzoli, A; Rappoldi, A; Raselli, G L; Rebuzzi, D; Rossella, M; Scannicchio, D A; Torre, P; Vignoli, C; Cline, D; Otwinowski, S; Wang, H; Woo, J

    1999-01-01

    A system to detect light from liquid argon scintillation has been implemented in a small, ICARUS-like, liquid argon time projection chamber. The system, which uses a VUV-sensitive photomultiplier to collect the light, has recorded many ionizing tracks from cosmic-rays in coincidence with scintillation signals. Our measurements demonstrate that scintillation light detection can provide an effective method for absolute time measurement of events and eventually a useful trigger signal. (19 refs).

  2. Rapid measurement of 210Po in seafood with large area grid ionization chamber α spectrometry

    Institute of Scientific and Technical Information of China (English)

    Li Yucheng; Yin Liangliang; Chen Fei; Shao Xianzhang; Shen Baoming; Kong Xiangyin; Ji Yanqin

    2015-01-01

    Objective To develop a rapid and reliable method for determination of 210Po using large-area grid ionization chamber α spectrometry.Methods Samples were digested using a microwave digestion system.After preparation of sample source,the concentration of 210Po in clam was detected by large-area grid ionization chamber (φ 25 cm).209Po tracer was used to obtain the recovery.Results Large-area grid ionization chamber could achieve better counting and α spectrum resolution when the optimized thickness was 250 μg/cm2.By spiking 209Po tracer in clam,the minimum detectable activity was 9.870 × 10 4 Bq and the recovery of 210Po was 98%.Conclusions Compared with the traditional method,the developed method can avoid separation process,using less quantity of sample (0.2-0.5 g dry) and simplify the measurement process.This method may be has broad application prospects.

  3. A position-sensitive twin ionization chamber for fission fragment and prompt neutron correlation experiments

    Energy Technology Data Exchange (ETDEWEB)

    Göök, A.; Geerts, W.; Hambsch, F.-J.; Oberstedt, S.; Vidali, M. [European Commission, Joint Research Centre, Institute for Reference Materials and Measurements, Retieseweg 111, B-2440 Geel (Belgium); Zeynalov, Sh. [Joint Institute for Nuclear Research, Joliot-Curie 6, 141980 Dubna, Mosow region (Russian Federation)

    2016-09-11

    A twin position-sensitive Frisch grid ionization chamber, intended as a fission fragment detector in experiments to study prompt fission neutron correlations with fission fragment properties, is presented. Fission fragment mass and energies are determined by means of the double kinetic energy technique, based on conservation of mass and linear momentum. The position sensitivity is achieved by replacing each anode plate in the standard twin ionization chamber by a wire plane and a strip anode, both readout by means of resistive charge division. This provides information about the fission axis orientation, which is necessary to reconstruct the neutron emission process in the fully accelerated fragment rest-frame. The energy resolution compared to the standard twin ionization chamber is found not to be affected by the modification. The angular resolution of the detector relative to an arbitrarily oriented axis is better than 7° FWHM. Results on prompt fission neutron angular distributions in {sup 235}U(n,f) obtained with the detector in combination with an array of neutron scintillation detectors is presented as a proof of principle.

  4. A position-sensitive twin ionization chamber for fission fragment and prompt neutron correlation experiments

    Science.gov (United States)

    Göök, A.; Geerts, W.; Hambsch, F.-J.; Oberstedt, S.; Vidali, M.; Zeynalov, Sh.

    2016-09-01

    A twin position-sensitive Frisch grid ionization chamber, intended as a fission fragment detector in experiments to study prompt fission neutron correlations with fission fragment properties, is presented. Fission fragment mass and energies are determined by means of the double kinetic energy technique, based on conservation of mass and linear momentum. The position sensitivity is achieved by replacing each anode plate in the standard twin ionization chamber by a wire plane and a strip anode, both readout by means of resistive charge division. This provides information about the fission axis orientation, which is necessary to reconstruct the neutron emission process in the fully accelerated fragment rest-frame. The energy resolution compared to the standard twin ionization chamber is found not to be affected by the modification. The angular resolution of the detector relative to an arbitrarily oriented axis is better than 7° FWHM. Results on prompt fission neutron angular distributions in 235U(n,f) obtained with the detector in combination with an array of neutron scintillation detectors is presented as a proof of principle.

  5. Comments on 'Ionization chamber volume determination and quality assurance using micro-CT imaging'.

    Science.gov (United States)

    Ross, C K

    2009-03-21

    The authors of a recent paper (McNiven et al 2008 Phys. Med. Biol. 53 5029-43) measured the volume of a particular type of a small ionization chamber using CT images. Using four Exradin A1SL chambers, they find that the volume measured using CT imaging is, on average, 4.3% larger than the value derived from the chamber calibration coefficient. Although they point out that the effective chamber volume is defined by electric field lines between the collector and the chamber body, they do not estimate how the mechanical volume might differ from the effective volume. We have used a commercial software package to calculate the electric field in the cavity and we show that the field lines define a volume that is about 11% smaller than the mechanical volume. We also show that the effective volume is very sensitive to small changes in the chamber geometry near the base of the collector. We conclude that simply determining the mechanical volume without careful consideration of the electric field lines within the cavity is not a useful dosimetric technique.

  6. A numerical model of initial recombination for high-LET irradiation: Application to liquid-filled ionization chambers

    Science.gov (United States)

    Aguiar, P.; Pardo-Montero, J.

    2016-02-01

    In this paper we present a numerical model of initial recombination in media irradiated with high linear energy transfer (LET) ions, which relies on an amorphous track model of ionization of high LET particles, and diffusion, drift and recombination of ionized charge carriers. The model has fundamental applications for the study of recombination in non-polar liquids, as well as practical ones, like in modelling hadrontherapy dosimetry with ionization chambers. We have used it to study the response of liquid-filled ionization chambers to hadrontherapy beams: dependence of initial recombination on ion species, energy and applied external electric field.

  7. Theoretical study of Jesse effect in tritium measurements using ionization chambers

    Science.gov (United States)

    Chen, Zhilin; Peng, Shuming; Lu, Hanghang; Tan, Zhaoyi; Wang, Heyi; Long, Xingui; Masao, Matsuyama

    2016-01-01

    Jesse effect caused by impurities in helium might enhance the output signal significantly in tritium measurements with ionization chamber, which will lead to overestimation of tritium concentration in experiments. A theoretical method was proposed to evaluate Jesse effect quantitatively. Results indicate that besides Penning ionization, sub-excitation electrons also place very important influence on ionization enhancement by Jesse effect. An experiential expression about the relationship between enhancement factor and impurity concentration was established, in which second order of it fits experimental results very well. Theoretical calculation method in this paper is also applicable to evaluate Jesse effect in other kinds of mixtures besides hydrogen as impurities in helium. In addition, Jesse effects about tritium molecules as impurities have also been investigated.

  8. Calibration of the KRISS reference ionization chamber for certification of ²²²Rn gaseous sources.

    Science.gov (United States)

    Lee, J M; Lee, K B; Lee, S H; Oh, P J; Park, T S; Kim, B C; Lee, M S

    2013-11-01

    A primary measurement system for gaseous (222)Rn based on the defined solid angle counting method has recently been constructed at KRISS and the reference ionization chamber used to measure the activities of gamma-emitting single radionuclides was adopted as a secondary standard for gaseous (222)Rn. A 20 mL flame-sealed glass ampoule source from the primary measurement system was used to calibrate the ionization chamber for (222)Rn. The (222)Rn efficiency of the ionization chamber was compared with that calculated by using a photon energy-dependent efficiency curve and that measured by using a standard (226)Ra solution. From the comparisons we draw the conclusion that the reference ionization chamber for gamma-emitting radionuclides can be a suitable secondary measurement system for gaseous (222)Rn sources.

  9. New chamber walls conditioning and cleaning strategies to improve the stability of plasma processes

    Science.gov (United States)

    Cunge, G.; Pelissier, B.; Joubert, O.; Ramos, R.; Maurice, C.

    2005-08-01

    One major challenge in plasma etching processes for integrated circuit fabrication is to achieve a good wafer-to-wafer repeatability. This requires a perfect control of the plasma chamber wall conditions. For silicon etching processes, which deposit SiOyClz layers on the chamber walls, this is achieved by cleaning the interior surfaces of the plasma chamber with an SF6-based plasma after each wafer is etched. However, x-ray photoelectron spectroscopy analysis of the reactor wall surfaces shows that the inner parts of the Al2O3 chamber are strongly fluorinated (formation of Al-F bonds) during the SF6 plasma. At the same time the AlFx layer is sputtered from some parts of the chamber (mostly from the roof, which is bombarded by high energy ions), and AlF redeposition is observed on other parts of the reactor body. Hence, the cleaning process of the reactor leaves AlF residues on the chamber wall on its own. This leads to several issues including flake off of AlxFy particles on the wafer and process drifts (due both to the progressive growth of AlF material on the SiO2 windows and to the release of F atoms from the chamber walls during the etching process). This indicates that a strategy other than dry-cleaning the Al2O3 chamber walls in fluorine-based plasmas should be found. In this paper we have investigated two different strategies. The first one consists of replacing Al2O3 covering the chamber walls by another material for the chamber walls inner coating. In particular, we have investigated the surface modification of several types of organic polymers (Teflon, Parylene and carbon-rich polymers), when exposed to SF6-based plasmas. We show that these materials can be reset to their original condition after exposure to a dry-cleaning process because carbon containing polymers are slowly etched away by the SF6/O2 plasma. This suggests that the replacement of the conventional Al2O3 chamber wall material by a carbon-coated liner should be possible. Alternatively, we

  10. Mass spectrometry of solid samples in open air using combined laser ionization and ambient metastable ionization

    Science.gov (United States)

    He, X. N.; Xie, Z. Q.; Gao, Y.; Hu, W.; Guo, L. B.; Jiang, L.; Lu, Y. F.

    2012-01-01

    Mass spectrometry of solid samples in open air was carried out using combined laser ionization and metastable ionization time-of-flight mass spectrometry (LI-MI-TOFMS) in ambient environment for qualitative and semiquantitative (relative analyte information, not absolute information) analysis. Ambient metastable ionization using a direct analysis in realtime (DART) ion source was combined with laser ionization time-of-flight mass spectrometry (LI-TOFMS) to study the effects of combining metastable and laser ionization. A series of metallic samples from the National Institute of Standards and Technology (NIST 494, 495, 498, 499, and 500) and a pure carbon target were characterized using LI-TOFMS in open air. LI-MI-TOFMS was found to be superior to laser-induced breakdown spectroscopy (LIBS). Laser pulse energies between 10 and 200 mJ at the second harmonic (532 nm) of an Nd:YAG laser were applied in the experiment to obtain a high degree of ionization in plasmas. Higher laser pulse energy improves signal intensities of trace elements (such as Fe, Cr, Mn, Ni, Ca, Al, and Ag). Data were analyzed by numerically calculating relative sensitivity coefficients (RSCs) and limit of detections (LODs) from mass spectrometry (MS) and LIBS spectra. Different parameters, such as boiling point, ionization potential, RSC, LOD, and atomic weight, were shown to analyze the ionization and MS detection processes in open air.

  11. Design and construction of the first prototype ionization chamber for CSNS and PA beam loss monitor (BLM) system

    Institute of Scientific and Technical Information of China (English)

    XU Mei-Hang; TIAN Jian-Min; CHEN Chang; CHEN Yuan-Bo; XU Tao-Guang; LU Shuang-Tong

    2009-01-01

    Design and construction of the first prototype ionization chamber for CSNS and Proton Accelerator (PA) beam loss monitor (BLM) system is reported. The low leakage current (<0.1 pA), good plateau (≈800 V) and linearity range up to 200 Roentgen/h axe obtained in the first prototype. All of these give us good experience for further improving the ionization chamber construction.

  12. Characterization of a 2D ionization chamber array for IMRT plan verification

    Energy Technology Data Exchange (ETDEWEB)

    Alashrah, S. [Universiti Sains Malaysia, Penang (Malaysia); Kandaiya, S., E-mail: sivamany@usm.m [Universiti Sains Malaysia, Penang (Malaysia); Yong, S.Y.; Cheng, S.K. [Mount Miriam Hospital, Penang (Malaysia)

    2010-07-21

    A commercialized array of 2D pixel ionization chambers MatriXX from Scanditronix Wellhoefer was evaluated with the objective to implement for quality assurance in IMRT treatment plan verification. The device consists of 1020 chambers arranged in a 32x32 grid. The distance between the chamber centres is 7.6 mm and the volume of the chamber is 0.08 cm{sup 3}. The effective point measurement of the MatriXX was verified and it agreed with the MatriXX's manual specifications. The start-up behaviour, and the short- and long-term reproducibilities of the array detector were tested. Dose linearity and energy independence were also analyzed. The results showed that the dose was linear within the range 9-800 cGy and the response of the 2D array was independent of energy for 6 and 10 MV photon beams. The MatriXX was independent of dose rate ranging from 183 to 483 cGy/min. For field sizes 3x3 cm{sup 2} and above the output factors of the 2D agreed within 1% with those obtained using the FC65-G ionization chamber. But at field size 2x2 cm{sup 2} the percentage difference was 5%. However, there was a poor correlation with differences greater than 1 mm in the penumbra region. The preliminary investigations indicate that the detector is suitable for IMRT plan verifications but corrections have to be applied in regions of high dose gradient.

  13. A liquid-filled ionization chamber for high precision relative dosimetry.

    Science.gov (United States)

    González-Castaño, D M; Gómez, F; Brualla, L; Roselló, J V; Planes, D; Sánchez, M; Pombar, M

    2011-04-01

    Radiosurgery and intensity modulated radiation therapy (IMRT) treatments are based on the delivery of narrow and/or irregularly shaped megavoltage photon beams. This kind of beams present both lack of charged particle equilibrium and steep dose gradients. Quality assurance (QA) measurements involved in these techniques must therefore be carried out with a dosimeter featuring high small volume. In order to obtain a good signal to noise ratio, a relatively dense material is needed as active medium. Non-polar organic liquids were proposed as active mediums with both good tissue equivalence and showing high signal to noise ratio. In this work, a liquid-filled ionization chamber is presented. Some results acquired with this detector in relative dosimetry are studied and compared with results obtained with unshielded diode. Medium-term stability measurements were also carried out and its results are shown. The liquid-filled ionization chamber presented here shows its ability to perform profile measurements and penumbrae determination with excellent accuracy. The chamber features a proper signal stability over the period studied.

  14. Measurement of photon flux with a miniature gas ionization chamber in a Material Testing Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Fourmentel, D., E-mail: damien.fourmentel@cea.fr [CEA, DEN, DER, Instrumentation Sensors and Dosimetry Laboratory, Cadarache, F-13108 St-Paul-Lez-Durance (France); Filliatre, P.; Villard, J.F.; Lyoussi, A. [CEA, DEN, DER, Instrumentation Sensors and Dosimetry Laboratory, Cadarache, F-13108 St-Paul-Lez-Durance (France); Reynard-Carette, C. [Aix-Marseille Université, LISA EA 4672, cedex 20, Marseille 13397 (France); Carcreff, H. [CEA, DEN, DRSN, Saclay, F-91191 Gif-sur-Yvette (France)

    2013-10-01

    Nuclear heating measurements in Material Testing Reactors (MTR) are crucial for the design of the experimental devices and the prediction of the temperature of the hosted samples. Nuclear heating in MTR materials (except fuel) is mainly due to the energy deposition by the photon flux. Therefore, the photon flux is a key input parameter for the computer codes which simulate nuclear heating and temperature reached by samples/devices under irradiation. In the Jules Horowitz MTR under construction at the CEA Cadarache, the maximal expected nuclear heating levels will be about 15 to 18 W g{sup −1} and it will be necessary to assess this parameter with the best accuracy. An experiment was performed at the OSIRIS reactor to combine neutron flux, photon flux and nuclear heating measurements to improve the knowledge of the nuclear heating in MTR. There are few appropriate sensors for selective measurement of the photon flux in MTR even if studies and developments are ongoing. An experiment, called CARMEN-1, was conducted at the OSIRIS MTR and we used in particular a gas ionization chamber based on miniature fission chamber design to measure the photon flux. In this paper, we detail Monte-Carlo simulations to analyze the photon fluxes with ionization chamber measurements and we compare the photon flux calculations to the nuclear heating measurements. These results show a good accordance between photon flux measurements and nuclear heating measurement and allow improving the knowledge of these parameters.

  15. Proton beam dosimetry: a comparison between a plastic scintillator, ionization chamber and Faraday cup.

    Science.gov (United States)

    Ghergherehchi, Mitra; Afarideh, Hossein; Ghannadi, Mohammad; Mohammadzadeh, Ahmad; Aslani, Golam Reza; Boghrati, Behzad

    2010-01-01

    In this study, a comparison was made between a plastic scintillator (BC400), a Faraday Cup (FC) and an ionization chamber (IC) used for routine proton dosimetry. Thin scintillators can be applied to proton dosimetry and consequently to proton therapy as relative dosimeters because of their water-equivalent nature, high energy-light conversion efficiency, low dimensions and good proportionality to the absorbed dose at low stopping powers. To employ such scintillators as relative dosimeters in proton therapy, the corrective factors must be applied to correct the quenching luminescence at the Bragg peak. A fine linear proportionality between the luminescence light yield Y and the proton flux in a thin (0.5 mm) scintillator for the 20 and 30 MeV proton beams were observed. The experimental peak/plateau ratios of Bragg Curve for 2, 1 and 0.5 mm scintillators with an accuracy of 0.5% were obtained to be 1.87, 1.91 and 2.30, respectively. With combination of the Markus chamber and the CR-39 detector, the peak/plateau ratio was improved to 3.26. The obtained data of the luminescence yield as a function of the specific energy loss is in agreement with the Craun-Birk's theory. Results show that the FC and Markus ionization chamber are in agreement within 4%, while the FC gives a lower dose evaluation. For a defined beam, the data for the fluence measurements are reproducible within a good accuracy.

  16. Use of relativistic rise in ionization chambers for measurement of high energy heavy nuclei

    Science.gov (United States)

    Barthelmy, S. D.; Israel, M. H.; Klarmann, J.; Vogel, J. S.

    1983-01-01

    A balloon-borne instrument has been constructed to measure the energy spectra of cosmic-ray heavy nuclei in the range of about 0.3 to about 100 GeV/amu. It makes use of the relativistic rise portion of the Bethe-Bloch curve in ionization chambers for energy determination in the 10- to 100-GeV/amu interval. The instrument consists of six layers of dual-gap ionization chambers for energy determination above 10 GeV/amu. Charge is determined with a NE114 scintillator and a Pilot 425 plastic Cerenkov counter. A CO2 gas Cerenkov detector (1 atm; threshold of 30 GeV/amu) calibrates the ion chambers in the relativistic rise region. The main emphasis of the instrument is the determination of the change of the ratio of Iron (26) to the Iron secondaries (21-25) in the energy range of 10 to 100 GeV/amu. Preliminary data from a balloon flight in the fall of 1982 from Palestine, TX is presented.

  17. Space charge effect measurements for a multi-channel ionization chamber used for synchrotron radiation

    Energy Technology Data Exchange (ETDEWEB)

    Nasr, Amgad

    2012-07-18

    In vivo coronary angiography is one of the techniques used to investigate the heart diseases, by using catheter to inject a contrast medium of a given absorption coefficient into the heart vessels. Taking X-ray images produced by X-ray tube or synchrotron radiation for visualizing the blood in the coronary arteries. As the synchrotron radiation generated by the relativistic charged particle at the bending magnets, which emits high intensity photons in comparison with the X-ray tube. The intensity of the synchrotron radiation is varies with time. However for medical imaging it's necessary to measure the incoming intensity with the integrated time. The thesis work includes building a Multi-channel ionization chamber which can be filled with noble gases N{sub 2}, Ar and Xe with controlled inner pressure up to 30 bar. This affects the better absorption efficiency in measuring the high intensity synchrotron beam fluctuation. The detector is a part of the experimental setup used in the k-edge digital subtraction angiography project, which will be used for correcting the angiography images taken by another detector at the same time. The Multi-channel ionization chamber calibration characteristics are measured using 2 kW X-ray tube with molybdenum anode with characteristic energy of 17.44 keV. According to the fast drift velocity of the electrons relative to the positive ions, the electrons will be collected faster at the anode and will induce current signals, while the positive ions is still drifting towards the cathode. However the accumulation of the slow ions inside the detector disturbs the homogeneous applied electric field and leads to what is known a space charge effect. In this work the space charge effect is measured with very high synchrotron photons intensity from EDR beam line at BESSYII. The strong attenuation in the measured amplitude signal occurs when operating the chamber in the recombination region. A plateau is observed at the amplitude signal when

  18. Characterization of a new ionization chamber in radiotherapy beams: angular dependence and variation of response with distance.

    Science.gov (United States)

    Silva, Jonas O; Linda V E, Caldas

    2012-10-01

    A new double faced ionization chamber was constructed at the Calibration Laboratory of IPEN. It has different collecting electrode materials: aluminum and graphite. It was irradiated in standard radiotherapy beams ((60)Co and X-rays). The response variation with distance and the angular dependence of this ionization chamber were evaluated. It was verified that the chamber response follows the inverse square law within a maximum variation of 11.2% in relation to the reference value. For the angular dependence it showed good agreement with international standards.

  19. Detection and measurement of delay in the yield of negative ions from the ionization chamber of a mass spectrometer

    Science.gov (United States)

    Lukin, V. G.; Khvostenko, O. G.; Tuimedov, G. M.

    2016-02-01

    The times of extraction of negative ions from the ionization chamber of a mass spectrometer have been measured. The obtained values amount to several dozen microseconds or above—that is, significantly exceed the time of free ion escape from the chamber. It is established that ions are retained in the ionization chamber because of their adsorption on the inner surface. This leads to distortion of the experimentally measured lifetimes of negative ions that become unstable with respect to autodetachment of the excess electron.

  20. Multi-Sampling Ionization Chamber (MUSIC) for measurements of fusion reactions with radioactive beams

    Science.gov (United States)

    Carnelli, P. F. F.; Almaraz-Calderon, S.; Rehm, K. E.; Albers, M.; Alcorta, M.; Bertone, P. F.; Digiovine, B.; Esbensen, H.; Fernández Niello, J.; Henderson, D.; Jiang, C. L.; Lai, J.; Marley, S. T.; Nusair, O.; Palchan-Hazan, T.; Pardo, R. C.; Paul, M.; Ugalde, C.

    2015-11-01

    A detection technique for high-efficiency measurements of fusion reactions with low-intensity radioactive beams was developed. The technique is based on a Multi-Sampling Ionization Chamber (MUSIC) operating as an active target and detection system, where the ionization gas acts as both target and counting gas. In this way, we can sample an excitation function in an energy range determined by the gas pressure, without changing the beam energy. The detector provides internal normalization to the incident beam and drastically reduces the measuring time. In a first experiment we tested the performance of the technique by measuring the 10,13,15C+12C fusion reactions at energies around the Coulomb barrier.

  1. Multi-Sampling Ionization Chamber (MUSIC) for measurements of fusion reactions with radioactive beams

    Energy Technology Data Exchange (ETDEWEB)

    Carnelli, P.F.F. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Laboratorio TANDAR, Comisión Nacional de Energía Atómica, Av. Gral. Paz 1499, B1650KNA, San Martín, Buenos Aires (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas, Av. Rivadavia 1917, C1033AAJ Buenos Aires (Argentina); Almaraz-Calderon, S. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Rehm, K.E., E-mail: rehm@anl.gov [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Albers, M.; Alcorta, M.; Bertone, P.F.; Digiovine, B.; Esbensen, H. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Fernández Niello, J. [Laboratorio TANDAR, Comisión Nacional de Energía Atómica, Av. Gral. Paz 1499, B1650KNA, San Martín, Buenos Aires (Argentina); Universidad Nacional de San Martín, Campus Miguelete, B1650BWA San Martín, Buenos Aires (Argentina); Henderson, D.; Jiang, C.L. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Lai, J. [Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 (United States); Marley, S.T.; Nusair, O.; Palchan-Hazan, T.; Pardo, R.C. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States); Paul, M. [Racah Institute of Physics, Hebrew University, Jerusalem (Israel); Ugalde, C. [Physics Division, Argonne National Laboratory, Argonne, IL 60439 (United States)

    2015-11-01

    A detection technique for high-efficiency measurements of fusion reactions with low-intensity radioactive beams was developed. The technique is based on a Multi-Sampling Ionization Chamber (MUSIC) operating as an active target and detection system, where the ionization gas acts as both target and counting gas. In this way, we can sample an excitation function in an energy range determined by the gas pressure, without changing the beam energy. The detector provides internal normalization to the incident beam and drastically reduces the measuring time. In a first experiment we tested the performance of the technique by measuring the {sup 10,13,15}C+{sup 12}C fusion reactions at energies around the Coulomb barrier.

  2. Calibration and efficiency curve of SANAEM ionization chamber for activity measurements.

    Science.gov (United States)

    Yeltepe, Emin; Kossert, Karsten; Dirican, Abdullah; Nähle, Ole; Niedergesäß, Christiane; Kemal Şahin, Namik

    2016-03-01

    A commercially available Fidelis ionization chamber was calibrated and assessed in PTB with activity standard solutions. The long-term stability and linearity of the system was checked. Energy-dependent efficiency curves for photons and beta particles were determined, using an iterative method in Excel™, to enable calibration factors to be calculated for radionuclides which were not used in the calibration. Relative deviations between experimental and calculated radionuclide efficiencies are of the order of 1% for most photon emitters and below 5% for pure beta emitters. The system will enable TAEK-SANAEM to provide traceable activity measurements.

  3. IFIN-HH ionization chamber calibration and its validation; electrometric system improvement.

    Science.gov (United States)

    Sahagia, M; Wätjen, A C; Luca, A; Ivan, C

    2010-01-01

    The paper presents the results obtained in the calibration of the CENTRONIC IG12/20A ionization chamber for 18 gamma ray emitters, and its improvement with a Keithley 6517A electrometer. The calibration figures were determined either directly in pA MBq(-1) units, or calculated from old units, by using the system capacity value. The calibration figures, determined with RML's standards, are compared with those deduced from the KCRV or the mean of the comparisons, and the values determined at PTB-Germany.

  4. Application of patent BR102013018500-0 in well type ionization chambers

    Science.gov (United States)

    Sousa, C. H. S.; Peixoto, J. G. P.

    2016-07-01

    The definition of the radioactive sample position in a well type ionization chamber is the largest source of uncertainty in the measurement of quantity activity. The determination of this parameter in two activimeters helped to improve their accuracies, from 2.62 and 2.59% to 3.87 and 1.74%, with and without the use of the positioning device, concluding, that with their use has reached an uncertainty of U =2276 and 0.2677% (k = 2) 95.45%.

  5. IFIN-HH ionization chamber calibration and its validation; electrometric system improvement

    Energy Technology Data Exchange (ETDEWEB)

    Sahagia, M., E-mail: msahagia@nipne.r [' Horia Hulubei' National Institute of R and D for Physics and Nuclear Engineering, IFIN-HH, P.O. Box MG-6, Bucharest, RO-77125 (Romania); Waetjen, A.C.; Luca, A.; Ivan, C. [' Horia Hulubei' National Institute of R and D for Physics and Nuclear Engineering, IFIN-HH, P.O. Box MG-6, Bucharest, RO-77125 (Romania)

    2010-07-15

    The paper presents the results obtained in the calibration of the CENTRONIC IG12/20A ionization chamber for 18 gamma ray emitters, and its improvement with a Keithley 6517A electrometer. The calibration figures were determined either directly in pA MBq{sup -1} units, or calculated from old units, by using the system capacity value. The calibration figures, determined with RML's standards, are compared with those deduced from the KCRV or the mean of the comparisons, and the values determined at PTB-Germany.

  6. Multi-layered parallel plate ionization chamber for cross-section measurements of minor actinides

    Energy Technology Data Exchange (ETDEWEB)

    Hirose, K., E-mail: hirose@lns.tohoku.ac.j [Research Center for Electron Photon Science, Tohoku University, Sendai 982-0826 (Japan); Ohtsuki, T.; Shibasaki, Y. [Research Center for Electron Photon Science, Tohoku University, Sendai 982-0826 (Japan); Iwasa, N. [Department of Physics, Tohoku University, Sendai 980-8578 (Japan); Hori, J.; Takamiya, K.; Yashima, H. [Research Reactor Institute, Kyoto University, Kumatori-cho, Sennangun, Osaka 590-0494 (Japan); Nishio, K. [Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 (Japan); Kiyanagi, Y. [Graduate School of Engineering, Hokkaido University, Kita-13, Nishi-8, Kita-ku, Sapporo 060-8628 (Japan)

    2010-09-21

    A multi-layered parallel plate ionization chamber (MLPPIC) has been developed for the measurement of neutron-induced fission cross-sections using the lead slowing-down neutron spectrometer at the Research Reactor Institute, Kyoto University. The MLPPIC consists of two sets of multi-layered electrodes to detect fission fragments from two samples located back-to-back between them. The performance of the MLPPIC was tested with a spontaneous fission of {sup 248}Cm. The cross-section for the neutron-induced fission of {sup 241}Am was successfully obtained using that of {sup 235}U as a reference.

  7. Application of patent BR102013018500-0 in well type ionization chambers

    Energy Technology Data Exchange (ETDEWEB)

    Sousa, C.H.S.; Peixoto, J.G.P., E-mail: chenriques2@ird.gov.br [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    The definition of the radioactive sample position in a well type ionization chamber is the largest source of uncertainty in the measurement of quantity activity. The determination of this parameter in two activimeter helped to improve their accuracies, from 2.62 and 2.59% to 3.87 and 1.74%, with and without the use of the positioning device, concluding, that with their use has reached an uncertainty of U = 0.2276 and 0.2677 % (k = 2) 95.45%. (author)

  8. (n,{alpha}) cross section measurement of gaseous sample using gridded ionization chamber. Cross section determination

    Energy Technology Data Exchange (ETDEWEB)

    Sanami, Toshiya; Baba, Mamoru; Saito, Keiichiro; Ibara, Yasutaka; Hirakawa, Naohiro [Tohoku Univ., Sendai (Japan). Faculty of Engineering

    1997-03-01

    We are developing a method of (n,{alpha}) cross section measurement using gaseous samples in a gridded ionization chamber (GIC). This method enables cross section measurements in large solid angle without the distortion by the energy loss in a sample, but requires a method to estimate the detection efficiency. We solve this problem by using GIC signals and a tight neutron collimation. The validity of this method was confirmed through the {sup 12}C(n,{alpha}{sub 0}){sup 9}Be measurement. We applied this method to the {sup 16}O(n,{alpha}){sup 13}C cross section around 14.1 MeV. (author)

  9. (n, {alpha}) cross section measurement of light nuclei using gridded ionization chamber and gaseous sample

    Energy Technology Data Exchange (ETDEWEB)

    Sanami, Toshiya; Baba, Mamoru; Saito, Keiichiro; Ibara, Yasutaka; Yamazaki, Tetsuro; Sato, Jun; Hirakawa, Naohiro [Tohoku Univ., Sendai (Japan)

    1998-03-01

    We have developed a measuring method of (n, {alpha}) cross section by using gaseous sample in a gridded ionization chamber. In this study, we measured the {sup 12}C(n, {alpha}{sub 0}) and the {sup 16}O(n, {alpha}{sub 0}), (n, {alpha}{sub 123}) cross sections for En=11.5 and 12.8 MeV neutrons. We also deduced the {sup 12}C(n, x{alpha}) spectrum and analyzed the data by a kinematic calculation combined with the reaction data of the {sup 12}C(n, n`3{alpha}). (author)

  10. Radiation induced currents in parallel plate ionization chambers: measurement and Monte Carlo simulation for megavoltage photon and electron beams.

    Science.gov (United States)

    Abdel-Rahman, Wamied; Seuntjens, Jan P; Verhaegen, Frank; Podgorsak, Ervin B

    2006-09-01

    Polarity effects in ionization chambers are caused by a radiation induced current, also known as Compton current, which arises as a charge imbalance due to charge deposition in electrodes of ionization chambers. We used a phantom-embedded extrapolation chamber (PEEC) for measurements of Compton current in megavoltage photon and electron beams. Electron contamination of photon beams and photon contamination of electron beams have a negligible effect on the measured Compton current. To allow for a theoretical understanding of the Compton current produced in the PEEC effect we carried out Monte Carlo calculations with a modified user code, the COMPTON/ EGSnrc. The Monte Carlo calculated COMPTON currents agree well with measured data for both photon and electron beams; the calculated polarity correction factors, on the other hand, do not agree with measurement results. The conclusions reached for the PEEC can be extended to parallel-plate ionization chambers in general.

  11. Resistive wall heating due to image current on the beam chamber for a superconducting undulator.

    Energy Technology Data Exchange (ETDEWEB)

    Kim, S. H. (Accelerator Systems Division (APS))

    2012-03-27

    The image-current heating on the resistive beam chamber of a superconducting undulator (SCU) was calculated based on the normal and anomalous skin effects. Using the bulk resistivity of copper for the beam chamber, the heat loads were calculated for the residual resistivity ratios (RRRs) of unity at room temperature to 100 K at a cryogenic temperature as the reference. Then, using the resistivity of the specific aluminum alloy 6053-T5, which will be used for the SCU beam chamber, the heat loads were calculated. An electron beam stored in a storage ring induces an image current on the inner conducting wall, mainly within a skin depth, of the beam chamber. The image current, with opposite charge to the electron beam, travels along the chamber wall in the same direction as the electron beam. The average current in the storage ring consists of a number of bunches. When the pattern of the bunched beam is repeated according to the rf frequency, the beam current may be expressed in terms of a Fourier series. The time structure of the image current is assumed to be the same as that of the beam current. For a given resistivity of the chamber inner wall, the application ofthe normal or anomalous skin effect will depend on the harmonic numbers of the Fourier series of the beam current and the temperature of the chamber. For a round beam chamber with a ratius r, much larger than the beam size, one can assume that the image current density as well as the density square, may be uniform around the perimeter 2{pi}r. For the SCU beam chamber, which has a relatively narrow vertical gap compared to the width, the effective perimeter was estimated since the heat load should be proportional to the inverse of the perimeter.

  12. Proton energy determination using activated yttrium foils and ionization chambers for activity assay

    Energy Technology Data Exchange (ETDEWEB)

    Avila-Rodriguez, M.A. [Turku PET Centre, University of Turku, Kiinamyllynkatu 4-8, 20520 Turku (Finland); Unidad PET/CT-Ciclotron, Facultad de Medicina, Universidad Nacional Autonoma de Mexico, Edificio de Investigacion P.B, Cd. Universitaria, Circ. Interior, C.P. 04510 Mexico D.F. (Mexico)], E-mail: avilarod@uwalumni.com; Rajander, J.; Lill, J.-O. [Turku PET Centre, Abo Akademi University, Porthansg 3, 20500 Turku (Finland); Gagnon, K. [Edmonton PET Centre, Cross Cancer Institute, 11560 University Ave., Edmonton, AB, T6G 1Z2 (Canada); Schlesinger, J. [Turku PET Centre, University of Turku, Kiinamyllynkatu 4-8, 20520 Turku (Finland); Wilson, J.S.; McQuarrie, S.A. [Edmonton PET Centre, Cross Cancer Institute, 11560 University Ave., Edmonton, AB, T6G 1Z2 (Canada); Solin, O. [Turku PET Centre, University of Turku, Kiinamyllynkatu 4-8, 20520 Turku (Finland)

    2009-05-15

    Excitation functions of the {sup 89}Y(p, xn) nuclear reactions were measured up to 18 MeV by the conventional activation method using the stacked-foil technique, and the irradiation of single foils. Activity assays of the irradiated foils were performed via ionization chamber and gamma spectroscopy methods. Activity ratios of the activation products were measured in two different facilities and evaluated for use as a practical and simple method for proton energy determinations. Cross section values measured in this work were compared with published data and with theoretical values as determined by the nuclear reaction model code EMPIRE II. In general, there was a good agreement between the experimental and theoretical values of the cross section data. Activity ratios of the isomeric and ground state of {sup 89}Zr measured via ionization chamber were found to be useful for proton energy determinations in the energy range from 7 to 15 MeV. Proton energies above 13 MeV were accurately determined using the {sup 89g}Zr/{sup 88}Zr and {sup 89g}Zr/{sup 88}Y activity ratios measured via gamma spectroscopy.

  13. High-rate axial-field ionization chamber for particle identification of Radioactive beams

    Science.gov (United States)

    Desouza, Romualdo; Vadas, Justin; Singh, Varinderjit; Visser, G.; Alexander, A.; Hudan, S.; Huston, J.; Wiggins, B.; Chbihi, A.; Famiano, M.; Bischak, M.

    2017-01-01

    The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. The detector is optimized for use with low-energy radioactive beams (<) 5 MeV/A. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a rise-time of 60 to 70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate while providing a time resolution of 6 to 8 ns. Tests with an α source establish the detector energy resolution as 8 % for an energy deposit of 3.5 MeV. Beam tests indicate that the detector is an effective tool for the characterization of low-energy radioactive beams at beam intensities up to 3 x 105 ions/s. Supported by the U.S. DOE under Award # DE-FG02-88ER-40404 and the NSF under Grant No. 1342962.

  14. High-rate axial-field ionization chamber for particle identification of radioactive beams

    CERN Document Server

    Vadas, J; Visser, G; Alexander, A; Hudan, S; Huston, J; Wiggins, B B; Chbihi, A; Famiano, M; Bischak, M M; deSouza, R T

    2016-01-01

    The design, construction and performance characteristics of a simple axial-field ionization chamber suitable for identifying ions in a radioactive beam are presented. Optimized for use with low-energy radioactive beams (< 5 MeV/A) the detector presents only three 0.5 $\\mu$m/cm$^2$ foils to the beam in addition to the detector gas. A fast charge sensitive amplifier (CSA) integrated into the detector design is also described. Coupling this fast CSA to the axial field ionization chamber produces an output pulse with a risetime of 60-70 ns and a fall time of 100 ns, making the detector capable of sustaining a relatively high rate. Tests with an $\\alpha$ source establish the detector energy resolution as $\\sim$8 $\\%$ for an energy deposit of $\\sim$3.5 MeV. The energy resolution with beams of 2.5 and 4.0 MeV/A $^{39}$K ions and the dependence of the energy resolution on beam intensity is measured. At an instantaneous rate of 3 x 10$^5$ ions/s the energy resolution has degraded to 14% with a pileup of 12%. The go...

  15. Development of Gas Ionization Chambers with Coplanar Electrodes for Alpha-ray Spectrometry

    Science.gov (United States)

    Iwasaki, Kenta; Tanaka, Naomichi; Murakami, Kohei; Kusano, Hiroki; Shibamura, Eido; Hasebe, Nobuyuki; Miyajima, Mitsuhiro

    A large-area alpha-ray spectrometer is required to measure the low level alpha emitters in environmental samples, which may be distributed in the vicinity of nuclear power plants. A gas ionization chamber with a coplanar electrode has attractive features such as with mechanical ruggedness, easy handling, easy fabrication of large electrode, and relatively well-known performance. We have investigated the performance of a gas ionization chamber with a coplanar electrode for alpha-ray spectrometry, particularly in the energy resolution. The present experiment shows that the energy resolution in the full width at half maximum (FWHM) is 129 keV (= 2.7%) for alpha-rays from Np with an energy of 4.78 MeV, 120 keV (= 2.2%) for those with 5.49 MeV from Am, and 109 keV (= 1.9%) for those with 5.81 MeV from Cm. It is found that the energy resolution obtained at the present experiment is dominated in the electronic noise caused by the large capacitance existed between the collecting anode (CA) and non-collecting anode (NCA) in the coplanar electrode.

  16. Strip Ionization Chamber as Beam Monitor in the Proton Therapy Eye Treatment

    Science.gov (United States)

    Marchetto, F.; Cirio, R.; Garella, M. A.; Giordanengo, S.; Boriano, A.; Givehchi, N.; La Rosa, A.; Peroni, C.; Donetti, M.; Bourhaleb, F.; Pitta', G.; Cirrone, G. A. P.; Cuttone, G.; Raffaele, L.; Sabini, M. G.; Valastro, L.

    2006-04-01

    Since spring 2002, ocular pathologies have been treated in Catania at the Centro di AdroTerapia e Applicazioni Nucleari Avanzate (CATANA) within a collaboration between INFN Laboratori Nazionali del Sud (LNS), Physics Department, Ophthalmology Institute, Radiology Institute of the Catania University and CSFNSM Catania. A beam line from a 62 MeV Superconducting Cyclotron is used to treat shallow tumors. The beam is conformed to the tumor shape with a passive delivery system. A detector system has been developed in collaboration with INFN-Torino to be used as real time beam monitor. The detector, placed upstream of the patient collimator, consists of two parallel plate ionization chambers with the anode segmented in strips. Each anode is made of 0.5 mm-wide 256 strips corresponding to (12.8 × 12.8) cm2 sensitive area. With the two strip ionization chambers one can measure the relevant beam parameters during treatment to probe both asymmetry and flatness. In the test carried out at CATANA the detector has been used under different and extreme beam conditions. Preliminary results are given for profiles and skewness, together with a comparison with reference detectors.

  17. Calibration of ionization chambers in IAEA water phantom; Kalibrering av ionekamre i IAEA-vannfantom

    Energy Technology Data Exchange (ETDEWEB)

    Bjerke, H.; Mikkelborg, O.

    1995-11-01

    The calibration in a water phantom is realised at the Secondary Standard Dosimetry Laboratory in Norway. The method is valid for chambers used in high energy radiation therapy. The method, setup and corrections in the calibration are described. The absorbed dose to air calibration factor, N{sub D}, will have an uncertainty of {approx}0.8% (k=1). 15 refs., 7 figs., 5 tabs.

  18. Monte Carlo Study of High Pressure Ion Chamber Energy Response

    Institute of Scientific and Technical Information of China (English)

    GAO; Fei; XIAO; Xue-fu; ZHANG; Li; NI; Ning; HOU; Jin-bing

    2012-01-01

    <正>High pressure gas ionization chamber (HPIC) is the most popular instrument for environmental radiation measurement because of low inherent background, good stability, better directional response and high precision. The energy response of HIPC is not good because its wall is not made of air effective material, and the response of 100 keV photons is about 60% higher than normal. The energy response of

  19. Real-time dielectric-film thickness measurement system for plasma processing chamber wall monitoring.

    Science.gov (United States)

    Kim, Jin-Yong; Chung, Chin-Wook

    2015-12-01

    An in-situ real-time processing chamber wall monitoring system was developed. In order to measure the thickness of the dielectric film, two frequencies of small sinusoidal voltage (∼1 V) signals were applied to an electrically floated planar type probe, which is positioned at chamber wall surface, and the amplitudes of the currents and the phase differences between the voltage and current were measured. By using an equivalent sheath circuit model including a sheath capacitance, the dielectric thickness can be obtained. Experiments were performed in various plasma condition, and reliable dielectric film thickness was obtained regardless of the plasma properties. In addition, availability in commercial chamber for plasma enhanced chemical vapor deposition was verified. This study is expected to contribute to the control of etching and deposition processes and optimization of periodic maintenance in semiconductor manufacturing process.

  20. A Fusion Chamber Design with a Liquid First Wall and Divertor

    Energy Technology Data Exchange (ETDEWEB)

    Nygren, R; Sze, D; Nelson, B; Fogarty, P; Eberle, C; Rognlien, T; Rensink, M; Smolentsev, S; Youssef, M; Sawan, M; Merrill, B; Majeski, R

    2003-11-11

    The APEX study is investigating the use of free flowing liquid surfaces to form the inner surface of the chamber around a fusion plasma. We present a design for the chamber of a 3840MW fusion reactor based on the configuration for the chamber and magnets from ARIESRS but with a fast flowing molten salt of mixed Be, Li and Na fluorides for the first wall and divertor and molten salt blanket with a ferritic steel structure. Our design analysis includes strong radiation from the core and edge plasma, (liquid) MHD effects on the weakly conducting molten salt, a recycling first wall stream that enables a high efficiency thermal conversion, and evaluations of breeding, neutronics, tritium recovery and safety.

  1. Evaluation of a special pencil ionization chamber by the Monte Carlo method; Avaliacao de uma camara de ionizacao tipo lapis especial pelo metodo de Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Mendonca, Dalila; Neves, Lucio P.; Perini, Ana P., E-mail: anapaula.perini@ufu.br [Universidade Federal de Uberlandia (INFIS/UFU), Uberlandia, MG (Brazil). Instituto de Fisica; Santos, William S.; Caldas, Linda V.E. [Instituto de Pesquisas Energeticas e Nucleres (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    A special pencil type ionization chamber, developed at the Instituto de Pesquisas Energeticas e Nucleares, was characterized by means of Monte Carlo simulation to determine the influence of its components on its response. The main differences between this ionization chamber and commercial ionization chambers are related to its configuration and constituent materials. The simulations were made employing the MCNP-4C Monte Carlo code. The highest influence was obtained for the body of PMMA: 7.0%. (author)

  2. Ozone deposition to an oat crop ( Avena sativa L.) grown in open-top chambers and in the ambient air

    Science.gov (United States)

    Pleijel, H.; Wallin, G.; Karlsson, P. E.; Skarby, L.; Sellden, G.

    Fluxes and deposition velocities for ozone were determined for open-top chambers with and without an oat crop, and for the adjacent field, using a resistance analogue model and the aerodynamic wind-profile method, respectively. During a period when the canopy was green and the ambient wind speeds modest, the fluxes and deposition velocities were higher in the chamber with plants than in the field crop. The deposition to chamber walls and soil in the chamber only accounted for part of that difference. The deposition velocity for ozone to the crop was light-dependent both in the chamber with plants and in the ambient air. With increasing plant senescence, the deposition velocity declined and the light dependence disappeared. Fluctuations in deposition velocity superimposed on the overall declining trend followed the same temporal pattern in the chambers with and without plants. These fluctuations in deposition velocity may partly be explained by variations in surface wetness. Differences in boundary layer conductance between chamber and ambient, which under certain conditions may significantly influence the validity of the chamber as a test system, were observed.

  3. Assessing the environmental performance of stabilised rammed earth walls using a climatic simulation chamber

    Energy Technology Data Exchange (ETDEWEB)

    Hall, Matthew R. [School of the Built Environment, University of Nottingham, University Park, Nottingham NG7 2RD (United Kingdom)

    2007-01-15

    The SHU climatic simulation chamber is a novel piece of apparatus that allows testing of full-sized walls with realistic inner and outer wall climatic conditions. Four SRE test walls were successfully constructed and tested over four separate regimes to measure physical properties such as pressure-driven moisture ingress, rate of moisture penetration, and internal/interstitial condensation. The walls far exceeded a series of cyclic pressure-driven rainfall penetration tests based on BS 4315-2. After 5 days of exposure to static pressure-driven moisture ingress there was no evidence of moisture penetration or erosion. The embedded sensor array detected no significant increase in the relative humidity or liquid moisture content inside the test walls, throughout a range of temperature differentials with high levels of humidity, indicating a negligible risk of internal or interstitial condensation. (author)

  4. Methodology for calibration of ionization chambers for X-ray of low energy in absorbed dose to water

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, C.T.; Vivolo, V.; Potiens, M.P.A., E-mail: camila_fmedica@hotmail.com [Instituto de Pesquisas Energeticas e Nucleres (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    The beams of low energy X-ray (10 to 150 kV) are used in several places in the world to treat a wide variety of surface disorders, and between these malignancies. As in Brazil, at this moment, there is no calibration laboratory providing the control service or calibration of parallel plate ionization chambers, the aim of this project was to establish a methodology for calibration of this kind of ionization chambers at low energy X-ray beams in terms of absorbed dose to water using simulators in the LCI. (author)

  5. Performance of a multi-axis ionization chamber array in a 1.5 T magnetic field.

    Science.gov (United States)

    Smit, K; Kok, J G M; Lagendijk, J J W; Raaymakers, B W

    2014-04-07

    At the UMC Utrecht a prototype MR-linac has been installed. The system consists of an 8 MV Elekta linear accelerator and a 1.5 T Philips MRI system. This paper investigates the performance of the IC PROFILER™, a multi-axis ionization chamber array, in a 1.5 T magnetic field. The influence of the magnetic field on the IC PROFILER™ reproducibility, dose response linearity, pulse rate frequency dependence, power to electronics, panel orientation and ionization chamber shape were investigated. The linearity, reproducibility, pulse rate frequency dependence, panel orientation and ionization chamber shape are unaffected by the magnetic field. When the measurements results are normalized to the centre reference chamber, the measurements can commence unaltered. Orientation of the ionization chambers in the magnetic field is of importance, therefore caution must be taken when comparing or normalizing results from several different axes. IC PROFILER™ dose profiles were compared with film dose profiles obtained simultaneously in the MR-linac. Deviation between the film and the IC PROFILER™ data was caused by the noise in the film, indicating correct performance of the IC PROFILER™ in the transverse 1.5 T magnetic field.

  6. Performance of a multi-axis ionization chamber array in a 1.5 T magnetic field

    Science.gov (United States)

    Smit, K.; Kok, J. G. M.; Lagendijk, J. J. W.; Raaymakers, B. W.

    2014-04-01

    At the UMC Utrecht a prototype MR-linac has been installed. The system consists of an 8 MV Elekta linear accelerator and a 1.5 T Philips MRI system. This paper investigates the performance of the IC PROFILER™, a multi-axis ionization chamber array, in a 1.5 T magnetic field. The influence of the magnetic field on the IC PROFILER™ reproducibility, dose response linearity, pulse rate frequency dependence, power to electronics, panel orientation and ionization chamber shape were investigated. The linearity, reproducibility, pulse rate frequency dependence, panel orientation and ionization chamber shape are unaffected by the magnetic field. When the measurements results are normalized to the centre reference chamber, the measurements can commence unaltered. Orientation of the ionization chambers in the magnetic field is of importance, therefore caution must be taken when comparing or normalizing results from several different axes. IC PROFILER™ dose profiles were compared with film dose profiles obtained simultaneously in the MR-linac. Deviation between the film and the IC PROFILER™ data was caused by the noise in the film, indicating correct performance of the IC PROFILER™ in the transverse 1.5 T magnetic field.

  7. [Theoretical investigation of the saturation correction for ionization chambers irradiated with pulsed beams of arbitrary pulse length].

    Science.gov (United States)

    Karsch, Leonhard; Pawelke, Jörg

    2014-09-01

    In ionization chambers, not all released charge is collected due to the recombination of charge carriers. This effect is taken into account by the saturation correction factor kS. A physical description of the correction factor has been established for pulsed radiation. However, it is only accurate when the pulse length is short compared with the collection time of the ionization chamber. In this paper we develop a description of the saturation correction for radiation pulses of arbitrary length. For this, a system of partial differential equations is solved iteratively. The numerical solutions are verified experimentally for a Roos ionization chamber (PTW TM34001) exposed to a pulsed electron beam. The results of this iterative procedure describe the experimental data well. The calculations are also possible for beam structures which are experimentally hard to get and thereby contribute to a better understanding and correct description of the saturation correction at arbitrary pulse length. Among other things the pulse length dependent distributions of the charge carriers in the ionization chamber is calculated, inclusive of the transition to the conditions prevailing in the case of continuous irradiation. Furthermore is shown that the formula for kS established by Hochhäuser and Balk is applicable even at arbitrary pulse length, if pulse duration dependent effective values are used for the parameters a and p. These effective values have been determined for the Roos chamber at pulse lengths up to 300 μs.

  8. Electron beam quality kQ,Q0 factors for various ionization chambers: a Monte Carlo investigation with penelope

    Science.gov (United States)

    Erazo, F.; Brualla, L.; Lallena, A. M.

    2014-11-01

    In this work we calculate the beam quality correction factor {{k}\\text{Q,{{\\text{Q}}0}}} for various plane-parallel ionization chambers. A set of Monte Carlo calculations using the code penelope/penEasy have been carried out to calculate the overall correction factor fc,Q for eight electron beams corresponding to a Varian Clinac 2100 C/D, with nominal energies ranging between 6 MeV and 22 MeV, for a 60Co beam, that has been used as the reference quality Q0 and also for eight monoenergetic electron beams reproducing the quality index R50 of the Clinac beams. Two field sizes, 10 × 10 cm2 and 20 × 20 cm2 have been considered. The {{k}\\text{Q,{{\\text{Q}}0}}} factors have been calculated as the ratio between fc,Q and {{f}\\text{c,{{\\text{Q}}0}}} . Values for the Exradin A10, A11, A11TW, P11, P11TW, T11 and T11TW ionization chambers, manufactured by Standard Imaging, as well as for the NACP-02 have been obtained. The results found with the Clinac beams for the two field sizes analyzed show differences below 0.6%, even in the case of the higher energy electron beams. The {{k}\\text{Q,{{\\text{Q}}0}}} values obtained with the Clinac beams are 1% larger than those found with the monoenergetic beams for the higher energies, above 12 MeV. This difference can be ascribed to secondary photons produced in the linac head and the air path towards the phantom. Contrary to what was quoted in a previous work (Sempau et al 2004 Phys. Med. Biol. 49 4427-44), the beam quality correction factors obtained with the complete Clinac geometries and with the monoenergetic beams differ significantly for energies above 12 MeV. Material differences existing between chambers that have the same geometry produce non-negligible modifications in the value of these correction factors.

  9. Improved design and construction of an ionization chamber for the CSNS beam loss monitor (BLM)

    Institute of Scientific and Technical Information of China (English)

    TIAN Jian-Min; XU Mei-Hang; ZHAO Zhong-Liang; CHEN Chang; RUAN Xiang-Dong; CHEN Yuan-Bo; XU Tao-Guang; LU Shuang-Tong

    2012-01-01

    Based on the first ionization chamber (IC) prototype,the structure,working gas component and electrode material of the IC are improved.The test of the improved IC shows that the plateau length is about 2000 V,the plateau slope is less than 0.2%/100 V,the sensitivity is 19.6 pA/rad.h-1,the up-limitation of the linearity can be up to 3.6× 105 rad/h,and the applied voltage can be operated to 3500 V.The test results show that the performance of the improved IC meets the requirements of the beam loss monitor.

  10. A new multi-strip ionization chamber used as online beam monitor for heavy ion therapy

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Zhiguo [Institute of Modern Physics, Chinese Academy of Sciences, 509 Nanchang Rd., Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Mao, Ruishi [Institute of Modern Physics, Chinese Academy of Sciences, 509 Nanchang Rd., Lanzhou 730000 (China); Duan, Limin, E-mail: lmduan@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Sciences, 509 Nanchang Rd., Lanzhou 730000 (China); She, Qianshun; Hu, Zhengguo; Li, He; Lu, Ziwei; Zhao, Qiecheng; Yang, Herun; Su, Hong; Lu, Chengui; Hu, Rongjiang; Zhang, Junwei [Institute of Modern Physics, Chinese Academy of Sciences, 509 Nanchang Rd., Lanzhou 730000 (China)

    2013-11-21

    A multi-strip ionization chamber has been built for precise and fast monitoring of the carbon beam spatial distribution at Heavy Ion Researched Facility of Lanzhou Cooling Storing Ring (HIRFL-CSR). All the detector's anode, cathode and sealed windows are made by 2μm aluminized Mylar film in order to minimize the beam lateral deflection. The sensitive area of the detector is (100×100)mm{sup 2}, with the anode segmented in 100 strips, and specialized front-end electronics has been developed for simplifying the data acquisition and quick feedback of the relevant parameters to beam control system. It can complete one single beam profile in 200μs.

  11. A large area position-sensitive ionization chamber for heavy-ion-induced reaction studies

    CERN Document Server

    Pant, L M; Dinesh, B V; Thomas, R G; Saxena, A; Sawant, Y S; Choudhury, R K

    2002-01-01

    A large area position-sensitive ionization chamber with a wide dynamic range has been developed to measure the mass, charge and energy of the heavy ions and the fission fragments produced in heavy-ion-induced reactions. The split anode geometry of the detector makes it suitable for both particle identification and energy measurements for heavy ions and fission fragments. The detector has been tested with alpha particles from sup 2 sup 4 sup 1 Am- sup 2 sup 3 sup 9 Pu source, fission fragments from sup 2 sup 5 sup 2 Cf and the heavy-ion beams from the 14UD Mumbai Pelletron accelerator facility. Using this detector, measurements on mass and total kinetic energy distributions in heavy-ion-induced fusion-fission reactions have been carried out for a wide range of excitation energies. Results on deep inelastic collisions and mass-energy correlations on different systems using this detector setup are discussed.

  12. A general algorithm for calculation of recombination losses in ionization chambers exposed to ion beams

    CERN Document Server

    Christensen, Jeppe brage; Bassler, Niels

    2016-01-01

    Dosimetry with ionization chambers in clinical ion beams for radiation therapy requires correction for recombination effects. However, common radiation protocols discriminate between initial and general recombination and provide no universal correction method for the presence of both recombination types in ion beams of charged particles heavier than protons. Here, we present the open source code IonTracks, where the combined initial and general recombination effects in principle can be predicted for any ion beam with arbitrary particle-energy spectrum and temporal structure. IonTracks uses track structure theory to distribute the charge carriers in ion tracks. The charge carrier movements are governed by a pair of coupled differential equations, based on fundamental physical properties as charge carrier drift, diffusion, and recombination, which are solved numerically while the initial and general charge carrier recombination is computed. The algorithm is numerically stable and in accordance with experimental...

  13. Ionization chamber array for patient specific VMAT, Tomotherapy and IMRT QA

    Energy Technology Data Exchange (ETDEWEB)

    Stathakis, Sotiri, E-mail: Stathakis@uthscsa.ed [Department of Radiation Oncology, Cancer Therapy and Research Center at the University of Texas Health Science Center, San Antonio TX 78229 (United States)

    2010-11-01

    The evaluation between measured and calculated dose is essential in the patient specific quality assurance procedures for intensity modulated radiation therapy. The high complexity of volumetric arc radiotherapy, Tomotherpay and intensity modulated radiation therapy deliveries attributed to the dynamic and synchronization requirements of such techniques require new methods and potentially new tools for the quality assurance of such techniques. Studies evaluating the dosimetric performance of EDR2 film and a 2D ionization chamber array quality assurance device have been performed in our institution. Our results showed that differences between the detector systems are small. The respective gamma index histograms showed that when 3% dose difference and 3mm distance to agreement are used, more than 90% of the evaluated points were within the tolerance criteria

  14. Performance of a Large Area Avalanche Photodiode in a Liquid Xenon Ionization and Scintillation Chamber

    CERN Document Server

    Ni, K; Day, D; Giboni, K L; Lopes, J A M; Majewski, P; Yamashita, M

    2005-01-01

    Scintillation light produced in liquid xenon (LXe) by alpha particles, electrons and gamma-rays was detected with a large area avalanche photodiode (LAAPD) immersed in the liquid. The alpha scintillation yield was measured as a function of applied electric field. We estimate the quantum efficiency of the LAAPD to be 45%. The best energy resolution from the light measurement at zero electric field is 7.5%(sigma) for 976 keV internal conversion electrons from Bi-207 and 2.6%(sigma) for 5.5 MeV alpha particles from Am-241. The detector used for these measurements was also operated as a gridded ionization chamber to measure the charge yield. We confirm that using a LAAPD in LXe does not introduce impurities which inhibit the drifting of free electrons.

  15. A large area position-sensitive ionization chamber for heavy-ion-induced reaction studies

    Energy Technology Data Exchange (ETDEWEB)

    Pant, L.M. E-mail: lalit.pant@exp2.physik.uni-giessen.de; Biswas, D.C.; Dinesh, B.V.; Thomas, R.G.; Saxena, A.; Sawant, Y.S.; Choudhury, R.K

    2002-12-11

    A large area position-sensitive ionization chamber with a wide dynamic range has been developed to measure the mass, charge and energy of the heavy ions and the fission fragments produced in heavy-ion-induced reactions. The split anode geometry of the detector makes it suitable for both particle identification and energy measurements for heavy ions and fission fragments. The detector has been tested with {alpha} particles from {sup 241}Am-{sup 239}Pu source, fission fragments from {sup 252}Cf and the heavy-ion beams from the 14UD Mumbai Pelletron accelerator facility. Using this detector, measurements on mass and total kinetic energy distributions in heavy-ion-induced fusion-fission reactions have been carried out for a wide range of excitation energies. Results on deep inelastic collisions and mass-energy correlations on different systems using this detector setup are discussed.

  16. Quality assurance of proton beams using a multilayer ionization chamber system

    Energy Technology Data Exchange (ETDEWEB)

    Dhanesar, Sandeep; Sahoo, Narayan; Kerr, Matthew; Taylor, M. Brad; Summers, Paige; Zhu, X. Ronald; Poenisch, Falk; Gillin, Michael [Department of Radiation Physics and Proton Therapy Center, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 94, Houston, Texas 77030 (United States); Department of Radiation Physics and Proton Therapy Center, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 94, Houston, Texas 77030 and The University of Texas at Houston Graduate School of Biomedical Sciences, 6767 Bertner Avenue, S3.8344, Houston, Texas 77030 (United States); Department of Radiation Physics and Proton Therapy Center, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 94, Houston, Texas 77030 (United States); Department of Radiation Physics and Proton Therapy Center, The University of Texas MD Anderson Cancer Center, 1515 Holcombe Boulevard, Unit 94, Houston, Texas 77030 and The University of Texas at Houston Graduate School of Biomedical Sciences, 6767 Bertner Avenue, S3.8344, Houston, Texas 77030 (United States)

    2013-09-15

    Purpose: The measurement of percentage depth-dose (PDD) distributions for the quality assurance of clinical proton beams is most commonly performed with a computerized water tank dosimetry system with ionization chamber, commonly referred to as water tank. Although the accuracy and reproducibility of this method is well established, it can be time-consuming if a large number of measurements are required. In this work the authors evaluate the linearity, reproducibility, sensitivity to field size, accuracy, and time-savings of another system: the Zebra, a multilayer ionization chamber system.Methods: The Zebra, consisting of 180 parallel-plate ionization chambers with 2 mm resolution, was used to measure depth-dose distributions. The measurements were performed for scattered and scanned proton pencil beams of multiple energies delivered by the Hitachi PROBEAT synchrotron-based delivery system. For scattered beams, the Zebra-measured depth-dose distributions were compared with those measured with the water tank. The principal descriptors extracted for comparisons were: range, the depth of the distal 90% dose; spread-out Bragg peak (SOBP) length, the region between the proximal 95% and distal 90% dose; and distal-dose fall off (DDF), the region between the distal 80% and 20% dose. For scanned beams, the Zebra-measured ranges were compared with those acquired using a Bragg peak chamber during commissioning.Results: The Zebra demonstrated better than 1% reproducibility and monitor unit linearity. The response of the Zebra was found to be sensitive to radiation field sizes greater than 12.5 × 12.5 cm; hence, the measurements used to determine accuracy were performed using a field size of 10 × 10 cm. For the scattered proton beams, PDD distributions showed 1.5% agreement within the SOBP, and 3.8% outside. Range values agreed within −0.1 ± 0.4 mm, with a maximum deviation of 1.2 mm. SOBP length values agreed within 0 ± 2 mm, with a maximum deviation of 6 mm. DDF

  17. Unexpected bias in NIST 4πγ ionization chamber measurements.

    Science.gov (United States)

    Unterweger, M P; Fitzgerald, R

    2012-09-01

    In January of 2010, it was discovered that the source holder used for calibrations in the NIST 4πγ ionization chamber (IC) has not been stable. The positioning ring that determines the height of the sample in the reentrant tube of the IC has slowly shifted during 35 years of use. This has led to a slow change in the calibration factors for the various radionuclides measured by this instrument. The changes are dependent on γ-ray energy and the time the IC was calibrated for a given radionuclide. A review of the historic data with regard to when the calibrations were done has enabled us to approximate the magnitude of the changes with time. This requires a number of assumptions, and corresponding uncertainty components, including whether the changes in height were gradual or in steps as will be shown in drawings of sample holder. For calibrations the changes in calibration factors have been most significant for low energy gamma emitters such as (133)Xe, (241)Am, (125)I and (85)Kr. The corrections to previous calibrations can be approximated and the results corrected with an increase in the overall uncertainty. At present we are recalibrating the IC based on new primary measurements of the radionuclides measured on the IC. Likewise we have been calibrating a new automated ionization-chamber system. A bigger problem is the significant number of half-life results NIST has published over the last 35 years that are based on IC measurements. The effect on half-life is largest for long-lived radionuclei, especially low-energy γ-ray emitters. This presentation will review our results and recommend changes in values and/or uncertainties. Any recommendation for withdrawal of any results will also be undertaken.

  18. SU-D-213-04: Accounting for Volume Averaging and Material Composition Effects in An Ionization Chamber Array for Patient Specific QA

    Energy Technology Data Exchange (ETDEWEB)

    Fugal, M; McDonald, D; Jacqmin, D; Koch, N; Ellis, A; Peng, J; Ashenafi, M; Vanek, K [Medical University of South Carolina, Charleston, SC (United States)

    2015-06-15

    Purpose: This study explores novel methods to address two significant challenges affecting measurement of patient-specific quality assurance (QA) with IBA’s Matrixx Evolution™ ionization chamber array. First, dose calculation algorithms often struggle to accurately determine dose to the chamber array due to CT artifact and algorithm limitations. Second, finite chamber size and volume averaging effects cause additional deviation from the calculated dose. Methods: QA measurements were taken with the Matrixx positioned on the treatment table in a solid-water Multi-Cube™ phantom. To reduce the effect of CT artifact, the Matrixx CT image set was masked with appropriate materials and densities. Individual ionization chambers were masked as air, while the high-z electronic backplane and remaining solid-water material were masked as aluminum and water, respectively. Dose calculation was done using Varian’s Acuros XB™ (V11) algorithm, which is capable of predicting dose more accurately in non-biologic materials due to its consideration of each material’s atomic properties. Finally, the exported TPS dose was processed using an in-house algorithm (MATLAB) to assign the volume averaged TPS dose to each element of a corresponding 2-D matrix. This matrix was used for comparison with the measured dose. Square fields at regularly-spaced gantry angles, as well as selected patient plans were analyzed. Results: Analyzed plans showed improved agreement, with the average gamma passing rate increasing from 94 to 98%. Correction factors necessary for chamber angular dependence were reduced by 67% compared to factors measured previously, indicating that previously measured factors corrected for dose calculation errors in addition to true chamber angular dependence. Conclusion: By comparing volume averaged dose, calculated with a capable dose engine, on a phantom masked with correct materials and densities, QA results obtained with the Matrixx Evolution™ can be significantly

  19. Development of improved free-air ionisation chamber as absolute dosimetry standard for low-energy X rays in INER.

    Science.gov (United States)

    Chu, Chien-Hau; Kuan, Wei-Peng; Kurosawa, T; Lin, Uei-Tyng; Chen, Ing-Jane; Chen, Wei-Li

    2010-02-01

    The National Radiation Standard Laboratory of the Institute of Nuclear Energy Research (INER) designed and constructed an improved Attix style free-air ionisation chamber (FAC) for low-energy X-ray measurements. Clinically, X rays in this energy range are used in mammography radiology. This chamber is also used to perform air-kerma measurements. The original Attix two-sectional design was redesigned by INER using the piston design. The correction factors were determined experimentally for volume estimation, ion recombination and air attenuation. The aperture transmission, wall transmission, electron loss and photon scatter correction factors were determined using Monte Carlo calculations. INER established the Bureau International des Poids et Mesures (BIPM) X-ray beam code and performed a comparison of secondary standard air-kerma calibration factors for 10-50 kV low- energy X rays to verify the experimental accuracy and measurement consistency of the improved chamber. The INER-NMIJ/National Institute of Advanced Industrial Science and Technology (AIST) experimental results comparison using a transfer chamber yielded a difference energy X-ray calibration services in Taiwan and even forming a basis for the future mammography X-ray air-kerma primary standard.

  20. IFE thick liquid wall chamber dynamics: Governing mechanisms andmodeling and experimental capabilities

    Energy Technology Data Exchange (ETDEWEB)

    Raffray, A.R.; Meier, W.; Abdel-Khalik, S.; Bonazza, R.; Calderoni, P.; Debonnel, C.S.; Dragojlovic, Z.; El-Guebaly, L.; Haynes,D.; Latkowski, J.; Olson, C.; Peterson, P.F.; Reyes, S.; Sharpe, P.; Tillack, M.S.; Zaghloul, M.

    2005-01-24

    For thick liquid wall concepts, it is important to understand the different mechanisms affecting the chamber dynamics and the state of the chamber prior to each shot a compared with requirements from the driver and target. These include ablation mechanisms, vapor transport and control, possible aerosol formation, as well as protective jet behavior. This paper was motivated by a town meeting on this subject which helped identify the major issues, assess the latest results, review the capabilities of existing modeling and experimental facilities with respect to addressing remaining issues, and helping guide future analysis and R&D efforts; the paper covers these exact points.

  1. Scintillation properties of N2 and CF4 and performances of a scintillating ionization chamber

    Science.gov (United States)

    Lehaut, G.; Salvador, S.; Fontbonne, J.-M.; Lecolley, F.-R.; Perronnel, J.; Vandamme, Ch.

    2015-10-01

    In this work, we studied the emission yields, decay times and coincidence resolving times (CRT) of two gases, nitrogen (N2) and tetrafluoromethane (CF4), used for particle detection in the context of fission products measurement. The set-up was made of an ionization chamber and two photomultiplier tubes (PMTs) placed front-to-front on each side of the active zone of the chamber. Using the photomultiplier tubes, the number of photoelectrons (phe) converted at the photocathodes from the scintillation processes in each gas was quantified and the scintillation time spectra were recorded. A scintillation emission yield of 24 phe MeV-1 with a decay time of τd = 2.5 ns in N2, and 225 phe MeV-1 with τd = 6.2 ns for CF4, has been measured. With our set-up, the coincidence resolving time (σ values) between the two PMTs have been measured using alpha particles at 1.4 ns and 0.34 ns for N2 and CF4, respectively.

  2. The magic cube and the pixel ionization chamber: detectors for monitor and dosimetry of radiotherapy beams

    Science.gov (United States)

    Amerio, S.; Boriano, A.; Bourhaleb, F.; Cirio, R.; Donetti, M.; Garelli, E.; Giordanengo, S.; Madon, E.; Marchetto, F.; Nastasi, U.; Peroni, C.; Sanz Freire, C. J.; Sardo, A.; Trevisiol, E.

    2003-09-01

    Tumor therapy takes advantage of the energy deposition of radiation to concentrate high doses in the target while sparing healthy tissue. Elective pathologies for highly conformal radiotherapies such as photon Intensity Modulated Radiotherapy (IMRT) and radiotherapy with hadrons are head and neck, eye, prostate and in general all tumors that are either deep or located close to critical organs. In the world there are several centers that are using such techniques and a common problem that is being experienced is the verification of treatment plans and monitoring of the beam. We have designed and built two detectors that allow 2D and 3D measurements of dose and fluence of such beams. The detectors allow measurements on big surfaces, up to 25∗25 cm2. The active media are parallel plate, strip and pixel segmented ionization chambers with front-end Very Large Scale Integration (VLSI) readout and PC based data acquistion. The description of dosimeter, chamber and electronics will be given with results from beam tests and therapy plan verification.

  3. The magic cube and the pixel ionization chamber: detectors for monitor and dosimetry of radiotherapy beams

    Energy Technology Data Exchange (ETDEWEB)

    Amerio, S.; Boriano, A.; Bourhaleb, F.; Cirio, R.; Donetti, M.; Garelli, E.; Giordanengo, S.; Madon, E.; Marchetto, F.; Nastasi, U.; Peroni, C.; Sanz Freire, C.J.; Sardo, A.; Trevisiol, E

    2003-09-01

    Tumor therapy takes advantage of the energy deposition of radiation to concentrate high doses in the target while sparing healthy tissue. Elective pathologies for highly conformal radiotherapies such as photon Intensity Modulated Radiotherapy (IMRT) and radiotherapy with hadrons are head and neck, eye, prostate and in general all tumors that are either deep or located close to critical organs. In the world there are several centers that are using such techniques and a common problem that is being experienced is the verification of treatment plans and monitoring of the beam. We have designed and built two detectors that allow 2D and 3D measurements of dose and fluence of such beams. The detectors allow measurements on big surfaces, up to 25*25 cm{sup 2}. The active media are parallel plate, strip and pixel segmented ionization chambers with front-end Very Large Scale Integration (VLSI) readout and PC based data acquistion. The description of dosimeter, chamber and electronics will be given with results from beam tests and therapy plan verification.

  4. Multiple sampling ionization chamber (MUSIC) for measuring the charge of relativistic heavy ions

    Energy Technology Data Exchange (ETDEWEB)

    Christie, W.B.; Romero, J.L.; Brady, F.P.; Tull, C.E.; Castaneda, C.M.; Barasch, E.F.; Webb, M.L.; Drummond, J.R.; Crawford, H.J.; Flores, I.

    1987-04-01

    A large area (1 m x 2 m) multiple sampling ionization chamber (MUSIC) has been constructed and tested. The MUSIC detector makes multiple measurements of energy 'loss', dE/dx, for a relativistic heavy ion. Given the velocity, the charge of the ion can be extracted from the energy loss distributions. The widths of the distributions we observe are much narrower than predicted by Vavilov's theory for energy loss while agreeing well with the theory of Badhwar which deals with the energy deposited. The versatile design of MUSIC allows a variety of anode configurations which results in a large dynamic range of charge. In our tests to date we have observed charge resolutions of 0.25e fwhm for 727 MeV/nucleon /sup 40/Ar and 0.30e fwhm for 1.08 GeV/nucleon /sup 139/La and /sup 139/La fragments. Vertical position and multiple track determination are obtained by using time projection chamber electronics. Preliminary tests indicate that the position resolution is also very good with sigmaapprox. =100 ..mu..m.

  5. Dosimetry for electron Intra-Operative RadioTherapy: Comparison of output factors obtained through alanine/EPR pellets, ionization chamber and Monte Carlo-GEANT4 simulations for IORT mobile dedicate accelerator

    Science.gov (United States)

    Marrale, Maurizio; Longo, Anna; Russo, Giorgio; Casarino, Carlo; Candiano, Giuliana; Gallo, Salvatore; Carlino, Antonio; Brai, Maria

    2015-09-01

    In this work a comparison between the response of alanine and Markus ionization chamber was carried out for measurements of the output factors (OF) of electron beams produced by a linear accelerator used for Intra-Operative Radiation Therapy (IORT). Output factors (OF) for conventional high-energy electron beams are normally measured using ionization chamber according to international dosimetry protocols. However, the electron beams used in IORT have characteristics of dose per pulse, energy spectrum and angular distribution quite different from beams usually used in external radiotherapy, so the direct application of international dosimetry protocols may introduce additional uncertainties in dosimetric determinations. The high dose per pulse could lead to an inaccuracy in dose measurements with ionization chamber, due to overestimation of ks recombination factor. Furthermore, the electron fields obtained with IORT-dedicated applicators have a wider energy spectrum and a wider angular distribution than the conventional fields, due to the presence of electrons scattered by the applicator's wall. For this reason, a dosimetry system should be characterized by a minimum dependence from the beam energy and from angle of incidence of electrons. This become particularly critical for small and bevelled applicators. All of these reasons lead to investigate the use of detectors different from the ionization chamber for measuring the OFs. Furthermore, the complete characterization of the radiation field could be accomplished also by the use of Monte Carlo simulations which allows to obtain detailed information on dose distributions. In this work we compare the output factors obtained by means of alanine dosimeters and Markus ionization chamber. The comparison is completed by the Monte Carlo calculations of OFs determined through the use of the Geant4 application "iort _ therapy" . The results are characterized by a good agreement of response of alanine pellets and Markus

  6. Radiation-induced foil electret chamber

    Science.gov (United States)

    Fallone, B. G.; Podgorsak, E. B.

    1983-10-01

    Saturation current densities, extrapolated electric fields, and electret-charging and -discharging current-density profiles in an ionization electret chamber are discussed as a function of various chamber parameters, such as air-gap and polymer thickness, polarizing electrode material, exposure rate, etc. Both the saturation current density and the extrapolated electric field consist of two components; one is linear with the air-gap thickness and is attributed to primary ionization in air, and the other exhibits exponential saturation and is attributed to air ionization caused by photoelectrons backscattered into the chamber sensitive volume from the polarizing electrode.

  7. An allene-doped liquid argon ionization chamber for Ar and Ca ions at around 100 MeV/n

    CERN Document Server

    Yunoki, A; Fukuda, N; Kase, M; Kato, T; Kikuchi, J; Masuda, K; Niimura, M; Okada, H; Ozaki, K; Piao, Y; Shibamura, E; Tanaka, M; Tanihata, I; Terasawa, K

    1999-01-01

    An allene-doped liquid argon ionization chamber with 48 mmx48 mmx40 mm sensitive volume has been constructed for precise energy measurement of heavy ions at around 100 MeV/n. An energy resolution of 0.6%-0.7% (FWHM) was achieved for Ca and Ar ions both at 78 MeV/n. (author)

  8. Effect of wall shear rate on biofilm deposition and grazing in drinking water flow chambers.

    Science.gov (United States)

    Paris, Tony; Skali-Lami, Salaheddine; Block, Jean-Claude

    2007-08-15

    The effect of four-wall shear rates (34.9, 74.8, 142.5, and 194.5 s(-1)) on bacterial deposition on glass slides in drinking water flow chambers was studied. Biofilm image acquisition was performed over a 50-day period. Bacterial accumulation and surface coverage curves were obtained. Microscopic observations allowed us to obtain information about the dynamics and spatial distribution of the biofilm. During the first stage of biofilm formation (210-518 h), bacterial accumulation was a function of the wall shear rate: the higher the wall shear rate, the faster the bacterial deposition (1.1 and 1.9 x 10(4) bacterial cells . cm(-2) for wall shear rates of 34.9 and 142.5 s(-1), respectively). A new similarity relationship characteristic of a non-dimensional time and function of the wall shear rate was proposed to describe initial bacterial deposition. After 50 days of exposure to drinking water, surface coverage was more or less identical under the entire wall shear rates (7.44 +/- 0.9%), suggesting that biofilm bacterial density cannot be controlled using hydrodynamics. However, the spatial distribution of the biofilm was clearly different. Under low wall shear rate, aggregates were composed of bacterial cells able to "vibrate" independently on the surface, whereas, under a high wall shear rate, aggregates were more cohesive. Therefore, susceptibility to the hydraulic discontinuities occurring in drinking water system may not be similar. In all the flow chambers, significant decreases in bacterial biomass (up to 77%) were associated with the presence of amoebae. This grazing preferentially targeted small, isolated cells.

  9. Super-resolution non-parametric deconvolution in modelling the radial response function of a parallel plate ionization chamber.

    Science.gov (United States)

    Kulmala, A; Tenhunen, M

    2012-11-07

    The signal of the dosimetric detector is generally dependent on the shape and size of the sensitive volume of the detector. In order to optimize the performance of the detector and reliability of the output signal the effect of the detector size should be corrected or, at least, taken into account. The response of the detector can be modelled using the convolution theorem that connects the system input (actual dose), output (measured result) and the effect of the detector (response function) by a linear convolution operator. We have developed the super-resolution and non-parametric deconvolution method for determination of the cylinder symmetric ionization chamber radial response function. We have demonstrated that the presented deconvolution method is able to determine the radial response for the Roos parallel plate ionization chamber with a better than 0.5 mm correspondence with the physical measures of the chamber. In addition, the performance of the method was proved by the excellent agreement between the output factors of the stereotactic conical collimators (4-20 mm diameter) measured by the Roos chamber, where the detector size is larger than the measured field, and the reference detector (diode). The presented deconvolution method has a potential in providing reference data for more accurate physical models of the ionization chamber as well as for improving and enhancing the performance of the detectors in specific dosimetric problems.

  10. Simulation of ionization-front-forming process at injection of relativistic electron beam with a gas chamber

    Energy Technology Data Exchange (ETDEWEB)

    Dolya, S.N.; Zhidkov, E.P.; Rubin, S.B.; Semerdzhiev, Kh.I.

    1982-01-01

    The methodical work on creation of computer program for numerical study of the processes of forming and motion of a virtual cathode at the injection of relativistic electron beam into a short cylindrical chamber, filled with gas, has been carried out. The obtained plots of the distributions of fields, potential and density appearing out of ion and electron gas of the beam itself are presented. The dependence of cross-section ionization on the electron velocity has been taken into account at the calculation; the resonance contribution into summarized cross-section of ionization was simulated. It is shown that the injection into the chamber without gas, some oscillations of the virtual cathode are observed. At the presence of the final front of the beam, the fields level at the initial stage is smaller than for the beam with a sharp front. However, in some time the field amplitudes are compared. The motion of simulated probe ions in the chamber is analyzed.

  11. Time-resolved dosimetry using a pinpoint ionization chamber as quality assurance for IMRT and VMAT

    Energy Technology Data Exchange (ETDEWEB)

    Louwe, Robert J. W., E-mail: rob.louwe@ccdbh.org.nz; Satherley, Thomas; Day, Rebecca A.; Greig, Lynne [Department of Radiation Oncology, Wellington Blood and Cancer Centre, Wellington Hospital, Wellington 6242 (New Zealand); Wendling, Markus; Monshouwer, René [Department of Radiation Oncology, Radboud University Medical Center, Nijmegen 6500 HB (Netherlands)

    2015-04-15

    Purpose: To develop a method to verify the dose delivery in relation to the individual control points of intensity modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) using an ionization chamber. In addition to more effective problem solving during patient-specific quality assurance (QA), the aim is to eventually map out the limitations in the treatment chain and enable a targeted improvement of the treatment technique in an efficient way. Methods: Pretreatment verification was carried out for 255 treatment plans that included a broad range of treatment indications in two departments using the equipment of different vendors. In-house developed software was used to enable calculation of the dose delivery for the individual beamlets in the treatment planning system (TPS), for data acquisition, and for analysis of the data. The observed deviations were related to various delivery and measurement parameters such as gantry angle, field size, and the position of the detector with respect to the field edge to distinguish between error sources. Results: The average deviation of the integral fraction dose during pretreatment verification of the planning target volume dose was −2.1% ± 2.2% (1 SD), −1.7% ± 1.7% (1 SD), and 0.0% ± 1.3% (1 SD) for IMRT at the Radboud University Medical Center (RUMC), VMAT (RUMC), and VMAT at the Wellington Blood and Cancer Centre, respectively. Verification of the dose to organs at risk gave very similar results but was generally subject to a larger measurement uncertainty due to the position of the detector at a high dose gradient. The observed deviations could be related to limitations of the TPS beam models, attenuation of the treatment couch, as well as measurement errors. The apparent systematic error of about −2% in the average deviation of the integral fraction dose in the RUMC results could be explained by the limitations of the TPS beam model in the calculation of the beam penumbra. Conclusions: This

  12. All- Ceramic Crown Preparation and the Remained wall Thickness of the Pulp Chamber

    Directory of Open Access Journals (Sweden)

    Mohammadzadeh Akhlaghi N.

    2012-12-01

    Full Text Available tatement of Problem: A minimally invasive method of preparation is essential to prevent tooth structure weakening and pulp irritation; especially for mandibular anterior single-tooth all-ceramic crowns. According to many investigations, one of the most important reasons of pulp injury caused by tooth preparation for different restorative procedures is reduced “remained wall thickness” (RWT. In order to protect the pulp from irritation, it is necessary to maintain a 0.5 mm of RWT.Purpose: The purpose of the present study was to evaluate the effect of all-ceramic crown preparation on pulp chamber RWT of mandibular incisors.Materials and Method: Mesiodistal and buccolingual initial images of 24 ex-tracted mandibular incisors were provided. The pulp chamber initial wall thick-nesses of buccal, lingual and proximal surfaces of cervical, 1and 2 mm above the cervical areas and also the incisal surfaces of incisal sections were measured using digital radiography and Photoshop software. After all-ceramic crown preparation, images were provided at the same initial positions. The initial and remained pulp chamber wall thicknesses were statistically evaluated and analyzed by ANOVA, paired t-test and a post hoc Tukey test.Results: Repeated measures ANOVA showed that the mean of pre- or post-preparation wall thicknesses were not significantly different for each surface at the three horizontal levels (p> 0.05. However, there were significant differences between the surfaces for each section. Comparison of pre- and post-preparation wall thicknesses revealed significant differences (p< 0.05. Proximal surfaces of cervical sections had the least RWT (0.42±0.12.Conclusion: According to the results of the present study, the least amount of initial and remained wall thicknesses of pulp chamber were related to the proximal surfaces, particularly in cervical areas. Therefore a reduction of preparation to 0.7 mm is suggested to prevent future pulp injury for

  13. The control system of the multi-strip ionization chamber for the HIMM

    Science.gov (United States)

    Li, Min; Yuan, Y. J.; Mao, R. S.; Xu, Z. G.; Li, Peng; Zhao, T. C.; Zhao, Z. L.; Zhang, Nong

    2015-03-01

    Heavy Ion Medical Machine (HIMM) is a carbon ion cancer treatment facility which is being built by the Institute of Modern Physics (IMP) in China. In this facility, transverse profile and intensity of the beam at the treatment terminals will be measured by the multi-strip ionization chamber. In order to fulfill the requirement of the beam position feedback to accomplish the beam automatic commissioning, less than 1 ms reaction time of the Data Acquisition (DAQ) of this detector must be achieved. Therefore, the control system and software framework for DAQ have been redesigned and developed with National Instruments Compact Reconfigurable Input/Output (CompactRIO) instead of PXI 6133. The software is Labview-based and developed following the producer-consumer pattern with message mechanism and queue technology. The newly designed control system has been tested with carbon beam at the Heavy Ion Research Facility at Lanzhou-Cooler Storage Ring (HIRFL-CSR) and it has provided one single beam profile measurement in less than 1 ms with 1 mm beam position resolution. The fast reaction time and high precision data processing during the beam test have verified the usability and maintainability of the software framework. Furthermore, such software architecture is easy-fitting to applications with different detectors such as wire scanner detector.

  14. Detecting MLC errors in stereotactic radiotherapy plans with a liquid filled ionization chamber array.

    Science.gov (United States)

    O'Connor, Patrick; Seshadri, Venkatakrisnan; Charles, Paul

    2016-03-01

    Quality assurance of stereotactic radiotherapy demands the use of equipment with the highest resolution and sensitivity available. This study examines the sensitivity of a commercially available liquid-filled ionization chamber array--the Octavius 1000 SRS (PTW, Frieburg, Germany) for detecting small (sub-millimetre) multi-leaf collimator (MLC) alignment errors in static square fields (side length 16-40 mm). Furthermore, the effectiveness of detecting small MLC errors in clinical stereotactic radiotherapy patient plans using the device was also evaluated. The commonly used gamma pass rate metric (of the measurements compared with treatment planning system generated results) was used. The gamma pass rates were then evaluated as a function of MLC position error (MLC error size 0.1-2.5 mm). The detector array exhibited a drop in pass rate between plans without error and those which had MLC errors induced. For example a drop in pass rate of 4.5% (gamma criteria 3%, 1 mm) was observed when a 0.8 mm error was introduced into a 16 mm square field. Furthermore the drop in pass rate increased as the MLC position error increased. This study showed that the Octavius 1000 SRS array could be a useful tool for applications requiring the detection of small geometric delivery uncertainties.

  15. Testing an ionization chamber with gaseous samples and measurements of the (n, alpha) reaction cross sections

    CERN Document Server

    Gledenov, Yu M; Salatskii, V I; Sedyshev, P V; Andrzejewski, J; Szalanski, P

    1999-01-01

    A new ionization chamber with gaseous samples (GIC) has been designed and tested on the thermal and resonance neutron beams of FLNP's neutron sources. The exposed gas volume serves as a target for neutrons. The obtained thermal cross sections for the sup 1 sup 7 O(n, alpha) sup 1 sup 4 C, sup 2 sup 1 Ne(n, alpha) sup 1 sup 8 O and sup 3 sup 6 Ar(n, alpha) sup 3 sup 3 S reactions are (233+-12) mb, (0.18+-0.09) mb and (5.43+-0.27) mb, respectively. These measurements have been performed on a pure beam of thermal neutrons from the high flux reactor IBR-2; and they demonstrated high efficiency and reliability of the method. Compared to samples on substrates, the application of gaseous samples makes the beam background essentially lower, and what is more important, the background component is totally absent due to the absence of Li and B microimpurities in gaseous samples while they do present in the samples on substrates. The method is also applicable to measurements with resonance neutrons. The recovery capabili...

  16. The control system of the multi-strip ionization chamber for the HIMM

    Energy Technology Data Exchange (ETDEWEB)

    Li, Min, E-mail: limin@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Science, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China); Yuan, Y.J. [Institute of Modern Physics, Chinese Academy of Science, Lanzhou 730000 (China); Mao, R.S., E-mail: Maorsh@impcas.ac.cn [Institute of Modern Physics, Chinese Academy of Science, Lanzhou 730000 (China); Xu, Z.G.; Li, Peng; Zhao, T.C.; Zhao, Z.L. [Institute of Modern Physics, Chinese Academy of Science, Lanzhou 730000 (China); Zhang, Nong [Institute of Modern Physics, Chinese Academy of Science, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100049 (China)

    2015-03-11

    Heavy Ion Medical Machine (HIMM) is a carbon ion cancer treatment facility which is being built by the Institute of Modern Physics (IMP) in China. In this facility, transverse profile and intensity of the beam at the treatment terminals will be measured by the multi-strip ionization chamber. In order to fulfill the requirement of the beam position feedback to accomplish the beam automatic commissioning, less than 1 ms reaction time of the Data Acquisition (DAQ) of this detector must be achieved. Therefore, the control system and software framework for DAQ have been redesigned and developed with National Instruments Compact Reconfigurable Input/Output (CompactRIO) instead of PXI 6133. The software is Labview-based and developed following the producer–consumer pattern with message mechanism and queue technology. The newly designed control system has been tested with carbon beam at the Heavy Ion Research Facility at Lanzhou-Cooler Storage Ring (HIRFL-CSR) and it has provided one single beam profile measurement in less than 1 ms with 1 mm beam position resolution. The fast reaction time and high precision data processing during the beam test have verified the usability and maintainability of the software framework. Furthermore, such software architecture is easy-fitting to applications with different detectors such as wire scanner detector.

  17. Quantitative Verification of Dynamic Wedge Dose Distribution Using a 2D Ionization Chamber Array.

    Science.gov (United States)

    Sahnoun, Tarek; Farhat, Leila; Mtibaa, Anis; Besbes, Mounir; Daoud, Jamel

    2015-10-01

    The accuracy of two calculation algorithms of the Eclipse 8.9 treatment planning system (TPS)--the anisotropic analytic algorithm (AAA) and pencil-beam convolution (PBC)--in modeling the enhanced dynamic wedge (EDW) was investigated. Measurements were carried out for 6 and 18 MV photon beams using a 2D ionization chamber array. Accuracy of the TPS was evaluated using a gamma index analysis with the following acceptance criteria for dose differences (DD) and distance to agreement (DTA): 3%/3 mm and 2%/2 mm. The TPS models the dose distribution accurately except for 20×20 cm(2) field size, 60 (°) and 45 (°) wedge angles using PBC at 6 MV photon energy. For these latter fields, the pass rate and the mean value of gamma were less than 90% and more than 0.5, respectively at the (3%/3 mm) acceptance criteria. In addition, an accuracy level of (2%/2 mm) was achieved using AAA with better agreement for 18 MV photon energy.

  18. A high dynamic Micro Strips Ionization Chamber featuring Embedded Multi DSP Processing

    CERN Document Server

    Voltolina, Francesco; Carrato, Sergio; 10.1109/NSSMIC.2004.1466924

    2010-01-01

    An X-ray detector will be presented that is the combination of a segmented ionization chamber featuring one-dimensional spatial resolution integrated with an intelligent ADC front-end, multi DSP processing and embedded PC platform. This detector is optimized to fan beam geometry with an active area of 192 mm (horizontal) and a vertical acceptance of 6 mm. Spatial resolution is obtained by subdividing the anode into readout strips, having pitch of 150 micrometers, which are connected to 20 custom made integrating VLSI chips (each capable of 64-channel read-out and multiplexing) and read out by 14 bits 10 MHz ADCs and fast adaptive PGAs into DSP boards. A bandwidth reaching 3.2Gbit/s of raw data, generated from the real time sampling of the 1280 micro strips, is cascaded processed with FPGA and DSP to allow data compression resulting in several days of uninterrupted acquisition capability. Fast acquisition rates reaching 10 kHz are allowed due to the MicroCAT structure utilized not only as a shielding grid in i...

  19. Calibration of ionization energy loss at relativistic rise with STAR Time Projection Chamber

    CERN Document Server

    Xu, Yichun; Bichsel, Hans; Dong, Xin; Fachini, Patricia; Fisyak, Yuri; Kocolosky, Adam; Mohanty, Bedanga; Netrakanti, Pawan; Ruan, Lijuan; Suarez, Maria Cristina; Tang, Zebo; van Buren, Gene; Xu, Zhangbu

    2008-01-01

    We derive a method to improve particle identification (PID) at high transverse momentum ($p_T$) using the relativistic rise of the ionization energy loss ($rdE/dx$) when charged particles traverse the Time Projection Chamber (TPC) at STAR. Electrons triggered and identified by the Barrel Electro-Magnetic Calorimeter (BEMC), pure protons and pions from $\\Lambda\\to p+\\pi^{-}$ ($\\bar{\\Lambda}\\to \\bar{p}+\\pi^{+}$), and $K^{0}_{S}\\to\\pi^{+}+\\pi^{-}$ decays are used to obtain the $dE/dx$ value and its width at given $\\beta\\gamma=p/m$. We found that the deviation of the $dE/dx$ from the Bichsel function can be up to $0.4\\sigma$ ($\\sim3%$) in p+p collisions at $\\sqrt{s_{NN}}=200$ GeV taken and subsequently calibrated in year 2005. The deviation is approximately a function of $\\beta\\gamma$ independent of particle species and can be described with a function of $f(x) = A+\\frac{B}{C+x^{2}}$. The deviations obtained with this method are used to re-calibrate the data sample from p+p collision for physics analysis of ident...

  20. Dose verifications by use of liquid ionization chamber of an electronic portal imaging device (EPID).

    Science.gov (United States)

    Tateoka, Kunihiko; Oouchi, Atsushi; Nakata, Kensei; Hareyama, Masato

    2008-07-01

    In this study, we examined the ability of an L-EPID to verify rectangular and irregular fields and to measure the transmitted exit doses. With respect to the beam profile of rectangular and irregular fields and the doses transmitted through an inhomogeneous phantom, the L-EPID dose obtained from the L-EPID measurement was compared with the conventional dose measured by use of a 0.12-cc ionization chamber and a 3D water phantom. In the comparison of the rectangular and irregular fields, the difference in the off-center ratio (OCR) between the L-EPID dose and the conventional dose was approximately 3% in the steep-dose-gradient region (penumbra regions, >30%/cm) and approximately +/-0.5% in the gentle-dose-gradient region (5%/cm). On the other hand, the dose differences between the L-EPID and the measured doses were less than approximately 2% in the gentle-dose-gradient region. In addition, in the steep-dose-gradient region, the maximum difference was 30%. However, the differences in the distance-to-agreement (DTA) were less than approximately +/-1 mm and were unrelated to the dose gradient. These results suggest that dose verification by L-EPID is very useful in clinical applications.

  1. Liquid ionization chamber initial recombination dependence on LET for electrons and photons.

    Science.gov (United States)

    Johansson, Erik; Andersson, Jonas; Johansson, Lennart; Tölli, Heikki

    2013-06-21

    The possibility of indirect measurements of linear energy transfer (LET) with a liquid ionization chamber (LIC) has been investigated by studying initial recombination losses at different applied voltages. A linear fit is made to the voltage-signal curve and the intersection point of the fit and the voltage-axis is shown to correlate with LET. The LIC applied voltages were 100-700 V, which corresponds to electric field strengths between 0.3 and 2.0 MV m(-1). Several different photon and electron beams have been studied, and by using MCNPX™ the respective LET spectra have been determined. The beam qualities in this study were found to have a fluence averaged LET between 0.17 and 1.67 keV µm(-1) and a corresponding dose averaged LET between 0.97 and 4.62 keV µm(-1). For the experimental data in this study the linear fit method yields consistent results with respect to Monte Carlo simulated LET values. A calibration curve for LET determination is provided for the LIC used in the present work.

  2. Preliminary results with a strip ionization chamber used as beam monitor for hadrontherapy treatments

    Science.gov (United States)

    Boriano, A.; Bourhaleb, F.; Cirio, R.; Cirrone, G. A. P.; Cuttone, G.; Donetti, M.; Garelli, E.; Giordanengo, S.; Luparia, A.; Marchette, F.; Peroni, C.; Raffaele, L.; Sabini, M. G.; Valastro, L.

    2006-01-01

    Preliminary results are presented from a test of a parallel plate ionization chamber with the anode segmented in strips (MOPI) to be used as a beam monitor for therapeutical treatments on the 62 MeV proton beam line of the INFN-LNS Superconducting Cyclotron. Ocular pathologies have been treated at the Catana facility since March 2002. The detector, placed downstream of the patient collimator, will allow the measurement of the relevant beam diagnostic parameters during treatment such as integrated beam fluence, for dose determination; the beam baricentre, width and asymmetry will be obtained from the fluence profile sampled with a resolution of about 100 Urn at a rate up to 1 kHz with no dead time. In this test, carried out at LNS, the detector has been exposed to different beam shapes and the integrated fluence derived by the measured beam profiles has been compared with that obtained with other dosimeters normally used for treatment. The skewness of the beam profile has been measured and shown to be suitable to on-line check variations of the beam shape.

  3. Measurement of differential (n,x{alpha}) cross section using 4{pi} gridded ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Sanami, Toshiya; Baba, Mamoru; Matsuyama, Shigeo; Kiyosumi, Takehide; Nauchi, Yasushi; Saito, Keiichiro; Hirakawa, Naohiro [Tohoku Univ., Sendai (Japan). Faculty of Engineering; Kawano, Toshihiko

    1997-03-01

    We carried out the measurements of high resolution {alpha} emission spectra of {sup 58}Ni and {sup nat}Ni between 4.5 and 6.5 MeV, and {sup 12}C(n,x{alpha}) cross section using a 4{pi} gridded ionization chamber. In Ni measurement, overall energy resolution was improved to around 200 keV by optimizing a sample thickness and a neutron source width. Measured alpha spectra showed separate peaks corresponding to the ground and low-lying excited states of the residual nucleus ({sup 55}Fe). These results were compared with another direct measurement and statistical model calculations. In {sup 12}C measurement, GIC was applied for (n,x{alpha}) reactions of light nuclei. This application is difficult to (n,x{alpha}) cross sections of light nuclei, because of the influences of large recoil energy and multi-body break-up. We developed new methods which eliminate the effects of recoil nuclei and multi-body break-up and applied them to {sup 12}C(n,x{alpha}) reaction at En=14.1 MeV. In our experiment, the {sup 12}C(n,{alpha}{sub 0}){sup 9}Be angular differential cross section and {sup 12}C(n,n`3{alpha}) cross section were obtained. (author)

  4. An evaluation of semiconductor and ionization chamber detectors for diagnostic x-ray dosimetry measurements.

    Science.gov (United States)

    Martin, C J

    2007-08-07

    Dosemeters for performance testing of x-ray equipment may utilize semiconductor technology or ionization chambers (ICs). Semiconductor dosemeters incorporate several elements into the detectors from which compensation for variations in response with photon energy is derived. The design of the detectors influences their response with angle and this is different from that of ICs. The responses of semiconductor detectors (SDs) and ICs to x-ray beams with a variety of radiation qualities have been measured in order to assess differences in response. Measurements have been made with experimental arrangements simulating use of the detectors in performance testing of digital radiography and fluoroscopy equipment. Results show that differences in photon energy responses between the detectors are small, but because ICs are sensitive to radiation incident from all angles, they record more scattered radiation than SDs. Implications of differences in detector responses are discussed and recommendations made about their use. SDs are more appropriate for measurements of image receptor doses and are recommended for setting up automatic exposure control devices for digital radiography. ICs are suitable for assessment of patient entrance surface dose rate measurements. Correction factors that could be applied to allow comparisons between measurements with different dosemeters are proposed.

  5. D-IMRT verification with a 2D pixel ionization chamber: dosimetric and clinical results in head and neck cancer

    Science.gov (United States)

    Stasi, M.; Giordanengo, S.; Cirio, R.; Boriano, A.; Bourhaleb, F.; Cornelius, I.; Donetti, M.; Garelli, E.; Gomola, I.; Marchetto, F.; Porzio, M.; Sanz Freire, C. J.; Sardo, A.; Peroni, C.

    2005-10-01

    Dynamic intensity-modulated radiotherapy (D-IMRT) using the sliding-window technique is currently applied for selected treatments of head and neck cancer at Institute for Cancer Research and Treatment of Candiolo (Turin, Italy). In the present work, a PiXel-segmented ionization Chamber (PXC) has been used for the verification of 19 fields used for four different head and neck cancers. The device consists of a 32 × 32 matrix of 1024 parallel-plate ionization chambers arranged in a square of 24 × 24 cm2 area. Each chamber has 0.4 cm diameter and 0.55 cm height; a distance of 0.75 cm separates the centre of adjacent chambers. The sensitive volume of each single ionization chamber is 0.07 cm3. Each of the 1024 independent ionization chambers is read out with a custom microelectronics chip. The output factors in water obtained with the PXC at a depth of 10 cm were compared to other detectors and the maximum difference was 1.9% for field sizes down to 3 × 3 cm2. Beam profiles for different field dimensions were measured with the PXC and two other types of ionization chambers; the maximum distance to agreement (DTA) in the 20-80% penumbra region of a 3 × 3 cm2 field was 0.09 cm. The leaf speed of the multileaf collimator was varied between 0.07 and 2 cm s-1 and the detector response was constant to better than 0.6%. The behaviour of the PXC was measured while varying the dose rate between 0.21 and 1.21 Gy min-1; the mean difference was 0.50% and the maximum difference was 0.96%. Using fields obtained with an enhanced dynamic wedge and a staircase-like (step) IMRT field, the PXC has been tested for simple 1D modulated beams; comparison with film gave a maximum DTA of 0.12 cm. The PXC was then used to check four different IMRT plans for head and neck cancer treatment: cervical chordoma, parotid, ethmoid and skull base. In the comparison of the PXC versus film and PXC versus treatment planning system, the number of pixels with γ parameter <=1 was 97.7% and 97

  6. D-IMRT verification with a 2D pixel ionization chamber: dosimetric and clinical results in head and neck cancer

    Energy Technology Data Exchange (ETDEWEB)

    Stasi, M [Institute for Cancer Research and Treatment (IRCC), Candiolo and A.S.O. Ordine Maurizano, Torino (Italy); Giordanengo, S [Istituto Nazionale di Fisica Nucleare (INFN), Via P. Giuria 1, I-10125 Torino (Italy); Cirio, R [Istituto Nazionale di Fisica Nucleare (INFN), Via P. Giuria 1, I-10125 Torino (Italy)] [and others

    2005-10-07

    Dynamic intensity-modulated radiotherapy (D-IMRT) using the sliding-window technique is currently applied for selected treatments of head and neck cancer at Institute for Cancer Research and Treatment of Candiolo (Turin, Italy). In the present work, a PiXel-segmented ionization Chamber (PXC) has been used for the verification of 19 fields used for four different head and neck cancers. The device consists of a 32 x 32 matrix of 1024 parallel-plate ionization chambers arranged in a square of 24 x 24 cm{sup 2} area. Each chamber has 0.4 cm diameter and 0.55 cm height; a distance of 0.75 cm separates the centre of adjacent chambers. The sensitive volume of each single ionization chamber is 0.07 cm{sup 3}. Each of the 1024 independent ionization chambers is read out with a custom microelectronics chip. The output factors in water obtained with the PXC at a depth of 10 cm were compared to other detectors and the maximum difference was 1.9% for field sizes down to 3 x 3 cm{sup 2}. Beam profiles for different field dimensions were measured with the PXC and two other types of ionization chambers; the maximum distance to agreement (DTA) in the 20-80% penumbra region of a 3 x 3 cm{sup 2} field was 0.09 cm. The leaf speed of the multileaf collimator was varied between 0.07 and 2 cm s{sup -1} and the detector response was constant to better than 0.6%. The behaviour of the PXC was measured while varying the dose rate between 0.21 and 1.21 Gy min{sup -1}; the mean difference was 0.50% and the maximum difference was 0.96%. Using fields obtained with an enhanced dynamic wedge and a staircase-like (step) IMRT field, the PXC has been tested for simple 1D modulated beams; comparison with film gave a maximum DTA of 0.12 cm. The PXC was then used to check four different IMRT plans for head and neck cancer treatment: cervical chordoma, parotid, ethmoid and skull base. In the comparison of the PXC versus film and PXC versus treatment planning system, the number of pixels with {gamma

  7. High energy photon reference for radiation protection: technical design of the LINAC beam and ionization chambers; and calculation of monoenergetic conversion coefficients

    Directory of Open Access Journals (Sweden)

    Dusciac D.

    2016-01-01

    Full Text Available In this work, we present the results of the first part of a research project aimed at offering a complete response to dosimeters providers and nuclear physicists’ demands for high-energy (6 – 9 MeV photon beams for radiation protection purposes. Classical facilities allowing the production of high-energy photonic radiation (proton accelerators, nuclear reactors are very rare and need large investment for development and use. A novel solution is proposed, consisting in the use of a medical linear accelerator, allowing a significant decrease of all costs.Using Monte Carlo simulations (MCNP5 and PENELOPE codes, a specifically designed electron-photon conversion target allowing for obtaining a high energy photon beam (with an average energy weighted by fluence of about 6 MeV has been built for radiation protection purposes. Due to the specific design of the target, this “realistic” radiation protection high-energy photon beam presents a uniform distribution of air kerma rate at a distance of 1 m, over a 30 × 30 cm2 surface. Two graphite cavity ionizing chambers for ionometric measurements have been built. For one of these chambers, the charge collection volume has been measured allowing for its use as a primary standard. The second ionizing chamber is used as a transfer standard; as such it has been calibrated in a 60Co beam, and in the high energy photon beam for radiation protection.The measurements with these ionizing chambers allowed for an evaluation of the air kerma rate in the LINAC based high-energy photon beam for radiation protection: the values cover a range between 36 mGy/h and 210 mGy/h, compatible with radiation protection purposes.Finally, using Monte Carlo simulations, conversion coefficients from air kerma to dose equivalent quantities have been calculated in the range between 10 keV and 22.4 MeV, for the spectral distribution of the fluence corresponding to the beam produced by the linear accelerator of the LNE-LNHB.

  8. High energy photon reference for radiation protection: technical design of the LINAC beam and ionization chambers; and calculation of monoenergetic conversion coefficients

    Science.gov (United States)

    Dusciac, D.; Bordy, J.-M.; Daures, J.; Blideanu, V.

    2016-09-01

    In this work, we present the results of the first part of a research project aimed at offering a complete response to dosimeters providers and nuclear physicists' demands for high-energy (6 - 9 MeV) photon beams for radiation protection purposes. Classical facilities allowing the production of high-energy photonic radiation (proton accelerators, nuclear reactors) are very rare and need large investment for development and use. A novel solution is proposed, consisting in the use of a medical linear accelerator, allowing a significant decrease of all costs.Using Monte Carlo simulations (MCNP5 and PENELOPE codes), a specifically designed electron-photon conversion target allowing for obtaining a high energy photon beam (with an average energy weighted by fluence of about 6 MeV) has been built for radiation protection purposes. Due to the specific design of the target, this "realistic" radiation protection high-energy photon beam presents a uniform distribution of air kerma rate at a distance of 1 m, over a 30 × 30 cm2 surface. Two graphite cavity ionizing chambers for ionometric measurements have been built. For one of these chambers, the charge collection volume has been measured allowing for its use as a primary standard. The second ionizing chamber is used as a transfer standard; as such it has been calibrated in a 60Co beam, and in the high energy photon beam for radiation protection.The measurements with these ionizing chambers allowed for an evaluation of the air kerma rate in the LINAC based high-energy photon beam for radiation protection: the values cover a range between 36 mGy/h and 210 mGy/h, compatible with radiation protection purposes.Finally, using Monte Carlo simulations, conversion coefficients from air kerma to dose equivalent quantities have been calculated in the range between 10 keV and 22.4 MeV, for the spectral distribution of the fluence corresponding to the beam produced by the linear accelerator of the LNE-LNHB.

  9. Use of a novel two-dimensional ionization chamber array for pencil beam scanning proton therapy beam quality assurance.

    Science.gov (United States)

    Lin, Liyong; Kang, Minglei; Solberg, Timothy D; Mertens, Thierry; Baeumer, Christian; Ainsley, Christopher G; McDonough, James E

    2015-05-08

    The need to accurately and efficiently verify both output and dose profiles creates significant challenges in quality assurance of pencil beam scanning (PBS) proton delivery. A system for PBS QA has been developed that combines a new two-dimensional ionization chamber array in a waterproof housing that is scanned in a water phantom. The MatriXX PT has the same detector array arrangement as the standard MatriXX(Evolution) but utilizes a smaller 2 mm plate spacing instead of 5mm. Because the bias voltage of the MatriXX PT and Evolution cannot be changed, PPC40 and FC65-G ionization chambers were used to assess recombination effects. The PPC40 is a parallel plate chamber with an electrode spacing of 2mm, while the FC65-G is a Farmer chamber FC65-G with an electrode spacing of 2.8 mm. Three bias voltages (500, 200, and 100 V) were used for both detectors to determine which radiation type (continuous, pulse or pulse-scanned beam) could closely estimate Pion from the ratios of charges collected. In comparison with the MatriXX(Evolution), a significant improvement in measurement of absolute dose with the MatriXX PT was observed. While dose uncertainty of the MatriXX(Evolution) can be up to 4%, it is 1%; chambers with an electrode spacing of 2 mm or smaller are recommended.

  10. Investigation of the initial and volume recombination losses in gamma versatile cylindrical ionization chamber VGIC developed for gamma ray dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Fares, M.; Mameri, S.; Abdlani, I.; Negara, K. [COMENA, Laboratoire Detection et Mesures, CRNB, BP no. 180 Ain-Oussera 17200 W. de Djelfa (Algeria)

    2015-07-01

    A versatile Gamma ionization chambers are used for flow control in systems with gamma nuclear reactors and reprocessing plants in and monitoring atmosphere around these facilities, this in order to protect staff. In the Laboratory Detection and Measures (LDM) Division for Study and Development of Nuclear Instrumentation (DSDNI) of CRNB, we designed, developed and characterized a versatile gamma ionization chamber (VGIC) to study experimentally its characteristics according to the geometry of the electrodes, the volume and pressure of the filler gas for the design of a gamma sealed chamber. The tests were conducted under the IEC (International Electro-technical Commission). In this paper, we present the results obtained in the various nuclear tests for characterization and calibration that we have made on the ionization chamber gamma VGIC prototype developed at our Department. To do this, three irradiators were operated at the Laboratory Calibration (SSDL) of the Department of Medical Physics Nuclear Research Center of Algiers (CRNA). Irradiator intensive gamma ({sup 60}Co: 1.25 MeV), one medium intensity gamma ({sup 137}Cs: 0.662 MeV) and 3rd low intensity ({sup 60}Co). Saturation curves and linearity were identified and the operating range and the sensitivity of the chamber have been deducted. The (I,V) characteristics of the chamber filled, with argon gas at 3 bar (0.3 M pa) pressure, for gamma ray irradiator sources were studied. To do so, the chamber was irradiated with gamma rays using different numbers of gamma sources (i.e. Up to 5). The plateau region is reached above 200 V and the detector operating voltage is found to be 600 V. It is observed that in the plateau region the slope is constant with an increase in the exposure rate. The (1/I, 1/V) and (I, l/V{sup 2}) characteristic curves reveal the presence of the initial and volume recombination losses. The volume recombination losses are found to be smaller than the initial recombination losses. Finally

  11. Determination of the recombination correction for the BIPM parallel-plate ionization chamber type in a pulsed photon beam

    Energy Technology Data Exchange (ETDEWEB)

    Picard, Susanne; Burns, David T. [Bureau International des Poids et Mesures, Pavillon de Breteuil, F92312 Sevres cedex (France); Ostrowsky, Aime [Laboratoire National Henri Becquerel - LNHB, CEA Saclay - 91191 Gif-sur-Yvette Cedex (France)

    2011-09-15

    The correction factor for recombination losses k{sub s} has been determined for the BIPM parallel-plate ionization chamber type in the pulsed photon beam of a clinical linear accelerator. Initial recombination is in agreement with that obtained for the same chamber type in a continuous beam, while linearity in the volume recombination loss is confirmed at dose rates up to 80 pC per pulse, which corresponds to about 0.33 mGy per pulse (or around 2 Gy min{sup -1} at 100 Hz)

  12. Ionization of Air in a Ranque-Hilsch Vortex Tube and the Method of Obtaining Uni- and Bipolar Ionization

    Science.gov (United States)

    Lebedinskii, K. V.; Kurnosov, N. E.; Nikolotov, A. A.; Alekseev, D. P.

    2015-11-01

    Results of investigations on determining the principles of ionization in a Ranque-Hilsch vortex tube have been given. The existing principles of ionization and the possibilities for them to occur in a Ranque-Hilsch vortex tube have been considered. Conclusions based on an analysis of ionization methods have been drawn. With the aim of establishing processes occurring in the vortex tube, the authors have developed a procedure, have identified the goal and objectives of testing, have created a test bench, and have conducted experimental investigations on the physical prototype of a vortex tube. Testing results have been given in the form of plots. An analysis of the results has been made, and conclusions have been drawn. On the basis of the conducted investigations, the authors have proposed a novel method of ionization of air and control over the parameters of uni- and bipolar ionization. A diagram of the device developed for air ionization has been presented.

  13. Air Ejection by a Flux of Particles of a Bulk Material in a Vertical Porous Pipe with a Bypass Cylindrical Chamber

    Science.gov (United States)

    Averkova, O. A.; Logachev, I. N.; Logachev, K. I.

    2015-07-01

    Hydrodynamic equations have been derived for a fl ux of particles free falling in an air-filled circular porous pipe which is surrounded by a cylindrical bypass chamber. In these equations, the reverse influence of air on the particles' dynamics is disregarded. Numerical and analytical investigations of the derived equations made it possible to establish the regularities of change in the velocity of ejected air in the porous chute and in the pressure in the bypass chamber along the chute length as a function of the porosity of the walls and the dimensions of the chamber, and also on the ejection number. A rational range has been determined for ejection parameters ensuring the greatest reduction in the ejection volume due to the recycling of air.

  14. The research on the consistency of the testing accuracy for smoke measuring equipment based on ionization chamber principle

    Directory of Open Access Journals (Sweden)

    Wang Ting Ting

    2016-01-01

    Full Text Available A convenient method is proposed here to determine the relative accuracy of measuring ionization chamber (MIC. A non-dimensional quantity is presented here to characterize the relative accuracy of the testing sample to the reference sample. There are two key points of the program. One is comparison by pairs. The other is eliminating the uncertainty in the program by exchanging the position and control unit in each testing group.

  15. Calculation of the charge spectrum generated by ionizing particles in Resistive Plate Chambers at low gas gain

    CERN Document Server

    Fonte, P

    2012-01-01

    The charge spectrum generated by ionizing particles in Resistive Plate Chambers under Townsend avalanche conditions, that is, for sufficiently small avalanches not affected by space-charge, has not been calculated from first principles. In this article it is shown that, just neglecting cluster statistics, it follows closely the statistical gamma distribution. Remarkably, this distribution seems to describe as well data measured beyond these assumptions, rising some interpretation issues.

  16. Study of ionization-chamber measurement systems for activity determination; Untersuchung von Ionisationskammer-Messsystemen fuer Aktivitaetsbestimmungen

    Energy Technology Data Exchange (ETDEWEB)

    Niedergesaess, Christiane; Schrader, Heinrich; Kossert, Karsten

    2011-04-15

    The present report describes the performance and results of a common project of the company MED Nuklear-Medizintechnik Dresden GmbH and the Working Group 6.11 ''Activity Unit'' of the Physikalisch-Technischen Bundesanstalt (PTB) in Braunschweig with the subject ''Activity measurements with radionuclide calibrators (activity meters) for nuclear medicine and metrology''. In the frame of this project, the company MED provided three ionization chamber measuring systems, whereas the PTB adjoined the necessary personal, technical support and the radioactive sources and standards for the calibration in terms of activity. The goal of the project was a systematic study of the performance of the ionization chambers for activity measurements. This covers the subject of determination of various radionuclide efficiencies (calibration factors) necessary for activity determinations in practice. Using two of the ionization chambers of identical construction, a comparison of the reproducibility within exemplars was made using common calibration results. Furthermore, the instrument stability during a period of about two years and the system linearity for activity values within a range of about four orders of magnitude were studied. In addition, the energy-dependent efficiency curves were determined, which allowed the calculation of calibration factors for the three ionization chamber measuring systems using emission probabilities of the corresponding radionuclide. The uncertainties of the involved measurands, particularly for the activity values to be determined, were calculated using the rules of the ''Guide to the expression of uncertainty in measurement'' (GUM, JCGM, 2008). (orig.)

  17. DBD Plasma Actuators for Flow Control in Air Vehicles and Jet Engines - Simulation of Flight Conditions in Test Chambers by Density Matching

    Science.gov (United States)

    Ashpis, David E.; Thurman, Douglas R.

    2011-01-01

    Dielectric Barrier Discharge (DBD) Plasma actuators for active flow control in aircraft and jet engines need to be tested in the laboratory to characterize their performance at flight operating conditions. DBD plasma actuators generate a wall-jet electronically by creating weakly ionized plasma, therefore their performance is affected by gas discharge properties, which, in turn, depend on the pressure and temperature at the actuator placement location. Characterization of actuators is initially performed in a laboratory chamber without external flow. The pressure and temperature at the actuator flight operation conditions need to be simultaneously set in the chamber. A simplified approach is desired. It is assumed that the plasma discharge depends only on the gas density, while other temperature effects are assumed to be negligible. Therefore, tests can be performed at room temperature with chamber pressure set to yield the same density as in operating flight conditions. The needed chamber pressures are shown for altitude flight of an air vehicle and for jet engines at sea-level takeoff and altitude cruise conditions. Atmospheric flight conditions are calculated from standard atmosphere with and without shock waves. The engine data was obtained from four generic engine models; 300-, 150-, and 50-passenger (PAX) aircraft engines, and a military jet-fighter engine. The static and total pressure, temperature, and density distributions along the engine were calculated for sea-level takeoff and for altitude cruise conditions. The corresponding chamber pressures needed to test the actuators were calculated. The results show that, to simulate engine component flows at in-flight conditions, plasma actuator should be tested over a wide range of pressures. For the four model engines the range is from 12.4 to 0.03 atm, depending on the placement of the actuator in the engine. For example, if a DBD plasma actuator is to be placed at the compressor exit of a 300 PAX engine, it

  18. A standard Fricke dosimeter compared to an ionization chamber used for dosimetric characterization of 60Co photon beam

    Science.gov (United States)

    Moussous, Ouiza; Medjadj, Toufik

    2016-06-01

    The main objective of this study was to investigate the Fricke dosimeter water equivalent system for measurement of dosimetric parameters for photon beam. The parameters measured with the Fricke dosimeter were compared to those obtained with an ionization chamber. In this work characteristics for 60Co γ-rays of field sizes ranging from 5 × 5 cm2 to 20 × 20 cm2 are reported. The measurements were carried out in the secondary standard dosimetry laboratory using a collimated 60Co gamma source therapy unit. The 60Co beam output in terms of absorbed dose to water was obtained as per IAEA TRS 398 recommendations using cylindrical ionization chamber, whose ND,w has been supplied by the IAEA's reference laboratory. Specific quantities measured include: output factors, peak scatter factor, lateral beam profiles and percentage depth dose. The Fricke dosimeters were irradiated in a water phantom using the suitable poly (methyl methacrylate), PMMA stand. Our results demonstrate that Fricke dosimeter and ionization chamber agree with each other.

  19. Monte Carlo calculation of beam quality correction factors in proton beams using detailed simulation of ionization chambers

    Science.gov (United States)

    Gomà, Carles; Andreo, Pedro; Sempau, Josep

    2016-03-01

    This work calculates beam quality correction factors (k Q ) in monoenergetic proton beams using detailed Monte Carlo simulation of ionization chambers. It uses the Monte Carlo code penh and the electronic stopping powers resulting from the adoption of two different sets of mean excitation energy values for water and graphite: (i) the currently ICRU 37 and ICRU 49 recommended {{I}\\text{w}}=75~\\text{eV} and {{I}\\text{g}}=78~\\text{eV} and (ii) the recently proposed {{I}\\text{w}}=78~\\text{eV} and {{I}\\text{g}}=81.1~\\text{eV} . Twelve different ionization chambers were studied. The k Q factors calculated using the two different sets of I-values were found to agree with each other within 1.6% or better. k Q factors calculated using current ICRU I-values were found to agree within 2.3% or better with the k Q factors tabulated in IAEA TRS-398, and within 1% or better with experimental values published in the literature. k Q factors calculated using the new I-values were also found to agree within 1.1% or better with the experimental values. This work concludes that perturbation correction factors in proton beams—currently assumed to be equal to unity—are in fact significantly different from unity for some of the ionization chambers studied.

  20. The stability of liquid-filled matrix ionization chamber electronic portal imaging devices for dosimetry purposes.

    Science.gov (United States)

    Louwe, R J W; Tielenburg, R; van Ingen, K M; Mijnheer, B J; van Herk, M B

    2004-04-01

    This study was performed to determine the stability of liquid-filled matrix ionization chamber (LiFi-type) electronic portal imaging devices (EPID) for dosimetric purposes. The short- and long-term stability of the response was investigated, as well as the importance of factors influencing the response (e.g., temperature fluctuations, radiation damage, and the performance of the electronic hardware). It was shown that testing the performance of the electronic hardware as well as the short-term stability of the imagers may reveal the cause of a poor long-term stability of the imager response. In addition, the short-term stability was measured to verify the validity of the fitted dose-response curve immediately after beam startup. The long-term stability of these imagers could be considerably improved by correcting for room temperature fluctuations and gradual changes in response due to radiation damage. As a result, the reproducibility was better than 1% (1 SD) over a period of two years. The results of this study were used to formulate recommendations for a quality control program for portal dosimetry. The effect of such a program was assessed by comparing the results of portal dosimetry and in vivo dosimetry using diodes during the treatment of 31 prostate patients. The improvement of the results for portal dosimetry was consistent with the deviations observed with the reproducibility tests in that particular period. After a correction for the variation in response of the imager, the average difference between the measured and prescribed dose during the treatment of prostate patients was -0.7%+/-1.5% (1 SD), and -0.6%+/-1.1% (1 SD) for EPID and diode in vivo dosimetry, respectively. It can be concluded that a high stability of the response can be achieved for this type of EPID by applying a rigorous quality control program.

  1. 一种直线加速器电离室保护装置的研制%Development and research of an ionization chamber protection device on linear accelerator

    Institute of Scientific and Technical Information of China (English)

    程江波; 陈卫彬; 张帅; 严勇

    2011-01-01

    目的:为了减少因电离室工作温度、湿度变化引起的直线加速器故障,延长直线加速器电离室使用寿命,设计一种电离室保护装置.方法:通过使用温度23℃、湿度15%、流量10L/min的干燥空气吹拂电离室的方法,改变电离室的工作环境,减少外部应用环境的变化对电离室产生的不良影响.结果:将装置安装在2台直线加速器上使用,同比上年同期的故障次数,故障率减少80%以上.结论:通过实际运行及参数检测,该电离室保护装置运行稳定,在一定程度上改善了电离室的工作环境,可以减少外部应用环境的变化对电离室产生的不良影响,减少电离室故障,延长使用寿命.%Objective: To design a protection device on ionization chamber to reduce the failure of linear accelerator that caused by changes in ionization chamber's temperature and humidity, and extend the service life of ionization chamber. Methods: The working environment of ionization chamber was changed by using the temperature 23 ℃ , humidity 15%, flow 10 l/min dry air blowing chamber, reducing the adverse effect of the ionization chamber by external environment changes. Results: This device was installed on two linear accelerator equipments. Number of failures compared the same period last year reduced by 80% at least. Conclusion: By the actual operation, the ionization chamber protection device is stable and can be used to improve the working environment of the ionization chamber and reduce the adverse environmental impacts, reduce failures and extend life.

  2. Affect of Air Leakage into a Thermal-Vacuum Chamber on Helium Refrigeration Heat Load

    Science.gov (United States)

    Garcia, Sam; Meagher, Daniel; Linza, Robert; Saheli, Fariborz; Vargas, Gerardo; Lauterbach, John; Reis, Carl; Ganni, Venkatarao (Rao); Homan, Jonathan

    2008-01-01

    NASA s Johnson Space Center (JSC) Building 32 houses two large thermal-vacuum chambers (Chamber A and Chamber B). Within these chambers are liquid nitrogen shrouds to provide a thermal environment and helium panels which operate at 20K to provide cryopumping. Some amount of air leakage into the chambers during tests is inevitable. This causes "air fouling" of the helium panel surfaces due to the components of the air that adhere to the panels. The air fouling causes the emittance of the helium panels to increase during tests. The increase in helium panel emittance increases the heat load on the helium refrigerator that supplies the 20K helium for those panels. Planning for thermal-vacuum tests should account for this increase to make sure that the helium refrigerator capacity will not be exceeded over the duration of a test. During a recent test conducted in Chamber B a known-size air leak was introduced to the chamber. Emittance change of the helium panels and the affect on the helium refrigerator was characterized. A description of the test and the results will be presented.

  3. A new visible spectroscopy diagnostic for the JET ITER-like wall main chamber.

    Science.gov (United States)

    Maggi, C F; Brezinsek, S; Stamp, M F; Griph, S; Heesterman, P; Hogben, C; Horton, A; Meigs, A; Morlock, C; Studholme, W; Zastrow, K-D

    2012-10-01

    In preparation for ITER, JET has been upgraded with a new ITER-like wall (ILW), whereby the main plasma facing components, previously of carbon, have been replaced by mainly Be in the main chamber and W in the divertor. As part of the many diagnostic enhancements, a new, survey, visible spectroscopy diagnostic has been installed for the characterization of the ILW. An array of eight lines-of-sight (LOS) view radially one of the two JET neutral beam shine through areas (W coated carbon fibre composite tiles) at the inner wall. In addition, one vertical LOS views the solid W tile at the outer divertor. The light emitted from the plasma is coupled to a series of compact overview spectrometers, with overall wavelength range of 380-960 nm and to one high resolution Echelle overview spectrometer covering the wavelength range 365-720 nm. The new survey diagnostic has been absolutely calibrated in situ by means of a radiometric light source placed inside the JET vessel in front of the whole optical path and operated by remote handling. The diagnostic is operated in every JET discharge, routinely monitoring photon fluxes from intrinsic and extrinsic impurities (e.g., Be, C, W, N, and Ne), molecules (e.g., BeD, D(2), ND) and main chamber and divertor recycling (typically Dα, Dβ, and Dγ). The paper presents a technical description of the diagnostic and first measurements during JET discharges.

  4. Ionization chamber dosimetry of small photon fields: a Monte Carlo study on stopping-power ratios for radiosurgery and IMRT beams.

    Science.gov (United States)

    Sánchez-Doblado, F; Andreo, P; Capote, R; Leal, A; Perucha, M; Arráns, R; Núñez, L; Mainegra, E; Lagares, J I; Carrasco, E

    2003-07-21

    Absolute dosimetry with ionization chambers of the narrow photon fields used in stereotactic techniques and IMRT beamlets is constrained by lack of electron equilibrium in the radiation field. It is questionable that stopping-power ratio in dosimetry protocols, obtained for broad photon beams and quasi-electron equilibrium conditions, can be used in the dosimetry of narrow fields while keeping the uncertainty at the same level as for the broad beams used in accelerator calibrations. Monte Carlo simulations have been performed for two 6 MV clinical accelerators (Elekta SL-18 and Siemens Mevatron Primus), equipped with radiosurgery applicators and MLC. Narrow circular and Z-shaped on-axis and off-axis fields, as well as broad IMRT configured beams, have been simulated together with reference 10 x 10 cm2 beams. Phase-space data have been used to generate 3D dose distributions which have been compared satisfactorily with experimental profiles (ion chamber, diodes and film). Photon and electron spectra at various depths in water have been calculated, followed by Spencer-Attix (delta = 10 keV) stopping-power ratio calculations which have been compared to those used in the IAEA TRS-398 code of practice. For water/air and PMMA/air stopping-power ratios, agreements within 0.1% have been obtained for the 10 x 10 cm2 fields. For radiosurgery applicators and narrow MLC beams, the calculated s(w,air) values agree with the reference within +/-0.3%, well within the estimated standard uncertainty of the reference stopping-power ratios (0.5%). Ionization chamber dosimetry of narrow beams at the photon qualities used in this work (6 MV) can therefore be based on stopping-power ratios data in dosimetry protocols. For a modulated 6 MV broad beam used in clinical IMRT, s(w,air) agrees within 0.1% with the value for 10 x 10 cm2, confirming that at low energies IMRT absolute dosimetry can also be based on data for open reference fields. At higher energies (24 MV) the difference in s(w,air

  5. Ionization chamber dosimetry of small photon fields: a Monte Carlo study on stopping-power ratios for radiosurgery and IMRT beams

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez-Doblado, F [Radiofisica, Hospital Univ Virgen Macarena, Avda Dr Fedriani s/n, E-41009 Sevilla (Spain); Andreo, P [Division of Medical Radiation Physics, University of Stockholm, Karolinska Institute, PO Box 260, SE-171 76 Stockholm (Sweden); Capote, R [Radiofisica, Hospital Univ Virgen Macarena, Avda Dr Fedriani s/n, E-41009 Sevilla (Spain); Leal, A [Radiofisica, Hospital Univ Virgen Macarena, Avda Dr Fedriani s/n, E-41009 Sevilla (Spain); Perucha, M [Dpto Fisica Medica y Biofisica, F Medicina, Universidad Sevilla (Spain); Arrans, R [Radiofisica, Hospital Univ Virgen Macarena, Avda Dr Fedriani s/n, E-41009 Sevilla (Spain); Nunez, L [Radiofisica, Clinica Puerta de Hierro, Madrid (Spain); Mainegra, E [National Research Council, Ottawa (Canada); Lagares, J I [Radiofisica, Hospital Univ Virgen Macarena, Avda Dr Fedriani s/n, E-41009 Sevilla (Spain); Carrasco, E [Radiofisica, Hospital Univ Virgen Macarena, Avda Dr Fedriani s/n, E-41009 Sevilla (Spain)

    2003-07-21

    Absolute dosimetry with ionization chambers of the narrow photon fields used in stereotactic techniques and IMRT beamlets is constrained by lack of electron equilibrium in the radiation field. It is questionable that stopping-power ratio in dosimetry protocols, obtained for broad photon beams and quasi-electron equilibrium conditions, can be used in the dosimetry of narrow fields while keeping the uncertainty at the same level as for the broad beams used in accelerator calibrations. Monte Carlo simulations have been performed for two 6 MV clinical accelerators (Elekta SL-18 and Siemens Mevatron Primus), equipped with radiosurgery applicators and MLC. Narrow circular and Z-shaped on-axis and off-axis fields, as well as broad IMRT configured beams, have been simulated together with reference 10 x 10 cm{sup 2} beams. Phase-space data have been used to generate 3D dose distributions which have been compared satisfactorily with experimental profiles (ion chamber, diodes and film). Photon and electron spectra at various depths in water have been calculated, followed by Spencer-Attix ({delta} = 10 keV) stopping-power ratio calculations which have been compared to those used in the IAEA TRS-398 code of practice. For water/air and PMMA/air stopping-power ratios, agreements within 0.1% have been obtained for the 10 x 10 cm{sup 2} fields. For radiosurgery applicators and narrow MLC beams, the calculated s{sub w,air} values agree with the reference within {+-}0.3%, well within the estimated standard uncertainty of the reference stopping-power ratios (0.5%). Ionization chamber dosimetry of narrow beams at the photon qualities used in this work (6 MV) can therefore be based on stopping-power ratios data in dosimetry protocols. For a modulated 6 MV broad beam used in clinical IMRT, s{sub w,air} agrees within 0.1% with the value for 10 x 10 cm{sup 2}, confirming that at low energies IMRT absolute dosimetry can also be based on data for open reference fields. At higher energies (24

  6. A micro-gap, air-filled ionisation chamber as a detector for criticality accident dosimetry.

    Science.gov (United States)

    Murawski, Ł; Zielczyński, M; Golnik, N; Gryziński, M A

    2014-10-01

    A micro-gap air-filled ionisation chamber was designed for criticality dosimetry. The special feature of the chamber is its very small gap between electrodes of only 0.3 mm. This prevents ion recombination at high dose rates and minimises the influence of gas on secondary particles spectrum. The electrodes are made of polypropylene because of higher content of hydrogen in this material, when compared with soft tissue. The difference between neutron and gamma sensitivity in such chamber becomes practically negligible. The chamber's envelope contains two specially connected capacitors, one for polarising the electrodes and the other for collecting the ionisation charge.

  7. Effect of Environmental Deflector on Air Exchange in Slurry Pit and Concentration Distribution in a Two-dimensional Ventilation Chamber

    DEFF Research Database (Denmark)

    Tong, Guohong; Zhang, Guoqiang; Ravn, Peter

    2008-01-01

    Variations of air exchanges in slurry pit with four angles of an environmental deflector, namely 0° (parallel to the side wall or without deflector), 30°, 45° and 90°, were investigated using a tracer gas method. The investigations were performed in a two-dimensional ventilation chamber in the Air...... physics Lab, University of Aarhus. Ventilation rates used in the experiments were 100 and 200 m3/h. The experiment results showed that using the deflectors of 30°, 45° and 90° the airflow patterns were obviously changed in the room space near the slatted floor and in the head space of the pit compared...... with the setup without deflector. It was also found that of all the deflector angle performances with respect to air-exchange ratio and concentration distribution, the deflector position of 45° in two airflow rates cases behaved better with the lowest pit ventilation and the highest concentration in the head...

  8. Development and characterization of special ionization chambers for computed tomography beams; Desenvolvimento e caracterizacao de camaras de ionizacao especiais para feixes de tomografia computadorizada

    Energy Technology Data Exchange (ETDEWEB)

    Castro, Maysa Costa de

    2016-10-01

    The use of computed tomography (CT) for imaging procedures is growing due to advances in the CT equipment technology, because they allow the obtention of images with better resolution than through other techniques. Therefore, they are responsible for increasing the dose radiation of patients during the procedure. This fact led to a greater concern about the doses received by patients who undergo this type of examination. To perform the dosimetry in CT beams, the most widely used instrument is the pencil type ionization chamber, because this dosimeter has a uniform response to the incident radiation beam for all angles. The conventional ionization chamber, which is available on the market, has a sensitive volume length of 10 cm; however, some studies have shown that this dosimeter has underestimated the dose values. Therefore, in this study two ionization chambers with sensitive volume lengths of 10 cm and 30 cm, making use of low cost national materials, were developed at the Calibration Laboratory of Instruments (LCI-IPEN/CNEN). The characterization of these chambers was performed, and the results were obtained within the international recommended limits. As an application, the developed ionization chambers and a commercial chamber were tested in a clinical tomograph. The developed ionization chambers were analyzed in a complete way for their possible uses. (author)

  9. An Efficient Computation of Coherent Synchrotron Radiation in a Rectangular Chamber, Applied to Resistive Wall Heating

    CERN Document Server

    Warnock, Robert L

    2016-01-01

    We study coherent synchrotron radiation (CSR) in a perfectly conducting vacuum chamber of rectangular cross section, in a formalism allowing an arbitrary sequence of bends and straight sections. We apply the paraxial method in the frequency domain, with a Fourier development in the vertical coordinate but with no other mode expansions. A line charge source is handled numerically by a new method that rids the equations of singularities through a change of dependent variable. The resulting algorithm is fast compared to earlier methods, works for short bunches with complicated structure, and yields all six field components at any space-time point. As an example we compute the tangential magnetic field at the walls. From that one can make a perturbative treatment of the Poynting flux to estimate the energy deposited in resistive walls. The calculation was motivated by a design issue for LCLS-II, the question of how much wall heating from CSR occurs in the last bend of a bunch compressor and the following straight...

  10. First demonstration of a sub-keV electron recoil energy threshold in a liquid argon ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Sangiorgio, S., E-mail: samuele@llnl.gov [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); Joshi, T.H. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); Department of Nuclear Engineering, University of California, Berkeley, CA 94720 (United States); Bernstein, A. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); Coleman, J. [Department of Physics, University of Liverpool, Oxford St, Liverpool L69 7Ze (United Kingdom); Foxe, M. [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Hagmann, C. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); Jovanovic, I. [Department of Mechanical and Nuclear Engineering, Pennsylvania State University, University Park, PA 16802 (United States); Kazkaz, K. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States); Mavrokoridis, K. [Department of Physics, University of Liverpool, Oxford St, Liverpool L69 7Ze (United Kingdom); Mozin, V.; Pereverzev, S.; Sorensen, P. [Lawrence Livermore National Laboratory, 7000 East Ave., Livermore, CA 94550 (United States)

    2013-11-11

    We describe the first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time projection chamber. This is an important step in an effort to develop a detector capable of identifying the ionization signal resulting from nuclear recoils with energies of order a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82 keV and 0.27 keV, following the K- and L-shell electron capture decay of {sup 37}Ar respectively. The {sup 37}Ar source preparation is described in detail, since it enables calibration that may also prove useful in dark matter direct detection experiments. An internally placed {sup 55}Fe x-ray source simultaneously provided another calibration point at 5.9 keV. We discuss the ionization yield and electron recombination in liquid argon at those three calibration energies. -- Highlights: • We measure sub-keV electron recoils in a dual-phase argon time projection chamber. • Ar-37 is produced via neutron irradiation and used as calibration source. • Ar-37 electron captures at 2.82 and 0.27 keV are measured together with Fe-55 x-rays. • Spurious single ionization electrons provided absolute calibration of charge signal. • Modified Thomas–Imel model describes low-energy electron-recoils in liquid Ar.

  11. Calculation of Generation Rate of Electron Ion Pairs Ionized by Radioactive Nuclide in Air

    Institute of Scientific and Technical Information of China (English)

    WU; Xiu-feng; ZHANG; Li-feng; LUO; Zhi-fu

    2015-01-01

    Alpha and beta nuclides are widely employed in industrial production and life for the ability of ionization.Static eliminator,ionization smoke detector,electron capture detector and radioactive lightning rod are some typical examples.Alpha/beta rays produce electrons by ionizing the air,and then the charge is transferred during

  12. A Liquid Xenon Ionization Chamber in an All-fluoropolymer Vessel

    Energy Technology Data Exchange (ETDEWEB)

    LePort, F.; Pocar, A.; Bartoszek, L.; DeVoe, R.; Fierlinger, P.; Flatt, B.; Gratta, G.; Green, M.; Montero Diez, M.; Neilson, R.; O' Sullivan, K.; Wodin, J.; Woisard, D.; Baussan, E.; Breidenbach, M.; Conley, R.; Fairbank, W., Jr.; Farine, J.; Hall, K.; Hallman, D.; Hargrove, C.; /Stanford U., Phys. Dept. /Applied Plastics Technology, Bristol

    2007-02-26

    A novel technique has been developed to build vessels for liquid xenon ionization detectors entirely out of ultra-clean fluoropolymer. We describe the advantages in terms of low radioactivity contamination, provide some details of the construction techniques, and show the energy resolution achieved with a prototype all-fluoropolymer ionization detector.

  13. A liquid xenon ionization chamber in an all-fluoropolymer vessel

    CERN Document Server

    LePort, F; Baussan, E; Breidenbach, M; Conley, R; DeVoe, R; Diez, M M; Fairbank, W; Farine, J; Fierlinger, P; Flatt, B; Gratta, G; Green, M; Hall, C; Hall, K; Hallman, D; Hargrove, C K; Hodgson, J; Jeng, S; Koffas, T; Leonard, D S; Mackay, D; Martin, Y; Neilson, R; O'Sullivan, K; Odian, A; Ounalli, L; Piepke, A; Pocar, A; Prescott, C Y; Rowson, P C; Schenker, D; Sinclair, D; Skarpaas, K V; Stekhanov, V; Strickland, V; Virtue, C; Vuilleumier, J L; Vuilleumier, J M; Waldman, S J; Wamba, K; Weber, P; Wodin, J; Woisard, D

    2006-01-01

    A novel technique has been developed to build vessels for liquid xenon ionization detectors entirely out of ultra-clean fluoropolymer. We describe the advantages in terms of low radioactivity contamination, provide some details of the construction techniques, and show the energy resolution achieved with a prototype all-fluoropolymer ionization detector.

  14. Numerical Analysis of Flow Distribution in a Sodium Chamber of a Finned-tube Sodium-to-Air Heat Exchanger

    Energy Technology Data Exchange (ETDEWEB)

    Jo, Youngchul; Son, Seokkwon; Kim, Hyungmo; Eoh, Jaehyuk; Jeong, Jiyoung [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-10-15

    DHR systems consist of two diverse heat removal loops such as passive and active DHR systems, and the heat load imposed on the primary sodium pool is safely rejected into the environment through different kinds of sodium-to-air heat exchangers, e.g. M-shape and helical-coil type air-coolers. The former is called as an FHX(Forced-draft sodium-to-air Heat Exchanger) and the latter is simply called as an AHX(natural-draft sodium-to-Air Heat Exchanger). In a general sodium-to-air heat exchanger design, convection resistance in a shell-side air flow path becomes dominant factor affecting the mechanism of conjugate heat transfer from the sodium flow inside the tube to the air path across the sodium tube wall. Hence verification of the flow and heat transfer characteristics is one of the most important tasks to demonstrate decay heat removal performance. To confirm a kind of ultimate heat sink heat exchanger, a medium-scale Sodium thermal-hydraulic Experiment Loop for Finned-tube sodium-to-Air Heat exchanger (here after called the SELFA) has been designed and is recently being constructed at KAERI site. The introduction of the flow baffle inside the upper sodium chamber of the model FHX unit in the SELFA facility is briefly proposed and discussed as well. The present study aims at introducing a flow baffle design inside the upper sodium chamber to make more equalized flowrates flowing into each heat transfer tube of the model FHX unit. In the cases without the flow baffle geometry, it was observed lager discrepancies in flowrates at the heat transfer tubes. However it was also found that those kinds of discrepancies could be definitely decreased at around 1/10 by employing a flow baffle.

  15. Patient specific quality assurance of RapidArc pre treatment plans using semiflex 0.125 cc ionization chamber

    Science.gov (United States)

    Kumar, S. A. Syam; Vivekanandan, Nagarajan

    2017-01-01

    Patient specific pre-treatment quality assurance for RapidArc plans were analyzed for hundred patients for different sites. Verification plan was created for each treatment plan in Eclipse 8.6 treatment planning system with the semiflex ionization chamber and the octavius phantom. Absolute point dose were measured for head and neck, thorax and abdomen cases using semiflex (0.125 cc) ionization chamber. Positive absolute mean dose variation of 0.56% was observed with thorax cases with a standard deviation (SD) of ±1.13 between the plans with a range of -1.78% to 2.70%. Negative percentage dose errors were found with head and neck and abdomen cases, with a mean variation of -0.43% (SD±1.50), (range -3.25% to 2.85%) and -0.35% (SD±1.48), (range -3.10% to 2.65%) for head and neck and abdomen cases respectively. Evaluation has been done using PTW verisoft software by keeping the passing criteria as 3 mm DTA, 3% DD, for 95% of the evaluated dose points. The maximum percentage value failed in gamma analysis was found to be 4.95, 4.75, and 4.88 for head and neck, thorax, and abdomen cases respectively. In all the cases analyzed the percentage dose points failed the gamma criteria is less than 5%. On the basis of the studies performed it can be concluded that the semiflex ionization chamber having a volume of 0.125 cc can be used efficiently for measuring the pre-treatment quality assurance of RapidArc plans for all the sites.

  16. First demonstration of a sub-keV electron recoil energy threshold in a liquid argon ionization chamber

    CERN Document Server

    Sangiorgio, S; Coleman, J; Foxe, M; Hagmann, C; Joshi, T H; Jovanovic, I; Kazkaz, K; Mavrokoridis, K; Mozin, V; Pereverzev, S; Sorensen, P

    2013-01-01

    We make a first demonstration of a sub-keV electron recoil energy threshold in a dual-phase liquid argon time-projection chamber. This is an important step in a program to build a detector capable of identifying the ionization signal resulting from nuclear recoils at a few keV and below. We obtained this result by observing the peaks in the energy spectrum at 2.82 keV and 0.27 keV, following the K- and L-shell electron capture decay of Ar-37. We describe the details of the Ar-37 source preparation, as this calibration technique may prove useful, e.g. for dark matter direct detection experiments. A Fe-55 internal x-ray source was also measured simultaneously and provided another calibration point at 5.9 keV. We discuss the ionization yield and electron recombination in liquid argon at the three calibration energies.

  17. A method for measuring the electron drift velocity in working gas using a Frisch-grid ionization chamber

    Science.gov (United States)

    Bai, Huaiyong; Wang, Zhimin; Zhang, Luyu; Chen, Jinxiang; Zhang, Guohui

    2016-12-01

    A method for measuring the electron drift velocity in working gas is proposed. Based on the cathode and the anode signal waveforms of the Frisch-grid ionization chamber, the electron drift velocity is extracted. With this method, the electron drift velocities in Ar + 10% CH4, Ar + 3.5% CO2 and Kr + 2.7% CO2 gases have been measured and the results are compared with the existing measurements and the simulating results. Using this method, the electron drift velocity can be monitored throughout the experiment of charged particle without bothering the measurement of other parameters, such as the energy and orientation.

  18. Evaluation of dosimetric characteristics of multi-leaf and conventional collimated radiation fields using a scanning liquid ionization chamber EPID.

    Science.gov (United States)

    Mohammadi, M; Bezak, E

    2008-12-01

    The characteristics of radiation fields set up using conventional and Multi-Leaf collimators were investigated using a Scanning Liquid Ionization Chamber Electronic Portal Imaging Device (SLIC-EPID). Results showed that the radiation fields set up using MLCs are generally larger than those set up using conventional collimators. A significant difference was observed between the penumbra width for conventional and MLC radiation fields. SLIC-EPID was found to be a sensitive device to evaluate the characteristics of the radiation fields generated with MLCs.

  19. A prototype liquid Argon Time Projection Chamber for the study of UV laser multi-photonic ionization

    CERN Document Server

    Rossi, B; Ereditato, A; Haug, S; Hanni, R; Hess, M; Janos, S; Juget, F; Kreslo, I; Lehmann, S; Lutz, P; Mathieu, R; Messina, M; Moser, U; Nydegger, F; Schutz, H U; Weber, M S; Zeller, M

    2009-01-01

    This paper describes the design, realization and operation of a prototype liquid Argon Time Projection Chamber (LAr TPC) detector dedicated to the development of a novel online monitoring and calibration system exploiting UV laser beams. In particular, the system is intended to measure the lifetime of the primary ionization in LAr, in turn related to the LAr purity level. This technique could be exploited by present and next generation large mass LAr TPCs for which monitoring of the performance and calibration plays an important role. Results from the first measurements are presented together with some considerations and outlook.

  20. Correction factors for ionization chamber dosimetry in CyberKnife: Machine-specific, plan-class, and clinical fields

    Energy Technology Data Exchange (ETDEWEB)

    Gago-Arias, Araceli; Antolin, Elena; Fayos-Ferrer, Francisco; Simon, Rocio; Gonzalez-Castano, Diego M.; Palmans, Hugo; Sharpe, Peter; Gomez, Faustino; Pardo-Montero, Juan [Departamento de Fisica de Particulas, Facultad de Fisica, Universidade de Santiago de Compostela, A Coruna 15782 (Spain); Servicio de Fisica Medica, Hospital Ruber Internacional, Madrid 28034 (Spain); Departamento de Fisica de Particulas, Facultad de Fisica, Universidade de Santiago de Compostela, A Coruna 15782, Spain and Laboratorio de Radiofisica, Universidade de Santiago de Compostela, Santiago de Compostela, A Coruna 15782 (Spain); National Physical Laboratory, Teddington, Middx TW11 OLW (United Kingdom); Departamento de Fisica de Particulas, Facultad de Fisica, Universidade de Santiago de Compostela, A Coruna 15782, Spain and Laboratorio de Radiofisica, Universidade de Santiago de Compostela, Santiago de Compostela, A Coruna 15782 (Spain); Departamento de Fisica de Particulas, Facultad de Fisica, Universidade de Santiago de Compostela, A Coruna 15782 (Spain)

    2013-01-15

    Purpose: The aim of this work is the application of the formalism for ionization chamber reference dosimetry of small and nonstandard fields [R. Alfonso, P. Andreo, R. Capote, M. S. Huq, W. Kilby, P. Kjaell, T. R. Mackie, H. Palmans, K. Rosser, J. Seuntjens, W. Ullrich, and S. Vatnitsky, 'A new formalism for reference dosimetry of small and nonstandard fields,' Med. Phys. 35, 5179-5186 (2008)] to the CyberKnife robotic radiosurgery system. Correction factors for intermediate calibration fields, a machine-specific reference field (msr) and two plan-class specific reference fields (pcsr), have been studied. Furthermore, the applicability of the new formalism to clinical dosimetry has been analyzed through the investigation of two clinical treatments. Methods: PTW31014 and Scanditronix-Wellhofer CC13 ionization chamber measurements were performed for the fields under investigation. Absorbed dose to water was determined using alanine reference dosimetry, and experimental correction factors were calculated from alanine to ionization chamber readings ratios. In addition, correction factors were calculated for the intermediate calibration fields and one of the clinical treatment fields using the Monte Carlo method and these were compared with the experimental values. Results: Overall correction factors deviating from unity by approximately 2% were obtained from both measurements and simulations, with values below and above unity for the studied intermediate calibration fields and clinical fields for the ionization chambers under consideration. Monte Carlo simulations yielded correction factors comparable with those obtained from measurements for the machine-specific reference field, although differences from 1% to 3.3% were observed between measured and calculated correction factors for the composite intermediate calibration fields. Dose distribution inhomogeneities are thought to be responsible for such discrepancies. Conclusions: The differences found between

  1. CFD SIMULATION OF AIR ION REGIME IN WORK AREAS AT CONDITION OF ARTIFICIAL AIR IONIZATION

    Directory of Open Access Journals (Sweden)

    M. M. Biliaiev

    2016-02-01

    Full Text Available Purpose. The paper supposes creation of a CFD model for calculating the air ion regime in the premises and in work areas at artificial ionization of the air by the ionizer installation indoors with considering the most important physical factors that influence the formation of ions concentration field. Methodology. The proposed CFD model for calculation of the air ion regime in work areas at artificial ionization of the air by installing ionizer indoors is based on the application of aerodynamics, electrostatics and mass transfer equations. The mass transfer equation takes into account the interaction of different polarities of ions with each other and with the dust particles. The calculation of air flow rate in the room is realized on the basis of the potential flow model by using the Laplace equation for the stream function. Poisson equation for the electric potential is used for calculation of the charged particles drift in an electric field. At the simulation to take into account: 1 influence of the working area geometric characteristics; 2 location of the ventilation holes; 3 placement of furniture and equipment; 4 ventilation regime in the room; 5 presence of obstacles on the ions dispersion process; 6 specific location of dust particles emission and ions of different polarity, and their interaction in the room and in the working zones. Findings. The developed CFD model allows determining the concentration of negative ions in the room and in the area of the human respiratory organs. The distribution of the negative ions concentration is presented in the form of concentration field isolines. Originality. The 2D CFD model for calculating the air ion regime in working areas, providing the ability to determine the ions concentration in a given place in the room was created. The proposed model is developed taking into account: placement of furniture and equipment in the room; geometric characteristics of the room; location of dust emissions

  2. Evaluation of the energy dependence of ionization chambers pencil type calibrated beam tomography standards; Avaliacao da dependencia energetica de camaras de ionizacao do tipo lapis calibradas em feixes padroes de tomografia

    Energy Technology Data Exchange (ETDEWEB)

    Fontes, Ladyjane Pereira; Potiens, Maria da Penha A., E-mail: lpfontes@ipen.br [Instituto de Pesquisas Energeticas e Nucleres (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    The Instrument Calibration Laboratory of IPEN (LCI - IPEN) performs calibrations of pencil-type ionization chambers (IC) used in measures of dosimetric survey on clinical systems of Computed Tomography (CT). Many users make mistakes when using a calibrated ionization chamber in their CT dosimetry systems. In this work a methodology for determination of factors of correction for quality (Kq) through the calibration curve that is specific for each ionization chamber was established. Furthermore, it was possible to demonstrate the energy dependence on an pencil-type Ionization Chamber(IC) calibrated at the LCI - IPEN. (author)

  3. Direct determination of k Q for Farmer-type ionization chambers in a clinical scanned carbon ion beam using water calorimetry

    Science.gov (United States)

    Osinga-Blättermann, J.-M.; Brons, S.; Greilich, S.; Jäkel, O.; Krauss, A.

    2017-03-01

    Until now, the dosimetry of carbon ions with ionization chambers has not reached the same level of accuracy as that of high-energy photons. This is mainly caused by the approximately threefold larger uncertainty of the k Q factor of ionization chambers, which, due to the lack of experimental data, is still derived by calculations. Measurements of absorbed dose to water, D w, by means of water calorimetry have now been performed in the entrance channel of a scanned 6 cm  ×  6 cm radiation field of 429 MeV/u carbon ions, allowing the direct calibration of ionization chambers and thus the experimental determination of k Q. Within this work, values for k Q have been determined for the Farmer-type ionization chambers FC65-G and TM30013. A detailed investigation of the radiation field enabled the accurate determination of correction factors needed for both calorimetric and ionometric measurements. Finally, a relative standard measurement uncertainty of 0.8% (k  =  1) could be achieved for the experimental k Q values. For both chambers, the experimental k Q factors were found to be about 1% larger than those tabulated in the German DIN 6801-1 protocol, whereas compared to the theoretical values stated in the TRS-398 protocol, the experimental k Q value agrees within 0.4% for the TM30013 chamber but is about 1% lower in the case of the FC65-G chamber.

  4. Metrology of the radon in air volume activity at the italian radon reference chamber

    Energy Technology Data Exchange (ETDEWEB)

    Sciocchetti, G.; Cotellessa, G.; Soldano, E.; Pagliari, M. [Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA Centro Ricerche Casaccia Roma (Italy)

    2006-07-01

    The approach of the Italian National Institute of Ionising Radiations (I.N.M.R.I.-ENEA) on radon metrology has been based on a complete and integrated system which can be used to calibrate the main types of {sup 222}Rn in air measuring instruments with international traceability. The Italian radon reference chamber is a research and calibration facility developed at the Casaccia Research Center in Roma. This facility has an inner volume of one m{sup 3}. The wall is a cylindrical stainless steel vessel coupled with an automated climate apparatus operated both at steady and dynamic conditions. The control and data acquisition equipment is based on Radotron system, developed to automate the multitasking management of different sets of radon monitors and climatic sensors. A novel approach for testing passive radon monitors with an alpha track detector exposure standard has been developed. It is based on the direct measurement of radon exposure with a set of passive integrating monitors based on the new ENEA piston radon exposure meter. This paper describes the methodological approach on radon metrology, the status-of-art of experimental apparatus and the standardization procedures. (authors)

  5. Kinetic analysis of competition between aerosol particle removal and generation by ionization air purifiers.

    Science.gov (United States)

    Alshawa, Ahmad; Russell, Ashley R; Nizkorodov, Sergey A

    2007-04-01

    Ionization air purifiers are increasingly used to remove aerosol particles from indoor air. However, certain ionization air purifiers also emit ozone. Reactions between the emitted ozone and unsaturated volatile organic compounds (VOC) commonly found in indoor air produce additional respirable aerosol particles in the ultrafine (air purifiers under conditions of a typical residential building. This model predicts that certain widely used ionization air purifiers may actually increase the mass concentration of fine and ultrafine particulates in the presence of common unsaturated VOC, such as limonene contained in many household cleaning products. This prediction is supported by an explicit observation of ultrafine particle nucleation events caused by the addition of D-limonene to a ventilated office room equipped with a common ionization air purifier.

  6. Chamber wall materials response to pulsed ions at power-plant level fluences

    Science.gov (United States)

    Renk, T. J.; Provencio, P. P.; Tanaka, T. J.; Olson, C. L.; Peterson, R. R.; Stolp, J. E.; Schroen, D. G.; Knowles, T. R.

    2005-12-01

    Candidate dry-wall materials for the reactor chambers of future laser-driven Inertial Fusion Energy (IFE) power plants have been exposed to ion pulses from RHEPP-1, located at Sandia National Laboratories. These pulses simulate the MeV-level ion pulses with fluences of up to 20 J/cm 2 that can be expected to impinge on the first wall of such future plants. Various forms of tungsten and tungsten alloy were subjected to up to 1600 pulses, usually while being heated to 600 °C. Other metals were exposed as well. Thresholds for roughening and material removal, and evolution of surface morphology were measured and compared with code predictions for materials response. Powder-metallurgy (PM) tungsten is observed to undergo surface roughening and subsurface crack formation that evolves over hundreds of pulses, and which can occur both below and above the melt threshold. This roughening is worse than for other metals, and worse than for either tungsten alloyed with rhenium (W25Re), or for CVD and single-crystal forms of tungsten. Carbon, particularly the form used in composite material, appears to suffer material loss well below its sublimation point. Some engineered materials were also investigated. It appears that some modification to PM tungsten is required for its successful use in a reactor environment.

  7. Analysis of Air Flow in the Ventilated Insulating Air Layer of the External Wall

    Science.gov (United States)

    Katunská, Jana; Bullová, Iveta; Špaková, Miroslava

    2016-12-01

    The paper deals with problems of impact of air flow in ventilated insulating air layer of the external wall on behaviour of thermal-technical parameters of the proposed external structure (according principles of STN 73 0549, which is not valid now), by comparing them in the calculation according to the valid STN standards, where air flow in the ventilated air layer is not taken into account, as well as by comparing them with behavior of thermal-technical parameters in the proposal of sandwich external wall with the contact heat insulation system without air cavity.

  8. Performance Analysis of a Solar Dryer Equipped with a Recycling Air System and Desiccant Chamber

    Directory of Open Access Journals (Sweden)

    M.H Aghkhani

    2013-09-01

    Full Text Available Drying is a high energy consuming process. Solar drying is one of the most popular methods for dehydration of agricultural products. In the present study, the performance of a forced convection solar dryer equipped with recycling air system and desiccant chamber was investigated. The solar dryer is comprised of solar collector, drying chamber, silica jell desiccant chamber, air ducts, fan and measuring and controlling system. Drying rate and energy consumption in three levels of air temperature (40, 45 and 50 oC and two modes of drying (with recycling air and no-recycling with open duct system were measured and compared. The results showed that increasing the drying air temperature decreased the drying time and increased the energy consumption in the mode of non-recycling air system. The dryer efficiency and drying rate were better in the mode of recycling air system than open duct system. The highest dryer efficiency was obtained from drying air temperature of 50 oC and the mode of recycling air system. In general, the efficiency of solar collector and the highest efficiency of the dryer were 0.34 and 0.41, respectively.

  9. Investigation of particle and vapor wall-loss effects on controlled wood-smoke smog-chamber experiments

    Directory of Open Access Journals (Sweden)

    Q. Bian

    2015-06-01

    Full Text Available Smog chambers are extensively used to study processes that drive gas and particle evolution in the atmosphere. A limitation of these experiments is that particles and gas-phase species may be lost to chamber walls on shorter timescales than the timescales of the atmospheric processes being studied in the chamber experiments. These particle and vapor wall losses have been investigated in recent studies of secondary organic aerosol (SOA formation, but they have not been systematically investigated in experiments of primary emissions from combustion. The semi-volatile nature of combustion emissions (e.g. from wood smoke may complicate the behavior of particle and vapor wall deposition in the chamber over the course of the experiments due to the competition between gas/particle and gas/wall partitioning. Losses of vapors to the walls may impact particle evaporation in these experiments, and potential precursors for SOA formation from combustion may be lost to the walls, causing underestimates of aerosol yields. Here, we conduct simulations to determine how particle and gas-phase wall losses contributed to the observed evolution of the aerosol during experiments in the third Fire Lab At Missoula Experiment (FLAME III. We use the TwO-Moment Aerosol Sectional (TOMAS microphysics algorithm coupled with the organic volatility basis set (VBS and wall-loss formulations to examine the predicted extent of particle and vapor wall losses. We limit the scope of our study to the dark periods in the chamber before photo-oxidation to simplify the aerosol system for this initial study. Our model simulations suggest that over one third of the initial particle-phase organic mass (36% was lost during the experiments, and roughly half of this particle organic mass loss was from direct particle wall loss (56% of the loss with the remainder from evaporation of the particles driven by vapor losses to the walls (44% of the loss. We perform a series of sensitivity tests to

  10. Controlled environment fumigation chambers for the study of reactive air pollutant effects on plants

    Science.gov (United States)

    Stokes, N. J.; Lucas, P. W.; Nicholas Hewitt, C.

    The design and construction of eight 1-m 3 fumigation chambers for exposing plants to reactive air pollutants at low concentrations are reported. Teflon surfaces are used where possible to minimize the adsorption, absorption, desorption and chemical reaction of the pollutants. A purified ambient air supply, to which metered quantities of gaseous pollutants are added, is used to give two air changes per minute at constant, low, pollutant concentrations. Comparative analysis of the chambers indicates that conditions may be maintained with a significant degree of precision, i.e. temperature ±0.3°C, RH ±6%, light intensity ±5 μmol m -2 s -1. Boundary layer analysis from models of cherry tree ( Prunus avium) leaves indicate that the minimum conductance value within these chambers is 2 cm s -1.

  11. A combined segmented anode gas ionization chamber and time-of-flight detector for heavy ion elastic recoil detection analysis

    Science.gov (United States)

    Ström, Petter; Petersson, Per; Rubel, Marek; Possnert, Göran

    2016-10-01

    A dedicated detector system for heavy ion elastic recoil detection analysis at the Tandem Laboratory of Uppsala University is presented. Benefits of combining a time-of-flight measurement with a segmented anode gas ionization chamber are demonstrated. The capability of ion species identification is improved with the present system, compared to that obtained when using a single solid state silicon detector for the full ion energy signal. The system enables separation of light elements, up to Neon, based on atomic number while signals from heavy elements such as molybdenum and tungsten are separated based on mass, to a sample depth on the order of 1 μm. The performance of the system is discussed and a selection of material analysis applications is given. Plasma-facing materials from fusion experiments, in particular metal mirrors, are used as a main example for the discussion. Marker experiments using nitrogen-15 or oxygen-18 are specific cases for which the described improved species separation and sensitivity are required. Resilience to radiation damage and significantly improved energy resolution for heavy elements at low energies are additional benefits of the gas ionization chamber over a solid state detector based system.

  12. Design and Development of Ionization Chamber for Detection of X-Ray Beam AT INDUS-2 RRCAT

    Directory of Open Access Journals (Sweden)

    Nawaz Ali Sayed

    2013-02-01

    Full Text Available The goal of this paper was to design and develop a Microcontroller based data acquisition unit for detection of X-ray flux through Ionization chamber that will remotely control and monitor the ultra-low current signal detection analog module precisely. This application will be useful to measure the intensity of x-ray flux through the ionization chamber in a beam line of synchrotron radiation source which is mounted in INDUS-2. The beam line area is highly restricted because of hazardous radiation, so through this application remote interfacing provides for the ultra-low current signal detection card that can be controlled by personal computer. To design a perfect embedded system there are many issues like designing a proper PCB, to achieve the specified resolution of the ADC used in chip, code developed using any compiler should be within the limit of the memory of the microcontroller system and integrity of the devices used in the circuit. Initially explore and gain the knowledge of embedded systems by doing a small project and writing the code for the same, and gain a knowledge how the system works. Programming has done in assembly language 8051, for schematic design PCB design tool ORCAD (VERSION 9.0 use

  13. General collection efficiency for liquid isooctane and tetramethylsilane used as sensitive media in a parallel-plate ionization chamber.

    Science.gov (United States)

    Johansson, B; Wickman, G

    1997-01-01

    The general collection efficiency has been measured in liquid isooctane (C8H18) and tetramethylsilane (Si(CH3)4) used as the sensitive media in a parallel-plate ionization chamber, with an electrode distance of 1 mm, intended for photon and electron dosimetry applications. The liquid ionization chamber was irradiated at different dose rates by 140 keV photons from the decay of radioactive 99mTc. The measurements were made at potential differences of 50, 100, 200 and 500 V. Measurements were performed for each liquid and electric field strength, with the decay rate of 99mTc used as the dose-rate reference. The maximum dose rate was about 150 mGy min-1 in each experiment. When the measured general collection efficiency values are compared with the theoretical predictions for collection efficiency in gases, it is found that the latter also describe the general collection efficiency in the two liquids within 1% of the saturation current for collection efficiencies down to 60% when using experimentally determined recombination rate constants and on mobilities characteristic of each of the liquids.

  14. Assaying multiple 125I seeds with the well-ionization chamber SourceCheck4π 33005 and a new insert

    Science.gov (United States)

    Ballester, Facundo; Perez-Calatayud, Jose; Vijande, Javier

    2015-01-01

    Purpose To provide a practical solution that can be adopted in clinical routine to fulfill the AAPM-ESTRO recommendations regarding quality assurance of seeds used in prostate permanent brachytherapy. The aim is to design a new insert for the well-ionization chamber SourceCheck4π 33005 (PTW, Germany) that allows evaluating the mean air-kerma strength of up to ten 125I seeds with one single measurement instead of measuring each seed individually. Material and methods The material required is: a) the SourceCheck4π 33005 well-ionization chamber provided with a PTW insert to measure the air-kerma strength S K of one single seed at a time; b) a newly designed insert that accommodates ten seeds in one column, which allows measuring the mean S K of the ten seeds in one single measurement; and c) a container with ten seeds from the same batch and class of the seeds used for the patient implant, and a set of nine non-radioactive seeds. The new insert is characterized by determining its calibration coefficient, used to convert the reading of the well-chamber when ten seeds are measured to their mean S K. The proposed method is validated by comparing the mean S K of the ten seeds obtained from the new insert with the individual measurement of S K of each seed, evaluated with the PTW insert. Results The ratio between the calibration coefficient of the new insert and the calibration coefficient of the PTW insert for the SourceCheck4π 33005 is 1.135 ± 0.007 (k = 1). The mean S K of a set of ten seeds evaluated with this new system is in agreement with the mean value obtained from measuring independently the S K of each seed. Conclusions The new insert and procedure allow evaluating the mean S K of ten seeds prior to the implant in a single measurement. The method is faster and more efficient from radiation protection point of view than measuring the individual S K of each seed. PMID:26816507

  15. Investigation and performance tests of a new parallel plate ionization chamber with double sensitive volume for measuring diagnostic X-rays

    Science.gov (United States)

    Sharifi, B.; Zamani Zeinali, H.; Soltani, J.; Negarestani, A.; Shahvar, A.

    2015-01-01

    Medical diagnostic equipment, like diagnostic radiology and mammography require a dosimeter with high accuracy for dosimetry of the diagnostic X-ray beam. Ionization chambers are suitable instruments for dosimetry of diagnostic-range X-ray beams because of their appropriate response and high reliability. This work introduces the design and fabrication of a new parallel plate ionization chamber with a PMMA body, graphite-coated PMMA windows (0.5 mm thick) and a graphite-foil central electrode (0.1 mm thick, 0.7 g/cm3 dense). This design improves upon the response characteristics of existing designs through the specific choice of materials as well as the appropriate size and arrangement of the ionization chamber components. The results of performance tests conducted at the Secondary Standard Dosimetry laboratory in Karaj-Iran demonstrated the short and long-term stability, the low leakage current, the low directional dependence, and the high ion collection efficiency of the design. Furthermore, the FLUKA Monte Carlo simulations confirmed the low effect of central electrode on this new ionization chamber response. The response characteristics of the parallel plate ionization chamber presented in this work makes the instrument suitable for use as a standard dosimeter in laboratories.

  16. Investigation and performance tests of a new parallel plate ionization chamber with double sensitive volume for measuring diagnostic X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Sharifi, B., E-mail: babak_sharifi88@yahoo.com [Graduate University of Advanced Technology, Kerman (Iran, Islamic Republic of); Zamani Zeinali, H. [Application of Radiation Research School, Nuclear Science and Technology Research Institute, AEOI, Karaj (Iran, Islamic Republic of); Soltani, J.; Negarestani, A. [Graduate University of Advanced Technology, Kerman (Iran, Islamic Republic of); Shahvar, A. [Application of Radiation Research School, Nuclear Science and Technology Research Institute, AEOI, Karaj (Iran, Islamic Republic of)

    2015-01-11

    Medical diagnostic equipment, like diagnostic radiology and mammography require a dosimeter with high accuracy for dosimetry of the diagnostic X-ray beam. Ionization chambers are suitable instruments for dosimetry of diagnostic-range X-ray beams because of their appropriate response and high reliability. This work introduces the design and fabrication of a new parallel plate ionization chamber with a PMMA body, graphite-coated PMMA windows (0.5 mm thick) and a graphite-foil central electrode (0.1 mm thick, 0.7 g/cm{sup 3} dense). This design improves upon the response characteristics of existing designs through the specific choice of materials as well as the appropriate size and arrangement of the ionization chamber components. The results of performance tests conducted at the Secondary Standard Dosimetry laboratory in Karaj-Iran demonstrated the short and long-term stability, the low leakage current, the low directional dependence, and the high ion collection efficiency of the design. Furthermore, the FLUKA Monte Carlo simulations confirmed the low effect of central electrode on this new ionization chamber response. The response characteristics of the parallel plate ionization chamber presented in this work makes the instrument suitable for use as a standard dosimeter in laboratories.

  17. Use of a two-dimensional ionization chamber array for proton therapy beam quality assurance.

    Science.gov (United States)

    Arjomandy, Bijan; Sahoo, Narayan; Ding, Xiaoning; Gillin, Michael

    2008-09-01

    Two-dimensional ion chamber arrays are primarily used for conventional and intensity modulated radiotherapy quality assurance. There is no commercial device of such type available on the market that is offered for proton therapy quality assurance. We have investigated suitability of the MatriXX, a commercial two-dimensional ion chamber array detector for proton therapy QA. This device is designed to be used for photon and electron therapy QA. The device is equipped with 32 x 32 parallel plate ion chambers, each with 4.5 mm diam and 7.62 mm center-to-center separation. A 250 MeV proton beam was used to calibrate the dose measured by this device. The water equivalent thickness of the buildup material was determined to be 3.9 mm using a 160 MeV proton beam. Proton beams of different energies were used to measure the reproducibility of dose output and to evaluate the consistency in the beam flatness and symmetry measured by MatriXX. The output measurement results were compared with the clinical commissioning beam data that were obtained using a 0.6 cc Farmer chamber. The agreement was consistently found to be within 1%. The profiles were compared with film dosimetry and also with ion chamber data in water with an excellent agreement. The device is found to be well suited for quality assurance of proton therapy beams. It provides fast two-dimensional dose distribution information in real time with the accuracy comparable to that of ion chamber measurements and film dosimetry.

  18. Correction of measured Gamma-Knife output factors for angular dependence of diode detectors and PinPoint ionization chamber.

    Science.gov (United States)

    Hršak, Hrvoje; Majer, Marija; Grego, Timor; Bibić, Juraj; Heinrich, Zdravko

    2014-12-01

    Dosimetry for Gamma-Knife requires detectors with high spatial resolution and minimal angular dependence of response. Angular dependence and end effect time for p-type silicon detectors (PTW Diode P and Diode E) and PTW PinPoint ionization chamber were measured with Gamma-Knife beams. Weighted angular dependence correction factors were calculated for each detector. The Gamma-Knife output factors were corrected for angular dependence and end effect time. For Gamma-Knife beams angle range of 84°-54°. Diode P shows considerable angular dependence of 9% and 8% for the 18 mm and 14, 8, 4 mm collimator, respectively. For Diode E this dependence is about 4% for all collimators. PinPoint ionization chamber shows angular dependence of less than 3% for 18, 14 and 8 mm helmet and 10% for 4 mm collimator due to volumetric averaging effect in a small photon beam. Corrected output factors for 14 mm helmet are in very good agreement (within ±0.3%) with published data and values recommended by vendor (Elekta AB, Stockholm, Sweden). For the 8 mm collimator diodes are still in good agreement with recommended values (within ±0.6%), while PinPoint gives 3% less value. For the 4 mm helmet Diodes P and E show over-response of 2.8% and 1.8%, respectively. For PinPoint chamber output factor of 4 mm collimator is 25% lower than Elekta value which is generally not consequence of angular dependence, but of volumetric averaging effect and lack of lateral electronic equilibrium. Diodes P and E represent good choice for Gamma-Knife dosimetry.

  19. DAVID--a translucent multi-wire transmission ionization chamber for in vivo verification of IMRT and conformal irradiation techniques.

    Science.gov (United States)

    Poppe, B; Thieke, C; Beyer, D; Kollhoff, R; Djouguela, A; Rühmann, A; Willborn, K C; Harder, D

    2006-03-07

    Permanent in vivo verification of IMRT photon beam profiles by a radiation detector with spatial resolution, positioned on the radiation entrance side of the patient, has not been clinically available so far. In this work we present the DAVID system, which is able to perform this quality assurance measurement while the patient is treated. The DAVID system is a flat, multi-wire transmission-type ionization chamber, placed in the accessory holder of the linear accelerator and constructed from translucent materials in order not to interfere with the light field. Each detection wire of the chamber is positioned exactly in the projection line of a MLC leaf pair, and the signal of each wire is proportional to the line integral of the ionization density along this wire. Thereby, each measurement channel essentially presents the line integral of the ionization density over the opening width of the associated leaf pair. The sum of all wire signals is a measure of the dose-area product of the transmitted photon beam and of the total radiant energy administered to the patient. After the dosimetric verification of an IMRT plan, the values measured by the DAVID system are stored as reference values. During daily treatment the signals are re-measured and compared to the reference values. A warning is output if there is a deviation beyond a threshold. The error detection capability is a leaf position error of less than 1 mm for an isocentric 1 cm x 1 cm field, and of 1 mm for an isocentric 20 cm x 20 cm field.

  20. Damping of double wall panels including a viscothermal air layer

    NARCIS (Netherlands)

    Basten, T.G.H.; Stainhaouer, G.; Bakamidis, S.; Charalabopoulou, F.

    2001-01-01

    This paper deals with the dynamic behaviour of double wall panels, with emphasis on damping and sound radiation. It will be shown that a narrow air layer separating the two plates of a panel significantly alters the mentioned quantities by its viscothermal properties. Numerical and experimental resu

  1. Calibration of well-type ionization chambers; Calibracao de camaras de ionizacao do tipo poco

    Energy Technology Data Exchange (ETDEWEB)

    Alves, C.F.E.; Leite, S.P.; Pires, E.J.; Magalhaes, L.A.G.; David, M.G.; Almeida, C.E. de, E-mail: cfealves@gmail.com [Universidade do Estado do Rio de Janeiro (UERJ), Rio de Janeiro, RJ (Brazil). Lab. de Ciencias Radiologicas; Di Prinzio, R. [Instituto de Radioprotecao e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2015-07-01

    This paper presents the methodology developed by the Laboratorio de Ciencias Radiologicas and presently in use for determining of the calibration coefficient for well-type chambers used in the dosimetry of {sup 192}Ir high dose rate sources. Uncertainty analysis involving the calibration procedure are discussed. (author)

  2. Off-site air monitoring following methyl bromide chamber and building fumigations and evaluation of the ISCST air dispersion model

    Energy Technology Data Exchange (ETDEWEB)

    Barry, T.; Swgawa, R.; Wofford, P. [Cal EPA, Sacramento, CA (United States)] [and others

    1995-12-31

    The Department of Pesticide Regulation`s preliminary risk characterization of methyl bromide indicated an inadequate margin of safety for several exposure scenarios. Characterization of the air concentrations associated with common methyl bromide use patterns was necessary to determine specific scenarios that result in an unacceptable margin of safety. Field monitoring data were used in conjunction with the Industrial Source Complex, Short Tenn (ISCST) air dispersion model to characterize air concentrations associated with various types of methyl bromide applications. Chamber and building fumigations were monitored and modelled. For each fumigation the emission rates, chamber or building specifications and on-site meteorological data were input into the ISCST model. The model predicted concentrations were compared to measured air concentrations. The concentrations predicted by the ISCST model reflect both the pattern and magnitude of the measured concentrations. Required buffer zones were calculated using the ISCST output.

  3. Modes of reaction front propagation and end-gas combustion of hydrogen/air mixtures in a closed chamber

    KAUST Repository

    Shi, Xian

    2017-01-05

    Modes of reaction front propagation and end-gas combustion of hydrogen/air mixtures in a closed chamber are numerically investigated using an 1-D unsteady, shock-capturing, compressible and reacting flow solver. Different combinations of reaction front propagation and end-gas combustion modes are observed, i.e., 1) deflagration without end-gas combustion, 2) deflagration to end-gas autoignition, 3) deflagration to end-gas detonation, 4) developing or developed detonation, occurring in the sequence of increasing initial temperatures. Effects of ignition location and chamber size are evaluated: the asymmetric ignition is found to promote the reactivity of unburnt mixture compared to ignitions at center/wall, due to additional heating from asymmetric pressure waves. End-gas combustion occurs earlier in smaller chambers, where end-gas temperature rise due to compression heating from the deflagration is faster. According to the ξ−ε regime diagram based on Zeldovich theory, modes of reaction front propagation are primarily determined by reactivity gradients introduced by initial ignition, while modes of end-gas combustion are influenced by the total amount of unburnt mixture at the time when autoignition occurs. A transient reactivity gradient method is provided and able to capture the occurrence of detonation.

  4. 圆柱形电离室的能响补偿%Energy Compensation of Cylindrical Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    陈法国; 靳根; 刘倍; 徐园

    2012-01-01

    电离室由于其具有结构简单、使用方便的特点,目前仍被广泛应用于辐射监测领域.用于X、γ射线测量时,必须研究电离室的能量响应,并通过能响补偿使其灵敏度在一定的误差范围内是与入射X、γ射线的能量无关的常数.利用蒙特卡罗方法,模拟计算了圆柱形电离室对X、γ射线的灵敏度和能量响应;并根据计算结果的规律,对圆柱形电离室的能量响应进行了补偿,给出了补偿参数的最优范围.%Ionization chamber is still being widely used in radiation monitoring because of its simple structure and convenience. Used in X or gamma ray monitoring, the energy response of the chamber needs intense investigation and proper compensation filters must be designed in order to achieve a constant sensitivity which is independent of the energy of the incident X or gamma ray among a specified error range. The Monte - Carlo method is used to calculate the sensitivity and energy response characteristics of cylindrical ionization chamber to X or gamma ray. According to the results of simulation, the energy compensation of chamber is studied and the optimized compensation parameters are given.

  5. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    Energy Technology Data Exchange (ETDEWEB)

    Saheed, M. Shuaib M.; Muti Mohamed, Norani; Arif Burhanudin, Zainal, E-mail: zainabh@petronas.com.my [Centre of Innovative Nanostructures and Nanodevices, Universiti Teknologi PETRONAS, Bandar Seri Iskandar, 31750 Tronoh, Perak (Malaysia)

    2014-03-24

    Ionization gas sensors using vertically aligned multi-wall carbon nanotubes (MWCNT) are demonstrated. The sharp tips of the nanotubes generate large non-uniform electric fields at relatively low applied voltage. The enhancement of the electric field results in field emission of electrons that dominates the breakdown mechanism in gas sensor with gap spacing below 14 μm. More than 90% reduction in breakdown voltage is observed for sensors with MWCNT and 7 μm gap spacing. Transition of breakdown mechanism, dominated by avalanche electrons to field emission electrons, as decreasing gap spacing is also observed and discussed.

  6. A novel convolution-based approach to address ionization chamber volume averaging effect in model-based treatment planning systems

    Science.gov (United States)

    Barraclough, Brendan; Li, Jonathan G.; Lebron, Sharon; Fan, Qiyong; Liu, Chihray; Yan, Guanghua

    2015-08-01

    The ionization chamber volume averaging effect is a well-known issue without an elegant solution. The purpose of this study is to propose a novel convolution-based approach to address the volume averaging effect in model-based treatment planning systems (TPSs). Ionization chamber-measured beam profiles can be regarded as the convolution between the detector response function and the implicit real profiles. Existing approaches address the issue by trying to remove the volume averaging effect from the measurement. In contrast, our proposed method imports the measured profiles directly into the TPS and addresses the problem by reoptimizing pertinent parameters of the TPS beam model. In the iterative beam modeling process, the TPS-calculated beam profiles are convolved with the same detector response function. Beam model parameters responsible for the penumbra are optimized to drive the convolved profiles to match the measured profiles. Since the convolved and the measured profiles are subject to identical volume averaging effect, the calculated profiles match the real profiles when the optimization converges. The method was applied to reoptimize a CC13 beam model commissioned with profiles measured with a standard ionization chamber (Scanditronix Wellhofer, Bartlett, TN). The reoptimized beam model was validated by comparing the TPS-calculated profiles with diode-measured profiles. Its performance in intensity-modulated radiation therapy (IMRT) quality assurance (QA) for ten head-and-neck patients was compared with the CC13 beam model and a clinical beam model (manually optimized, clinically proven) using standard Gamma comparisons. The beam profiles calculated with the reoptimized beam model showed excellent agreement with diode measurement at all measured geometries. Performance of the reoptimized beam model was comparable with that of the clinical beam model in IMRT QA. The average passing rates using the reoptimized beam model increased substantially from 92.1% to

  7. Comparison of the half-value layer: ionization chambers vs solid-state meters; Comparacao entre medidas de camada semirredutora: camara de ionizacao vs medidores de estado solido

    Energy Technology Data Exchange (ETDEWEB)

    Pereira, L.C.S.; Navarro, V.C.C.; Navarro, M.V.T.; Macedo, E.M., E-mail: larapereira@ifba.edu.br [Instituto Federal da Bahia (LABPROSAUD/IFBA), Salvador, BA (Brazil). Laboratorio de Produtos para a Saude

    2015-07-01

    Generally, the half value layer (HVL) is determined by using ionization chambers and aluminum filters. However, some solid-state dosimeters allow simultaneous measurements of X-ray's parameters, among which the HVL. The main objective of this study was to compare the HVL's values indicated by four different solid-state dosimeters, whose values were measured by ionization chambers. The maximum difference found between the two methods was 11.42%, one the solid-state dosimeters, showing that the use these instruments to determine CSR in industrial X-ray should be subject to a more thorough evaluation. (author)

  8. Two-dimensional and quasi-three-dimensional dosimetry of hadron and photon beams with the Magic Cube and the Pixel Ionization Chamber

    Science.gov (United States)

    Cirio, R.; Garelli, E.; Schulte, R.; Amerio, S.; Boriano, A.; Bourhaleb, F.; Coutrakon, G.; Donetti, M.; Giordanengo, S.; Koss, P.; Madon, E.; Marchetto, F.; Nastasi, U.; Peroni, C.; Santuari, D.; Sardo, A.; Scielzo, G.; Stasi, M.; Trevisiol, E.

    2004-08-01

    Two detectors for fast two-dimensional (2D) and quasi-three-dimensional (quasi-3D) verification of the dose delivered by radiotherapy beams have been developed at University and Istituto Nazionale di Fisica Nucleare (INFN) of Torino. The Magic Cube is a stack of strip-segmented ionization chambers interleaved with water-equivalent slabs. The parallel plate ionization chambers have a sensitive area of 24 × 24 cm2, and consist of 0.375 cm wide and 24 cm long strips. There are a total of 64 strips per chamber. The Magic Cube has been tested with the clinical proton beam at Loma Linda University Medical Centre (LLUMC), and was shown to be capable of fast and precise quasi-3D dose verification. The Pixel Ionization Chamber (PXC) is a detector with pixel anode segmentation. It is a 32 × 32 matrix of 1024 cylindrical ionization cells arranged in a square 24 × 24 cm2 area. Each cell has 0.4 cm diameter and 0.55 cm height, at a pitch of 0.75 cm separates the centre of adjacent cells. The sensitive volume of each single ionization cell is 0.07 cm3. The detectors are read out using custom designed front-end microelectronics and a personal computer-based data acquisition system. The PXC has been used to verify dynamic intensity-modulated radiotherapy for head-and-neck and breast cancers.

  9. Development for PRESPEC: New front end electronic for multi sampling ionization chambers of the GSI-fragment separator

    Energy Technology Data Exchange (ETDEWEB)

    Pietri, Stephane; Gerl, Juergen; Kurz, Nik; Nociforo, Chiara; Schaffner, Henning; Simon, Haik [GSI, Planckstrasse 1, 64291 Darmstadt (Germany)

    2009-07-01

    To study detailed structure effects during in-beam gamma spectroscopy experiments at the GSI fragment separator high particles rates are needed at the final focal plane. The use of new position detector (TPC) having higher rate capability than the previous Multi-Wire Proportional Counter put the ionization chambers (MUSICs) used for the {delta}-E measurement as the limiting factor. The current electronics used for those detector does not allow to sustain rates of up to 100 kHz that the coming experimental program will request. Indeed at those rates the analog electronic is not able to disentangle pile-up events and thus give a wrong Z identification for the incoming nucleus. The ongoing work on new digital electronic and on signal characterization to allow higher rates capability of those detectors is presented.

  10. Study of the performance of the ATLAS monitored drift tube chambers under the influence of heavily ionizing $\\alpha$-particles

    CERN Document Server

    Sampsonidis, Dimitrios; Liolios, Anastasios; Manolopoulou, Metaxia; Petridou, C

    2004-01-01

    The MDT chambers of the ATLAS Muon Spectrometer will operate in a heavy LHC background environment mainly from photons and neutrons. The ionization produced by neutron recoils is much higher than the one from photons or muons and can be simulated by the use of alpha particles. A systematic study of the behavior of the ATLAS Monitored Drift Tubes (MDTs) under controlled irradiation has been performed. The presence of alpha particles results in the reduction of the gas gain due to space charge effects. The gas gain reduction has been studied in a single tube set up using a well controlled radium (/sup 226/Ra) source in order to enrich the tube gas (Ar/CO/sub 2/) with the alpha emitter /sup 220/Rn and irradiate the tubes internally. The results are confronted with Garfield simulations.

  11. A pixel ionization chamber used as beam monitor at the Institut Curie-Centre de Protontherapie de Orsay (CPO)

    Energy Technology Data Exchange (ETDEWEB)

    La Rosa, A. [Dipartimento di Fisica Sperimentale, Universita di Torino. Via P. Giuria 1, Torino 10125 (Italy) and INFN. Via P. Giuria 1, Turin 10125 (Italy)]. E-mail: larosa@to.infn.it; Garella, M.A. [INFN. Via P. Giuria 1, Turin 10125 (Italy); Bourhaleb, F. [Fondazione TERA. Via Puccini 11, Novara 28100 (Italy); Cirio, R. [INFN. Via P. Giuria 1, Turin 10125 (Italy); Donetti, M. [INFN. Via P. Giuria 1, Turin 10125 (Italy); Fondazione CNAO. Via Caminadella 16, Milan 20123 (Italy); Giordanengo, S. [INFN. Via P. Giuria 1, Turin 10125 (Italy); Givehchi, N. [Dipartimento di Fisica Sperimentale, Universita di Torino. Via P. Giuria 1, Turin 10125 (Italy); INFN. Via P. Giuria 1, Turin 10125 (Italy); Marchetto, F. [INFN. Via P. Giuria 1, Turin 10125 (Italy); Martin, F. [Institut Curie-Centre de Protontherapie de Orsay. Bat. 101 Campus Universitaire, Orsay Cedex 91898 (France); Meyroneinc, S. [Institut Curie-Centre de Protontherapie de Orsay. Bat. 101 Campus Universitaire, Orsay Cedex 91898 (France); Peroni, C. [Dipartimento di Fisica Sperimentale, Universita di Torino. Via P. Giuria 1, Turin 10125 (Italy); INFN. Via P. Giuria 1, Turin 10125 (Italy); Pitta, G. [Fondazione TERA. Via Puccini 11, Novara 28100 (Italy)

    2006-09-15

    The Dipartimento di Fisica Sperimentale and the Istituto Nazionale di Fisica Nucleare (INFN), Torino, in collaboration with the Institut Curie-Centre de Protontherapie de Orsay (CPO), have developed and built a pixel parallel plate ionization chamber to be used as monitor for the proton therapy beam line at the Institut Curie-CPO (Orsay, France). The sensitive area of the detector is (160x160) mm{sup 2}, with the anode segmented in 1024 square pixels arranged in a 32x32 matrix; the area of each pixel is (5x5) mm{sup 2}. The detector has been placed on the beam line just upstream of the last collimator to monitor the beam shape and to measure the stability and reproducibility of the delivery system. In this paper, we present a detailed description of the detector and the results of a set of preliminary tests.

  12. A pixel ionization chamber used as beam monitor at the Institut Curie—Centre de Protontherapie de Orsay (CPO)

    Science.gov (United States)

    La Rosa, A.; Garella, M. A.; Bourhaleb, F.; Cirio, R.; Donetti, M.; Giordanengo, S.; Givehchi, N.; Marchetto, F.; Martin, F.; Meyroneinc, S.; Peroni, C.; Pittà, G.

    2006-09-01

    The Dipartimento di Fisica Sperimentale and the Istituto Nazionale di Fisica Nucleare (INFN), Torino, in collaboration with the Institut Curie—Centre de Protontherapie de Orsay (CPO), have developed and built a pixel parallel plate ionization chamber to be used as monitor for the proton therapy beam line at the Institut Curie—CPO (Orsay, France). The sensitive area of the detector is (160×160) mm 2, with the anode segmented in 1024 square pixels arranged in a 32×32 matrix; the area of each pixel is (5×5) mm 2. The detector has been placed on the beam line just upstream of the last collimator to monitor the beam shape and to measure the stability and reproducibility of the delivery system. In this paper, we present a detailed description of the detector and the results of a set of preliminary tests.

  13. Simulation of the Mg(Ar) ionization chamber currents by different Monte Carlo codes in benchmark gamma fields

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Yi-Chun [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Taiwan (China); Liu, Yuan-Hao, E-mail: yhl.taiwan@gmail.com [Boron Neutron Capture Therapy Center, Nuclear Science and Technology Development Center, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Road, Hsinchu City 30013, Taiwan (China); Nievaart, Sander [Institute for Energy, Joint Research Centre, European Commission, Petten (Netherlands); Chen, Yen-Fu [Department of Engineering and System Science, National Tsing Hua University, Taiwan (China); Wu, Shu-Wei; Chou, Wen-Tsae [Department of Biomedical Engineering and Environmental Sciences, National Tsing Hua University, Taiwan (China); Jiang, Shiang-Huei [Institute of Nuclear Engineering and Science, National Tsing Hua University, Taiwan (China)

    2011-10-01

    High energy photon (over 10 MeV) and neutron beams adopted in radiobiology and radiotherapy always produce mixed neutron/gamma-ray fields. The Mg(Ar) ionization chambers are commonly applied to determine the gamma-ray dose because of its neutron insensitive characteristic. Nowadays, many perturbation corrections for accurate dose estimation and lots of treatment planning systems are based on Monte Carlo technique. The Monte Carlo codes EGSnrc, FLUKA, GEANT4, MCNP5, and MCNPX were used to evaluate energy dependent response functions of the Exradin M2 Mg(Ar) ionization chamber to a parallel photon beam with mono-energies from 20 keV to 20 MeV. For the sake of validation, measurements were carefully performed in well-defined (a) primary M-100 X-ray calibration field, (b) primary {sup 60}Co calibration beam, (c) 6-MV, and (d) 10-MV therapeutic beams in hospital. At energy region below 100 keV, MCNP5 and MCNPX both had lower responses than other codes. For energies above 1 MeV, the MCNP ITS-mode greatly resembled other three codes and the differences were within 5%. Comparing to the measured currents, MCNP5 and MCNPX using ITS-mode had perfect agreement with the {sup 60}Co, and 10-MV beams. But at X-ray energy region, the derivations reached 17%. This work shows us a better insight into the performance of different Monte Carlo codes in photon-electron transport calculation. Regarding the application of the mixed field dosimetry like BNCT, MCNP with ITS-mode is recognized as the most suitable tool by this work.

  14. Quality assurance for radon exposure chambers at the National Air and Radiation Environmental Laboratory, Montgomery, Alabama

    Energy Technology Data Exchange (ETDEWEB)

    Semler, M.O.; Sensintaffar, E.L. [National Air and Radiation Environmental Laboratory, Montgomery, AL (United States)

    1993-12-31

    The Office of Radiation and Indoor Air, U.S. Environmental Protection Agency (EPA), operates six radon exposure chambers in its two laboratories, the National Air and Radiation Environmental Laboratory (NAREL) in Montgomery, Alabama, and the Las Vegas Facility, Las Vegas, Nevada. These radon exposure chambers are used to calibrate and test portable radon measuring instruments, test commercial suppliers of radon measurement services through the Radon Measurement Proficiency Program, and expose passive measurement devices to known radon concentrations as part of a quality assurance plan for federal and state studies measuring indoor radon concentrations. Both laboratories participate in national and international intercomparisons for the measurement of radon and are presently working with the National Institute of Standards and Technology (NIST) to receive a certificate of traceability for radon measurements. NAREL has developed an estimate of the total error in its calibration of each chamber`s continuous monitors as part of an internal quality assurance program. This paper discusses the continuous monitors and their calibration for the three chambers located in Montgomery, Alabama, as well as the results of the authors intercomparisons and total error analysis.

  15. Progress on a Cavity with Beryllium Walls for Muon Ionization Cooling Channel R&D.

    Energy Technology Data Exchange (ETDEWEB)

    Bowring, D. L.; DeMello, A. J.; Lambert, A. R.; Li, D.; Virostek, S.; Zisman, M.; Kaplan, D.; Palmer, R. B.

    2012-05-20

    The Muon Accelerator Program (MAP) collaboration is working to develop an ionization cooling channel for muon beams. An ionization cooling channel requires the operation of high-gradient, normal-conducting RF cavities in multi-Tesla solenoidal magnetic fields. However, experiments conducted at Fermilab?s MuCool Test Area (MTA) show that increasing the solenoidal field strength reduces the maximum achievable cavity gradient. This gradient limit is characterized by an RF breakdown process that has caused significant damage to copper cavity interiors. The damage may be caused by field-emitted electrons, focused by the solenoidal magnetic field onto small areas of the inner cavity surface. Local heating may then induce material fatigue and surface damage. Fabricating a cavity with beryllium walls would mitigate this damage due to beryllium?s low density, low thermal expansion, and high electrical and thermal conductivity. We address the design and fabrication of a pillbox RF cavity with beryllium walls, in order to evaluate the performance of high-gradient cavities in strong magnetic fields.

  16. A method to increase the nominal range resolution of a stack of parallel-plate ionization chambers

    Science.gov (United States)

    Rinaldi, I.; Brons, S.; Jäkel, O.; Voss, B.; Parodi, K.

    2014-09-01

    A detector prototype based on a stack of 61 parallel-plate ionisation chambers (PPIC) interleaved with absorber plates of polymethyl methacrylate (PMMA) was assembled for transmission imaging purposes in ion beam therapy. The thickness of the absorber sheets in the PPIC stack determines the nominal range resolution of the detector. In the current set-up, 3 mm PMMA slabs are used. The signal of the 61 active channels of the stack thereby provides a discrete approximation of the Bragg curve in the detector. In this work, a data processing method to increase the range resolution (MIRR) in a stack of ionization chambers is presented. In the MIRR the position of the maximum of the Bragg curve is deduced from the ratio of measured signals in adjacent PPIC channels. The method is developed based on Bragg curves obtained from Monte Carlo simulations and validated with experimental data of a wedge-shaped PMMA phantom acquired with the PPIC stack using carbon ion beams. The influence of the initial beam energy and of phantom inhomogeneities on the MIRR is quantitatively evaluated. Systematic errors as well as inaccuracies related to signal noise are discussed and quantified. It is shown that with the MIRR an increased range resolution of 0.7 mm PMMA equivalent or 0.8 mm water equivalent thickness is achieved for the considered experimental data.

  17. Characterization and performances of a monitoring ionization chamber dedicated to IBA-universal irradiation head for Pencil Beam Scanning

    Energy Technology Data Exchange (ETDEWEB)

    Courtois, C. [LPC (IN2P3-ENSICAEN-UNICAEN), 6 Boulevard Maréchal Juin, 14050 Caen (France); Boissonnat, G., E-mail: boissonnat@lpccaen.in2p3.fr [LPC (IN2P3-ENSICAEN-UNICAEN), 6 Boulevard Maréchal Juin, 14050 Caen (France); Brusasco, C. [IBA, 3 Chemin du Cyclotron, 31348 Louvain-la-Neuve (Belgium); Colin, J.; Cussol, D.; Fontbonne, J.M. [LPC (IN2P3-ENSICAEN-UNICAEN), 6 Boulevard Maréchal Juin, 14050 Caen (France); Marchand, B.; Mertens, T.; Neuter, S. de [IBA, 3 Chemin du Cyclotron, 31348 Louvain-la-Neuve (Belgium); Peronnel, J. [LPC (IN2P3-ENSICAEN-UNICAEN), 6 Boulevard Maréchal Juin, 14050 Caen (France)

    2014-02-01

    Every radiotherapy center has to be equipped with real-time beam monitoring devices. In 2008, we developed an ionization chamber in collaboration with the IBA (Ion Beam Applications) company. This monitoring device called IC2/3 was developed to be used in IBA universal irradiation head for Pencil Beam Scanning (PBS). Here we present the characterization of the IC2/3 monitor in the energy and flux ranges used in protontherapy. The equipment has been tested with an IBA cyclotron able to deliver proton beams from 70 to 230 MeV. This beam monitoring device has been validated and is now installed at the Westdeutsches Protonentherapiezentrum Essen protontherapy center (WPE, Germany). The results obtained in both terms of spatial resolution and dose measurements are at least equal to the initial specifications needed for PBS purposes. The detector measures the dose with a relative uncertainty lower than 1% in the range from 0.5 Gy/min to 8 Gy/min while the spatial resolution is better than 250μm. The technology has been patented and five IC2/3 chambers were delivered to IBA. Nowadays, IBA produces the IC2/3 beam monitoring device as a part of its Proteus 235 product.

  18. Trace analysis of organics in air by corona discharge atmospheric pressure ionization using an electrospray ionization interface.

    Science.gov (United States)

    Nikolaev, Eugene; Riter, Leah S; Laughlin, Brian C; Handberg, Eric; Cooks, R Graham

    2004-01-01

    A corona discharge ion source operating at atmospheric pressure in the point-to-plane configuration was constructed by reconfiguring the ion source of a commercial electrospray ionization (ESI) quadrupole mass spectrometer. This new source allows direct air analysis without modification to the mass spectrometer. Detection and quantitation of semi-volatile compounds in air is demonstrated. The analytical performance of the system was established using the chemical warfare agent simulants methyl salicylate and dimethyl methylphosphonate. Limits of detection are 60 pptr in the negative-ion mode and 800 pptr in the positive-ion mode for methyl salicylate and 800 pptr in the negative-ion mode and 3.6 ppb in the positive-ion mode for dimethyl methylphosphonate. A linear response was observed from 60 pptr to 8 ppb for methyl salicylate in air in the negative-ionization mode. Cluster ion formation versus production of analyte ions was investigated and it was found that dry air or an elevated capillary interface temperature (130 degrees C) was needed to avoid extensive clustering, mostly of water. Reagent gases are not needed as proton sources, as is usually the case for atmospheric pressure chemical ionization, and this, together with the simplicity, sensitivity and speed of the technique, makes it promising for miniaturization and future field studies.

  19. Air-based coal gasification in a two-chamber gas reactor with circulating fluidized bed

    Science.gov (United States)

    Dubinin, A. M.; Tuponogov, V. G.; Kagramanov, Y. A.

    2017-01-01

    During the bed gasification of solid fuels, the process temperature in the reaction zone is not high enough for reaching the maximum rate of the chemical efficiency factor of the gasification process. In order to increase the chemical efficiency factor, it is necessary to supply extra heat to the reaction zone to increase the reaction temperature. In this article, coal gasification in a chamber with forced fluidized bed is considered and it is proposed to supply extra heat with a circulating flow of an inert particulate heat transfer agent. Circulating inert particulate material is successively heated by coal combustion in a cone chamber with bubbling fluidized bed and in a combustion chamber with a spherical nozzle that inhibits the forced fluidized bed. After that, the heat transfer agent heated to 930-950°C enters first in a gasification chamber with bubbling bed and then in a chamber with forced fluidized bed, where it transfers the physical heat to the air fuel mixture. The experiments conducted with crushed Borodinsky coal and inert particulate heat transfer agent (electrocorundum) showed the temperature rise in a gasification chamber with from 760 to 870°C and the increase in the combustible component (CO) concentration in the gasification products by 5.5%. Based on the kinetic equations of the fuel combustion reactions and the CO2 reduction to CO and on the thermal balance equations of combustion and gasification chambers, the simulation model for the gas composition and the temperature rate calculated by the height of reaction chambers was developed. The experimental temperature rates and product gas compositions are in good agreement with the simulation results based on the proposed kinetic gasification model.

  20. Extrapolation Ionization Chamber Dosimetry of Fluorescent X-Ray Energies from 4.5 to 19.6 keV.

    Science.gov (United States)

    Rakowski, Joseph T; Tucker, Mark A; Snyder, Michael G; Makar, Simon P; Yudele, Mark; Burmeister, Jay; Joiner, Michael C

    2016-09-01

    Characteristic X rays of energies less than approximately 20 keV are of interest in radiobiology and radiation oncology. There is evidence that these low-energy photons produce higher relative biological effectiveness (RBE) and lower oxygen enhancement ratio (OER) relative to higher energies. Lower energy X rays also offer the advantage of healthy tissue sparing beyond the target treatment depth. Electronic brachytherapy systems that can deliver characteristic and bremsstrahlung X rays of varying energy are in clinical use as well as under development. We performed low-energy extrapolation ionization chamber dosimetry using two methods: 1. the exposure-to-dose method; and 2. the Burlin theory method combined with the extrapolation chamber method of Klevenhagen. We investigated fluorescent X rays emitted from seven metals: titanium (Ti, Z = 22); chromium (Cr, Z = 24); iron (Fe, Z = 26); cobalt (Co, Z = 27); copper (Cu, Z = 29); zinc (Zn, Z = 30); and molybdenum (Mo, Z = 42). X rays were produced by irradiation of the metals with a 55 kVp, 45 mA silver anode spectrum. The data obtained were air kerma rate (cGy/min), and radiation dose rate (cGy/min) in phosphate-buffered saline (PBS) solution and water. Air kerma rates ranged from 3.55 ± 0.10 to 14.36 ± 0.39 cGy/min. Dose rates ranged from 3.85 ± 0.10 to 16.96 ± 0.46 cGy/min in PBS and 3.59 ± 0.10 to 16.06 ± 0.43 cGy/min in water. Dose-rate energy dependence of both models was examined by taking a ratio of measured to Monte Carlo calculated dose rates. Dosimetry method 1 exhibited a linear relationship across all energies with a slope of 0.0127 keV(-1) and R(2) of 0.9276. Method 2 exhibited a linear relationship across all energies with a slope of 0.0467 keV(-1) and R(2) of 0.9933. Method 1 or 2 may be used as a relative dosimetry system to derive dose rates to water by using a second reference ion chamber with a NIST-traceable calibration for the molybdenum spectrum.

  1. Fast-Neutron Spectrometry Using a 3He Ionization Chamber and Digital Pulse Shape Analysis

    Energy Technology Data Exchange (ETDEWEB)

    D. L. Chichester; J. T. Johnson; E. H. Seabury

    2010-05-01

    Digital pulse shape analysis (dPSA) has been used with a Cuttler-Shalev type 3He proportional counter to measure the fast neutron spectra of bare 252Cf and 241AmBe neutron sources. Measurements have also been made to determine the attenuated fast neutron spectra of 252Cf shielded by several materials including water, graphite, liquid nitrogen, magnesium, and tungsten. Rise-time dPSA has been employed using the common rise-time approach for analyzing n +3He ? 1H + 3H ionization events and a new approach has been developed to improve the fidelity of these measurements. Simulations have been performed for the different experimental arrangements and are compared, demonstrating general agreement between the dPSA processed fast neutron spectra and predictions.

  2. Technical Note : A direct ray-tracing method to compute integral depth dose in pencil beam proton radiography with a multilayer ionization chamber

    NARCIS (Netherlands)

    Farace, Paolo; Righetto, Roberto; Deffet, Sylvain; Meijers, Arturs; Vander Stappen, Francois

    2016-01-01

    Purpose: To introduce a fast ray-tracing algorithm in pencil proton radiography (PR) with a multilayer ionization chamber (MLIC) for in vivo range error mapping. Methods: Pencil beam PR was obtained by delivering spots uniformly positioned in a square (45x45 mm(2) field-of-view) of 9x9 spots capable

  3. Dosimetry for the MRI accelerator: the impact of a magnetic field on the response of a Farmer NE2571 ionization chamber.

    Science.gov (United States)

    Meijsing, I; Raaymakers, B W; Raaijmakers, A J E; Kok, J G M; Hogeweg, L; Liu, B; Lagendijk, J J W

    2009-05-21

    The UMC Utrecht is constructing a 1.5 T MRI scanner integrated with a linear accelerator (Lagendijk et al 2008 Radiother. Oncol. 86 25-9). The goal of this device is to facilitate soft-tissue contrast based image-guided radiotherapy, in order to escalate the dose to the tumour while sparing surrounding normal tissues. Dosimetry for the MRI accelerator has to be performed in the presence of a magnetic field. This paper investigates the feasibility of using a Farmer NE2571 ionization chamber for absolute dosimetry. The impact of the mcagnetic field on the response of this ionization chamber has been measured and simulated using GEANT4 Monte Carlo simulations. Two orientations of the ionization chamber with respect to the incident beam and the magnetic field which are feasible in the MRI accelerator configuration are taken into account. Measurements are performed using a laboratory magnet ranging from 0 to 1.2 T. In the simulations a range from 0 to 2 T is used. For both orientations, the measurements and simulations agreed within the uncertainty of the measurements and simulations. In conclusion, the response of the ionization chamber as a function of the magnetic field is understood and can be simulated using GEANT4 Monte Carlo simulations.

  4. Numerical Simulation of 3—D Temperature Distribution of the Flame Tube of the Combustion Chamber with Air Film COoling

    Institute of Scientific and Technical Information of China (English)

    ChangHaiping; HuangTaiping; 等

    1996-01-01

    The wall temperature distribution of the flame tube of the combustion chamber is strongly affected by the combustion,radiation and flow.The interaction of these influential factors froms a coupling system.In this paper,a new method,which is different from the previous methods,has been developed for calcuating the temperature distribution of the flame tube wall together with the flow field inside and outside the flame tube,In the calculation.the combustion,heat radiation,cooling air film and injection stream mixing inside the flame tube as well as the secondary air flowing outside the flame tube have been simulated.The calculation,in this paper,uses the SIMPLE algorithm,the κ-εturbulence model and the auto-adjustable damping method .By using this method ,the 3-D temperature distribution of the floame tube wall of the combustion chamber of an aeroengine has been simulated successfully.The calculation results are compared to the experimetal data.The error of wall temperature is less than 10%.

  5. NUMERICAL SIMULATION FOR AIR AND AIR-PM FLOW IN WALL FLOW DIESEL PARTICULATE FILTERS

    Institute of Scientific and Technical Information of China (English)

    Zhao Binjuan; Yuan Shouqi; Seizo Kato; Akira Nishimura

    2005-01-01

    Numerical simulations are performed both for the single airflow and air-PM two-phase flow in wall flow diesel particulate filters (DPF) for the first time. The calculation domain is divided into two regions. In the inlet and outlet flow channels, the simulations are performed for the steady and laminar flow; In the porous filtration walls, the calculation model for flow in porous media is used. The Lagrange two-phase flow model is used to calculate the air-PM flow in DPF, for the dispersed phase (PM), its flow tracks are obtained by the integrating of the Lagrange kinetic equation. The calculated velocity, pressure distribution and PM flow tracks in DPF are obtained, which exhibits the main flow characteristics in wall flow DPF and will be help for the optimal design and performance prediction of wall flow DPF.

  6. 核电站事故后监测电离室设计方法%Designing methods for nuclear power station accident condition ionization chamber

    Institute of Scientific and Technical Information of China (English)

    孙光智; 王益元; 李亚坚; 代传波; 粱云; 左亮周

    2011-01-01

    介绍了一种用于核电站事故后γ辐射剂量率监测的电离室设计所需的模拟计算方法;用MCNP程序模拟计算了射线在不同结构、不同工作气体的电离室中灵敏度的能量响应特性,为事故后监测电离室的设计提供了理论依据.%Simulation and calculation methods for designing of ionization chamber used in nuclear power station during accident conditions were introduced in this paper. Using MCNP program,we calculated energy response of this chamber with various structures and sensitive gas,supplied theoretic dependence for designing of ionization chamber used during accident conditions.

  7. An automatic flux chamber for investigating gas flux at water - air interfaces

    Science.gov (United States)

    Duc, N. T.; Silverstein, S.; Lundmark, L.; Reyier, H.; Crill, P. M.; Bastviken, D.

    2011-12-01

    Aquatic ecosystems are major sources of greenhouse gases (GHG) and representative measurements of GHG fluxes from aquatic ecosystems to the atmosphere are vital in climate related biogeochemistry. One of the most important fluxes, ebullition (bubble flux) of methane (CH4) is episodic, with large fluxes during short time periods. To properly capture such fluxes long term measurement approaches are necessary which is labor intensive for manual flux chamber based methods, or require expensive equipment with e.g. eddy correlation methods. An inexpensive and easily mobile automatic flux chamber for long-term measurements has been designed to approach these drawbacks. This device includes a flux chamber, with a controller/datalogger, valves, a pump, a 12 V battery and a solar cell. Sensors used so far record CH4 concentration in the chamber headspace, temperature in water and air, barometric pressure. Other sensors for e.g. CO2 and weather variables can be attached. The unit can be programmed to measure in situ accumulation of gas in the chamber and also to collect gas samples in an array of sample bottles for subsequent analysis in the laboratory. Simultaneous deployment of many such units represent a cost efficient and easily managed solution for local long term flux monitoring.

  8. Expected signal for the TBID and the ionization chambers downstream of the CNGS target station

    CERN Document Server

    Sarchiapone, L; Gschwendtner, E; Lorenzo-Sentis, M

    2006-01-01

    Downstream of the carbon graphite target of the CNGS (CERN Neutrinos to Gran Sasso) facility at CERN a secondary emission monitor called TBID (Target Beam Instrumentation Downstream) is installed to measure the multiplicities and the left/right as well as up/down asymmetries of secondary particles from the target. Calculations show that the titanium windows used to close off the TBID vacuum tank might not withstand the highest beam intensities with small spot sizes expected at CNGS, in case the proton beam accidentally misses the 4-5 mm diameter target rods. Therefore it has been suggested to place two ionisation chambers as a backup for the TBID, located left and right of the TBID monitor. Monte Carlo simulations with the particle transport code FLUKA were performed firstly to obtain the fluence of charged particles in the region of interest and secondly to estimate the induced radioactivity (background signal) in this area. This allows to assess the actual signal/noise situation and thus to determine the op...

  9. Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device.

    Science.gov (United States)

    Mohammadi, Mohammad; Bezak, Eva

    2012-01-01

    The dose delivery verification for a head and neck static intensity modulated radiation therapy (IMRT) case using a scanning liquid ionization chamber electronic portal imaging device (SLIC-EPID) was investigated. Acquired electronic portal images were firstly converted into transmitted dose maps using an in-house developed method. The dose distributions were then compared with those calculated in a virtual EPID using the Pinnacle(3) treatment planning system (TPS). Using gamma evaluation with the ΔD(max) and DTA criteria of 3%/2.54 mm, an excellent agreement was observed between transmitted dose measured using SLIC-EPID and that calculated by TPS (gamma score approximately 95%) for large MLC fields. In contrast, for several small subfields, due to SLIC-EPID image blurring, significant disagreement was found in the gamma results. Differences between EPID and TPS dose maps were also observed for several parts of the radiation subfields, when the radiation beam passed through air on the outside of tissue. The transmitted dose distributions measured using portal imagers such as SLIC-EPID can be used to verify the dose delivery to a patient. However, several aspects such as accurate calibration procedure and imager response under different conditions should be taken into the consideration. In addition, SLIC-EPID image blurring is another important issue, which should be considered if the SLIC-EPID is used for clinical dosimetry verification.

  10. Evaluation of relative transmitted dose for a step and shoot head and neck intensity modulated radiation therapy using a scanning liquid ionization chamber electronic portal imaging device

    Directory of Open Access Journals (Sweden)

    Mohammad Mohammadi

    2012-01-01

    Full Text Available The dose delivery verification for a head and neck static intensity modulated radiation therapy (IMRT case using a scanning liquid ionization chamber electronic portal imaging device (SLIC-EPID was investigated. Acquired electronic portal images were firstly converted into transmitted dose maps using an in-house developed method. The dose distributions were then compared with those calculated in a virtual EPID using the Pinnacle3 treatment planning system (TPS. Using gamma evaluation with the DDmax and DTA criteria of 3%/2.54 mm, an excellent agreement was observed between transmitted dose measured using SLIC-EPID and that calculated by TPS (gamma score approximately 95% for large MLC fields. In contrast, for several small subfields, due to SLIC-EPID image blurring, significant disagreement was found in the gamma results. Differences between EPID and TPS dose maps were also observed for several parts of the radiation subfields, when the radiation beam passed through air on the outside of tissue. The transmitted dose distributions measured using portal imagers such as SLIC-EPID can be used to verify the dose delivery to a patient. However, several aspects such as accurate calibration procedure and imager response under different conditions should be taken into the consideration. In addition, SLIC-EPID image blurring is another important issue, which should be considered if the SLIC-EPID is used for clinical dosimetry verification.

  11. Laser Induced Fluorescence Spectroscopy of Neutral and Ionized Polycyclic Aromatic Hydrocarbons in the Cosmic Simulation Chamber

    Science.gov (United States)

    Bejaoui, Salma; Salama, Farid; Contreras, Cesar; Sciamma O'Brien, Ella; Foing, Bernard; Pascale, Ehrenfreund

    2015-01-01

    Polycyclic aromatic hydrocarbon (PAH) molecules are considered the best carriers to account for the ubiquitous infrared emission bands. PAHs have also been proposed as candidates to explain the diffuse interstellar bands (DIBs), a series of absorption features seen on the interstellar extinction curve and are plausible carriers for the extended red emission (ERE), a photoluminescent process associated with a wide variety of interstellar environments. Extensive efforts have been devoted over the past two decades to characterize the physical and chemical properties of PAH molecules and ions in space. Absorption spectra of PAH molecules and ions trapped in solid matrices have been compared to the DIBs. Absorption spectra of several cold, isolated gas-phase PAHs have also been measured under experimental conditions that mimic the interstellar conditions. The purpose of this study is to provide a new dimension to the existing spectroscopic database of neutral and single ionized PAHs that is largely based on absorption spectra by adding emission spectroscopy data. The measurements are based on the laser induced fluorescence (LIF) technique and are performed with the Pulsed Discharge Nozzle (PDN) of the COSmIC laboratory facility at NASA Ames laboratory. The PDN generates a plasma in a free supersonic jet expansion to simulate the physical and the chemical conditions in interstellar environments. We focus, here, on the fluorescence spectra of large neutral PAHs and their cations where there is a lack of fluorescence spectroscopy data. The astronomical implications of the data (e.g., ERE) are examined.

  12. Comparison between IAEA/TRS-277 and IAEA/TRS-398 protocols for electron beam dosimetry with cylindrical ionization chambers; Comparacao entre os protocolos IAEA/TRS-277 e IAEA/TRS-398 para dosimetria em feixes de eletrons com camaras de ionizacao cilindricas

    Energy Technology Data Exchange (ETDEWEB)

    Souza, Roberto Salomon de

    2004-07-01

    With the purpose to guarantee an uncertainty in the dosimetry in radiation therapy, the International Atomic Energy Agency (IAEA) published in 1987 the Technical Reports Series (TRS) number 277 - Absorbed Dose Determination in Photon and Electron Beams - An International Code of Practice -, updated in 1997, when was published its second edition. In 2000 was published the TRS number 398 - Absorbed Dose Determination in External Beam Radiotherapy - An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water. The TRS number 398 brings a great conceptual change in relation to the basis of the formalism, before based on calibration factor in terms of air kerma, and now based on calibration factor in terms of absorbed dose in water. Since the TRS number 398 was published, the Secondary Standard Dosimetry Laboratories are calibrating the user's ionization chambers in terms of absorbed dose to water. However, nor all the clinics in Rio de Janeiro and Brazil have its ionization chambers calibrated in terms of absorbed dose to water. The National Cancer Institute, where the measurements were taken, was the first institution in the Rio de Janeiro to have its ionization chambers calibrated in terms of a new formalism. This work describes a comparison between dosimetry done with a cylindrical ionization chamber under electron beams utilizing the TRS number 277 formalism, based on air kerma, and the TRS number 398 formalism, based on absorbed dose to water, reporting the uncertainties variation of the dosimetry associated to each protocol. (author)

  13. Comparison of two dose-area-product ionization chambers with different conductive surface coating for over-table and under-table tube configurations

    Energy Technology Data Exchange (ETDEWEB)

    Bednarek, D.R.; Rudin, S.

    2000-03-01

    A custom-built graphite-coated transmission ionization chamber is compared to the VacuDAP 2001 (VacuTec, Dresden, Germany), which has transparent conductive electrodes. A study was made of the dependence of response on x-ray tube potential for both types of chamber under identical conditions of exposure using over-table and under-table x-ray tubes. Since the calibration factor is the dose-area product of the radiation incident on the patient per chamber reading, it depends on the intrinsic response of the chamber as well as the effect of material in the beam between the x-ray tube and patient. Differences of about 20% were measured between the intrinsic and the over-table calibration factors and between the over-table and the under-table calibration factors for both chambers. The VacuDAP display is specifically calibrated for the over-table condition and would overstate the actual DAP in the under-table case. The intrinsic response of the graphite chamber is nearly independent of tube potential. Although the variation of response with tube potential of the graphite chamber is increased when it is used as an over-table and an under-table patient monitor, it shows less overall variation of response than the VacuDAP. The average deviation of each range of 40 to 140 kVp for both chambers.

  14. DESIGNING HYDRAULIC AIR CHAMBER IN WATER TRANSMISSION SYSTEMS USING GENETIC ALGORITHM

    Directory of Open Access Journals (Sweden)

    Abdorahim Jamal

    2016-09-01

    Full Text Available Transient flow control in Water Transmission Systems (WTS is one of the requirements of designing these systems. Hence, among control equipment, air chambers offer the best solution to control transient flow effects, i.e. both prevents water column separation and absorbs pressure increase. It is essential to carry out an accurate and optimized design of air chambers, not only due to high costs of their manufacturing but also their important protective role. Accordingly, hydraulic design parameters comprise tank volume, diameter of nozzle and coefficients of inflow and outflow of nozzle. In this paper, it is intended to optimize these parameters in order to minimize manufacturing costs. On the other hand, maximum and minimum pressures in main pipeline are considered as constraints which shall fall in allowed range. Therefore, a model has been developed which is a combination of a hydraulic simulation model of WTS and an optimization model based on genetic algorithm. This model is first applied to WTS of Dehgolan-Ghorveh plain as a case study. Results of this research demonstrate that based on suggested model, negative wave creation and pressure increase in pipeline is prevented as well as decrease in manufacturing costs of air chamber.

  15. Water hammer in the pump-rising pipeline system with an air chamber

    Institute of Scientific and Technical Information of China (English)

    KIM Sang-Gyun; LEE Kye-Bock; KIM Kyung-Yup

    2014-01-01

    Water hammer following the tripping of pumps can lead to overpressure and negative pressure. Reduction in overpressure and negative pressure may be necessary to avoid failure, to improve the efficiency of operation and to avoid fatigue of system components. The field tests on the water hammer have been conducted on the pump rising pipeline system with an air chamber. The hydraulic transient was simulated using the method of characteristics. Minimizing the least squares problem representing the difference between the measured and predicted transient response in the system performs the calibration of the simulation program. Among the input variables used in the water hammer analysis, the polytropic exponent, the discharge coefficient and the wave speed were calibrated. The computer program developed in this study will be useful in designing the optimum parameters of an air chamber for the real pump pipeline system. The correct selection of air chamber size and the effect of the inner diameter of the orifice to minimize water hammer have been investigated by both field measurements and numerical modeling.

  16. Experimental analysis of general ion recombination in a liquid-filled ionization chamber in high-energy photon beams

    Energy Technology Data Exchange (ETDEWEB)

    Chung, Eunah; Seuntjens, Jan [Medical Physics Unit, McGill University, Montreal General Hospital (L5-113), 1650 Cedar Avenue, Montreal, Quebec H3G 1A4 (Canada); Davis, Stephen [Department of Medical Physics, McGill University Health Centre, Montreal General Hospital (L5-112), 1650 Cedar Avenue, Montreal, Quebec H3G 1A4 (Canada)

    2013-06-15

    Purpose: To study experimentally the general ion recombination effect in a liquid-filled ionization chamber (LIC) in high-energy photon beams. Methods: The general ion recombination effect on the response of a micro liquid ion chamber (microLion) was investigated with a 6 MV photon beam in normal and SRS modes produced from a Varian{sup Registered-Sign} Novalis Tx{sup TM} linear accelerator. Dose rates of the linear accelerator were set to 100, 400, and 1000 MU/min, which correspond to pulse repetition frequencies of 60, 240, and 600 Hz, respectively. Polarization voltages applied to the microLion were +800 and +400 V. The relative collection efficiency of the microLion response as a function of dose per pulse was experimentally measured with changing polarization voltage and pulse repetition frequencies and was compared with the theoretically calculated value. Results: For the 60 Hz pulse repetition frequency, the experimental relative collection efficiency was not different from the theoretical one for a pulsed beam more than 0.3% for both polarization voltages. For a pulsed radiation beam with a higher pulse repetition frequency, the experimental relative collection efficiency converged to the theoretically calculated efficiency for continuous beams. This result indicates that the response of the microLion tends toward the response to a continuous beam with increasing pulse repetition frequency of a pulsed beam because of low ion mobility in the liquid. Conclusions: This work suggests an empirical method to correct for differences in general ion recombination of a LIC between different radiation fields. More work is needed to quantitatively explain the LIC general ion recombination behavior in pulsed beams generated from linear accelerators.

  17. Laser Induced Fluorescence Spectroscopy of Neutral and Ionized Polycyclic Aromatic Hydrocarbons in a Cosmic Simulation Chamber

    Science.gov (United States)

    Bejaoui, Salma; Salama, Farid

    2015-08-01

    Polycyclic aromatic hydrocarbon (PAH) molecules are considered the best carriers to account for the ubiquitous infrared emission bands. PAHs have also been proposed as candidates to explain the diffuse interstellar bands (DIBs), a series of absorption features seen on the interstellar extinction curve and are plausible carriers for the extended red emission (ERE), a photoluminescent process associated with a wide variety of interstellar environments. Extensive efforts have been devoted over the past two decades to characterize the physical and chemical properties of PAH molecules and ions in space. Absorption spectra of PAH molecules and ions trapped in solid matrices have been compared to the DIBs [1, 2]. Absorption spectra of several cold, isolated gas-phase PAHs have also been measured under experimental conditions that mimic the interstellar conditions [see 3 for a review]. The purpose of this study is to provide a new dimension to the existing spectroscopic database of neutral and single ionized PAHs that is largely based on absorption spectra by adding emission spectroscopy data. The measurements are based on the laser-induced fluorescence (LIF) technique [4] and are performed with the Pulsed Discharge Nozzle (PDN) of the COSmIC laboratory facility at NASA Ames laboratory. The PDN generates plasma in a free supersonic jet expansion to simulate the physical and the chemical conditions in interstellar environments. We focus, here, on the fluorescence spectra of large neutral PAHs and their cations where there is a lack of fluorescence spectroscopy data. The astronomical implications of the data (e.g., ERE) are examinedReferences[1] F. Salama, E. Bakes, L.J. Allamandola, A.G.G.M. Tielens, Astrophys. J., 458 (1996) p.621[2] F. Salama, The ISO Revolution, EDP Sciences, Les Ulis, France (1999) p.65[3] Salama F., In Organic Matter in Space, IAU Symposium 251, Kwok & Sandford Eds.Cambridge University Press,4, S251,(2008), p. 357 (2008) and references therein.[4

  18. Combined complementary plasma diagnostics to characterize a 2f plasma with additional DC current with conditioning effects at the chamber wall

    Science.gov (United States)

    Klick, Michael; Rothe, Ralf; Baek, Kye Hyun; Lee, Eunwoo

    2016-09-01

    Multiple frequencies and DC current used in a low-pressure plasma rf discharge result in an increased complexity. This needs plasma diagnostics applied, in particular in a plasma process chamber. That is done under manufacturing conditions which restrict the applicable plasma diagnostics to non-invasive methods with small footprint. So plasma chamber parameters, optical emission spectroscopy (OES), and self-excited electron spectroscopy (SEERS) are used to characterize the plasma and to understand chamber wall conditioning effects in an Ar plasma. The parameters are classified according to their origin--the region they are representative for. The center ion density is estimated from the DC current and compared to the SEERS electron density reflecting the electron density close to that at the chamber wall. The conditioning effects are caused by Si sputtering at a Si wafer changing the chamber wall state only when the chamber is clean, subsequent plasmas in the same chamber are not affected in that way. Through the combination of the complementary methods it can be shown that the chamber wall condition finally changes the radial plasma density distribution. Also the heating of electrons in the sheath is shown to be influenced by conditioning effects.

  19. 42 CFR 84.143 - Terminal fittings or chambers; Type B supplied-air respirators; minimum requirements.

    Science.gov (United States)

    2010-10-01

    ... respirators; minimum requirements. 84.143 Section 84.143 Public Health PUBLIC HEALTH SERVICE, DEPARTMENT OF... RESPIRATORY PROTECTIVE DEVICES Supplied-Air Respirators § 84.143 Terminal fittings or chambers; Type B supplied-air respirators; minimum requirements. (a) Blowers or connections to air supplies...

  20. A two-dimensional liquid-filled ionization chamber array prototype for small-field verification: characterization and first clinical tests.

    Science.gov (United States)

    Brualla-González, Luis; Gómez, Faustino; Vicedo, Aurora; González-Castaño, Diego M; Gago-Arias, Araceli; Pazos, Antonio; Zapata, Martín; Roselló, Joan V; Pardo-Montero, Juan

    2012-08-21

    In this work we present the design, characterization and first clinical tests of an in-house developed two-dimensional liquid-filled ionization chamber prototype for the verification of small radiotherapy fields and treatments containing such small fields as in radiosurgery, which consists of 2 mm × 2 mm pixels arranged on a 16×8 rectangular grid. The ionization medium is isooctane. The characterization of the device included the study of depth, field-size and dose-rate dependences, which are sufficiently moderate for a good operation at therapy radiation levels. However, the detector presents an important anisotropic response, up to ≃ 12% for front versus near-lateral incidence, which can impact the verification of full treatments with different incidences. In such a case, an anisotropy correction factor can be applied. Output factors of small square fields measured with the device show a small systematic over-response, less than 1%, when compared to unshielded diode measurements. An IMRT radiosurgery treatment has been acquired with the liquid-filled ionization chamber device and compared with film dosimetry by using the gamma method, showing good agreement: over 99% passing rates for 1.2% and 1.2 mm for an incidence-per-incidence analysis; 100% passing rates for tolerances 1.8% and 1.8 mm when the whole treatment is analysed and the anisotropy correction factor is applied. The point dose verification for each incidence of the treatment performed with the liquid-filled ionization chamber agrees within 1% with a CC01 ionization chamber. This prototype has shown the utility of this kind of technology for the verification of small fields/treatments. Currently, a larger device covering a 5 cm × 5 cm area is under development.

  1. On the interpretation of current-voltage curves in ionization chambers using the exact solution of the Thomson problem

    Science.gov (United States)

    Ridenti, M. A.; Pascholati, P. R.; Gonçalves, J. A. C.; Bueno, C. C.

    2015-09-01

    The I - ΔV characteristic curve of a well type ionization chamber irradiated with 192Ir sources (0.75 Ci-120 Ci) was fitted using the exact solution of the Thomson problem. The recombination coefficient and saturation current were estimated using this new approach. The saturation current was compared with the results of the conventional method based on Boag-Wilson formula. It was verified that differences larger than 1% between both methods only occurred at activities higher than 55 Ci. We concluded that this new approach is recommended for a more accurate estimate of the saturation current when it is not possible to measure currents satisfying the condition I /Isat > 0.95. From the calibration curve the average value of pairs of carriers created per unit volume was estimated to be equal to η = 8.1 ×10-3cm-3s-1 Bq-1 and from that value it was estimated that ~ 17 pairs were created on average per second for each decay of the source.

  2. Characterization and performances of a monitoring ionization chamber dedicated to IBA-universal irradiation head for Pencil Beam Scanning

    CERN Document Server

    Courtois, C; Brusasco, C; Colin, J; Cussol, D; Fontbonne, J M; Marchand, B; Mertens, T; De Neuter, S; Peronnel, J

    2013-01-01

    Every radiotherapy center has to be equipped with real-time beam monitoring devices. In 2008, the medical application group from the Laboratory of Corpuscular Physics (LPC Caen) developed an Ionization Chamber in collaboration with the company IBA (Ion Beam Applications). This monitoring device called IC2/3 was developed to be used in IBAs universal irradiation head for Pencil Beam Scanning (PBS). The objectives presented in this article are to characterize the IC2/3 monitor in the energy and ux ranges used in protontherapy. The equipment has been tested with an IBAs cyclotronable to deliver proton beams from 70 to 230 MeV. This beam monitoring device has been validated and is now installed at the Westdeutsches Protonentherapiezentrum Essen protontherapy center (WPE, Germany). The results obtained in both terms of spatial resolution and dose measurements are at least equal to the initials speci cations needed for PBS purposes. The detector measures the dose with a relative precision better than 1% in the rang...

  3. Time-of-flight ERD with a 200 mm2 Si3N4 window gas ionization chamber energy detector

    Science.gov (United States)

    Julin, Jaakko; Laitinen, Mikko; Sajavaara, Timo

    2014-08-01

    Low energy heavy ion elastic recoil detection work has been carried out in Jyväskylä since 2009 using home made timing detectors, a silicon energy detector and a timestamping data acquisition setup forming a time-of-flight-energy telescope. In order to improve the mass resolution of the setup a new energy detector was designed to replace the silicon solid state detector, which suffered from radiation damage and had poor resolution for heavy recoils. In this paper the construction and operation of an isobutane filled gas ionization chamber with a 14 × 14 mm2 100 nm thick silicon nitride window are described. In addition to greatly improved energy resolution for heavy ions, the detector is also able to detect hydrogen recoils simultaneously in the energy range of 100-1000 keV. Additionally the detector has position sensitivity by means of timing measurement, which can be performed without compromising the performance of the detector in any other way. The achieved position sensitivity improves the depth resolution near the surface.

  4. Chamber and field evaluations of air pollution tolerances of urban trees

    Energy Technology Data Exchange (ETDEWEB)

    Karnosky, D.F.

    1981-04-01

    Results are presented for a study of the relative air pollution tolerances of 32 urban-tree cultivars as determined by both chamber fumigations and field exposures. Tolerances to ozone and sulfur dioxide, alone and in combination, were determined using short-term, acute doses administered while the plants were inside a plastic fumigation chamber located inside the Cary Arboretum greenhouses. In a follow-up study still underway, representatives of the same cultivars were outplanted at four locations in the greater New York City area. To date, only oxidant-type injury has been observed on trees in the field plots. Cultivars tolerant to all chamber and field exposures were Acer platanoides Cleveland, Crimson King, Emerald Queen, Jade Glen, and Summershade; Acer rubrum Autumn Flame and Red Sunset; Acer saccharum Green Mountain and Temple's Upright; Fagus sylvatica Rotundifolia; Fraxinus pennsylvanica Summit; and Ginkgo biloba Fastigate and Sentry. Cultivars sensitive to ozone as determined by the chamber and field tests and that may serve as bioindicators of the presence of ozone were Gleditsia triacanthos inermis imperial and Platanus acerifolia Bloodgood.

  5. Constraints on target chamber first wall and target designs that will enable NIF debris shields to survive

    Science.gov (United States)

    Burnham, Alan K.; Gerassimenko, Michel; Scott, J. M.; Latkowski, Jeff F.; Whitman, Pamela K.; Genin, Francois Y.; Hibbard, Wilthea; Peterson, P. F.; Tokheim, R. E.; Curran, D. R.

    1999-07-01

    The NIF target chamber interior materials and target designs themselves have to be compatible with survival of the final- optics debris shields. To meet the planned maintenance and refinishing rate, the contamination of the debris shields cannot exceed about 1 nm equivalent thickness per shot of total material. This implies that he target mass must be limited to no more than 1 gram and the ablated mass released to the chamber from all other components must not exceed 3 grams. In addition, the targets themselves must either completely vaporize or send any minor amounts of shrapnel towards the chamber waist to prevent excessive catering of the debris shields. The constraints on the first-wall debris will remobilize at a rate fast enough to require cleaning every 3 weeks, about three times more frequent than possible with planned robotics. Furthermore, a comparison of ablatants from B4C and stainless-steel louvers suggest that remobilization of target debris by x-rays will be greater than that of the base material in both cases, thereby reducing the performance advantage of clean B4C over much cheaper stainless steel. Neutronics calculations indicate that activation of thin Ni-free stainless steel is not a significant source of maintenance personnel radiation dose. Consequently, the most attractive first wall design consists of stainless-steel louvers. Evaluation of various unconverted-light beam dump designs indicates that stainless steel louvers generate no more debris than other matrices, so one single design can serve as both first wall and beam dumps, eliminating beam steering restrictions caused by size and location of the beam dumps. One reservation is that the allowable contamination rate of the debris shield is not yet completely understood. Consequently, it is likely that either a protruding beam tube, a rapid post-shot gas purge of the final optics assembly, or thin polymeric pre-shield will be required to prevent low-velocity contamination from reaching

  6. Air-soil exchange of organochlorine pesticides in a sealed chamber

    Institute of Scientific and Technical Information of China (English)

    Bing Yang; Baolu Han; Nandong Xue; Lingli Zhou; Fasheng Li

    2015-01-01

    So far little is known about air-soil exchange under any sealed circumstances (e.g.,in plastic and glass sheds),which however has huge implications for the soil-air-plant pathways of persistent organic pollutants including organochlorine pesticides (OCPs).A newly designed passive air sampler was tested in a sealed chamber for measuring the vertical concentration profiles of gaseous phase OCPs (hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs)).Air was sampled at 5,15,and 30 cm above ground level every 10th day during a 60-day period by deploying polyurethane foam cyhnders housed in acrylonitrile butadiene styrene-covered cartridges.Concentrations and compositions of OCPs along the vertical sections indicated a clear relationship with proximity to the mixture of HCHs and DDTs which escapes from the soils.In addition,significant positive correlations were found between air temperatures and concentrations of HCHs and DDTs.These results indicated revolatilization and re-deposition being at or close to dynamic pseudo-equilibrium with the overlying air.The sampler used for addressing air-soil exchange of persistent organic pollutants in any sealed conditions is discussed.

  7. Air-soil exchange of organochlorine pesticides in a sealed chamber.

    Science.gov (United States)

    Yang, Bing; Han, Baolu; Xue, Nandong; Zhou, Lingli; Li, Fasheng

    2015-01-01

    So far little is known about air-soil exchange under any sealed circumstances (e.g., in plastic and glass sheds), which however has huge implications for the soil-air-plant pathways of persistent organic pollutants including organochlorine pesticides (OCPs). A newly designed passive air sampler was tested in a sealed chamber for measuring the vertical concentration profiles of gaseous phase OCPs (hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs)). Air was sampled at 5, 15, and 30 cm above ground level every 10th day during a 60-day period by deploying polyurethane foam cylinders housed in acrylonitrile butadiene styrene-covered cartridges. Concentrations and compositions of OCPs along the vertical sections indicated a clear relationship with proximity to the mixture of HCHs and DDTs which escapes from the soils. In addition, significant positive correlations were found between air temperatures and concentrations of HCHs and DDTs. These results indicated revolatilization and re-deposition being at or close to dynamic pseudo-equilibrium with the overlying air. The sampler used for addressing air-soil exchange of persistent organic pollutants in any sealed conditions is discussed.

  8. Calibration methods of plane-parallel ionization chambers used in electron dosimetry; Metodos de calibracao de camaras de ionizacao de placas paralelas para dosimetria de feixes de eletrons

    Energy Technology Data Exchange (ETDEWEB)

    Bulla, Roseli Tadeu

    1999-07-01

    The use of linear accelerators in radiotherapy is of great importance in Medicine, and according to international recommendations the electron beam dosimetry has to be performed using plane-parallel ionization chambers, previously calibrated in standard gamma radiation fields at accredited laboratories. In this work, calibration methods of plane-parallel ionization chambers used in dosimetry procedures of high energy electron beams of clinical accelerators were presented, tested and intercompared. The experiments were carried out using gamma radiation beams of {sup 60} Co at the Calibration Laboratory of Clinical Dosemeters at IPEN and electron beams od 4 to 16 MeV at the Radiotherapy Department of Hospital Israelita Albert Einstein, Sao Paulo. A method was chosen to be established at IPEN. Proposals of the calibration procedure, calibration certificate and data sheets are presented. (author)

  9. Gas gain operations with single photon resolution using an integrating ionization chamber in small-angle X-ray scattering experiments

    CERN Document Server

    Menk, R H; Besch, H J; Walenta, Albert H; Amenitsch, H; Bernstorff, S

    2000-01-01

    In this work a combination of an ionization chamber with one-dimensional spatial resolution and a MicroCAT structure will be presented. Initially, MicroCAT was thought of as a shielding grid (Frisch-grid) but later was used as an active electron amplification device that enables single X-ray photon resolution measurements at low fluxes even with integrating readout electronics. Moreover, the adjustable gas gain that continuously covers the entire range from pure ionization chamber mode up to high gas gains (30000 and more) provides stable operation yielding a huge dynamic range of about 10 sup 8 and more. First measurements on biological samples using small angle X-ray scattering techniques with synchrotron radiation will be presented.

  10. Identification of hydrogen and helium in elastic recoil detection measurements using a compact ({delta}E - E {sub r}) ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Pantelica, D. [HH National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest, Magurele (Romania)]. E-mail: pantel@ifin.nipne.ro; Isbasescu, A. [HH National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest, Magurele (Romania); Negoita, F. [HH National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest, Magurele (Romania); Petrascu, H. [HH National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest, Magurele (Romania); Petrascu, M. [HH National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest, Magurele (Romania); Ionescu, P. [HH National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest, Magurele (Romania); Scintee, N. [HH National Institute for Physics and Nuclear Engineering, P.O. Box MG-6, 76900 Bucharest, Magurele (Romania)

    2006-08-15

    Recoil spectrometry with heavy ions has evolved into a rather universal IBA technique. Hydrogen is an important element in a wide variety of thin film materials. In this paper we present the capabilities of a compact {delta}E(gas ionization chamber) - E {sub res}(solid) telescope for simultaneous light and medium heavy element detection. To increase the resolution an integrated preamplifier was mounted close to the ionization chamber. To achieve the simultaneous detection of very light elements (H and He) and of the heavier ones (C, O, Mg, Al) the two outputs from the preamplifier were fed into two main amplifiers, operated with high and low gain, respectively. The calibration procedure for the telescope and the software for the quantitative evaluation of the data are briefly presented. The results obtained in some ERDA measurements using a {sup 63}Cu beam from the FN tandem accelerator of NIPNE are also presented.

  11. Optimal laser pulse energy partitioning for air ionization

    CERN Document Server

    Schubert, Elise; Matthews, Mary; Courjaud, Antoine; Kasparian, Jérôme; Wolf, Jean-Pierre

    2016-01-01

    We investigate the pulse partitioning of a 6.3 mJ, 450 fs pulse at 1030 nm to produce plasma channels. At such moderate energies, splitting the energy into several sub-pulses reduces the ionization efficiency and thus does not extend the plasma lifetime. We numerically show that when sufficient energy to produce multifilamentation is available, splitting the pulse temporally in a pulse train increases the gas temperature compared to a filament bundle of the same energy. This could improve the mean free path of the free electrons, therefore enhancing the efficiency of discharge triggering.

  12. Chamber bioaerosol study: outdoor air and human occupants as sources of indoor airborne microbes.

    Science.gov (United States)

    Adams, Rachel I; Bhangar, Seema; Pasut, Wilmer; Arens, Edward A; Taylor, John W; Lindow, Steven E; Nazaroff, William W; Bruns, Thomas D

    2015-01-01

    Human occupants are an important source of microbes in indoor environments. In this study, we used DNA sequencing of filter samples to assess the fungal and bacterial composition of air in an environmental chamber under different levels of occupancy, activity, and exposed or covered carpeting. In this office-like, mechanically ventilated environment, results showed a strong influence of outdoor-derived particles, with the indoor microbial composition tracking that of outdoor air for the 2-hour sampling periods. The number of occupants and their activity played a significant but smaller role influencing the composition of indoor bioaerosols. Human-associated taxa were observed but were not particularly abundant, except in the case of one fungus that appeared to be transported into the chamber on the clothing of a study participant. Overall, this study revealed a smaller signature of human body-associated taxa than had been expected based on recent studies of indoor microbiomes, suggesting that occupants may not exert a strong influence on bioaerosol microbial composition in a space that, like many offices, is well ventilated with air that is moderately filtered and moderately occupied.

  13. Comparison of depth-dose distributions of proton therapeutic beams calculated by means of logical detectors and ionization chamber modeled in Monte Carlo codes

    Science.gov (United States)

    Pietrzak, Robert; Konefał, Adam; Sokół, Maria; Orlef, Andrzej

    2016-08-01

    The success of proton therapy depends strongly on the precision of treatment planning. Dose distribution in biological tissue may be obtained from Monte Carlo simulations using various scientific codes making it possible to perform very accurate calculations. However, there are many factors affecting the accuracy of modeling. One of them is a structure of objects called bins registering a dose. In this work the influence of bin structure on the dose distributions was examined. The MCNPX code calculations of Bragg curve for the 60 MeV proton beam were done in two ways: using simple logical detectors being the volumes determined in water, and using a precise model of ionization chamber used in clinical dosimetry. The results of the simulations were verified experimentally in the water phantom with Marcus ionization chamber. The average local dose difference between the measured relative doses in the water phantom and those calculated by means of the logical detectors was 1.4% at first 25 mm, whereas in the full depth range this difference was 1.6% for the maximum uncertainty in the calculations less than 2.4% and for the maximum measuring error of 1%. In case of the relative doses calculated with the use of the ionization chamber model this average difference was somewhat greater, being 2.3% at depths up to 25 mm and 2.4% in the full range of depths for the maximum uncertainty in the calculations of 3%. In the dose calculations the ionization chamber model does not offer any additional advantages over the logical detectors. The results provided by both models are similar and in good agreement with the measurements, however, the logical detector approach is a more time-effective method.

  14. Evaluating the variation of response of ionizing chamber type pencil for different collimators; Avaliando a variacao da resposta da camara de ionizacao tipo lapis para diferentes colimadores

    Energy Technology Data Exchange (ETDEWEB)

    Andrade, Lucio das Chagas de; Peixoto, Jose Guilherme Pereira, E-mail: lucio-andrade@hotmail.com [Instituto de Radioprotecao e Dosimetria, (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

    2014-07-01

    The pencil ionization chamber is used in dosimetric procedures for X-ray beams in the energy range of a scanner. Calibration of such camera is still being extensively studied because the procedure is different from the others. To study the variation of response of the camera for different collimators was analyzed three different collimators. It was found that among the other showed the best response was the opening of 30 mm. (author)

  15. Generation of Diffuse Large Volume Plasma by an Ionization Wave from a Plasma Jet

    Science.gov (United States)

    Laroussi, Mounir; Razavi, Hamid

    2015-09-01

    Low temperature plasma jets emitted in ambient air are the product of fast ionization waves that are guided within a channel of a gas flow, such as helium. This guided ionization wave can be transmitted through a dielectric material and under some conditions can ignite a discharge behind the dielectric material. Here we present a novel way to produce large volume diffuse low pressure plasma inside a Pyrex chamber that does not have any electrodes or electrical energy directly applied to it. The diffuse plasma is ignited inside the chamber by a plasma jet located externally to the chamber and that is physically and electrically unconnected to the chamber. Instead, the plasma jet is just brought in close proximity to the external wall/surface of the chamber or to a dielectric tubing connected to the chamber. The plasma thus generated is diffuse, large volume and with physical and chemical characteristics that are different than the external plasma jet that ignited it. So by using a plasma jet we are able to ``remotely'' ignite volumetric plasma under controlled conditions. This novel method of ``remote'' generation of a low pressure, low temperature diffuse plasma can be useful for various applications including material processing and biomedicine.

  16. The Introduction of Clinical Ionization Chamber and New Model Application%医用电离室介绍与新型应用

    Institute of Scientific and Technical Information of China (English)

    单晓晖; 赵明宇; 王姝; 迟戈

    2016-01-01

    The ionization chamber as the core part of the automatic exposure control in the medical DR system has been widely used in DR diagnosis nowadays. The paper mainly introduces the mechanism and structure of the ionization chamber,the fast transient pulse and quality of the image were tested in the new double three-ifeld ionization chamber. The test results show that is reliable and it has good interference immunity, and it can meet the clinical requirements wel and it has good practical value.%电离室作为医用DR系统中自动曝光控制环节的核心部件,如今在DR诊断中已得到了广泛的应用。本文主要从电离室的机制及构造等作以详尽的介绍,并针对新型复式电离室进行了脉冲群及图像测试。测试结果表明,新型复式电离室性能可靠,具有很好的抗干扰性,可以较好地满足临床摄影要求,具有较好的实用价值。

  17. SU-E-T-561: Development of Depth Dose Measurement Technique Using the Multilayer Ionization Chamber for Spot Scanning Method

    Energy Technology Data Exchange (ETDEWEB)

    Takayanagi, T; Fujitaka, S; Umezawa, M [Hitachi, Ltd., Hitachi Research Laboratory, Hitachi-shi, Ibaraki-ken (Japan); Ito, Y; Nakashima, C; Matsuda, K [Hitachi, Ltd., Hitachi Works, Hitachi-shi, Ibaraki-ken (Japan)

    2014-06-01

    Purpose: To develop a measurement technique which suppresses the difference between profiles obtained with a multilayer ionization chamber (MLIC) and with a water phantom. Methods: The developed technique multiplies the raw MLIC data by a correction factor that depends on the initial beam range and water equivalent depth. The correction factor is derived based on a Bragg curve calculation formula considering range straggling and fluence loss caused by nuclear reactions. Furthermore, the correction factor is adjusted based on several integrated depth doses measured with a water phantom and the MLIC. The measured depth dose profiles along the central axis of the proton field with a nominal field size of 10 by 10 cm were compared between the MLIC using the new technique and the water phantom. The spread out Bragg peak was 20 cm for fields with a range of 30.6 cm and 6.9 cm. Raw MLIC data were obtained with each energy layer, and integrated after multiplying by the correction factor. The measurements were performed by a spot scanning nozzle at Nagoya Proton Therapy Center, Japan. Results: The profile measured with the MLIC using the new technique is consistent with that of the water phantom. Moreover, 97% of the points passed the 1% dose /1mm distance agreement criterion of the gamma index. Conclusion: We have demonstrated that the new technique suppresses the difference between profiles obtained with the MLIC and with the water phantom. It was concluded that this technique is useful for depth dose measurement in proton spot scanning method.

  18. Comparing of the yield curve of the pediatric X-ray equipment using thermoluminescent dosimeters and cylindrical ionization chamber; Comparacao da curva de rendimento de um aparelho de raios X pediatrico utilizando dosimetros termoluminescentes e camara de ionizacao cilindrica

    Energy Technology Data Exchange (ETDEWEB)

    Filipov, Danielle, E-mail: dfilipov@utfpr.edu.br [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Schelin, Hugo R., E-mail: ledesmaiorgealberto@gmail.com [Instituto de Pesquisa Pele Pequeno Principe, Curitiba, PR (Brazil); Tilly Junior, Joao G., E-mail: joao.tilly@derax.com.br [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil). Hospital de Clinicas

    2014-07-01

    The determination of the yield curve of a radiographic equipment should be realized once a year, or when the unit be serviced. Besides being a requirement of ANVISA, through this test is possible to determine the incident air kerma (at a given point in the center of the beam) - INAK. Based on these concepts, the main objective of this work is the comparison of yield curves of the pediatric X-ray apparatus using two different detectors: one cylindrical ionization chamber and thermoluminescent dosimeters type LiF: Mg, Cu, P, as per protocol RLA / 9/057 IAEA. Then the equation of the yield curve (generated by each detector) was used to determine the INAK of 10 pediatric examinations, performed on this equipment. After the process of calibration of both detectors, they were placed side by side at a focus of the tube equipment for determining the performance of the same curve. Finally, using the curves generated by two detectors, INAK values of the 10 tests were calculated (from the kVp values, and mAs focus-patient of each exams), generating difference values at most 5%. As a conclusion, it can be said that the TLD lithium fluoride doped with Mg, Cu and P and the cylindrical ionization chambers may be used satisfactorily to determine the yield curve, whether as quality control or dosimetry.

  19. The effect of a compression paddle on energy response, calibration and measurement with mammographic dosimeters using ionization chambers and solid-state detectors.

    Science.gov (United States)

    Hourdakis, C J; Boziari, A; Koumbouli, E

    2009-02-21

    A compression paddle is always used in mammography x-ray examinations, in order to improve image quality and reduce patient doses. Although clinical dose measurements should be performed with the paddle to interfere with the x-ray beam, calibration of mammography dosimeters is performed free in air without the presence of the paddle. The paddle hardens the x-ray beam, which has an impact on a dosimeter performance, particularly on high-energy-dependent detectors. Due to the paddle, clinical mammography x-ray systems may exhibit beams with HVL values exceeding those of the IEC 61267 RQR-M series qualities at which dosimeters are usually calibrated. In this study, the influence of the paddle in mammography dosimetry is examined, in Mo/Mo anode/filter x-ray qualities. PMMA slabs of 1, 2 and 3 mm thickness and Al foils of 0.05, 0.10 and 0.15 mm thicknesses were used to simulate the paddles, producing beams with HVL values from 0.28 up to 0.43 mmAl. In these qualities, four solid-state (ST) detectors and three ionizations chambers (IC) were calibrated in terms of Kair and N(K) and k(Q) were deduced. The results showed that all IC and two modern-type ST dosimeters have a flat energy response in the above HVL range (less than 3%), so their calibration factor at RQR-M2 quality could be safely used for clinical measurements. Two other ST dosimeters exhibit up to 20% energy response, so differences up to 15% in dose measurement may be observed if the effect of paddle on their performance is ignored. Finally, the need of additional mammographic calibration qualities to the existing IEC 61267 RQR-M series is examined and discussed.

  20. Fatigue cracking of a bare steel first wall in an inertial confinement fusion chamber

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, R. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Abbott, R. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Havstad, M. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Dunne, A. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2013-06-01

    Inertial confinement fusion power plants will deposit high energy X-rays onto the outer surfaces of the first wall many times a second for the lifetime of the plant. These X-rays create brief temperature spikes in the first few microns of the wall, which cause an associated highly compressive stress response on the surface of the material. The periodicity of this stress pulse is a concern due to the possibility of fatigue cracking of the wall. We have used finite element analyses to simulate the conditions present on the first wall in order to evaluate the driving force of crack propagation on fusion-facing surface cracks. Analysis results indicate that the X-ray induced plastic compressive stress creates a region of residual tension on the surface between pulses. This tension film will likely result in surface cracking upon repeated cycling. Additionally, the compressive pulse may induce plasticity ahead of the crack tip, leaving residual tension in its wake. However, the stress amplitude decreases dramatically for depths greater than 80–100 μm into the fusion-facing surface. Crack propagation models as well as stress-life estimates agree that even though small cracks may form on the surface of the wall, they are unlikely to propagate further than 100 μm without assistance from creep or grain erosion phenomena.

  1. Comparison of depth-dose distributions of proton therapeutic beams calculated by means of logical detectors and ionization chamber modeled in Monte Carlo codes

    Energy Technology Data Exchange (ETDEWEB)

    Pietrzak, Robert [Department of Nuclear Physics and Its Applications, Institute of Physics, University of Silesia, Katowice (Poland); Konefał, Adam, E-mail: adam.konefal@us.edu.pl [Department of Nuclear Physics and Its Applications, Institute of Physics, University of Silesia, Katowice (Poland); Sokół, Maria; Orlef, Andrzej [Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Center, Institute of Oncology, Gliwice (Poland)

    2016-08-01

    The success of proton therapy depends strongly on the precision of treatment planning. Dose distribution in biological tissue may be obtained from Monte Carlo simulations using various scientific codes making it possible to perform very accurate calculations. However, there are many factors affecting the accuracy of modeling. One of them is a structure of objects called bins registering a dose. In this work the influence of bin structure on the dose distributions was examined. The MCNPX code calculations of Bragg curve for the 60 MeV proton beam were done in two ways: using simple logical detectors being the volumes determined in water, and using a precise model of ionization chamber used in clinical dosimetry. The results of the simulations were verified experimentally in the water phantom with Marcus ionization chamber. The average local dose difference between the measured relative doses in the water phantom and those calculated by means of the logical detectors was 1.4% at first 25 mm, whereas in the full depth range this difference was 1.6% for the maximum uncertainty in the calculations less than 2.4% and for the maximum measuring error of 1%. In case of the relative doses calculated with the use of the ionization chamber model this average difference was somewhat greater, being 2.3% at depths up to 25 mm and 2.4% in the full range of depths for the maximum uncertainty in the calculations of 3%. In the dose calculations the ionization chamber model does not offer any additional advantages over the logical detectors. The results provided by both models are similar and in good agreement with the measurements, however, the logical detector approach is a more time-effective method. - Highlights: • Influence of the bin structure on the proton dose distributions was examined for the MC simulations. • The considered relative proton dose distributions in water correspond to the clinical application. • MC simulations performed with the logical detectors and the

  2. SU‐C‐105‐05: Reference Dosimetry of High‐Energy Electron Beams with a Farmer‐Type Ionization Chamber

    Energy Technology Data Exchange (ETDEWEB)

    Muir, B; Rogers, D [Carleton University, Ottawa, ON (Canada)

    2013-06-15

    Purpose: To investigate gradient effects and provide Monte Carlo calculated beam quality conversion factors to characterize the Farmer‐type NE2571 ion chamber for high‐energy reference dosimetry of clinical electron beams. Methods: The EGSnrc code system is used to calculate the absorbed dose to water and to the gas in a fully modeled NE2571 chamber as a function of depth in a water phantom. Electron beams incident on the surface of the phantom are modeled using realistic BEAMnrc accelerator simulations and electron beam spectra. Beam quality conversion factors are determined using calculated doses to water and to air in the chamber in high‐energy electron beams and in a cobalt‐60 reference field. Calculated water‐to‐air stopping power ratios are employed for investigation of the overall ion chamber perturbation factor. Results: An upstream shift of 0.3–0.4 multiplied by the chamber radius, r-cav, both minimizes the variation of the overall ion chamber perturbation factor with depth and reduces the difference between the beam quality specifier (R{sub 5} {sub 0}) calculated using ion chamber simulations and that obtained with simulations of dose‐to‐water in the phantom. Beam quality conversion factors are obtained at the reference depth and gradient effects are optimized using a shift of 0.2r-cav. The photon‐electron conversion factor, k-ecal, amounts to 0.906 when gradient effects are minimized using the shift established here and 0.903 if no shift of the data is used. Systematic uncertainties in beam quality conversion factors are investigated and amount to between 0.4 to 1.1% depending on assumptions used. Conclusion: The calculations obtained in this work characterize the use of an NE2571 ion chamber for reference dosimetry of high‐energy electron beams. These results will be useful as the AAPM continues to review their reference dosimetry protocols.

  3. Study of the ventilation at ATLAS cavern UX15 air velocity and temperature around the muon chambers

    CERN Document Server

    Vigo-Castellví, E

    2000-01-01

    The Muon Chambers of ATLAS detector cannot work under temperature differences between two opposed faces above 3 K. In addition, a low velocity of the air around the Muon Chambers is essential to avoid vibration problems. The CV group at the ST division is involved in an airflow simulation inside UX15 cavern to check air temperature and velocity profiles around the ATLAS Muon Chambers. In this paper, the status and the content of the performed theoretical studies will be explained. Three simulation models, which helped to understand the Muon Spectrometer thermal environment and the efficiency of the ventilation system at ATLAS cavern, will be presented. Besides, it will be shown how these studies support the proposal of a deeper individual Muon Chamber study.

  4. Upper-room ultraviolet light and negative air ionization to prevent tuberculosis transmission.

    Directory of Open Access Journals (Sweden)

    A Roderick Escombe

    2009-03-01

    Full Text Available BACKGROUND: Institutional tuberculosis (TB transmission is an important public health problem highlighted by the HIV/AIDS pandemic and the emergence of multidrug- and extensively drug-resistant TB. Effective TB infection control measures are urgently needed. We evaluated the efficacy of upper-room ultraviolet (UV lights and negative air ionization for preventing airborne TB transmission using a guinea pig air-sampling model to measure the TB infectiousness of ward air. METHODS AND FINDINGS: For 535 consecutive days, exhaust air from an HIV-TB ward in Lima, Perú, was passed through three guinea pig air-sampling enclosures each housing approximately 150 guinea pigs, using a 2-d cycle. On UV-off days, ward air passed in parallel through a control animal enclosure and a similar enclosure containing negative ionizers. On UV-on days, UV lights and mixing fans were turned on in the ward, and a third animal enclosure alone received ward air. TB infection in guinea pigs was defined by monthly tuberculin skin tests. All guinea pigs underwent autopsy to test for TB disease, defined by characteristic autopsy changes or by the culture of Mycobacterium tuberculosis from organs. 35% (106/304 of guinea pigs in the control group developed TB infection, and this was reduced to 14% (43/303 by ionizers, and to 9.5% (29/307 by UV lights (both p < 0.0001 compared with the control group. TB disease was confirmed in 8.6% (26/304 of control group animals, and this was reduced to 4.3% (13/303 by ionizers, and to 3.6% (11/307 by UV lights (both p < 0.03 compared with the control group. Time-to-event analysis demonstrated that TB infection was prevented by ionizers (log-rank 27; p < 0.0001 and by UV lights (log-rank 46; p < 0.0001. Time-to-event analysis also demonstrated that TB disease was prevented by ionizers (log-rank 3.7; p = 0.055 and by UV lights (log-rank 5.4; p = 0.02. An alternative analysis using an airborne infection model demonstrated that ionizers prevented

  5. Dynamics of ionization processes in high-pressure nitrogen, air, and SF{sub 6} during a subnanosecond breakdown initiated by runaway electrons

    Energy Technology Data Exchange (ETDEWEB)

    Tarasenko, V. F., E-mail: vft@loi.hcei.tsc.ru; Beloplotov, D. V.; Lomaev, M. I. [Siberian Branch, Russian Academy of Sciences, Institute of High-Current Electronics (Russian Federation)

    2015-10-15

    The dynamics of ionization processes in high-pressure nitrogen, air, and SF{sub 6} during breakdown of a gap with a nonuniform distribution of the electric field by nanosecond high-voltage pulses was studied experimentally. Measurements of the amplitude and temporal characteristics of a diffuse discharge and its radiation with a subnanosecond time resolution have shown that, at any polarity of the electrode with a small curvature radius, breakdown of the gap occurs via two ionization waves, the first of which is initiated by runaway electrons. For a voltage pulse with an ∼500-ps front, UV radiation from different zones of a diffuse discharge is measured with a subnanosecond time resolution. It is shown that the propagation velocity of the first ionization wave increases after its front has passed one-half of the gap, as well as when the pressure in the discharge chamber is reduced and/or when SF{sub 6} is replaced with air or nitrogen. It is found that, at nitrogen pressures of 0.4 and 0.7 MPa and the positive polarity of the high-voltage electrode with a small curvature radius, the ionization wave forms with a larger (∼30 ps) time delay with respect to applying the voltage pulse to the gap than at the negative polarity. The velocity of the second ionization wave propagating from the plane electrode is measured. In a discharge in nitrogen at a pressure of 0.7 MPa, this velocity is found to be ∼10 cm/ns. It is shown that, as the nitrogen pressure increases to 0.7 MPa, the propagation velocity of the front of the first ionization wave at the positive polarity of the electrode with a small curvature radius becomes lower than that at the negative polarity.

  6. SU-E-T-645: Qualification of a 2D Ionization Chamber Array for Beam Steering and Profile Measurement

    Energy Technology Data Exchange (ETDEWEB)

    Gao, S [MD Anderson Cancer Ctr., Houston, TX (United States); Balter, P [UT MD Anderson Cancer Center, Houston, TX (United States); Rose, M [Sun Nuclear Inc., Melbourne, FL (Australia); Simon, W [Sun Nuclear Corp, Melbourne, FL (Australia)

    2015-06-15

    Purpose: Establish a procedure for beam steering and profile measurement using a 2D ionization chamber array and show equivalence to a water scanning system. Methods: Multiple photon beams (30×30cm{sup 2} field) and electron beams (25×25cm{sup 2} cone) were steered in the radial and transverse directions using Sun Nuclear’s IC PROFILER (ICP). Solid water was added during steering to ensure measurements were beyond the buildup region. With steering complete, servos were zeroed and enabled. Photon profiles were collected in a 30×30cm{sup 2} field at dmax and 2.9 cm depth for flattened and FFF beams respectively. Electron profiles were collected with a 25×25cm{sup 2} cone and effective depth (solid water + 0.9 cm intrinsic buildup) as follows: 0.9 cm (6e), 1.9 cm (9e), 2.9 cm (12e, 16e, 20e). Profiles of the same energy, field size and depth were measured in water with Sun Nuclear’s 3D SCANNER (3DS). Profiles were re-measured using the ICP after the in-water scans. Profiles measured using the ICP and 3DS were compared by (a) examining the differences in Varian’s “Point Difference Symmetry” metric, (b) visual inspection of the overlaid profile shapes and (c) calculation of point-by-point differences. Results: Comparing ICP measurements before and after water scanning showed very good agreement indicating good stability of the linac and measurement system. Comparing ICP Measurements to water phantom measurements using Varian’s symmetry metric showed agreement within 0.5% for all beams. The average magnitude of the agreement was within 0.2%. Comparing ICP Measurements to water phantom measurements using point-by-point difference showed agreement within 0.5% inside of 80% area of the field width. Conclusion: Profile agreement to within 0.5% was observed between ICP and 3DS after steering multiple energies with the ICP. This indicates that the ICP may be used for steering electron beams, and both flattened and FFF photon beams. Song Gao: Sun Nuclear

  7. Monte Carlo simulations and benchmark measurements on the response of TE(TE) and Mg(Ar) ionization chambers in photon, electron and neutron beams

    Science.gov (United States)

    Lin, Yi-Chun; Huang, Tseng-Te; Liu, Yuan-Hao; Chen, Wei-Lin; Chen, Yen-Fu; Wu, Shu-Wei; Nievaart, Sander; Jiang, Shiang-Huei

    2015-06-01

    The paired ionization chambers (ICs) technique is commonly employed to determine neutron and photon doses in radiology or radiotherapy neutron beams, where neutron dose shows very strong dependence on the accuracy of accompanying high energy photon dose. During the dose derivation, it is an important issue to evaluate the photon and electron response functions of two commercially available ionization chambers, denoted as TE(TE) and Mg(Ar), used in our reactor based epithermal neutron beam. Nowadays, most perturbation corrections for accurate dose determination and many treatment planning systems are based on the Monte Carlo technique. We used general purposed Monte Carlo codes, MCNP5, EGSnrc, FLUKA or GEANT4 for benchmark verifications among them and carefully measured values for a precise estimation of chamber current from absorbed dose rate of cavity gas. Also, energy dependent response functions of two chambers were calculated in a parallel beam with mono-energies from 20 keV to 20 MeV photons and electrons by using the optimal simple spherical and detailed IC models. The measurements were performed in the well-defined (a) four primary M-80, M-100, M120 and M150 X-ray calibration fields, (b) primary 60Co calibration beam, (c) 6 MV and 10 MV photon, (d) 6 MeV and 18 MeV electron LINACs in hospital and (e) BNCT clinical trials neutron beam. For the TE(TE) chamber, all codes were almost identical over the whole photon energy range. In the Mg(Ar) chamber, MCNP5 showed lower response than other codes for photon energy region below 0.1 MeV and presented similar response above 0.2 MeV (agreed within 5% in the simple spherical model). With the increase of electron energy, the response difference between MCNP5 and other codes became larger in both chambers. Compared with the measured currents, MCNP5 had the difference from the measurement data within 5% for the 60Co, 6 MV, 10 MV, 6 MeV and 18 MeV LINACs beams. But for the Mg(Ar) chamber, the derivations reached 7

  8. SU-E-T-460: Impact of the LINAC Repetition Rate On a High-Resolution Liquid Ionization Chamber Array for Patient-Specific QA

    Energy Technology Data Exchange (ETDEWEB)

    Wang, S; Driewer, J; Zheng, D; Lei, Y; Zhang, Q; Zhu, X; Li, S; Enke, C; Zhou, S [University of Nebraska Medical Center, Omaha, NE (United States); Xu, B [The Fujian Medical University Union Hospital, Fu Zhou, Fu Jian (China)

    2015-06-15

    Purpose: The purpose of this study is to investigate the LINAC repetition-rate (dose-rate) dependence of OCTAVIUS 1000SRS liquid ionization chamber (LIC) array for patient specific QA of SRT plans delivered with flattening-filter-free (FFF) beams. Methods: 1) The repetition-rate dependence of 1000SRS was measured in a phantom constructed with 5-cm solid water above and below the array for build-up and backscatter. A 0.3cc calibrated ion chamber was also placed along the central axis 2.3cm below the center chamber of the array for normalizing LINAC output fluctuation. The signals from the center chamber of the array under different repetition rates in the range of 400–2400 MU/min for 6xFFF and 10xFFF beams on a Varian TrueBeamSTx LINAC, normalized by the independent chamber readings, were analyzed for the array response dependence on repetition rates. 2) Twelve Step-and-shoot IMRS QA plans (6xFFF and 10xFFF) were delivered to the array under different repetition rates for analysis and comparison. 3) The absolute doses measured by the center chamber were compared to measurements using an independent ionization chamber with the identical setup, taken as the gold standard. 4) The correction factors based on the actual delivery repetition rate were applied to the measurements, and the results were compared again to the gold standard. Results: 1) The 1000SRS array exhibited repetition-rate dependence for FFF beams, up to 5% for 6xFFF and 10% for 10xFFF; 2) The array showed clinically-acceptable repetition-rate dependence for regular flattened beams; 3) This repetition-rate dependence significantly affected the measurement accuracy, thereby affecting IMRS QA results; 4) By applying an empirical repetition-rate correction, the corrected measurements agreed better with the gold standard ion chamber measurements. Conclusion: OCTAVIUS 1000SRS LIC array exhibited considerable repetition-rate dependence for FFF beams, which will affect the accuracy of the absolute QA

  9. Correction factors for A1SL ionization chamber dosimetry in TomoTherapy: Machine-specific, plan-class, and clinical fields

    Energy Technology Data Exchange (ETDEWEB)

    Gago-Arias, Araceli; Rodriguez-Romero, Ruth; Sanchez-Rubio, Patricia; Miguel Gonzalez-Castano, Diego; Gomez, Faustino; Nunez, Luis; Palmans, Hugo; Sharpe, Peter; Pardo-Montero, Juan [Departamento de Fisica de Particulas, Facultad de Fisica, Universidad de Santiago de Compostela (Spain); Servicio de Radiofisica, Hospital Universitario Puerta de Hierro, Madrid 28222 (Spain); Departamento de Fisica de Particulas, Facultad de Fisica, Universidad de Santiago de Compostela, 15782 (Spain) and Radiation Physics Laboratory, Universidad de Santiago de Compostela, 15782 (Spain); Servicio de Radiofisica, Hospital Universitario Puerta de Hierro, Madrid, 28222 (Spain); National Physical Laboratory, Teddington, Middx, TW11 OLW (United Kingdom); Departamento de Fisica de Particulas, Facultad de Fisica, Universidad de Santiago de Compostela, 15782 (Spain)

    2012-04-15

    Purpose: Recently, an international working group on nonstandard fields presented a new formalism for ionization chamber reference dosimetry of small and nonstandard fields [Alfonso et al., Med. Phys. 35, 5179-5186 (2008)] which has been adopted by AAPM TG-148. This work presents an experimental determination of the correction factors for reference dosimetry with an Exradin A1SL thimble ionization chamber in a TomoTherapy unit, focusing on: (i) machine-specific reference field, (ii) plan-class-specific reference field, and (iii) two clinical treatments. Methods: Ionization chamber measurements were performed in the TomoTherapy unit for intermediate (machine-specific and plan-class-specific) calibration fields, based on the reference conditions defined by AAPM TG-148, and two clinical treatments (lung and head-and-neck). Alanine reference dosimetry was employed to determine absorbed dose to water at the point of interest for the fields under investigation. The corresponding chamber correction factors were calculated from alanine to ionization chamber measurements ratios. Results: Two different methods of determining the beam quality correction factor k{sub Q,Q{sub 0}} for the A1SL ionization chamber in this TomoTherapy unit, where reference conditions for conventional beam quality determination cannot be met, result in consistent values. The observed values of overall correction factors obtained for intermediate and clinical fields are consistently around 0.98 with a typical expanded relative uncertainty of 2% (k = 2), which when considered make such correction factors compatible with unity. However, all of them are systematically lower than unity, which is shown to be significant when a hypothesis test assuming a t-student distribution is performed (p=1.8x10{sup -2}). Correction factors k{sub Q{sub c{sub l{sub i{sub n,Q{sub p{sub c{sub s{sub r}{sup f{sub c}{sub l}{sub i}{sub n},f{sub p}{sub c}{sub s}{sub r}}}}}}}}}} and k{sub Q{sub c{sub l{sub i{sub n,Q{sub m{sub s

  10. Heat insulation of combustion chamber walls - A measure to decrease the fuel consumption of I. C. engines

    Energy Technology Data Exchange (ETDEWEB)

    Woschni, G.; Spindler, W.; Kolesa, K.

    1987-01-01

    Experimental investigations were made with a single-cylinder direct-injection Diesel engine with heat-insulated piston. The most important result is an inferior economy compared with the not insulated aluminum-piston engine. It was found that this phenomenon is not caused by neither a changed combustion process nor increased blowby nor different friction losses, but rather by a drastic increase of the heat transfer coefficient during the first part of combustion with increasing surface temperature. This is taken into account in a modified equation for the heat transfer coefficient. Cycle-simulations using this modified equation show that there is neither a gain in fuel economy of naturally aspirated nor of turbocharged nor of turbocompound Diesel engines with ''heat insulated'' combustion chamber walls.

  11. [Experimental investigation of the collection efficiency of a PTW Roos ionization chamber irradiated with pulsed beams at high pulse dose with different pulse lengths].

    Science.gov (United States)

    Karsch, Leonhard; Richter, Christian; Pawelke, Jörg

    2011-01-01

    In gas-filled ionization chambers as radiation detectors, the collection of the charge carriers is affected by the recombination effect. In dosimetry this effect must be accounted for by the saturation correction factor k(S). The physical description of the correction factor by Boag, Hochhäuser and Balk for pulsed radiation is well established. However, this description is only accurate when the pulse length is short compared to the collection time of the ionization chamber. In this work experimental investigations of the saturation correction factor have been made for pulses of 4 μ s up to pulse doses of about 230 mGy, and the theory of Boag, Hochhäuser and Balk was again confirmed. For longer pulses, however, the correction factor decreases and at a pulse duration of about 200μs reaches 75% of the value valid for short pulses. This reduced influence of the ion recombination is interpreted by the reaction kinetics of ion recombination as a second-order reaction. This effect is negligible for PTW Roos chambers at clinical linear accelerators with 4 μ s pulse duration for pulse doses up to 120 mGy.

  12. Response of the first wetted wall of an IFE reactor chamber to the energy release from a direct-drive DT capsule

    Science.gov (United States)

    Medin, Stanislav A.; Basko, Mikhail M.; Orlov, Yurii N.; Suslin, Victor M.

    2012-07-01

    Radiation hydrodynamics 1D simulations were performed with two concurrent codes, DEIRA and RAMPHY. The DEIRA code was used for DT capsule implosion and burn, and the RAMPHY code was used for computation of X-ray and fast ions deposition in the first wall liquid film of the reactor chamber. The simulations were run for 740 MJ direct drive DT capsule and Pb thin liquid wall reactor chamber of 10 m diameter. Temporal profiles for DT capsule leaking power of X-rays, neutrons and fast 4He ions were obtained and spatial profiles of the liquid film flow parameter were computed and analyzed.

  13. A simplified analytical approach to estimate the parameters required for strength determination of HDR 192Ir brachytherapy sources using a Farmer-type ionization chamber.

    Science.gov (United States)

    Kumar, Sudhir; Srinivasan, P; Sharma, S D; Mayya, Y S

    2012-01-01

    Measuring the strength of high dose rate (HDR) (192)Ir brachytherapy sources on receipt from the vendor is an important component of a quality assurance program. Owing to their ready availability in radiotherapy departments, the Farmer-type ionization chambers are also used to determine the strength of HDR (192)Ir brachytherapy sources. The use of a Farmer-type ionization chamber requires the estimation of the scatter correction factor along with positioning error (c) and the constant of proportionality (f) to determine the strength of HDR (192)Ir brachytherapy sources. A simplified approach based on a least squares method was developed for estimating the values of f and M(s). The seven distance method was followed to record the ionization chamber readings for parameterization of f and M(s). Analytically calculated values of M(s) were used to determine the room scatter correction factor (K(sc)). The Monte Carlo simulations were also carried out to calculate f and K(sc) to verify the magnitude of the parameters determined by the proposed analytical approach. The value of f determined using the simplified analytical approach was found to be in excellent agreement with the Monte Carlo simulated value (within 0.7%). Analytically derived values of K(sc) were also found to be in good agreement with the Monte Carlo calculated values (within 1.47%). Being far simpler than the presently available methods of evaluating f, the proposed analytical approach can be adopted for routine use by clinical medical physicists to estimate f by hand calculations.

  14. Calculation of 18F, 99mTc, 111In and 123I calibration factor using the penelope ionization chamber simulation method.

    Science.gov (United States)

    Amiot, M N

    2004-01-01

    A new method using the Monte Carlo code PENELOPE for ionization chamber simulation has already been successfully used for calculating calibration factors needed for the measurements of radionuclides with photon emission (2003, Appl. Radiat. Isot., to be published). This work has been continued at (Laboratoire National Henri Becquerel) in order to calculate the calibration factors for radionuclides with short half-lives used in medical services. Activity measurements of 18F, 99mTc,111In and 123I using the calculated calibration factors were obtained with standard uncertainties equal to 0.6% for 18F, 99mTc and 1.5% for 111In and 123I.

  15. (18)F primary standard at ENEA-INMRI by three absolute techniques and calibration of a well-type IG11 ionization chamber.

    Science.gov (United States)

    Capogni, Marco; Carconi, Pierluigi; De Felice, Pierino; Fazio, Aldo

    2016-03-01

    A new (18)F primary standardization carried out at ENEA-INMRI by three different absolute techniques, i.e. 4πγNaI(Tl)γ high-efficiency counting, TDCR and 4πβ(LS)-γ[NaI(Tl)] coincidence counting method, allowed the calibration of a fixed well-reentrant IG11 ionization chamber (IC), with an uncertainty lower than 1%, and to check the calibration factor of a portable well-type IC NPL-CRC model, previously calibrated. By the new standard the ENEA-INMRI was linked to the BIPM International Reference System (SIR) through the BIPM SIR Transfer Instrument (SIRTI).

  16. Standardization of 64Cu and 68Ga by the 4π(PC)β-γ coincidence method and calibration of the ionization chamber.

    Science.gov (United States)

    Sahagia, M; Luca, A; Antohe, A; Ivan, C

    2012-09-01

    The paper treats the application of the 4π(PC)β-γ coincidence method for the standardization of the radionuclides (64)Cu and (68)Ga. The general coincidence equations are written. Two types of extrapolation were described and used in measurement: the positron-annihilation coincidence, and the counting of all emitted radiations; both methods are compared with respect to results, advantages and drawbacks. The impurities' content correction was applied. The standardized solutions were used to calibrate the ionization chamber CENTRONIC IG12/20A and to determine the gamma-rays emission intensities.

  17. Modelling ELM heat flux deposition on the ITER main chamber wall

    Energy Technology Data Exchange (ETDEWEB)

    Kočan, M., E-mail: martin.kocan@iter.org [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, F-13067 St Paul lez Durance Cedex (France); Pitts, R.A.; Lisgo, S.W.; Loarte, A. [ITER Organization, Route de Vinon-sur-Verdon, CS 90 046, F-13067 St Paul lez Durance Cedex (France); Gunn, J.P. [Association Euratom-CEA, CEA/DSM/IRFM, Cadarache, 13108 Saint-Paul-lez-Durance (France); Fuchs, V. [Institute of Plasma Physics, Association EURATOM/IPP.CR, Praha 18200 (Czech Republic)

    2015-08-15

    The interaction of ELM filaments with the ITER beryllium first wall panels (FWPs) is studied using a simple ad-hoc fluid model of the filament parallel transport, taking into account the full, three-dimensional structure of the FWPs, including magnetic shadowing effects. The calculated ELM surface heat loads are used as input to the RACLETTE heat transfer code to estimate the FWP surface temperature rise. The results indicate that controlled ELMs in ITER during burning plasma operation (ΔW{sub ELM} ≈ 0.6 M J) will not lead to melting or significant evaporation of the beryllium surfaces, even in the case of high ELM broadening and the minimum allowable distance between the primary and secondary separatrices. The ELM-averaged steady-state heat load also stays below the maximum power handling capability of the FWPs.

  18. Spectroscopic analysis of high electric field enhanced ionization in laser filaments in air for corona guiding

    Institute of Scientific and Technical Information of China (English)

    Yingxia Wei; Yaoxiang Liu; Tie-Jun Wang; Na Chen; Jingjing Ju; Yonghong Liu; Haiyi Sun; Cheng Wang; Jiansheng Liu; Haihe Lu; See Leang Chin; Ruxin Li

    2016-01-01

    We report on a systematic experimental study on the fluorescence spectra produced from a femtosecond laser filament in air under a high electric field. The electric field alone was strong enough to create corona discharge(CD). Fluorescence spectra from neutral and ionic air molecules were measured and compared with pure high-voltage CD and pure laser filamentation(FIL). Among them, high electric field assisted laser FIL produced nitrogen fluorescence more efficiently than either pure CD or pure FIL processes. The nonlinear enhancement of fluorescence from the interaction of the laser filament and corona discharging electric field resulted in a more efficient ionization along the laser filament zone, which was confirmed by the spectroscopic measurement of both ionization-induced fluorescence and plasma-scattered 800 nm laser pulses. This is believed to be the key precursor process for filament-guided discharge.

  19. Portable meter study of ionizing radiation Teletector in high rates of air kerma

    Energy Technology Data Exchange (ETDEWEB)

    Damatto, Willian Behling; Potiens, Maria da Penha A.; Vivolo, Vitor, E-mail: willbdamatto@gmail.com [Instituto de Pesquisas Energeticas e Nucleres (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2015-07-01

    A set of portable meters of ionizing radiation high rates of air kerma (teletectors) commonly used in emergencies in Brazil and sent to the Calibration Laboratory of IPEN were under several tests and analyst is parameters for the detectors behavior were established. Applied tests were: energy dependence and primarily overload with the new irradiation system. Thus it was possible to determine the most common characteristic found in these equipment (quality control programs) and new calibration criteria were established following international recommendations. (author)

  20. A COMPARATIVE EVALUATION OF EFFECT OF SODIUM HYPOCHLORITE ON MICROTENSILE BOND STRENGTH OF THREE DIFFERENT BONDING AGENTS TO THE LATERAL WALLS OF PULP CHAMBER: AN IN VITRO STUDY

    Directory of Open Access Journals (Sweden)

    Bhat Gowrish S.

    2013-03-01

    Full Text Available The advent of adhesive materials has revolutionized the field of restorative dentistry. Lack of adhesion and sealing between the final restoration and tooth structure may lead to microleakage and ultimate failure of the restoration. These adhesive restorations are also being used in the field of endodontics. A good coronal seal is very important, since the penetration of microorganisms from a coronal direction can reinfect the root canal system and affect the prognosis of the non-surgical root canal therapy. Coronal leakage is particularly significant in multi rooted teeth, in which accessory canal may allow inflammatory change to occur in the periodontal tissues from the pulp chambers. Improper restoration can lead to loss of endodontically treated teeth more than actual failure of endodontic therapy. The restorations with adhesive systems offer the advantage of transmission of functional stresses across the bonded interface to the tooth (mono bloc restoration and potentially reinforce the weakened tooth structure. Bonding to pulp chamber lateral walls is different from bonding other dentinal surface. The structure of pulp chamber wall is complicated and not much is known about the bonding characteristics of pulp chamber, it becomes essential to study the same. This study was done evaluate the effect of sodium hypochlorite on bond strength of bonding agent to the lateral walls of the pulp chamber. However, chemical irrigants, such as sodium hypochlorite used in the endodontic treatment have been shown to affect the bond strength of resin composite to dentin adversely.

  1. Air flow assisted ionization for remote sampling of ambient mass spectrometry and its application.

    Science.gov (United States)

    He, Jiuming; Tang, Fei; Luo, Zhigang; Chen, Yi; Xu, Jing; Zhang, Ruiping; Wang, Xiaohao; Abliz, Zeper

    2011-04-15

    Ambient ionization methods are an important research area in mass spectrometry (MS) analysis. Under ambient conditions, the gas flow and atmospheric pressure significantly affect the transfer and focusing of ions. The design and implementation of air flow assisted ionization (AFAI) as a novel and effective, remote sampling method for ambient mass spectrometry are described herein. AFAI benefits from a high extracting air flow rate. A systematic investigation of the extracting air flow in the AFAI system has been carried out, and it has been demonstrated not only that it plays a role in the effective capture and remote transport of charged droplets, but also that it promotes desolvation and ion formation, and even prevents ion fragmentation during the ionization process. Moreover, the sensitivity of remote sampling ambient MS analysis was improved significantly by the AFAI method. Highly polar and nonpolar molecules, including dyes, pharmaceutical samples, explosives, drugs of abuse, protein and volatile compounds, have been successfully analyzed using AFAI-MS. The successful application of the technique to residue detection on fingers, large object analysis and remote monitoring in real time indicates its potential for the analysis of a variety of samples, especially large objects. The ability to couple this technique with most commercially available MS instruments with an API interface further enhances its broad applicability.

  2. Accuracy of the electron transport in mcnp5 and its suitability for ionization chamber response simulations: A comparison with the egsnrc and penelope codes

    Energy Technology Data Exchange (ETDEWEB)

    Koivunoro, Hanna; Siiskonen, Teemu; Kotiluoto, Petri; Auterinen, Iiro; Hippelaeinen, Eero; Savolainen, Sauli [Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki University (Finland) and Department of Oncology, Helsinki University Central Hospital, FI-00029 HUS (Finland); STUK-Radiation and Nuclear Safety Authority, P.O. Box 14, FI-00881 Helsinki (Finland); VTT Technical Research Centre of Finland, P.O. Box 1000, FI-02044 VTT (Finland); Department of Physics, University of Helsinki, P.O. Box 64, FI-00014 Helsinki University (Finland); HUS Medical Imaging Centre, Helsinki University Central Hospital, FI-00029 HUS (Finland)

    2012-03-15

    Purpose: In this work, accuracy of the mcnp5 code in the electron transport calculations and its suitability for ionization chamber (IC) response simulations in photon beams are studied in comparison to egsnrc and penelope codes. Methods: The electron transport is studied by comparing the depth dose distributions in a water phantom subdivided into thin layers using incident energies (0.05, 0.1, 1, and 10 MeV) for the broad parallel electron beams. The IC response simulations are studied in water phantom in three dosimetric gas materials (air, argon, and methane based tissue equivalent gas) for photon beams ({sup 60}Co source, 6 MV linear medical accelerator, and mono-energetic 2 MeV photon source). Two optional electron transport models of mcnp5 are evaluated: the ITS-based electron energy indexing (mcnp5{sub ITS}) and the new detailed electron energy-loss straggling logic (mcnp5{sub new}). The electron substep length (ESTEP parameter) dependency in mcnp5 is investigated as well. Results: For the electron beam studies, large discrepancies (>3%) are observed between the mcnp5 dose distributions and the reference codes at 1 MeV and lower energies. The discrepancy is especially notable for 0.1 and 0.05 MeV electron beams. The boundary crossing artifacts, which are well known for the mcnp5{sub ITS}, are observed for the mcnp5{sub new} only at 0.1 and 0.05 MeV beam energies. If the excessive boundary crossing is eliminated by using single scoring cells, the mcnp5{sub ITS} provides dose distributions that agree better with the reference codes than mcnp5{sub new}. The mcnp5 dose estimates for the gas cavity agree within 1% with the reference codes, if the mcnp5{sub ITS} is applied or electron substep length is set adequately for the gas in the cavity using the mcnp5{sub new}. The mcnp5{sub new} results are found highly dependent on the chosen electron substep length and might lead up to 15% underestimation of the absorbed dose. Conclusions: Since the mcnp5 electron

  3. Effects of hydraulic pressure on the performance of single chamber air-cathode microbial fuel cells.

    Science.gov (United States)

    Cheng, Shaoan; Liu, Weifeng; Guo, Jian; Sun, Dan; Pan, Bin; Ye, Yaoli; Ding, Weijun; Huang, Haobin; Li, Fujian

    2014-06-15

    Scaling up of microbial fuel cells (MFCs) without losing power density requires a thorough understanding of the effect of hydraulic pressure on MFC performance. In this work, the performance of an activated carbon air-cathode MFC was evaluated under different hydraulic pressures. The MFC under 100 mmH2O hydraulic pressure produced a maximum power density of 1260 ± 24 mW m(-2), while the power density decreased by 24.4% and 44.7% as the hydraulic pressure increased to 500 mmH2O and 2000 mmH2O, respectively. Notably, the performance of both the anode and the cathode had decreased under high hydraulic pressures. Electrochemical impedance spectroscopy tests of the cathode indicated that both charge transfer resistance and diffusion transfer resistance increased with the increase in hydraulic pressure. Denaturing gradient gel electrophoresis of PCR-amplified partial 16S rRNA genes demonstrated that the similarity among anodic biofilm communities under different hydraulic pressures was ≥ 90%, and the communities of all MFCs were dominated by Geobacter sp. These results suggested that the reduction in power output of the single chamber air-cathode MFC under high hydraulic pressures can be attributed to water flooding of the cathode and suppression the metabolism of anodic exoelectrogenic bacteria.

  4. A single-chamber microbial fuel cell without an air cathode.

    Science.gov (United States)

    Nimje, Vanita Roshan; Chen, Chien-Cheng; Chen, Hau-Ren; Chen, Chien-Yen; Tseng, Min-Jen; Cheng, Kai-Chien; Shih, Ruey-Chyuan; Chang, Young-Fo

    2012-01-01

    Microbial fuel cells (MFCs) represent a novel technology for wastewater treatment with electricity production. Electricity generation with simultaneous nitrate reduction in a single-chamber MFC without air cathode was studied, using glucose (1 mM) as the carbon source and nitrate (1 mM) as the final electron acceptor employed by Bacillus subtilis under anaerobic conditions. Increasing current as a function of decreased nitrate concentration and an increase in biomass were observed with a maximum current of 0.4 mA obtained at an external resistance (R(ext)) of 1 KΩ without a platinum catalyst of air cathode. A decreased current with complete nitrate reduction, with further recovery of the current immediately after nitrate addition, indicated the dependence of B. subtilis on nitrate as an electron acceptor to efficiently produce electricity. A power density of 0.0019 mW/cm(2) was achieved at an R(ext) of 220 Ω. Cyclic voltammograms (CV) showed direct electron transfer with the involvement of mediators in the MFC. The low coulombic efficiency (CE) of 11% was mainly attributed to glucose fermentation. These results demonstrated that electricity generation is possible from wastewater containing nitrate, and this represents an alternative technology for the cost-effective and environmentally benign treatment of wastewater.

  5. A Single-Chamber Microbial Fuel Cell without an Air Cathode

    Directory of Open Access Journals (Sweden)

    Ruey-Chyuan Shih

    2012-03-01

    Full Text Available Microbial fuel cells (MFCs represent a novel technology for wastewater treatment with electricity production. Electricity generation with simultaneous nitrate reduction in a single-chamber MFC without air cathode was studied, using glucose (1 mM as the carbon source and nitrate (1 mM as the final electron acceptor employed by Bacillus subtilis under anaerobic conditions. Increasing current as a function of decreased nitrate concentration and an increase in biomass were observed with a maximum current of 0.4 mA obtained at an external resistance (Rext of 1 KΩ without a platinum catalyst of air cathode. A decreased current with complete nitrate reduction, with further recovery of the current immediately after nitrate addition, indicated the dependence of B. subtilis on nitrate as an electron acceptor to efficiently produce electricity. A power density of 0.0019 mW/cm2 was achieved at an Rext of 220 Ω. Cyclic voltammograms (CV showed direct electron transfer with the involvement of mediators in the MFC. The low coulombic efficiency (CE of 11% was mainly attributed to glucose fermentation. These results demonstrated that electricity generation is possible from wastewater containing nitrate, and this represents an alternative technology for the cost-effective and environmentally benign treatment of wastewater.

  6. Quantitative and enantioselective analysis of monoterpenes from plant chambers and in ambient air using SPME

    Directory of Open Access Journals (Sweden)

    N. Yassaa

    2010-08-01

    Full Text Available A solid-phase microextraction (HS-SPME and gas chromatography/mass spectrometry (GC/MS system has been developed for quantifying enantiomeric and nonenantiomeric monoterpenes in plant chamber studies and ambient air. Performance of this system was checked using a capillary diffusion system to produce monoterpene standards. The adsorption efficiency, competitive adsorption and chromatographic peak resolution of monoterpene enantiomer pairs were compared for three SPME fibre coatings: 75 μm Carboxen-PDMS (CAR-PDMS, 50/30 μm, divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS and 65 μm divinylbenzene-polydimethyl-siloxane (DVB-PDMS. Key parameters such as the linearity and reproducibility of the SPME system have been investigated in this work. The best compromise between the enantiomeric separation of monoterpenes and competitive adsorption of the isoprenoids on the solid SPME fibre coating was found for DVB-PDMS fibres. The optimum conditions using DVB-PDMS fibres were applied to measure the exchange rates of monoterpenes in the emission of Quercus ilex using a laboratory whole plant enclosure under light and dark conditions, as well as in ambient air. With 592 and 223 ng m−2 s−1, respectively, β-myrcene and limonene were the predominant monoterpenes in the emission of Q. ilex. These values were closely comparable to those obtained using a zNose and cartridge GC-FID systems.

  7. Quantitative and enantioselective analysis of monoterpenes from plant chambers and in ambient air using SPME

    Directory of Open Access Journals (Sweden)

    N. Yassaa

    2010-11-01

    Full Text Available A headspace solid-phase microextraction (HS-SPME and gas chromatography/mass spectrometry (GC/MS system has been developed for quantifying enantiomeric and nonenantiomeric monoterpenes in plant chamber studies and ambient air. Performance of this system was checked using a capillary diffusion system to produce monoterpene standards. The adsorption efficiency, competitive adsorption and chromatographic peak resolution of monoterpene enantiomer pairs were compared for three SPME fibre coatings: 75 μm Carboxen-PDMS (CAR-PDMS, 50/30 μm divinylbenzene-carboxen-polydimethylsiloxane (DVB-CAR-PDMS and 65 μm divinylbenzene-polydimethylsiloxane (DVB-PDMS. Key parameters such as the linearity and reproducibility of the SPME system have been investigated in this work. The best compromise between the enantiomeric separation of monoterpenes and competitive adsorption of the isoprenoids on the solid SPME fibre coating was found for DVB-PDMS fibres. The optimum conditions using DVB-PDMS fibres were applied to measure the exchange rates of monoterpenes in the emission of Quercus ilex using a laboratory whole plant enclosure under light and dark conditions, as well as in ambient air. With 592 and 223 ng m−2 s−1 respectively, β-myrcene and limonene were the predominant monoterpenes in the emission of Q. ilex. These values were closely comparable to those obtained using a zNose and cartridge GC-FID systems.

  8. Quantification of ozone levels in indoor environments generated by ionization and ozonolysis air purifiers.

    Science.gov (United States)

    Britigan, Nicole; Alshawa, Ahmad; Nizkorodov, Sergey A

    2006-05-01

    Indoor air purifiers are advertised as safe household products for health-conscious individuals, especially for those suffering from allergies and asthma. However, certain air purifiers produce ozone (O3) during operation, either intentionally or as a byproduct of air ionization. This is a serious concern, because O3 is a criteria air pollutant regulated by health-related federal and state standards. Several types of air purifiers were tested for their ability to produce ozone in various indoor environments at 40-50% relative humidity, including office rooms, bathrooms, bedrooms, and cars. O3 levels generated by personal wearable air purifiers were also tested. In many cases, O3 concentrations were well in excess of public and/or industrial safety levels established by U.S. Environmental Protection Agency, California Air Resources Board, and Occupational Safety and Health Administration. Simple kinetic equations were obtained that can predict the steady-state level of O3 in a room from the O3 emission rate of the air purifier and the first-order decay rate of O3 in the room. The additivity of O3 levels generated by independent O3 generators was experimentally demonstrated.

  9. A correlation to predict the heat flux on the air-side of a vapor chamber with overturn-U flattened tubes

    Science.gov (United States)

    Srimuang, Wasan; Limkaisang, Viroj

    2016-08-01

    The heat transfer characteristics of a conventional vapor chamber (CVC) and a loop vapor chamber (LVC) are compared. The vapor chambers consisted of a stainless steel box with different covers. The results indicated that the heat flux and convective heat transfer coefficient of the air-side of LVC is higher than CVC. An empirical correlation was developed to predict the convective heat transfer coefficient of the air-side of the LVC.

  10. Intercomparison of ionization chambers in standard X-ray beams, at radiotherapy, diagnostic radiology and radioprotection levels; Intercomparacao de camaras de ionizacao em feixes padroes de raios X, niveis radioterapia, radiodiagnostico e radioprotecao

    Energy Technology Data Exchange (ETDEWEB)

    Bessa, Ana Carolina Moreira de

    2006-07-01

    Since the calibration of radiation measurement instruments and the knowledge of their major characteristics are very important subjects, several different types of ionization chambers were intercompared in terms of their calibration coefficients and their energy dependence, in radiotherapy, diagnostic radiology and radioprotection standard beams. An intercomparison of radionuclide calibrators for nuclear medicine was performed, using three radionuclides: {sup 67}Ga, {sup 201}Tl and {sup 99m}Tc; the results obtained were all within the requirements of the national standard CNEN-NE-3.05. In order to complete the range of radiation qualities of the Calibration Laboratory of IPEN, standard radiation beam qualities, radiation protection and low energy radiation therapy levels, were established, according international recommendations. Three methodologies for the calibration of unsealed ionization chambers in X-ray beams were studied and compared. A set of Victoreen ionization chambers, specially designed for use in laboratorial intercomparisons, was submitted to characterization tests. The performance of these Victoreen ionization chambers showed that they are suitable for use in radioprotection beams, because the results obtained agree with international recommendations. However, these Victoreen ionization chambers can be used in radiotherapy and diagnostic radiology beams only with some considerations, since their performance in these beams, especially in relation to the energy dependence and stabilization time tests, did not agree with the international recommendations for dosimeters used in radiotherapy and diagnostic radiology beams. This work presents data on the performance of several types of ionization chambers in different X-ray beams, that may be useful for choosing the appropriate instrument for measurements in ionizing radiation beams. (author)

  11. Low-voltage ionization of air with carbon-based materials

    Science.gov (United States)

    Peterson, M. S.; Zhang, W.; Fisher, T. S.; Garimella, S. V.

    2005-11-01

    Polycrystalline diamond and carbon nanotubes (CNTs) exhibit excellent vacuum field emission properties, characterized by low turn-on voltage and high current density. Their atmospheric field emission and ionization capabilities are reported in this paper. Highly graphitic polycrystalline diamond (HGPD) film was grown in a plasma-enhanced chemical vapour deposition process, and its ability to ionize atmospheric air was characterized and compared against CNTs. The HGPD sample was activated by applying a moderate voltage bias (340 V) for an extended period across a 10 µm electrode gap. After activation, a turn-on voltage of 20 V and a sustainable current of 10 µA were observed with the same gap. Results also indicate that field emission helps to create a moderate ionization effect without catastrophic air breakdown. A hydrogen plasma treatment is shown to restore emission current back to or even exceeding the original level, which suggests an important role of surface termination in the electron emission process. CNTs were grown and tested but did not perform as well under similar conditions.

  12. Roos and NACP-02 ion chamber perturbations and water-air stopping-power ratios for clinical electron beams for energies from 4 to 22 MeV.

    Science.gov (United States)

    Bailey, M; Shipley, D R; Manning, J W

    2015-02-07

    Empirical fits are developed for depth-compensated wall- and cavity-replacement perturbations in the PTW Roos 34001 and IBA / Scanditronix NACP-02 parallel-plate ionisation chambers, for electron beam qualities from 4 to 22 MeV for depths up to approximately 1.1 × R₅₀,D. These are based on calculations using the Monte Carlo radiation transport code EGSnrc and its user codes with a full simulation of the linac treatment head modelled using BEAMnrc. These fits are used with calculated restricted stopping-power ratios between air and water to match measured depth-dose distributions in water from an Elekta Synergy clinical linear accelerator at the UK National Physical Laboratory. Results compare well with those from recent publications and from the IPEM 2003 electron beam radiotherapy Code of Practice.

  13. Atmospheric pressure air direct current glow discharge ionization source for ion mobility spectrometry.