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Sample records for air wall ionization chambers

  1. Air ionization wire plane chamber

    International Nuclear Information System (INIS)

    Radiation Measurement for protection level instrumentation requires large number of detectors. Since the number is large, the detector should be cost effective and yet should have good sensitivity. Gas detectors with presently available microelectronics and signal processing capabilities opened a new era in radiation monitoring. Present paper describes the use of air filled multi anode grid planes as detector for alpha detection. Due to multiple anode wire planes, the charge collection efficiency of the air ionization chamber is higher as compared to conventional ionization chamber. The signal from this Wire Plane Chamber (WPC) has a faster and narrower pulse shape as compared to conventional two-electrode chamber of similar dimensions. The reduction in capacitance also improves the signal to noise ratio so that air can be used as the ionization medium without any special cleaning procedure etc and it may be possible to use even engineering plastic as the structural material for the chamber. The paper gives the results obtained so far with this air ionization chamber. (author)

  2. Effects of air humidity on ionization chamber response

    International Nuclear Information System (INIS)

    A study of the effect of air humidity on four different ionization chamber cap materials verified earlier studies (Kristensen and Sundbom, 1981; Mijnheer et al., 1983) and extended our understanding of the problem. We found nylon and A-150 plastic caps swell as they absorb water from the air. This accounts for as much as 2.5% increase in ionization response. Graphite chambers readily absorb and desorb water from the air. This creates a problem in maintaining dry air in a wet graphite chamber. Humid air has a different density and W value than dry air (Niatel, 1969, 1975). This decreases the charge collected in a wet graphite chamber. We observe a decrease in response of approximately 2%, a value greater than can be accounted for by these effects alone. Polyethylene chambers are unaffected by humid air. 4 refs., 9 figs

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

    International Nuclear Information System (INIS)

    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)

  4. 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.

  5. Monte Carlo simulation for correction of cavity ionization chamber wall effects

    International Nuclear Information System (INIS)

    The 2 graphite cylindrical ionization chambers are used at AIST to measure absolute air-kerma in 60Co and 137Cs gamma ray fields. They differ in size: one having an ionization volume 40 mm in diameter and 50 mm long and the other 20 mm in diameter and 19.3 mm long. They are placed at 45 degrees angle from the direction of gamma ray beams so that gamma ray attenuation does not increase at the end or side walls. Correction factors for wall induced attenuation and scatter were determined by measuring the variation in chamber response as a function of wall thickness in the full build-up region, extrapolating to infer the response at zero wall thickness, and applying a correction factor to account for the center of electron production. These values are not logically valid, however, so we plan to use correction factors obtained by Monte Carlo calculation for primary standards of air kerma for 60Co and 137Cs gamma rays. In January 2001, we brought our ionization chambers to BIPM and measured air kerma in 60Co and 137Cs gamma ray fields for key comparisons, obtaining values for chamber wall correction factors by both measurement and Monte Carlo calculation. Correction factor kwall, corresponding to kat x ksc x kCEP, for points 1 m from gamma ray sources are shown. knu obtained by Monte Carlo calculation is also shown. Experimental values are noted as 1 because the nonuniformity effect has been neglected at AIST before. Table 3 shows kwall x knu. Differences between values obtained by Monte Carlo and experiments are small for both 60Co and 137Cs gamma rays and also for both ionization chambers. We reported to BIPM the values of air-kerma rate on August 22. BIPM replied that, for the first interpretation, our result was 1.0056 for the key comparison of air kerma in 60Co gamma rays with standard uncertainty of the comparison of 0.0023. After sending the previous report, we recalculated correction factors for wall effect and non-uniformity. Differences between new and previous

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

    International Nuclear Information System (INIS)

    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. - Author-Highlights: • 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

  7. Scattering study at free air ionization chamber diaphragm

    International Nuclear Information System (INIS)

    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 kRQR-M1=0,9946, kRQR-M2=0,9932, kRQR-M3=0,9978 and kRQR-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)

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

    International Nuclear Information System (INIS)

    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 β particles produced by tritium decay. The minimum detection limit of the chamber is 3.7x105 Bq/m3.

  9. Improved free-air ionization chamber for the measurement of X-rays

    International Nuclear Information System (INIS)

    Based on an original design by F. H. Attix, an improved free-air ionization chamber was constructed at the National Radiation Standard Laboratory of the Institute of Nuclear Energy Research (INER, Taiwan), as the primary standard for x-ray generated at energy levels between 50 keV and 300 keV. Various improvements were made to the Attix design, including modifications of the chamber structure and the measurement technique. The changes include: a three-section design with fixed central cylinder; thickening of the shielding box; a circuitous mechanism for the operational handle, to avoid unwanted scattering; a ruler mechanism to provide fine position control; and increased thickness of the aluminium wall of the chamber. After initial experimental verification, a comparison with the National Institute of Standards and Technology (NIST, USA) using a transfer standard chamber yielded differences in calibration factors of less than 1 %. In addition, the overall uncertainty for the x-ray measurement in terms of air kerma is less than 1 % at the 95 % confidence level. These results indicate that the improved free-air ionization chamber can serve as a primary standard at the NRSL. (authors)

  10. New primary ionization chambers at LNE-LNHB for determining the air kerma in a cobalt-60 beam

    International Nuclear Information System (INIS)

    For radioprotection, the reference quantity is air kerma. For an cobalt-60 beam, the reference dosimeter is a cavity ionization chamber whose volume is measured. The new LNE-LNHB reference is based on six different chambers instead of one as was done previously. Although every new ionization chamber was treated as much as possible in the same way (manufacturing, measurements of volumes, wall effect calculations, current corrections), a maximum discrepancy of 0.2% was observed between the final measurement results from each chamber. The final value of the air kerma rate in reference conditions was determined as the mean value of the measurement results from all six chambers. Among the different factors whose determination is necessary to calculate the air kerma rate, some are considered independent of or common to all the graphite-walled ionization chambers (for example, mean energy expended by an electron to produce an ion pair in dry air), while others vary for each chamber (for example, air cavity ionic collection volume). Considering that the uncertainties of the individual ionization chamber measurement results seem slightly underestimated, the uncertainty on the mean of the six chamber-dependent factors products was taken equal to the standard deviation of the sample composed of the six chamber-dependent factors products (0.08%). Compared to the previous standard, the air kerma rate of the 60Co photon beam would then increase by 0.09% and the air kerma rate uncertainty would drop from 0.38% to 0.31%. This article describes the procedure used to establish the primary standard in terms of absorbed dose to tissue of LNE-LNHB. (authors)

  11. Ionization chamber

    International Nuclear Information System (INIS)

    An ionization chamber X-ray detector is described. It comprises a flat cathode sheet parallel to an anode which has a perforated insulating layer on its surface. An open grid, a thin perforated metal sheet is disposed on the insulating layer - the perforations of the layer and sheet are aligned. There is a detector gas and means for maintaining the grid at an electric potential between that of the anode and cathode and for measuring the current flow from the anode to the cathode. The grid shields the anode from the electric field produced by the positive ions which flow towards the cathode and this permits an independent measurement of the electron current flowing to the anode; even when the X-ray pulse length is not much shorter than the ion drift time. The recovery time of the ionization chamber is thus decreased by several orders of magnitude over previous chambers. The grid will normally be fixed to the anode and by shielding the anode from the cathode electric field, tends to eliminate capacitive microphone currents which would otherwise flow in the anode circuit. (U.K.)

  12. 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)

  13. Measurement of air kerma rate for Cs-137 using different ionization chambers

    International Nuclear Information System (INIS)

    Due to the importance of radiation doses in medical field quality assurance should be established in order to maintain a reasonable balance between the purpose of application and exposure. This study had been carried out to achieve quality control for protection based on air kerma rate. Measurements were performed by using Cs-137 for the comparison of two working ionization chambers in secondary standard dosimetry laboratory of Sudan. Spherical ionization chamber L S-01 1000 cc S/N 912 and Farmer ionization chamber 2675 A 600 cc S/N 0511, respectively. The results obtained from this study have been represented as mean and their standard deviations shown in most cases remains at 5% uncertainly. Comparison between kinetic energy released per unit mass in air rate (air kerma rate) were obtained by using spherical ionization chamber L S-01 1000 cc S/N 912 and results have been determined using inverse square law. The differences have been represented as means and standard deviations with significant P-value less than 0.05. Spherical ionization chamber gives accurate, reproducible results with acceptable uncertainty which is more suitable for calibration of radiation detectors.(Author)

  14. A new approach to the determination of air kerma using primary-standard cavity ionization chambers

    International Nuclear Information System (INIS)

    A consistent formalism is presented using Monte Carlo calculations to determine the reference air kerma from the measured energy deposition in a primary-standard cavity ionization chamber. A global approach avoiding the use of cavity ionization theory is discussed and its limitations shown in relation to the use of the recommended value for W. The role of charged-particle equilibrium is outlined and the consequent requirements placed on the calculations are detailed. Values for correction factors are presented for the BIPM air-kerma standard for 60Co, making use of the Monte Carlo code PENELOPE, a detailed geometrical model of the BIPM 60Co source and event-by-event electron transport. While the wall correction factor kwall = 1.0012(2) is somewhat lower than the existing value, the axial non-uniformity correction kan = 1.0027(3) is significantly higher. The use of a point source in the evaluation of kan is discussed. A comparison is made of the calculated dose ratio with the Bragg-Gray and Spencer-Attix stopping-power ratios, the results indicating a preference for the Bragg-Gray approach in this particular case. A change to the recommended value for W of up to 2 parts in 103 is discussed. The uncertainties arising from the geometrical models, the use of phase-space files, the radiation transport algorithms and the underlying radiation interaction coefficients are estimated

  15. 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...

  16. PTRAC file utilization for calculation of free-air ionization chamber correction factors by MCNPX

    International Nuclear Information System (INIS)

    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: k(loss) and for additional ionization current caused by photon scatter: k(sc), photon fluorescence: k(fl), photon transmission through diaphragm edge k(dtr), and photon scatter from the surface of the diaphragm aperture k(dsc) 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 the literature for similar free-air chambers and low-energy photons. (authors)

  17. Current saturation in free-air ionization chambers with chopped synchrotron radiation

    International Nuclear Information System (INIS)

    An expression for ion recombination in free-air ionization chambers irradiated by chopped X-rays is presented. The expression is validated by comparison with experiments using synchrotron radiation. Saturation curves for free-air ionization chambers with electrode gap widths of 4.2, 8.4 and 18 mm were obtained for 10 and 15 keV undulator synchrotron radiation thinned with a 230 Hz rotating-disk chopper. Ion recombination in free-air ionization chambers was found to be inversely proportional to the applied electric field, and an expression that satisfactorily reproduced the ion-recombination rate is determined. A comparison of the expressions for continuous and pulsed X-rays revealed that chopped high-intensity X-rays require a higher voltage to attain saturation when the product of the pulse width and electric field exceeds a value that depends on the X-ray energy. This behaviour was observed explicitly for 10 keV X-rays in measurements with the ionization chamber placed before and after the chopper

  18. 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.

  19. 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.

  20. 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.

  1. Testing the Accuracy of Electron Transport in the Monte Carlo Code FLUKA for Calculation of Ionization Chamber Wall Perturbation Factors

    International Nuclear Information System (INIS)

    The aim of this study was to investigate the Monte Carlo (MC) code FLUKA, regarding its ability to accurately simulate electron transport at density inhomogeneities and in ionization chamber geometries. In order to evaluate the accuracy of FLUKA's electron transport algorithm and the implementation of the condensed history technique, a Fano test was used. This test allows the comparison of calculated and theoretically expected results. The ratio of the two results is ideally equal to unity, and a deviation usually indicates artifacts in the treatment of density interfaces. As a more practical problem, wall perturbation factors pwall of a plane parallel chamber in electron beams were calculated and compared with results based on the EGSnrc MC code. Additionally, the impact of wall material and thickness on calculated cavity dose was investigated for two different thimble chambers irradiated by 60Co. The correct choice of parameters within FLUKA's electron transport algorithm ensured passing the Fano test within ∼0.7% and a good agreement for practical examples within 0.4% compared to results of the EGSnrc MC code. The latter is known to allow an artifact free simulation of ionization chamber response in photon and electron beams. Based on these results, the electron transport accuracy within the FLUKA code can generally be regarded as much better than 1% for typical ionization chamber dosimetry problems. (author)

  2. Electrode-emission effects on the saturation current in free-air ionization chamber

    International Nuclear Information System (INIS)

    The saturation current Isub(s) in a free-air parallel grid-plate ionization chamber is found to differ for positive and negative ion-collection at the plate. The difference deltaIsub(s)=(Isub(s)+-Isub(s)-) is sensitive to the metallic nature of the collector and is explained by the electron-emission due to the impact of positive ions on the electrode's metal surface. These results can be of practical interest in radiation exposure measurements and the study of electrode emission effects from the metal surfaces. (Auth.)

  3. 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

  4. Gridded ionization chamber

    International Nuclear Information System (INIS)

    An improved ionization chamber type x-ray detector comprises a heavy gas at high pressure disposed between an anode and a cathode. An open grid structure is disposed adjacent the anode and is maintained at a voltsge intermediate between the cathode and anode potentials. The electric field which is produced by positive ions drifting toward the cathode is thus shielded from the anode. Current measuring circuits connected to the anode are, therefore, responsive only to electron current flow within the chamber and the recovery time of the chamber is shortened. The grid structure also serves to shield the anode from electrical currents which might otherwise be induced by mechanical vibrations in the ionization chamber structure

  5. Monte Carlo Simulation in the Optimization of a Free-Air Ionization Chamber for Dosimetric Control in Medical Digital Radiography

    International Nuclear Information System (INIS)

    During the earliest tests of a free-air ionization chamber a poor response to the X-rays emitted by several sources was observed. Then, the Monte Carlo simulation of X-rays transport in matter was employed in order to evaluate chamber behavior as X-rays detector. The photons energy deposition dependence with depth and its integral value in all active volume were calculated. The obtained results reveal that the designed device geometry is feasible to be optimized

  6. Gridded Ionization Chamber

    International Nuclear Information System (INIS)

    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

  7. Scintillations in ionization chambers

    International Nuclear Information System (INIS)

    High purity Ar and mixtures of Ar with 1% CH4, 3% CH4, CO2 and N2, respectively, have been applied for fission fragment detection in a gridded ionization chamber. Gas scintillation has been observed simultaneously with a photomultiplier VALVO-XP 2041. Whereas all mixtures work equally well as an ionization gas, only Ar + 3% N2 shows a primary scintillation yield sufficient for fas timing. (orig.)

  8. Ionization chamber kit for in core dosimetry

    International Nuclear Information System (INIS)

    Sensitivity of a set of ionization walled precise chambers, including chambers with a wall made of a material with different atomic number Z (from 6 to 92), is investigated. It is noted that the considered chambers differ by high radiation stability at slight leakage current on isolators. Using the chambers for determining effective energy of gamma-radiation of the stopped IRT-2000 reactor has shown a good agreement of measuring results with the calculation

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

    International Nuclear Information System (INIS)

    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 125I seeds.Methods: Four different SourceCheck chambers were analyzed. With each one of them, two series of measurements of the air kerma strength for 125I selectSeedTM 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 changes in the

  10. 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

  11. Characterization of a free-air ionization chamber in direct X-ray beams as used in mammography

    International Nuclear Information System (INIS)

    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)

  12. Verification of traceability and backscattering in surface entrance air kerma measurements with detector type ionizing chamber

    Energy Technology Data Exchange (ETDEWEB)

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

    2013-07-01

    Measurements of doses in radiology services by ionizing chambers are easier than those made by TLD, however the protocols for measurements differ regarding the calibration. The objectives were to verify the traceability in the measures of ESAK corrected by the inverse square law, due to the difference in position between the source and IC and the influence of the backscattered radiation in bringing the detector to the table. Was defined a procedure practiced by the radiological services and designed experimental arrangements for the same technique. Was noted that the approximation of the detector to the table generated a significant backscattered. (author)

  13. The performance of the INER improved free-air ionization chamber in the comparison of air kerma calibration coefficients for medium-energy X-rays

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J.-H. E-mail: jhlee@iner.gov.tw; Kotler, L.H.; Bueermann, Ludwig; Hwang, W.-S.; Chiu, J.-H.; Wang, C.-F

    2005-01-01

    This paper describes modifications to an original design, correction factors and uncertainty evaluations for an improved free-air ionization chamber constructed at the Institute of Nuclear Energy Research (INER, Taiwan). In addition, a comparison of secondary standard air kerma calibration coefficients for 100-250 kV medium-energy X-rays was performed to verify the experimental accuracy and measurement consistency of the improved chamber. The comparison results showed a satisfactory agreement in the measurements which were within the combined expanded uncertainties (k=2)

  14. The performance of the INER improved free-air ionization chamber in the comparison of air kerma calibration coefficients for medium-energy X-rays

    International Nuclear Information System (INIS)

    This paper describes modifications to an original design, correction factors and uncertainty evaluations for an improved free-air ionization chamber constructed at the Institute of Nuclear Energy Research (INER, Taiwan). In addition, a comparison of secondary standard air kerma calibration coefficients for 100-250 kV medium-energy X-rays was performed to verify the experimental accuracy and measurement consistency of the improved chamber. The comparison results showed a satisfactory agreement in the measurements which were within the combined expanded uncertainties (k=2)

  15. Multi-chamber ionization detector

    International Nuclear Information System (INIS)

    For the detector a single beta ionization source and a double- or three-chamber set-up is used, the chambers being designed in the shape of a truncated cone and facing each other with their bases. The source can be positioned with respect to the common center or modal electrode, the adjustment of the ionization in each chamber this becoming easier. The center or modal electrode also can be adjusted with respect to the source. (DG)

  16. 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)

  17. Deformation mechanisms and impact attenuation characteristics of thin-walled collapsible air chambers used in head protection.

    Science.gov (United States)

    Lamb, L; Hoshizaki, T B

    2009-11-01

    Head injuries are a major cause of morbidity and mortality worldwide, many resulting from sporting activities. There is a constant need in the head protection industry for improved methods to manage impacts and to reduce the risk of mild and severe head injuries. Contemporary head protection primarily consists of foam with several inherent disadvantages, including a limited ability to provide effective energy absorption under both low and high impact velocities. Recently, thin-walled collapsible chambers were engineered to address this problem and have been implemented into sport helmets. The chambers consist of four engineering elements which define their dynamic performance: geometry, air volume, material, and venting system. This research analysed the contribution of air flow through an orifice to the chamber's management of impact energy. The objective of this study was to determine the effect of the chamber's vent diameter and material stiffness on peak force and venting rate during an impact. Two material stiffnesses (thermoplastic polyurethane 45D and thermoplastic polyurethane 90A) and five vent diameters (1 mm, 2 mm, 3 mm, 4 mm, and 5 mm) were tested at three inbound velocities (1.3 m/s, 2.3 m/s, and 3.0 m/s). Each chamber was impacted ten times using a monorail drop system. Analysis of the results revealed that the material stiffness, vent diameter, and inbound velocity all had a significant effect on peak force and venting rate (p force than the smallest vent, while this relationship reversed at high inbound velocities. Under low velocities the air flowrate was negatively correlated and the flow duration was positively correlated to the peak force. Under high velocities, the air flowrate was positively correlated and the duration was negatively correlated to the peak force. This suggested that, under low velocities, chambers performed optimally when air was dissipated quickly, for a short duration; however, as the chamber approached a critical failure

  18. Beam halo monitoring at J-PARC 3-50 beam transport line using long air ionization chamber

    International Nuclear Information System (INIS)

    3 long-type Air Ionization Chambers (AICs) have been installed along 350BT which is the beam transport from the 3GeV Rapid Cycling Synchrotron (RCS) to the Main Ring synchrotron (MR) to monitor beam losses. 3-50BT collimators are used to remove beam halo components outside the emittance larger than 54[πmm · mrad] for horizontal and 60[πmm · mrad] for vertical plane, at present operations. By measuring the beam loss induced radiations from the 3-50BT collimators, the beam halo components have been monitoring on line. Details of the system, calibration results, and resolution of the system will be described in this paper. (author)

  19. Ionization chamber with build-up cup spectral sensitivity to megavoltage (0.5-20 MeV) photon fluences in free air

    International Nuclear Information System (INIS)

    In-air measurements of photon beam properties, used in radiation therapy, is common practice for determining radiation output dependence from the field size, known as head scatter factors (HSF). PMMA and brass build-up caps are most popular miniphantoms for providing electron equilibrium. Discrepancies up to 2% in HSF measurements by different combinations of detectors and equilibrium caps have been published. One of the main reasons of those discrepancies is the detector system spectral sensitivity and differences in primary and scatter radiation spectra. In the light of new model based dose calculation methods direct radiation fluence measurement is of great interest. So, understanding of detector spectral sensitivity is important task for modern dosimetry of radiation therapy. In the present study Monte Carlo (MC) method was employed to calculate ionization chamber response to monoenergetic photon fluences, normalized to water kerma units. Simulation was done using EGS4 package. Electron transport was performed with ESTEPE equal to 4%. PEGS cross sections were generated for maximal energy 20 MeV with cutoff kinetic energy 10 KeV both for photons and electrons. Scanditronix RK-05 ionization chamber was chosen as a prototype. Eight cylindrical miniphantoms, representing four materials (PMMA, Al, Cu, Pb) and two front wall thickness, were simulated. Results are presented. Miniphantom front wall thicknesses in each case are shown in the figure. Diameter depends on the material and equal respectively: PMMA - 4, Al - 2.5, Cu - 1.5, and PB - 1.5 cm. Ionization chamber outer diameter is equal to 0.7 cm. Detector sensitivity has considerable energy dependence. Two effects explain it. First is the radiation attenuation in the miniphantom. Second is pair production, which dominates in high atomic number miniphantoms for energies above 5 MeV. Depending on the miniphantom material detector response changes from 1.5 to 5 times in the energy range from 0.5 to 20 MeV. Correct

  20. Ionization chamber smoke detectors

    International Nuclear Information System (INIS)

    One kind of smoke detector, the ionization-type, is regulated by the Atomic Energy Control Board (AECB) because it uses a radioactive substance in its mechanism. Radioactivity and radiation are natural phenomena, but they are not very familiar to the average householder. This has led to a number of questions being asked of the AECB. These questions and AECB responses are outlined

  1. Energy dependence of the air kerma response of a liquid ionization chamber at photon energies between 8 keV and 1250 keV

    International Nuclear Information System (INIS)

    Full text: In its recent reports on cardiovascular brachytherapy the DGMP recommends the source strength of brachytherapy sources being characterized in terms of absorbed dose to water at a distance of 2 mm from the central axis of the source. As a consequence, the response of a detector suitable for characterizing such sources with respect to absorbed dose to water should depend only to a small extent on radiation energy. Additionally, the detection volume of the detector has to be sufficiently small for the necessary spatial resolution to be obtained. The liquid ionization chamber as described in seems to be a promising means for this type of measurements. The two components of the ionization liquid (TMS and isooctane) can be mixed in a ratio which ensures that the mass-energy absorption coefficient of the resulting mixture deviates from that of water by less than ±15 % down to photon energies of 10 keV. Due to the high density of the ionization medium, the spacing between the two electrodes of the ionization chamber can be made as small as a few tenths of a millimeter and still the resulting ionization current is sufficiently large. The ionization chamber used in the present investigation is a plane parallel chamber 5 mm in diameter and of 0.3 mm electrode spacing. The ionization medium is a mixture of 40 % TMS and 60 % isooctane. The irradiations were carried out with the ISO wide spectra series with tube voltages between 10 kV and 300 kV and with 137Cs and 60Co γ-radiation. As a first step, the response of the liquid ionization chamber was investigated with respect to air kerma instead of absorbed dose to water. Although the mass-energy absorption coefficient of the liquid deviates from that of air by less than ±10 % over the photon energy range, the measured chamber response varies by a factor of about 3.5. Monte Carlo calculations carried out with EGSnrc show a variation of the chamber response smaller than ±20 %. Measurements of the ion yield of the

  2. Numerical solutions of differential equations of an ionization chamber

    International Nuclear Information System (INIS)

    A system of reduced differential equations generally valid for plane-parallel, cylindrical, and spherical ionization chambers filled with air, which is appropriate for numerical solution, has been derived. The system has been solved for all three geometries. The comparison of the calculated results of Armstrong and Tate, for plane-parallel ionization chambers, and Sprinkle and Tate, for spherical ionization chambers, with the present calculations has shown a good agreement. The calculated values for ionization chambers filled with CO2 were also in good agreement with the experimental data of Moriuchi et al (author)

  3. Design of an ionization diffusion chamber detector

    International Nuclear Information System (INIS)

    Prototype of an Ionization Diffusion Chamber detector has been made. It is a silindrical glass, 20 cm in diameter, 13,5 cm in height, air gas filled, operated at room pressure and room temperature at the top of this instrument while for the box temperature dry ice (CO2 solid) temperature is used. This detector is ready for seeing alpha and beta particle tracks. (author)

  4. Contributions of the different ion chamber walls to the fluence perturbation in clinical electron beams: A Monte Carlo study of the NACP-02 parallel-plate chamber

    International Nuclear Information System (INIS)

    Parallel-plate ionization chambers are widely used and highly recommended in clinical electron dosimetry. They are constructed to minimize possible electron fluence perturbations due to the presence of the chamber walls and the air-filled cavity itself, therefore the wall correction factor pwall is assumed to be unity in all current dosimetry protocols independent of electron energy and depth. Already early experimental investigations have given considerable evidence that the perturbations are not always negligible. Especially the back wall was identified as a source of fluence perturbation as the electrons that are backscattered from the rear wall make a significant contribution to the dose within the active volume of the chamber. The influence of different backscattering materials behind the cavity of parallel-plate chambers was experimentally investigated by Hunt et. al. and Klevenhagen. According to their results, the electron backscatter is proportional to the atomic number of the scatterer and inversely proportional to the electron energy. Especially the rear wall of the NACP chamber is quite massive (thickness: 5.6 mm) and consists of graphite, which has an atomic number Z = 6 which is about 10% smaller than the effective atomic number of water. So the wall perturbation concerning the back wall directly reflects the backscatter deficiency due to the back wall of the NACP chamber. Several years ago McEwen reinvestigated the backscattering of different parallel-plate chambers in clinical electron beams and determined the wall perturbation correction due to the rear wall of the NACP chamber experimentally. Monte Carlo simulations are a good tool for investigating perturbation corrections of ionization chambers. For the NACP chamber several studies have been performed during the last years. In all studies the wall perturbation for the whole chamber was calculated, resulting in significant larger values than those measured by McEwen. In the light of these

  5. Optimization studies on pulse ionization chambers

    International Nuclear Information System (INIS)

    The results are presented of optimization studies on two models of an air-filled, pulse, ionization chamber intended for detecting air impurities. Studies were conducted on the effect of dosage grids, procedure of controlling them, field configuration, type of radioactive source, surface of collecting electrode, and length of dosage pulse. The most critical parameters that have an effect upon the pulse shape, i.t. upon the pulse-amplitude and -length are: procedure of controlling the dosage grid, dosage dosage-pulse length and electric-field intensity. (author)

  6. Ionization chambers for LET determination

    DEFF Research Database (Denmark)

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

    2010-01-01

    Modern radiotherapy facilities for cancer treatment such as the Heavy Ion Therapy Centre (HIT) in Heidelberg (Germany) enable sub millimetre precision in dose deposition. For the measurement of such dose distributions and  characterization of the particle beams, detectors with high spatial...... 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...

  7. Liquid-argon cylindrical pulsed ionization chamber

    International Nuclear Information System (INIS)

    A liquid-argon cylindrical ionization chamber with a working volume of 200 cm2 is described. The chamber anode is made of stainless steel in the form of a hollow cylinder 30 mm in diameter and 140 mm in length. A beryllium bronze wire in diameter of 0.1 mm and at a spacing of 1 mm is used for winding the chamber screen grid. The chamber cathode is a brass thin-walled cylinder having an internal diameter of 56 mm and a height of 156 mm. The cathode-grid gap is 10 mm, the cathode-case gap is 2 mm. A 0.5 l cooling bath filled with liquid nitrogen is used to refrigirate the chamber. The chamber is evacuated to about 10-5 mm Hg. The total concentration of electronegative impurities in argon does not exceed 6x10-9. Dependences of the chamber counting and amplitude responses, on the cathode voltage under irradiation with γ-quanta at energies of 0.898 MeV and 1.836 MeV are given. The value of the energy resolution was evaluated by differentiating the high-energy edge of the Compton spectrum. The total width at a peak half-height constitutes 5% for an electron energy of 1.612 MeV. To achieve better resolution of the chamber it is necessary to reduce preamplifier noises by three times, to increase the working gap of the chamber and decrease the grid-anode gap

  8. LET measurements with a liquid ionization chamber

    International Nuclear Information System (INIS)

    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.

  9. Room temperature liquid ionization chambers using tetramethylsilane

    International Nuclear Information System (INIS)

    Ionization pulse signals due to 207Bi conversion electrons were observed in ionization chambers filled with tetramethylsilane which was purified by a simple method. Pulse height spectra and its variation with the electric field were measured. (orig.)

  10. 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)

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

    International Nuclear Information System (INIS)

    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. - Highlights: • In order to verify the photon beam model of the FiR 1 BNCT facility in Finland, the photon beam spectrum is determined experimentally through ionization chamber measurements with multiple build-up caps of different thickness. • Large discrepancy is found between free in air measurements with the ionization chamber and the Monte Carlo calculations indicating that the initial beam model needs to be adjusted. • The unfolded spectrum and photon beam intensity may be applicable as a more correct photon beam model

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

    International Nuclear Information System (INIS)

    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

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

    International Nuclear Information System (INIS)

    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

  14. Calibration of working standard ionization chambers and dose standardization

    International Nuclear Information System (INIS)

    Measurements were performed for the calibration of two working standard ionization chambers in the secondary standard dosimetry laboratory of Sudan. 600 cc cylindrical former type and 1800 cc cylindrical radical radiation protection level ionization chambers were calibrated against 1000 cc spherical reference standard ionization chamber. The chamber were calibrated at X-ray narrow spectrum series with beam energies ranged from (33-116 KeV) in addition to 1''3''7''Cs beam with 662 KeV energy. The chambers 0.6 cc and 0.3 cc therapy level ionization were used for dose standardization and beam output calibrations of cobalt-60 radiotherapy machine located at the National Cancer Institute, University of Gazira. Concerning beam output measurements for 6''0''Co radiotherapy machine, dosimetric measurements were performed in accordance with the relevant per IAEA dosimetry protocols TRS-277 and TRS-398. The kinetic energy released per unit mass in air (air kerma) were obtained by multiplying the corrected electrometer reading (nC/min) by the calibration factors (Gy/n C) of the chambers from given in the calibration certificate. The uncertainty of measurements of air kerma were calculated for the all ionization chambers (combined uncertainty) the calibration factors of these ionization chambers then were calculated by comparing the reading of air kerma of secondary standard ionization chambers to than from radical and farmer chambers. The result of calibration working standard ionization chambers showed different calibration factors ranged from 0.99 to 1.52 for different radiation energies and these differences were due to chambers response and specification. The absorbed dose to to water calculated for therapy ionization chamber using two code of practice TRS-277 and TRS-398 as beam output for 6''0''Co radiotherapy machine and it can be used as a reference for future beam output calibration in radiotherapy dosimetry. The measurement of absorbed dose to water showed that the

  15. Comparison among different CT ionization chambers

    International Nuclear Information System (INIS)

    The dosimetry in computed tomography (CT) is carried out by the use of a pencil type ionization-chamber, because it has a uniform response at all angles relative to the incident beam of radiation, which is essential for CT equipment since the X-ray tube executes a circular movement around the table during irradiation. The commercial ionization chamber used to perform quality control procedures of this kind of equipment has a length of the sensitive volume of 10 cm. In the Calibration Laboratory of Instruments (LCI) of the IPEN there were already developed some prototypes with small differences in construction, when compared to commercially available ionization chambers. They have been used in previous studies and showed results within internationally acceptable limits. The ionization chambers tested in this study present the sensitive volume lengths of 1 cm, 3 cm and 10 cm. The objective of this study was to present results on the stability test of the three homemade ionization chambers and a commercial chamber, as well to obtain the calibration coefficients for each of them in CT standard X radiation beams. The obtained results for both characterization tests are within the recommended limits, except for the homemade ionization chambers with sensitive volume lengths of 3 cm and 1 cm in the case of the stability test. (author)

  16. Contamination of ionization chamber due to tritium exposure

    International Nuclear Information System (INIS)

    The contamination of three ionization chambers (Cu, Ni-plated, and Au-plated chambers) due to exposure to HT or HTO was measured. Considerable contamination took place for all of the chambers due to exposure to HTO. This is caused by the physical adsorption of HTO. The extent of the contamination differed from each other (Ni > Au > Cu), being considered due to difference in their surface roughness. In case of the exposure to HT, the Cu-chamber was contaminated in room air, whereas the Ni-chamber did in dry air atmosphere. This is considered due to the adsorption of HTO (being formed with catalytic exchange reaction between HT and H2O) on the Cuchamber and that of HT on the Ni-chamber. The Au-chamber was not contaminated with the exposure to HT. This is because neither the adsorption of HT nor the catalytic exchange reaction takes place on this surface

  17. Ionization-chamber smoke detector system

    Science.gov (United States)

    Roe, Robert F.

    1976-10-19

    This invention relates to an improved smoke-detection system of the ionization-chamber type. In the preferred embodiment, the system utilizes a conventional detector head comprising a measuring ionization chamber, a reference ionization chamber, and a normally non-conductive gas triode for discharging when a threshold concentration of airborne particulates is present in the measuring chamber. The improved system is designed to reduce false alarms caused by fluctuations in ambient temperature. Means are provided for periodically firing the gas discharge triode and each time recording the triggering voltage required. A computer compares each triggering voltage with its predecessor. The computer is programmed to energize an alarm if the difference between the two compared voltages is a relatively large value indicative of particulates in the measuring chamber and to disregard smaller differences typically resulting from changes in ambient temperature.

  18. Cylindrical ionization chamber on compressed krypton

    International Nuclear Information System (INIS)

    A cylindrical ionization chamber with a grid is described. The chamber is used in experiments to search for double positron decay and conversion of atom electron into positron in Kr78. The working substance of the chamber is krypton. The spectrometric characteristics of the chamber filled with krypton and xenon are presented. Energy resolution is 2.1% for 1.84 MeV energy (the gamma quantum source is 88Y) when using the chamber filled with Kr+0.2%H2 mixture at pressure of 25 atm

  19. Determination of the correction factor for attenuation, dispersion and production of electrons (Kwall) in the wall of graphite of a ionization chamber Pattern National Type CC01 in fields of gamma radiation of 60Co

    International Nuclear Information System (INIS)

    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 60Co. 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 χ2 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 dont 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 agreement with the

  20. Vapor wall deposition in Teflon chambers

    OpenAIRE

    Zhang, X; R. H. Schwantes; R. C. McVay; H Lignell; M. M. Coggon; Flagan, R C; Seinfeld, J.H.

    2014-01-01

    Teflon chambers are ubiquitous in studies of atmospheric chemistry. Secondary organic aerosol (SOA) formation can be substantially underestimated owing to deposition of SOA-forming compounds to chamber walls. We present here an experimental protocol to constrain the nature of wall deposition of organic vapors in Teflon chambers. We measured the wall deposition rates of 25 oxidized organic compounds generated from the photooxidation of isoprene, toluene, α-pinene, and dodecan...

  1. Laboratory implantation for well type ionization chambers calibration

    International Nuclear Information System (INIS)

    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. 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

  3. 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

    International Nuclear Information System (INIS)

    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

  4. Walls shielding against ionizing radiation

    International Nuclear Information System (INIS)

    These specifications are to help the users of lead bricks as under DIN 25407, leaf 1, with the construction of walls shielding against ionizing radiation by examples for the uses of the different types of lead bricks and by recommendations for the construction of shielding walls and for the determination of the wall thickness necessary for shielding against γ-radiation as a function of energy. (orig./AK)

  5. Cylindrical ionization chamber with compressed krypton

    International Nuclear Information System (INIS)

    A cylindrical ionization chamber with a grid is used to search for double positron decay and atomic electron conversion to a positron in 78Kr. Krypton is the working gas material of the chamber. The spectrometric characteristics of the chamber filled with krypton and xenon are presented. The energy resolution is 2.1% for an energy of 1.84 MeV (the source of γ-quanta is 88Y) when the chamber is filled with a mixture of Kr+0.2% H2 under a pressure of 25 atm

  6. Design, construction and characterization of special ionization chambers for X radiation beams monitoring

    International Nuclear Information System (INIS)

    X radiation equipment may show fluctuations in the radiation beam intensity, as they are connected to the power net. These intensity variations can, in turn, modify the air kerma rate produced by this radiation beam. In a calibration laboratory, where radiation detectors (from clinics and hospital services) are calibrated, variations in the radiation beam intensity may cause an error in the absorbed dose determination. The monitor ionization chambers are used to verify the radiation beam intensity constancy, and to provide a correction for possible fluctuations. In this work, monitor ionization chambers for X radiation beams were designed, assembled and characterized. The developed ionization chambers have an innovative design, ring-shaped, with aluminium or graphite electrodes. These ring-shaped ionization chambers have the advantage of not interfering in the direct radiation beams. A double-volume ionization chamber with graphite electrodes was also developed. This ionization chamber is similar to the commercial monitor ionization chamber used in the Calibration Laboratory of the Instituto de Pesquisas Energeticas e Nucleares. All developed ionization chambers were tested in several standardized radiation beams and their performances were compared with those of commercial ionization chambers. The results show that two of the four ionization chambers developed showed performance comparable to that of the commercial ionization chambers tested. Besides presenting good results, the ionization chambers were designed and manufactured using low cost materials, which are easily found on the Brazilian market. (author)

  7. 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.

  8. 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.

  9. Making MUSIC: A multiple sampling ionization chamber

    Science.gov (United States)

    Shumard, B.; Henderson, D. J.; Rehm, K. E.; Tang, X. D.

    2007-08-01

    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 (α, 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 (α, 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 (α, 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. × 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 (α, 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 (α, p) reaction to reach the anode segment below the reaction.

  10. Making MUSIC: A multiple sampling ionization chamber

    International Nuclear Information System (INIS)

    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 (α, 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 (α, 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 (α, 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 (α, 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 (α, p) reaction to reach the anode segment below the reaction

  11. Pressurized ionization chamber detectors for industrial use

    International Nuclear Information System (INIS)

    The measurement of the thickness of the sheets made of different materials, e.g. metal, plastic, paper, cellulose, rubber, etc., is one of many industrial applications of nuclear techniques. The ionizing radiation detectors of ionization chamber type are based on measuring the variations in either exposure rate (for gamma radiation) or absorbed dose rate (for beta radiation) occurring in materials of different thickness, placed between the radiation source and the detector. The variations in exposure rate and absorbed dose rate can be traced by using radiation detectors of the ionization chamber type, which convert the exposure rate, X point, or the absorbed dose rate, D point, into a proportional electric current. The more stable the ionization current of the chambers (keeping a constant exposure rate or absorbed dose rate), the slighter the variations that can be detected in either exposure rate or absorbed dose rate, hence in the absorbing material placed between the radiation source and the detector. Based on these facts, several variants of such detectors, including the ionization chamber CIS-P5M-100Kr, CIS-P2M-1000Kr and CIS-P8M-70Kr, have been made. (author)

  12. Development of an α grid ionization chamber

    International Nuclear Information System (INIS)

    The article introduces the parallel grid ionization chamber used to measure the α radioactivity, which has a independent vacuum system. The system is composed of main body of the chamber, gas-filled and electronics system. Energy resolution is 25 keV for 239Pu, background is 4 counts for one hour from 4 MeV to 6 MeV energy range, detect efficiency approach to 50%. The chamber can measure the energy of nuclide, analyze the structure, moreover authenticate both the nuclide and the relative and absolute content. (authors)

  13. Development and characterization of a new graphite ionization chamber for dosimetry of 60Co beams

    International Nuclear Information System (INIS)

    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 60Co 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 cm3. 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 60Co 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 60Co gamma beams. (author)

  14. IKAR, a ionization chamber for WA9

    CERN Multimedia

    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.

  15. Proportional chamber application to ionization measurements

    International Nuclear Information System (INIS)

    The possibility is investigated to use a proportional chamber measuring ionization particle losses in developing a detector capable of tracking the simultaneous passage of several particles against the background of a large number of single particles. The chamber used, with a 100x100 mm2 working plane, has three high-voltage electrodes and two signal planes spaced at 6 mm. The operating gas is argon + methylal (C3H8O2) at atmospheric pressure. The calculations made with consideration for the resolution obtained in the chamber, i.e., approximately 20% (5.9 keV) indicate that by using four chamber clearances it is possible to obtain the tracking efficiency of three particles over 99%

  16. Transmission ionization chambers for measurements of air collision kerma integrated over beam area. Factors limiting the accuracy of calibration

    International Nuclear Information System (INIS)

    Kerma-area product meters (KAP meters) are frequently used in diagnostic radiology to measure the integral of air-collision kerma over an area A(∫A Kc,air dA) perpendicular to the x-ray beam. In this work, a precise method for calibrating a KAP meter to measure ∫A Kc,air dA is described and calibration factors determined for a broad range of tube potentials (40-200kV). The integral is determined using a large number of TL dosimeters spread over and outside the nominal field area defined as the area within 50% of maximum Kc,air. The method is compared to a simplified calibration method which approximates the integral by multiplying the kerma in the centre of the field by the nominal field area Anom. While the calibration factor using the precise method is independent of field area and distance from the source, that using the simplified method depends on both. This can be accounted for by field inhomogeneities caused by the heel effect, extrafocal radiation and scattered radiation from the KAP meter. The deviations between the calibration factors were as large as ±15% for collimator apertures of 5-100cm2 and distances from the source of 50 - 160 cm. The uncertainty in the calibration factor using the precise method was carefully evaluated and the expanded relative uncertainty estimated to be ±3% with a confidence level of 95%. (author)

  17. Development of special ionization chambers for a quality control program in mammography

    International Nuclear Information System (INIS)

    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)

  18. Alpha particle spectroscopy by gridded ionization chamber

    International Nuclear Information System (INIS)

    A gridded ionization chamber has been constructed with the aim of determining its ultimate energy resolution in alpha spectroscopy, utilizing a cooled FET pre-amplifier of the type normally employed with semiconductor detectors. With suitable mechanical collimation of the alpha particles, their fine structure has been measured with an energy resolution of -11.5 keV (fwhm), achieved using an Ar + 0.75% C2H2 mixture as the filling gas. (orig.)

  19. Calorimeter tests with liquid ionization chambers

    International Nuclear Information System (INIS)

    Configurations of sampling calorimeters with iron, lead and uranium as absorbers have been investigated using liquid ionization chambers as active elements. As liquid tetramethylsilane has been used. Results of beam tests with electrons, pions and muons in the energy range of 2 to 6 GeV are presented and compared with Monte Carlo simulations. In particular the questions regarding which configuration can compensate and the separation of sampling from intrinsic fluctuations have been studied. (orig.)

  20. 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.

  1. Project, construction and characterization of ionization chambers for use as standard systems in X and gamma radiation beams

    International Nuclear Information System (INIS)

    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)

  2. Ionization chamber for high dose measurements

    International Nuclear Information System (INIS)

    Industrial gamma irradiators facilities are designed for processing large amounts of products, which are exposed to large doses of gamma radiation. The irradiation, in industrial scale, is usually carried out in a dynamic form, where the products go through a 60Co gamma source with activity of TBq to P Bq (k Ci to MCi). The dose is estimated as being directly proportional to the time that the products spend to go through the source. However, in some situations, mainly for research purposes or for validation of customer process following the ISO 11137 requirements, it is required to irradiate small samples in a static position with fractional deliver doses. The samples are put inside the irradiation room at a fixed distance from the source and the dose is usually determined using dosimeters. The dose is only known after the irradiation, by reading the dosimeter. Nevertheless, in the industrial irradiators, usually different kinds of products with different densities go through between the source and the static position samples. So, the dose rate varies in function of the product density. A suitable methodology would be to monitor the samples dose in real time, measuring the dose on line with a radiation detector, which would improve the dose accuracy and avoid the overdose. A cylindrical ionization chamber of 0.9 cm3 has been developed for high-doses real-time monitoring, during the sample irradiation at a static position in a 60Co gamma industrial plant. Nitrogen and argon gas at pressure of 10 exp 5 Pa (1 bar) was utilized to fill the ionization chamber, for which an appropriate configuration was determined to be used as a detector for high-dose measurements. To transmit the signal generated in the ionization chamber to the associated electronic and processing unit, a 20 m mineral insulated cable was welded to the ionization chamber. The signal to noise ratio produced by the detector was about 100. The dosimeter system was tested at a category I gamma irradiator

  3. 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)

  4. High efficiency ionization chamber for fission experiments

    International Nuclear Information System (INIS)

    Complete text of publication follows. The width of fission fragment mass distribution indicates the number of di rent fragments which are produced during the fission process from a given excited state. Smaller width means more limited variety of fission fragments which can indicate clusterization effect in hyperdeformed states before fission and also means less amount of nuclear waste. A new gridded ionization chamber was constructed at Atomki to examine the mass distribution of the fission fragments from neutron induced fission of some U and Th isotopes. The design is based on a twin ionization chamber developed by C. Budtz-Jorgensen et al. Our aim was to increase the efficiency of the measurements by applying multiple detector units. This compound detector permits simultaneous measurement of the total kinetic energy and fission fragment emission angle with respect to the detector symmetry axis. The chamber consists of five twin parallel plate ionization chambers with Frisch grids. Assuming that at low counting rates only one target emits fission fragments in one event, the an- odes and the grids were interconnected form- ing two groups (A1-G1, A2-G2). In order to identify which target emitted the fission fragments the signals from each cathodes are also processed. The energy of the fission fragments is determined from the anode pulse heights, while the sum of the grid and anode signals is used to deduce the fragment emission angle θ with respect to the symmetry axis of the chamber: Qsum = -n0e[1 - (X/D)cosθ). The angle dependent energy losses in the tar get can be determined using this angular information. In order to minimize the distance between the targets and the neutron source, smaller distance between the plates and a smaller diameter had to be chosen as in Ref. This arrangement required higher gas pressure, which is necessary to stop the fission fragments before reaching the electrodes. A gas mixture of 90% Ar + 10% CH4 at 2 atm pressure was used. With a

  5. 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. PMID:22153889

  6. Electret ionization chamber: a new method for detection and dosimetry of thermal neutrons

    International Nuclear Information System (INIS)

    An electret ionization chamber with boron coated walls is presented as a new method for detecting thermal neutrons. The efficiency of electret ionization chambers with different wall materials for the external electrode was inferred from the results. Detection of slow neutrons with discrimination against the detection of γ-rays and energetic neutrons was shown to depend on the selection of these materials. The charge stability over a long period of time and the charge decay owing to natural radiation were also studied. Numerical analysis was developed by the use of a micro-computer PC-XT. Both the experimental and numerical results show that the sensitivity of the electret ionization chamber for detection of thermal neutrons is comparable with that of the BF3 ionization chamber and that new technologies for deposition of the boron layer will produce higher efficiency detectors. (author). 102 refs, 32 fig, 10 tabs

  7. Perturbation correction factors for the NACP-02 plane-parallel ionization chamber in water in high-energy electron beams.

    Science.gov (United States)

    Verhaegen, F; Zakikhani, R; Dusautoy, A; Palmans, H; Bostock, G; Shipley, D; Seuntjens, J

    2006-03-01

    Recent dosimetry protocols for clinical high-energy electron beams recommend measurements of absorbed dose-to-water with a plane-parallel or cylindrical ionization chamber. For well-guarded plane-parallel ionization chambers, the ionization chamber perturbation factor in water, p(Q), has a recommended value of unity in all protocols. This assumption was investigated in detail in this study for one of the recommended ionization chambers in the protocols: the Scanditronix NACP-02 plane-parallel ionization chamber. Monte Carlo (MC) simulations of the NACP-02 ionization chamber with the EGSnrc code were validated against backscatter experiments. MC simulations were then used to calculate p(wall), p(cav) and p(Q) perturbation factors and water-to-air Spencer-Attix stopping powers in 4-19 MeV electron beams of a calibration laboratory (NPL), and in 6-22 MeV clinical electron beams from a Varian CL2300 accelerator. Differences between calculated and the currently recommended (Burns et al 1996 Med. Phys. 23 383-8) stopping powers, water-to-air, were found to be limited to 0.9% at depths between the reference depth z(ref) and the depth where the dose has decreased to 50% of the maximum dose, R50. p(wall) was found to exceed unity by 2.3% in the 4 MeV NPL calibration beam at z(ref). For higher energy electron beams p(wall) decreased to a value of about 1%. Combined with a p(cav) about 1% below unity for all energies at z(ref), this was found to cause p(Q) to exceed unity significantly for all energies. In clinical electron beams all three perturbation factors were found to increase with depth. Our findings indicate that the perturbation factors have to be taken into account in calibration procedures and for clinical depth dose measurements with the NACP-02 ionization chamber. PMID:16481689

  8. Perturbation correction factors for the NACP-02 plane-parallel ionization chamber in water in high-energy electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Verhaegen, F [Medical Physics Department, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec H3G1A4 (Canada); Zakikhani, R [Medical Physics Department, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec H3G1A4 (Canada); DuSautoy, A [Radiation Dosimetry, National Physical Laboratory, TW11 0LW Teddington (United Kingdom); Palmans, H [Radiation Dosimetry, National Physical Laboratory, TW11 0LW Teddington (United Kingdom); Bostock, G [Radiation Dosimetry, National Physical Laboratory, TW11 0LW Teddington (United Kingdom); Shipley, D [Radiation Dosimetry, National Physical Laboratory, TW11 0LW Teddington (United Kingdom); Seuntjens, J [Medical Physics Department, McGill University, Montreal General Hospital, 1650 Cedar Avenue, Montreal, Quebec H3G1A4 (Canada)

    2006-03-07

    Recent dosimetry protocols for clinical high-energy electron beams recommend measurements of absorbed dose-to-water with a plane-parallel or cylindrical ionization chamber. For well-guarded plane-parallel ionization chambers, the ionization chamber perturbation factor in water, p{sub Q}, has a recommended value of unity in all protocols. This assumption was investigated in detail in this study for one of the recommended ionization chambers in the protocols: the Scanditronix NACP-02 plane-parallel ionization chamber. Monte Carlo (MC) simulations of the NACP-02 ionization chamber with the EGSnrc code were validated against backscatter experiments. MC simulations were then used to calculate p{sub wall}, p{sub cav} and p{sub Q} perturbation factors and water-to-air Spencer-Attix stopping powers in 4-19 MeV electron beams of a calibration laboratory (NPL), and in 6-22 MeV clinical electron beams from a Varian CL2300 accelerator. Differences between calculated and the currently recommended (Burns et al 1996 Med. Phys. 23 383-8) stopping powers, water-to-air, were found to be limited to 0.9% at depths between the reference depth z{sub ref} and the depth where the dose has decreased to 50% of the maximum dose, R{sub 50}. p{sub wall} was found to exceed unity by 2.3% in the 4 MeV NPL calibration beam at z{sub ref}. For higher energy electron beams p{sub wall} decreased to a value of about 1%. Combined with a p{sub cav} about 1% below unity for all energies at z{sub ref}, this was found to cause p{sub Q} to exceed unity significantly for all energies. In clinical electron beams all three perturbation factors were found to increase with depth. Our findings indicate that the perturbation factors have to be taken into account in calibration procedures and for clinical depth dose measurements with the NACP-02 ionization chamber.

  9. A multiplication ionization chamber survey meter for low level X and gamma ray monitoring

    International Nuclear Information System (INIS)

    A survey meter utilizing a sealed 35 cm3 polythene-walled multiplication ionization chamber with air at atmospheric pressure is described. The electronic measuring system comprises a high stability EHT supply (3.3 kV) a micropower MOSFET-input operational amplifier and a battery voltage regulator. Three ranges of tissue dose rates, 0.20 μGy. hr-1, 0-200 μGy. hr-1, and 0-2 mGy. hr-1 are provided with a facility to measure dose rates up to 2 Gy. hr-1, by operating in the usual ion chamber mode. This instrument is not affected by environmental conditions and operates on flashlight cells. Further extensions of the survey meter using other gases to monitor mixed fields are also outlined. (author)

  10. 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.

  11. 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

    2015-11-21

    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. PMID:26510214

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

    International Nuclear Information System (INIS)

    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. (paper)

  13. Characterization tests of a homemade ionization chamber in mammography standard radiation beams

    International Nuclear Information System (INIS)

    A mammography homemade ionization chamber was developed to be applied for mammography energy range dosimetry. This chamber has a sensitive volume of 6 cm3 and is made of a Lucite body and graphite coated collecting electrode. Characteristics such as saturation, ion collection efficiency, linearity of chamber response versus air kerma rate and energy dependence were determined. The results obtained with the mammography homemade ionization chamber are within the limits stated in international recommendations. This chamber can be used in quality control programs in the diagnostic radiology area. All measurements were carried out at the Calibration Laboratory of IPEN. - Highlights: • We constructed a mammography homemade ionization chamber. It was submitted to standard mammography X-rays beam qualities. • The results obtained showed good agreement with international standards. • This chamber can be used in quality control programs of diagnostic radiology area

  14. Compatibility results of some diagnostic ionization chambers

    International Nuclear Information System (INIS)

    The most important task of the National Laboratory for Metrology of the Ionizing Radiations at the Institute for Radiation Protection and Dosimetry - LNMRI/IRD-CNEN/MCT is to realize and maintain the legal units in compliance with the International System of Units - Si and disseminate them, above all within the framework of legal and scientific metrology. The LNMRI/IRD thus is on top of the metrological hierarchy in Brazil. Calibration certificates issued is the document that was result of the calibrations, that is, the instrument was calibrated and now it is traceable to national standards. Groups of a similar model of the ion chambers design specific for using at conventional diagnostic dosimetric, attenuated and no attenuated and dental applications, are placed under similar calibration condition at the LNMRI/IRD. The main objective is to observe how is the compatibilities' measurements obtained through 10 equipment set dedicated for clinical dosimetry, and how are the dispersion conclusion for these. (author)

  15. Development of an optical digital ionization chamber

    Energy Technology Data Exchange (ETDEWEB)

    Turner, J.E.; Hunter, S.R.; Hamm, R.N.; Wright, H.A.; Hurst, G.S.; Gibson, W.A.

    1988-01-01

    We are developing a new device for optically detecting and imaging the track of a charged particle in a gas. The electrons in the particle track are made to oscillate rapidly by the application of an external, short-duration, high-voltage, RF electric field. The excited electrons produce additional ionization and electronic excitation of the gas molecules in their immediate vicinity, leading to copious light emission (fluorescence) from the selected gas, allowing the location of the electrons along the track to be determined. Two digital cameras simultaneously scan the emitted light across two perpendicular planes outside the chamber containing gas. The information thus obtained for a given track can be used to infer relevant quantities for microdosimetry and dosimetry, e.g., energy deposited, LET, and track structure in the gas. The design of such a device now being constructed and methods of obtaining the dosimetric data from the digital output will be described. 4 refs., 4 figs.

  16. Simulation studies on a prototype ionization chamber for measurement of personal dose equivalent, Hp(10)

    International Nuclear Information System (INIS)

    Full text: The Metrological Laboratory of lonizing Radiation and Radioactivity (LMRIR) of Nuclear and Technological Institute (ITN) has designed and constructed a prototype ionization chamber for direct measurement of the personal dose equivalent, Hp(10), similar to the developed by the Physikalisch-Technische Bundesanstalt (PTB) and now commercialized by PTW. Tests already performed had shown that the behaviour of this chamber is very close to the PTB chamber, namely the energy dependence for the x-ray radiation qualities of the ISO 4037-1 narrow series N-30, N-40, N-60, N-80, N-100 and N-120 and also for gamma radiation of 137Cs and 60Co. However, the results obtained also show a high dependence on the energy for some incident radiation angles and a low magnitude of the electrical response of the ionization chamber. In order to try to optimize the performance of the chamber, namely to decrease the energy dependence and to improve the magnitude of the electrical response of the ionization chamber, the LMRIR initiated numerical simulation of this ionization chamber using a Monte-Carlo method for simulation of radiation transport using, in a first step, the MCNPX code. So, simulation studies of some physical parameters are been performed in order to optimize the response of the ionization chamber, namely the diameter of the central electrode of the ionization chamber, the thickness of the front wall of the ionization chamber, among others. Preliminary results show that probably the actual geometry of the ionization chamber is not yet the optimized configuration. The simulation study will carry on in order to find the optimum geometry. (author)

  17. A novel micro liquid ionization chamber for clinical dosimetry

    International Nuclear Information System (INIS)

    Absorbed-dose-based protocols recommend calibration of clinical linear accelerators using airfilled ionization chambers for which an absorbed-dose to water calibration factor has been established in a 60Co beam. The factor kQ in these protocols involves the ratio of the mean restricted collision mass stopping power water-to-air, which is energy dependent. For high-energy clinical photon beams, the stopping power ratio water-to-air varies by up to 4%, whereas for electron beams the variation is even larger. For certain insulating liquids, however, the stopping power ratio water-to-liquid shows very little energy dependence, making a liquid-filled ionization chamber a potentially attractive dosimeter for clinical reference dosimetry. In this work some properties of two liquid-filled ionization chambers are investigated including ion recombination and variation of response as a function of energy for photon beams. In this work we used an Exradin A14P planar microchamber with chamber body and electrodes composed of C552 plastic. This chamber was modified, reducing the gap between the cap and collecting electrode to 0.5 mm. The diameter of the collecting electrode is 1.5 mm and the nominal sensitive volume of 1.12 mm3 was filled with isooctane. This chamber will be referred to as the MicroLIC. The energy response of the MicroLIC was compared to previous results measured using the LIC 9902-mix chamber, developed by G. Wickman of Umea University, Sweden. The sensitive volume of this chamber has a diameter of 2.5 mm, thickness of 0.35 mm and is filled with 60% isooctane, 40% tetramethylsilane by weight. The linear accelerator used was a Varian Clinac 21EX with nominal photon beam energies of 6 and 18 MV. Measurements were done in a 20x20x20 cm3 RMI Solid Water phantom at 10 cm depth with a 10x10 cm2 field at the phantom surface. Absorbed dose was determined using an Exradin A12 chamber with an absorbed-dose to water calibration factor for 60Co established at a primary

  18. Intercomparison of ionization chamber calibration factors in the IAEA/WHO network of SSDLS

    International Nuclear Information System (INIS)

    In 1995 an intercomparison of ionization chamber calibration factors was performed. It was open to Member laboratories within the IAEA/WHO Network of SSDLs. The aim of this exercise was to test a new quality audit system for these laboratories. The intercomparison has 17 participating laboratories; calibration factors for 24 ionization chambers were checked. The participants were asked to calibrate the ionization chambers both in terms of air kerma and absorbed dose to water. The results show that most of the SSDLs perform air kerma calibration of acceptable quality, while some misunderstandings regarding calibrations in terms of absorbed dose to water were discovered. This type of intercomparison will from now on become a normal service of the Network secretariat in collaboration with the IAEA dosimetry laboratory. It will be expanded to cover all Member laboratories which perform therapy level ionization chamber calibrations as part of their normal service. (author). 6 refs, 3 figs, 1 tab

  19. 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

  20. 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

  1. Tritium measurement and monitoring in experimental and process systems with ionization chambers

    International Nuclear Information System (INIS)

    Historically, ionization chambers have been used successfully to measure low-level tritium concentrations in air for radiation protection purposes. Problems have been encountered in applying this technique to measure much higher concentrations of tritium in gases other than air, particularly to measure tritium in argon and helium. An experimental program was initiated to investigate the various factors that affect the response of ionization chambers. Carrier gas effects on the measurement of elemental tritium were investigated in the concentration range 0-150 Ci/m3. Higher than theoretical calibration factors were obtained consistently with low-level tritium gas standards in both helium and argon, while with high-level gas standards the experimental calibration factors were close to the theoretical value. Use of a commercial ionization chamber to measure tritiated water vapour in dry air streams resulted in severe contamination of the chamber. Water swamping of the dry air stream reduced the ionization chamber contamination to a negligible level, allowing reliable measurements to be made. The calibration of ionization chambers with representative process gases and operating conditions is necessary to ensure reliable tritium concentration measurements. (Author) (15 refs., 7 figs., 3 tabs.)

  2. A compact gas ionization chamber for VERA

    International Nuclear Information System (INIS)

    Full text: The increasing demand for measuring long-lived radionuclides with small AMS machines at energies below 1 MeV per nucleon raises the need for compact detectors which still have a decent energy resolution and allow for a clear identification of the incident particles. Based on a design by the AMS group at the ETH Zurich a compact gas ionization chamber was built and installed at the VERA 3 MV AMS facility. Due to its compact design, the detector easily fits into a DN100 cross-piece and can be inserted and retracted without breaking the vacuum. The anode is split into two active regions which allows the simultaneous measurement of ΔE and ERES. An identification of the incident particles is therefore possible via their different stopping powers. For the entrance window silicon nitride foils are used. These foils are remarkably homogeneous and can be obtained pinhole-free with thicknesses down to 50 nm. In this work the setup of the detector together with the results of first measurements of the previously difficult to measure AMS-relevant radionuclides 10Be, 36Cl and 41Ca will be presented. (author)

  3. Monolithic JFET preamplifier for ionization chamber calorimeters

    International Nuclear Information System (INIS)

    A prototype preamplifier circuit is presented for use in SSC ionization chamber calorimeters. It consists of a new type of silicon integrated circuit comprised of very low noise junction FET (JFET) components. Presently, monolithic preamplifier circuits for use in highly segmented detectors are made of implanted channel JFETs or MOS devices. While such circuits solve the density problems, they do not perform to the same level of low noise characteristics as found in discrete JFET components. The JFETs which comprise this new integrated circuit preserve the excellent low noise performance normally found only in discrete JFETs. JFETs also are much more radiation resistant and less prone to damage by electromagnetic discharges than MOS transistors. Two innovative fabrication processes are discussed. They solve the difficult gate-to-gate isolation problem needed to manufacture JFET integrated circuits. Both allow the use of an epitaxially formed channel and a diffused gate, as in standard discrete JFET processing. This, presumably, results in JFETs which exhibit lower noise than those made with implanted channels. 11 refs., 9 figs

  4. Air density correction in ionization dosimetry

    International Nuclear Information System (INIS)

    Air density must be taken into account when ionization dosimetry is performed with unsealed ionization chambers. The German dosimetry protocol DIN 6800-2 states an air density correction factor for which current barometric pressure and temperature and their reference values must be known. It also states that differences between air density and the attendant reference value, as well as changes in ionization chamber sensitivity, can be determined using a radioactive check source. Both methods have advantages and drawbacks which the paper discusses in detail. Barometric pressure at a given height above sea level can be determined by using a suitable barometer, or data downloaded from airport or weather service internet sites. The main focus of the paper is to show how barometric data from measurement or from the internet are correctly processed. Therefore the paper also provides all the requisite equations and terminological explanations. Computed and measured barometric pressure readings are compared, and long-term experience with air density correction factors obtained using both methods is described

  5. Development of emanometer of normal atomosphere air mesh grid pulse lonization chamber

    International Nuclear Information System (INIS)

    Aiming at harmfulness of radon in the air, normal atmosphere air mesh grid pulse ionization chamber Emanometer has been developed, which can measure radon content in the air effectively. Emanometer is composed of normal atmosphere air mesh grid pulse ionization chamber, signal magnify and screen unit and MCU system. At signal magnify part, choosing high resistance and low noise field-effect tube amplified IC instead of field-effect transistor increases its interference immunity and stability significantly. (authors)

  6. Calibration of ionization chambers used in LDR brachytherapy

    International Nuclear Information System (INIS)

    In this work was developed a calibration procedure of well-type ionization chambers used for measurements of I-125, seed type. It was used as a standard an ionization chamber Capintec CRC-15BT, with calibration certificate of the University of Wisconsin. It were calibrated two well-type ionization chambers of Capintec CRC-15R model. A source of I-125 was used in clinical use (18.5 to 7.4 MBq). The results showed that with the application of calibration factors was possible to decrease read deviate from 16% to just 1.0%

  7. Time expansion chamber and single ionization cluster measurement

    International Nuclear Information System (INIS)

    The time expansion chamber (TEC), a new type of drift chamber, allows the measurement of microscopic details of ionization. The mean drift time interval from subsequent sngle ionization clusters of a relativistic particle in the TEC can be made large enough compared to the width of a anode signal to allow the recording of the clusters separately. Since single primary electrons can be detected, the cluster counting would allow an improved particle separation using the relativistic rise of primary ionization. In another application, very high position accuracy for track detectors or improved energy resolution may be obtained. Basic ionization phenomena and drift properties can be measured at the single electron level

  8. 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

  9. 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.

  10. Performance of ionization chambers in X radiation beams, radioprotection level

    International Nuclear Information System (INIS)

    Narrow beams, radioprotection level, were implanted in an X ray system, based on ISO 4037-1, as recommended by IAEA (SRS 16). Energy dependency tests were carried out and short-term stability in ionization chambers for use in radiation protection of trademark Physikalisch-Technische Werkstaetten (PTW), 32002 and 23361 models. The ionization chambers were studied with regard to short-term stability within the program of quality control of the laboratory, with a 90Sr + 90Y. The results of the short-term stability test were compared with the recommendations of IEC 60731, respect to dosemeters used in radiotherapy, since this standard presents the more restrictive limits with regard to the behaviour of ionization chambers. All cameras showed results within the limits recommended by this standard. With respect to the energy dependency of the response, the model Chamber 32002 presented a maximum dependence of only 2.7%, and the model Chamber 23361, 4.5%

  11. Thin wall vacuum reaction chamber for neutron measurement

    International Nuclear Information System (INIS)

    A thin wall (3 mm) stainless steel vacuum reaction chamber has been designed, fabricated and installed in the K500 superconducting beam hall at VECC for the in-beam experiment. The chamber is spherical in shape, with inner diameter 1010 mm, having three independent sections. The middle segment is fixed to the beam line, whereas the two hemispherical sections are removable type with the help of hydraulic trolleys. This specific design facilitates almost 360 degree access of the chamber for setting up an experiment. The typical vacuum ∼ 4 x 10-7 mbar is achieved by two 550 lit/sec air cooled turbo molecular pumps backed by two 35 m3/hr scroll pumps in ∼ 8 hours. PLC based control system has been developed for the operation of pumps. 12 rings are fabricated to mount detectors, each having 440 mm radius and separated by 30° from each other in polar angle. These rings are supported inside the chamber by two flanges placed along the beam line. These rings are properly calibrated in polar and azimuthal angles with respect to the centre of the chamber. (author)

  12. Characterisation of an ionization chamber of the radioisotope metrology laboratory

    International Nuclear Information System (INIS)

    The sensitivity as a function of the photon energy up to 1.9 MeV has been studied for a special ionization chamber (50 cm length, stainless steel, high pressure Ar). The response of the chamber to 16 of the most frequently used radionuclides has been also determined. (author)

  13. 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. PMID:27192396

  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. Shielding walls against ionizing radiation

    International Nuclear Information System (INIS)

    The standard contains specifications for the shape and requirements set for lead bricks such that they can be used to construct radiation-shielding walls according to the building kit system. The dimensions of the bricks are selected in such a way as to permit any modification of the length, height and thickness of said shielding walls in units of 50 mm. The narrow side of the lead bricks juxtaposed to one another in a wall construction to shield against radiation have to form prismatic grooves and tongues; in this way, direct penetration by radiation is prevented. Only cuboid bricks (serial nos. 55-60 according to Table 10) do not have prismatic tongues and grooves. (orig.)

  16. Shielding walls against ionizing radiation

    International Nuclear Information System (INIS)

    This standard shall be applied to closed shielding facilities which, together with the lead bricks according to DIN 25 407 part 1 and the functional elements according to this standard, are designed to make possible the setting-up of complete shieldings for hot cells in beta-gamma-technique (see DIN 25 407 part 3) according to modular principles. This standard is intended to facilitate the design and construction of hot cells with shielding walls made of lead as well as the interchangeability of individual constructional elements in existing shielding walls. (orig./HP)

  17. Insertion effects of the aluminium on the sensitive volume of a parallel plates ionization chamber

    International Nuclear Information System (INIS)

    In this work one searched to analyze the influence of the materials of the walls of a chamber of ionization in its energy dependence and capacity in collecting electrons. For in such a way it varied constitution of the walls of the chamber, with different ratios in area, of polycarbonate and aluminum, respectively with thickness of 0.25 and 0.01 mm. The energy dependence, in the band of energy used in radiodiagnostic, can be reduced of 10 for 5% when an aluminum leaf is added with 8 cm 2 of area, on a window of polycarbonate with 24 cm2 of area. (author)

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

    International Nuclear Information System (INIS)

    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. - Highlights: • A special ionization chamber, inserted in a slab phantom, was designed and evaluated. • This dosimeter was utilized for the Hp(10) determination. • The evaluation of this dosimeter followed international standards. • The PENELOPE Monte Carlo code was used to evaluate the design of this dosimeter. • The tests indicated that this dosimeter may be used as a reference dosimeter

  19. Damage Diagnosis for High Temperature Coke-oven Chamber Walls

    Science.gov (United States)

    Sugiura, Masato; Sakaida, Michitaka; Fujikake, Yohichi; Irie, Keisuke

    Metallurgical coke is needed as reducing reagent and energy source in blast furnaces. Most of coke ovens in Japan have been working over 30 years and have become gradually decrepit. A coke oven consists of many coking chambers, and each chamber is 6 m high, 16 m long and 0.4m wide. Uneven damage at the chamber-wall surface such as brick erosion and carbon deposition disturbs production because the coke is pushed horizontally when discharged from the chamber. To diagnose the chamber wall which is constantly sustained at a high temperature, we have developed a water-cooling heat-resistance probe. Line scan cameras mounted in the probe obtain thermal images of the entire chamber-wall surfaces with high resolution. In addition, to measure topographical information of the wall, a laser light-section method combined with line-scan-camera imaging has been considered. It is emphasized that the diagnosis probe works under enormously severe conditions, such as at a temperature of over 1000°C and inside a width of only 0.4m. Clarifying the appearance of chamber-wall damages in operating aged coke ovens, we proposed the index relating unevenness of a chamber-wall surface to pushing load. The index is utilized for the guidance enabling effective repairs of damaged oven walls.

  20. The properties of the ultramicrocylindrical ionization chamber for small field used in stereotactic radiosurgery

    International Nuclear Information System (INIS)

    Accurate dosimetry of small-field photon beams tends to be difficult to perform due to the presence of lateral electronic disequilibrium and steep dose gradients. In stereotactic radiosurgery (SRS), small fields of 6-30 mm in diameter are used. Generally thermoluminescence dosimetry chips, Farmer, Thimble ion chamber, and film dosimetry are not adequate to measure dose in SRS beams. These techniques generally do not provide the required precision due to their energy dependence and/or poor resolution. It is necessary to construct a small, accurate detector with high spatial resolution for the small fields used in SRS. The ultramicrocylindrical ionization chamber (UCIC) with a gold wall of 2.2 mm in diameter and 4.0 mm in length has dual sensitive volumes of air (8.0 mm3) and borosilicate (2.6 mm3) cavity. Reproducibility, linearity, and radiation damage with respect to absorbed dose, beam profile of small beam, and independence of dose rate of the UCIC are tested by the dose measurements in high energy photon (5, 15 MV) and electron (9 MeV) beams. The UCIC with a unique supporting system in the polystyrene phantom is demonstrated to be a suitable detector for the dose measurements in a small beam size

  1. Development of single gridded liquid xenon ionization drift chamber

    International Nuclear Information System (INIS)

    We have simulated gamma-ray events in single gridded liquid xenon ionization drift chamber by EGS/PRESTA Monte Carlo code to construct data-sets for analyzing the basic performance as ionization chamber from ionization and scintillation signals. The size of effective volume is about 100 cc and a drift length is 42 mm. The collectors are segmented into 20 parallel strips of 2 mm wide with 0.5 mm space. We assumed that the energy resolution is 8.5% at 1.064 MeV. The comparison of the ionization signals between the experimental result and calculated result were similar shape and the each photo-peak was at the same position. Also the number of scintillation photons observed at two photomultipliers was calculated from the data-sets. (author)

  2. Calibration of Pencil Type Ionization Chambers at Various Irradiation Lengths and Beam Qualities

    International Nuclear Information System (INIS)

    Pencil type ionization chambers are being used in several diagnostic radiology applications, for the measurement of the air kerma length product, PKL. This work investigates several aspects of the pencil chamber calibration. The air kerma behind the apertures that are used for the partial irradiation of the pencil chambers depends on the irradiation set-up and equals to the air kerma free in air only under 'good geometry' irradiation conditions. Appropriate correction factors, kw, may be needed for this. The residual signal of four pencil chamber models was measured using various apertures widths. The residual signal should be subtracted from chamber signal in order to improve accuracy. Twenty-three commercial pencil type chambers were calibrated at RQT radiation qualities. The variation of performance between chambers of the same model and between different models is discussed, while the energy dependence of their response is presented. Finally, a comparison of the two calibration methods (total and partial irradiation of chamber) showed that both methods deduce similar calibration coefficients. The uncertainties of the measurements are assessed and discussed. (author)

  3. A new parallel-plate graphite ionization chamber as a 60Co gamma radiation reference instrument

    International Nuclear Information System (INIS)

    The calibration procedure in radiotherapy treatments is very important and a sensitive task due to the high doses delivered to the patients. Generally, the air-kerma cavity standards for 60Co gamma rays are graphite cavity ionization chambers. In this work a new parallel-plate graphite ionization chamber was studied to analyze its potential use as a reference instrument. In order to evaluate its performance in 60Co beams, it was submitted to several characterization tests. Moreover, Monte Carlo simulations were undertaken using the EGSnrc code to study the influence of the chamber components on its response. The results obtained showed that this new ionization chamber presented a satisfactory performance in all evaluated tests. - Highlights: ► A new ionization chamber was characterized as a reference dosimeter for 60Co beams. ► The EGSnrc code was used to determine the influence of the chamber components. ► The characterization test results were within the recommended limits. ► The results showed that this dosimeter may be used as a reference dosimeter

  4. Measurement of dose rate components of the BNCT beam at THOR using paired ionization chambers

    International Nuclear Information System (INIS)

    Paired ionization chambers were used in this work to measure the neutron and gamma-ray dose rates of the BNCT epithermal neutron beam at THOR along the beam axis free-in-air and in the water phantom. The position dependent and kerma rate weighted neutron sensitivities of the TE(TE) chamber were adopted in the measurements. Monte Carlo calculations of the neutron fluence rates and neutron kerma rates using the MCNP4C code were used to support the measurements and compare with the measured results. It concludes that the relative neutron sensitivity of the Mg(Ar) chamber warrants a detailed investigation to improve the accuracy of the dose rate measurement using paired ionization chambers in a mixed field. (author)

  5. Direct experimental determination of Frisch grid inefficiency in ionization chamber

    Science.gov (United States)

    Khriachkov, V. A.; Goverdovski, A. A.; Ketlerov, V. V.; Mitrofanov, V. F.; Semenova, N. N.

    1997-07-01

    The present work describes the method of direct experimental determination of the Frisch grid inefficiency in an ionization chamber. The method is based on analysis of the anode signal after Waveform Digitizer. It is shown that the calculated grid inefficiency value can differ much from the measured ones.

  6. A Bragg curve ionization chamber for acceleration mass spectrometry

    International Nuclear Information System (INIS)

    An ionization chamber based on the Bragg curve spectrometry method to be used as the final detector in a accelerator mass spectrometry system is described. The first tests with a Cl beam give energy resolution of 1% and Z resolving power of 72 at Z=17

  7. Cold fission studies using a double-ionization chamber

    International Nuclear Information System (INIS)

    An investigation on spontaneous fission of 252Cf is described. Both fission fragments are detected coincidentally with a double ionization chamber as a 4 π detector. Special techniques are demonstrated which allow the determination of nuclear masses and charges for cold fission fragments. Detector properties such as systematic errors and their correction are studied with the help of α particles. (orig.)

  8. Multi-parameter measurement using gridded-ionization chamber

    International Nuclear Information System (INIS)

    The multi-parameter measurement with a gridded-ionization-chamber enables the study of neutron-induced charged-particle emission reactions with very high efficiency and fairly good signal-to-background ratio. This technique will be applicable for various fields in nuclear measurements such as charged-particle spectroscopy and neutronics. (J.P.N.)

  9. Automatic control system for measuring currents produced by ionization chambers

    International Nuclear Information System (INIS)

    Ionization Chambers in current mode operation are usually used in Nuclear Metrology. Activity measurements are quickly performed by Ionization Chambers, with very good precision. For this purpose measurements of very low ionization currents, carried out by high quality instrumentation, are required. Usually, electrometers perform the current integration method under command of signals from an automation system, in order to reduce the measurement uncertainties. Among the measurement systems at the Laboratorio de Metrologia Nuclear (LMN) of IPEN, there are two ionization chamber systems. In the present work, an automation system developed for current integration measurements is described. This automation system is composed by software (graphic interface and control) and an electronic module connected to a microcomputer, by means of a commercial data acquisition card. Several test measurements were performed in order to determine the intrinsic uncertainty, linearity and stability of the system. Using calibrated radioactive solutions, the IG12/A20 chamber calibration factors for 18F and 153Sm were obtained, making possible to determine activities of these radionuclides. (author)

  10. Direct experimental determination of Frisch grid inefficiency in ionization chamber

    International Nuclear Information System (INIS)

    The present work describes the method of direct experimental determination of the Frisch grid inefficiency in an ionization chamber. The method is based on analysis of the anode signal after waveform digitizer. It is shown that the calculated grid inefficiency value can differ much from the measured ones. (orig.)

  11. Fabrication process of ionization chamber multidetector and multidetector got by this process

    International Nuclear Information System (INIS)

    The multidetector ionization chamber walls are fixed one related to the others and carried together with a tool above a resin bath to polymerize. After resin hardening, the detector includes resin basis. To contain the resin bath, the realization of a mould cut in a massive resin block are been provided for. This allows for its manutention all along the process without any deterioration risk

  12. HPXe ionization chambers for γ spectrometry at room temperature

    Science.gov (United States)

    Ottini-Hustache, S.; Monsanglant-Louvet, C.; Haan, S.; Dmitrenko, V.; Grachev, V.; Ulin, S.

    2004-01-01

    High pressure xenon (HPXe) ionization chambers exhibit many characteristics which make them particularly suitable for industrial γ spectrometry at room or higher temperature. The use of a gas as detection medium allows one to reach very large effective volumes and makes these chambers relatively insensitive to radiation damage. Further, the high atomic number of xenon ( Z=54) enhances the total absorption of incident photons and provides, combined to high pressure, a good enough detection efficiency with respect to solid state detectors. Furthermore, such ionization chambers with Frisch grid appear to be very stable over wide periods (e.g. a research prototype has been used aboard MIR orbital station for several years) and temperature range (up to 180°), without maintenance. The characteristics of different prototypes are presented. Their detection efficiency and energy resolution are studied as a function of incident γ ray energy. New developments in electronics and signal processing are also investigated to improve their performances.

  13. HPXe ionization chambers for γ spectrometry at room temperature

    International Nuclear Information System (INIS)

    High pressure xenon (HPXe) ionization chambers exhibit many characteristics which make them particularly suitable for industrial γ spectrometry at room or higher temperature. The use of a gas as detection medium allows one to reach very large effective volumes and makes these chambers relatively insensitive to radiation damage. Further, the high atomic number of xenon (Z=54) enhances the total absorption of incident photons and provides, combined to high pressure, a good enough detection efficiency with respect to solid state detectors. Furthermore, such ionization chambers with Frisch grid appear to be very stable over wide periods (e.g. a research prototype has been used aboard MIR orbital station for several years) and temperature range (up to 180 deg. ), without maintenance. The characteristics of different prototypes are presented. Their detection efficiency and energy resolution are studied as a function of incident γ ray energy. New developments in electronics and signal processing are also investigated to improve their performances

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

    International Nuclear Information System (INIS)

    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.

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

    International Nuclear Information System (INIS)

    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 γ-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 about 1.3x10-17 A

  16. 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

    International Nuclear Information System (INIS)

    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

  17. 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.

  18. Ionization chamber gradient effects in nonstandard beam configurations

    International Nuclear Information System (INIS)

    Purpose: For the purpose of nonstandard beam reference dosimetry, the current concept of reporting absorbed dose at a point in water located at a representative position in the chamber volume is investigated in detail. As new nonstandard beam reference dosimetry protocols are under development, an evaluation of the role played by the definition of point of measurement could lead to conceptual improvements prior to establishing measurement procedures. Methods: The present study uses the current definition of reporting absorbed dose to calculate ionization chamber perturbation factors for two cylindrical chamber models (Exradin A12 and A14) using the Monte Carlo method. The EGSnrc based user-code EGS lowbar chamber is used to calculate chamber dose responses of 14 IMRT beams chosen to cause considerable dose gradients over the chamber volume as previously used by Bouchard and Seuntjens [''Ionization chamber-based reference dosimetry of intensity modulated radiation beams,'' Med. Phys. 31(9), 2454-5465 (2004)]. Results: The study shows conclusively the relative importance of each physical effect involved in the nonstandard beam correction factors of 14 IMRT beams. Of all correction factors involved in the dosimetry of the beams studied, the gradient perturbation correction factor has the highest magnitude, on average, 11% higher compared to reference conditions for the Exradin A12 chamber and about 5% higher for the Extradin A14 chamber. Other perturbation correction factors (i.e., Pwall, Pstem, and Pcel) are, on average, less than 0.8% different from reference conditions for the chambers and beams studied. The current approach of reporting measured absorbed dose at a point in water coinciding with the location of the centroid of the chamber is the main factor responsible for large correction factors in nonstandard beam deliveries (e.g., intensity modulated radiation therapy) reported in literature. Conclusions: To reduce or eliminate the magnitude of perturbation

  19. Crossed-microwave-beam air ionization laboratory experiments

    International Nuclear Information System (INIS)

    Chamber experiments to study ionization layers formed by crossed microwave beams in conditions of low pressure air have been conducted. The experiment consisted of a high power 2.856 GHz microwave pulse focused in a pressure chamber onto a reflecting plate oriented at 450 to the incident beam such that the E-field of the beam is in the plane of the reflector. This geometry simulates two phase-locked beams intersecting at 900 with respect to each other. The resulting air breakdown pattern consists of ionization layers at surfaces of constructive interference. The experiment goals were to measure ionization thresholds for single and multiple layer formation, characterize the geometry of layer formation and determine density and effective collision rates in the ionization layer. The present paper describes ionization threshold measurements over the parameter range of 75 to 1780 ns pulse lengths and .01 to 3.0 Torr air pressure. The measured thresholds are compared to previous threshold measurements and discussed in the context of optimization for lowest energy and lowest power requirements for ionization. Steady-state modeling of the breakdown is presented in which the pulse shape is included in describing the approach to breakdown. A description of the breakdown geometry (through CCD camera imaging) is presented. Pressure dependent structure observed within the ionization layer is discussed

  20. Design and construction of a radiation monitor with ionization chamber

    International Nuclear Information System (INIS)

    The design and construction of a portable radiation monitor with ionization chamber for gamma and x rays measurements in the range from 40 KeV to 2 MeV are described in detail. The monitor is calibrated to give the exposure rate in Roentgens/hour in three linear ranges: 0-25 mR/h, 0-250 mR/h and 0-2500 mR/h for an ionization chamber with a sensitive volume of 600 cubic centimeters. Two conventional 9 V alkaline batteries are used to energize the monitor. The small current coming from the ionization chamber is measured by an operational amplifier with electrometer characteristics. The high voltage power supply to bias the chamber is made with a blocking oscillator and a ferrite transformer. Starting form a discussion of the desired characteristics of the monitor, the technical specifications are established. The design criteria for every section are shown. The testing procedures used to qualify every block and the results for three units are reported. (Author)

  1. 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)

  2. Pre-irradiation effects on ionization chambers used in radiation therapy

    International Nuclear Information System (INIS)

    Dosimetry protocols recommend that ionization chambers used in radiation therapy be pre-irradiated until they 'settle', i.e., until a stable reading is obtained. Previous reports have claimed that a lack of pre-irradiation could result in errors up to several per cent. Recently, data collected for a large number of commonly used ion chambers at the Institute for National Measurement Standards, NRC, Canada, have been collated and analysed, with additional data contributed by the National Physical Laboratory, UK. With this data set, it was possible to relate patterns of ion chamber behaviour to design parameters. While several mechanisms seem to contribute to this behaviour, the most obvious correlations implicate the type of insulator surrounding the central collector electrode, the extent of collector electrode shielding and possibly the area of the insulator exposed at the base of the active air volume. The results show that ion chambers with electrode connections guarded up to the active air volume settle quickly (∼9 min) and the change in response is small (less than ∼0.2%). For ion chambers where the guard connection surrounding the central collector does not extend up to the active air volume, settling times of 15-20 min and an associated change in response of up to 1% are typical. For some models of ion chambers, the irradiation rate may also play a role in settling behaviour. Settling times for the ion chambers studied here were found to be independent of beam quality. (note)

  3. Intercomparison of ionization chamber calibration factors in the IAEA/WHO network of SSDLs

    International Nuclear Information System (INIS)

    An intercomparison of ionization chamber calibration factors was conducted in 1995 which included 17 participants. The results were published in the SSDL Newsletter No. 35. In 1997, a second intercomparison was carried out involving 21 participants. The calibration factors of 24 ionization chambers were checked. For all chambers, mean ratios of SSDL to IAEA measured factors of 1.002 (standard deviation of 1.3%) and 1.004 (standard deviation of 1.3%) were obtained for the air-kerma and absorbed dose to water calibration factors, respectively. Four SSDLs had large deviations and three of them took immediate corrective actions. One deviation has not yet been resolved. The results of the intercomparison are presented and discussed in this report. (author)

  4. Ionization chamber intended to use in a system of a valuation of patient exposition on ionizing radiation during X-ray diagnostic examinations

    International Nuclear Information System (INIS)

    The construction of the air ionization chamber intended to use in a system of a valuation of patient exposition on ionizing radiation during X-ray diagnostic examinations is described. A collaboration system with X-ray limiter is discussed and a measuring method is presented. The results of testing a model of the chamber obtained in conditions of its collaboration with the X-ray limiter and X-ray generator are presented and discussed. An analysis of the experimental results is made. In a recapitulation the different possibilities of a wide application of the chamber are presented. (author)

  5. Development of a portable gas-filled ionization chamber

    Science.gov (United States)

    Chae, K. Y.; Cha, S. M.; Gwak, M. S.

    2014-02-01

    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 ˜105 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 241Am ( t 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.

  6. Development of a portable gas-filled ionization chamber

    International Nuclear Information System (INIS)

    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 ∼ 105 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 241Am (t1/2 = 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.

  7. Ion collection efficiency of ionization chambers in electron beams

    International Nuclear Information System (INIS)

    When ionization chambers are used in pulsed radiation beams the high-density of ions produced per pulse permits ion recombination, demanding the use of a correction factor. An experimental technique using the charge collected at two different voltages permits the calculation of the ion collection efficiency. The ion collection efficiency of some common ionization chambers in pulsed electron beams were studied as a function of electron energy, dose rate and depth. Accelerators with magnetic scanning system, in which the instantaneous dose rate is much greater than the average dose rate, present a smaller collection efficiency than accelerators with scattering foil. The results lead to the introduction of a correction factor for ion recombination that is the reciprocal of the ion collection efficiency. It is also suggested a simple technique to connect an external variable DC power supply in a Baldwin Farmer dosemeter. (Author)

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

    International Nuclear Information System (INIS)

    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

  9. Development of the VE-12 gridded ionization chamber

    International Nuclear Information System (INIS)

    A VE-12 gridded ionization chamber has been constructed by Northwest Institute of Nuclear Technology and Institute of Electric Vacuum Technology together. it was confirmed as a second grade standard instrument to determine the surface specific emission of alpha surface source by National Scientific Technology and Industry Committee in Dec. 1991. It's total indefinite degree is better than 1%. It has the advantages of low background high efficiency, high accuracy and easy operation

  10. A multi-anode transverse field gas ionization chamber

    International Nuclear Information System (INIS)

    A transverse field gas ionization chamber for particle identification at the Radioactive Ion Beam Line in Lanzhou (RIBLL) is described. It consists of cathode, Frisch grid and 4 anodes (20, 40, 80, 136 mm). The plateau is as long as 700 V and the energy resolution (ΔE/E) is 2.93%, as setting operating gas P10 (10%CH4 + 90%Ar) to 100 mb and Vanode= +225 V, Vcathode= -700 V for 3 components α sources

  11. 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...

  12. Fission fragments spectrometer based on ionization chamber and waveform digitizer

    International Nuclear Information System (INIS)

    The method for fission process investigation which allows to get full information on fission fragments properties is suggested. The method is based on using the fission fragment spectrometer with the twin ionization chamber having the Frisch grid and the waveform digitizer. The new design of the twin ionization chamber is described in details. The main and very important difference is the distances between the cathode and the grid and the anode. These values are 40 and 2 mm correspondingly, so the ratio is equal to 20 instead of 3 - 5 as usual. The diameter of the electrodes is 120 mm. The working gas is the mixture of argon plus 10% of methane under the pressure of 0.65 atm. High voltage of 3.5 kV is applied to the cathode. The scheme of the spectrometer electronic circuit is given. The method of simultaneous measurements of the signal amplitudes from the ionization chamber electrodes is applied, but the shape of the signals is processed by means of the waveform digitizer which gives an opportunity to obtain much more information on the fission fragments properties. It is shown that the described spectrometer can be successfully used for fission fragment energy, mass and charge distribution measurements

  13. 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.

  14. 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)

  15. Development of a multi-anode ionization chamber

    Science.gov (United States)

    Makino, Hiroki; Morikawa, Tsuneyasu; Noro, Tetsuo; Maeda, Toyokazu

    2009-10-01

    A multi-anode ionization chamber with a Frisch grid has been developed. An immediate purpose is the use in accelerator mass spectrometry (AMS), but the system will also be applied to measurements in heavy-ion nuclear physics. In order to identify the incident heavy ions, the anode is divided into 16 sections so that the ionization distribution along the ion trajectory (Bragg curve) can be analyzed. Layout of the electrodes, for field shaping, has been determined based on calculations by using a computer code, Poisson-Superfish. A good discrimination of ^36Cl ions from background ^36S ions has been shown by the Monte Carlo simulation. For the signal readout, an originally designed charge-sensitive preamplifier was newly made by using conventional operational amplifiers so as to integrate the ionization charge and interface the shaped signal to the electronic modules of existing data acquisition system. These developments are still in progress. In the meeting, the overall performance of the ionization-chamber system investigated by using accelerated heavy ion beams will be presented.

  16. A prototype of an ionization chamber for gamma radiation beams of 60Co: Experimental and Monte Carlo preliminary results

    International Nuclear Information System (INIS)

    Ionization chambers are the most widely used instruments for dosimetry in radiotherapy. With the aim to test new configurations and materials using low-cost and easily-available components, verify the possibility of its application in the gamma radiation field of 60Co and fulfill the need of a chamber for scientific metrological purposes, in this paper the prototype of a plane-parallel ionization chamber has been designed and built, and its performance has been studied at the SSDL of KARAJ. The front wall and back wall of the chamber were made of graphite and Plexiglas respectively, as opposed to the one type of material in commercially available chambers. The collecting electrode has a diameter of 20 mm. The sensitive volume is 0.63 cm3. It was found that the Leakage current, the short-term stability and the polarity effect were within the international recommendations. The results were compared with those of a reference cylindrical chamber. The maximum difference observed in this comparison was 1.1%. The relative uncertainty was below 0.2%. Moreover, Monte Carlo simulation was undertaken using MCNP4C code and the relative difference of 1.9% was observed compared to the experiment. As a result the chamber presented a satisfactory performance in all evaluated tests in Gamma radiation field of 60Co. -- Highlights: • The prototype of a plane-parallel Ionization Chamber was designed. • Its performance was studied in Gamma radiation field of 60Co. • The response of the chamber was measured and compared with that of the cylindrical ionization chamber. • The chamber was simulated using the MCNP4C Monte Carlo code. • The Leakage current, the short-term stability and the polarity effect were within the international recommendations

  17. 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.

  18. Ionization Impact on the Air Cleaning Efficiency in the Interior

    Directory of Open Access Journals (Sweden)

    Černecký Jozef

    2015-08-01

    Full Text Available The paper deals with ionization impact on efficient cleaning of air in a measuring chamber which has been cleaned and closed against any outer impacts (e.g. impurities, dust from another room, human odours. Smoking has an impact on the number of positive and negative ions including the concentration of particulate matter PM10. We investigated the ion concentration according to the presence of cigarette smoke in the room and according to the change of lit cigarette distance from the supply of ionized air. Due to the experiment there was simulated smoking at the relative air humidity φ = 37 % and φ = 39 % and temperature of 20 °C in the room. Increased PM10 concentrations were caused only by cigarette smoke pollution or more precisely by artificially created higher humidity in the measuring room excluding ambient environment impacts. The aim of the experiments was to prove influence of ionization on the elimination of cigarette smoke. The measurements showed that the highest efficiency of PM10 particulate removal was achieved when the distance of smoking cigarettes from ionization source was 3 m and the air humidity was 39 %. The consequent increase of the distance of smoking cigarettes from the ionization source significantly decreased the efficiency of particle removal. The difference between ionized and natural air is minimal at the bigger distance.

  19. Growth Of 222Rn By Using Merlin Gerin, Vinten 271/671 And Centronic Ionization Chambers

    International Nuclear Information System (INIS)

    Growth measurements of exp.222 Rn by using Merlin Gerin, Vinten 271/671 and Centronic 1G 11/A20 ionization chamber have been studied. The aim of this measurement is to determine the optimum growth in the seculer equilibrium of exp.222 Rn by using three ionization chambers. The optimum growth of exp.222 Rn by using merlin Gerin ionization chamber was (19.06 n 0.07) days, by using Vinten 271/671 ionization chamber was (19.20 n 0.01) days and with Centronic 1G 11/A20 ionization chamber was (19.64 n 0.43) days

  20. 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

  1. A gridded ionization chamber for measurement of environmental radioactivity

    International Nuclear Information System (INIS)

    In order to detect low level alpha radioactivities in various natural materials, a single gridded ionization chamber was constructed. This chamber of the Frischgrid type has a very large source area of 200 cm2 and provides a resolution of about 79 keV for 5.48 MeV alpha particles of a Americium-241 source. It was attempted to eliminate the background pulses, by making use of cathode pulses. The resultant background counting rate was in the order of 3 counts per hour, which corresponds to a good figure of merit of about 106. As a preliminary measurement, radioactive contamination levels in a sample of aluminum have been measured. It was found that (0.014 +- 0.011) pCi of Radium-226 is contained in 1 gram of the sample. (author)

  2. Development of a cathode strip chamber for minimum ionizing particles

    International Nuclear Information System (INIS)

    A cathode strip chamber (CSC) capable of measuring position information for minimum ionizing particles (MIPS) has been developed. The chamber operates in the proportional or limited proportional region, where the avalanche on the anode wire is localised to a small region around the anode wire. The position of the avalanche can be obtained by the pulse heights induced on the cathode strips which run perpendicular to direction of the anode wire. The pulse height induced on the cathode strips is proportional directly to the strip width and inversely to the distance between the strip centre to the avalanche location. Thus by measuring the pulse heights on at least three cathode strips for every event, one can reconstruct the centroid that would give the location of the avalanche on the anode

  3. 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.

  4. Developing a fast ionization chamber for transfer reaction studies

    Science.gov (United States)

    Chae, K. Y.; Bardayan, D. W.; Smith, M. S.; Schmitt, K. T.; Ahn, S. H.; Peters, W. A.; Strauss, S.

    2011-10-01

    Detection of beam and beam like recoils at far forward angles is often critical for radioactive beam measurements in inverse kinematics. Gas-filled ionization chambers are well suited for these applications, since they have moderately good energy resolution and can take prolonged exposure to beam compared to fragile semiconductor detectors. Conventional ion counters using a Frisch grid, however, have slow response times because the ionized electrons must travel long distances to the anodes. To reduce response times, a fast ion counter using a tilted window and tilted electrodes was developed and tested at ORNL's Holifield Radioactive Ion Beam Facility, modified from an original design by Kimura et al.. The maximum counting rate and energy resolution, along with future plans for using the new ion counter, will be presented. This work was sponsored by the Office of Nuclear Physics, U.S. Department of Energy.

  5. Ionization Impact on the Air Cleaning Efficiency in the Interior

    OpenAIRE

    Černecký Jozef; Valentová Karina; Pivarčiová Elena; Božek Pavol

    2015-01-01

    The paper deals with ionization impact on efficient cleaning of air in a measuring chamber which has been cleaned and closed against any outer impacts (e.g. impurities, dust from another room, human odours). Smoking has an impact on the number of positive and negative ions including the concentration of particulate matter PM10. We investigated the ion concentration according to the presence of cigarette smoke in the room and according to the change of lit cigarette distance from the supply of...

  6. Perturbation correction factors for the NACP-02 plane-parallel ionization chamber in water in high-energy electron beams

    International Nuclear Information System (INIS)

    Recent dosimetry protocols for clinical high-energy electron beams recommend measurements of absorbed dose-to-water with a plane-parallel or cylindrical ionization chamber. For well-guarded plane-parallel ionization chambers, the ionization chamber perturbation factor in water, pQ, has a recommended value of unity in all protocols. This assumption was investigated in detail in this study for one of the recommended ionization chambers in the protocols: the Scanditronix NACP-02 plane-parallel ionization chamber. Monte Carlo (MC) simulations of the NACP-02 ionization chamber with the EGSnrc code were validated against backscatter experiments. MC simulations were then used to calculate pwall, pcav and pQ perturbation factors and water-to-air Spencer-Attix stopping powers in 4-19 MeV electron beams of a calibration laboratory (NPL), and in 6-22 MeV clinical electron beams from a Varian CL2300 accelerator. Differences between calculated and the currently recommended (Burns et al 1996 Med. Phys. 23 383-8) stopping powers, water-to-air, were found to be limited to 0.9% at depths between the reference depth zref and the depth where the dose has decreased to 50% of the maximum dose, R50. pwall was found to exceed unity by 2.3% in the 4 MeV NPL calibration beam at zref. For higher energy electron beams pwall decreased to a value of about 1%. Combined with a pcav about 1% below unity for all energies at zref, this was found to cause pQ to exceed unity significantly for all energies. In clinical electron beams all three perturbation factors were found to increase with depth. Our findings indicate that the perturbation factors have to be taken into account in calibration procedures and for clinical depth dose measurements with the NACP-02 ionization chamber

  7. Twin ionization chamber for studies of (n, p), (n, α) reactions

    International Nuclear Information System (INIS)

    For investigation of the fast neutron induced (n, p), (n, α) reactions the new twin grid ionization chamber was constructed. The working conditions of the chamber were investigated. Using the ionization chamber, the energy spectra, angular distributions and cross sections of the (n, p), (n, α) reactions were obtained for some nuclei

  8. Evaluation of a transfer system for calibration of kVp meters and ionization chambers

    International Nuclear Information System (INIS)

    The assessment and control of the performance characteristics of X-ray generators and tubes is an essential part of a quality assurance programme, because the use of the X-rays in medicine for diagnosis of injuries and diseases represents the largest man-made source of public exposure to ionizing radiation. Others authors have suggested methods to determine the correct X-ray tube voltage to complete the characterization of standard radiation qualities. A method by spectrometry to calibrate ionization chambers and kVp meters used for quality control tests in diagnostic radiology has been applied at the Calibration Laboratory at IPEN. A transfer system for diagnostic radiology calibration was developed at IPEN as an alternative to calibrate those instruments that measure kVp and air kerma values. It consists of a pair of identical ionization chambers in form, but differing only by the electrode material: one is made of aluminum, and the other is made of graphite. It was calibrated using a spectrometer and a standard ionization chamber traceable to the German Primary Laboratory (Physikalisch-Technische Bundesanstalt - PTB). In this study the behaviour of the transfer system was analysed in the standard beams of two X-ray equipment of the Calibration Laboratory. The low energy X-ray generating system consists of a Rigaku Denki generator, model Geigerflex, coupled to a Philips tube model PW/2184/00 (Tungsten target and Beryllium window). Measurements were taken from 30 to 50 kV. The diagnostic radiology X-ray generating system consists of a Medicor Moevek Roentgengyara X-ray generator, model Neo-Diagnomax (125 kV). Measurements were taken from 50 to 90 kV. The established qualities are listed. As reference to the air kerma rate determination, a 1.0 cm3 parallel plate ionization chamber, Physikalisch-Technische Werkstaetten (PTW), model 77334, traceable to PTB, Germany, was utilized in this work. The transfer system was placed in the X-ray beams, using a Lucite holder is

  9. 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.

  10. 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 ...

  11. 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...

  12. Development of calibration procedures for the electron beam calibration of plane parallel ionization chambers

    International Nuclear Information System (INIS)

    In Finland, plane parallel (pp) ionization chambers have been used more than ten years for absolute dose measurements in electron beams of radiation therapy accelerators, for energies below 15 MeV. Before 1997 all pp chambers were calibrated in a 60Co gamma beam at the Finnish SSDL (STUK) for air kerma. Since 1999 all pp chambers have been calibrated by STUK in accelerator electron beams. The local absolute dose measurements (beam calibrations) at hospitals are verified every second year by independent comparative dose measurements by STUK, carried out by ionization chambers during a site visit. All absolute dose measurements are done in a water phantom. The acceptable conditions of the beam for the calibration are always verified by the measurement of beam profiles and depth doses. In regular site visits at the time of 60Co beam calibrations, discrepancies larger than 3% in comparative dose measurements between STUK and the hospitals were constantly observed with some of the hospitals' chambers, despite the chambers had had recalibrations at a 60Co beam. Based on further studies and preliminary electron beam calibrations of those problematic chambers, it became clear that pp chambers had individual characteristics as for the 60Co beam calibration. Therefore, it was decided to introduce an electron beam calibration as the routine method for the pp chambers. By the help of the electron beam calibrations, discrepancies in the comparative dose measurements between STUK and hospitals generally diminished to less than 1 %. The first electron beam calibrations were made by manual construction and it was not sure if repeatability was good enough. Therefore, a high precision jig for pp chamber calibration was constructed. In the precision jig, all chambers are in fixed positions and the only movement in the calibration process is to slide a sledge to change the reference cylindrical chamber (0,6 cm3) to the pp chamber to be calibrated. The depths of the chambers in water

  13. 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.

  14. Pressure vessel rupture within a chamber: the pressure history on the chamber wall

    International Nuclear Information System (INIS)

    Generally there is a large number of pressure vessels containing high pressure gas on power stations and chemical plant. In many instances, particularly on power plant, these vessels are within the main building. If a pressure vessel were to fail, the surrounding structures would be exposed to blast loads and the forces resulting from jets of fluid issuing from the breached vessel. In the case where the vessel is in a relatively closed chamber there would also be a general overpressurisation of the chamber. At the design stage it is therefore essential to demonstrate that the plant could be safely shut down in the event of a pressure vessel failure, that is, it must be shown that the chamber will not collapse thus putting the building at risk or hazarding equipment essential for a safe shut down. Such an assessment requires the loads applied to the chamber walls, roof, etc. to be known. (author)

  15. Green Walls for Clean Air

    OpenAIRE

    Gölsdorf, Katrin; Müller, Hans; Collier, Marcus

    2013-01-01

    Can plants help to improve the air quality? People have often complained about Ivy on buildings, but research by Helix Pflanzen GmbH, a company that is specialised in the cultivation of ivy species and the development of green wall technology, is shedding new light on an old problem. Using a cultivated variety of ivy (Hedera helix 'Wörner'), experiments were carried out that illustrated the binding effect that this Ivy has on fine dust particles. This is particularly important in urban ...

  16. Energy resolution in liquid Ar or Xe ionization chamber doped with photo-ionizing molecules

    International Nuclear Information System (INIS)

    The energy resolution for γ-rays and conversion electrons from 207Bi has been studied with a liquid Ar or Xe ionization chamber. As a photoionizing dopant, allene was added to liquid Ar or TEA to liquid Xe. Although the improvement in the resolution was significant at a low electric field by the doping in both cases, it was small at a high electric field in marked contrast to a 'δ-ray combination model'. (orig.)

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

    International Nuclear Information System (INIS)

    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.

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

    International Nuclear Information System (INIS)

    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. - Highlights: • An ionization chamber was developed to be used in radiotherapy electron beams. • The ionization chamber was submitted to several characterization tests. • The test results showed values within the international standard limits

  19. Testing a ring-shaped ionization chamber in standard beta radiation

    International Nuclear Information System (INIS)

    A ring-shaped ionization chamber, developed at Instituto de Pesquisas Energeticas e Nucleares, was tested in standard beta radiation fields. This ionization chamber was primarily developed to be used as a monitor chamber in X-ray diagnostic radiology beams. It has a large sensitive volume and parallel-plate aluminium electrode. Its entrance window is made of a thin aluminized polyester foil, which allows the collection of electrons. The ring-shaped monitor chamber was already tested in X radiation beams, showing a good performance. The aim of this work was to verify the applicability of the ionization chamber for beta radiation field dosimetry at calibration distances. (author)

  20. Attachment of membrane separator for removal of radon to ionization chamber installed for tritium stack monitor

    International Nuclear Information System (INIS)

    The effect of background counts induced by α-particles mainly from Rn in air was removed by the attachment of a water-permselective membrane separator to a tritium stack monitor equipped previously. Water vapor, after permeating the membrane selectively, was carried by N2 gas into an ionization chamber where the activity of tritium was measured. The consumption of N2 gas for carrier was reduced by recycling the gas through dehumidification processes; (1) condensation by pressure, (2) condensation by refrigeration and (3) adsorption (by adsorbents), so that there is no added daily work arising from the attachment for maintenance of the tritium monitor. (author)

  1. 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)

  2. Modification of neutron response of a TE ionization chamber for radiological protection purpose

    International Nuclear Information System (INIS)

    A tissue equivalent ionization chamber is applied in all known methods for measuring dose equivalent in mixed radiation fields. Most of the TE ionization chambers are not fully homogeneous. The deviation of a TE ionization chamber from homogeneity leads to inaccurate neutron dosimetry. It is shown that a controlled inhomogeneity of a TE gas filled cavity in a TE ionization chamber results in suitable modification of the response to neutrons particularly in a set of detectors consisting of a TE ionization chamber and an organic scintillation detector designed to determine dose equivalent index quantities of mixed radiation. The response of a TE chamber having infinite cavity filled with following gas mixtures: TE methane based composition, CH4 + N2 -TE only for hydrogen, CH4 + N2 + 3He -TE only for hydrogen was calculated for neutrons in the energy range from thermal to 1 MeV

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

    International Nuclear Information System (INIS)

    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)

  4. 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

  5. A well-type ionization chamber geometric correction factor

    International Nuclear Information System (INIS)

    To correct for the influence of source configuration on the measured activity of spherical and cylindrical brachytherapy sources, a geometric correction factor was calculated for the Standard Imaging HDR-1000 well-type ionization chamber. A Fortran program modelled each source as a lattice of point sources. Because of the cylindrical symmetry of the well chamber, it could be uniquely modelled by point detectors along the perimeter of the radial plane of the detection volume. Path lengths were calculated and attenuation factors were applied to each source - detector point combination individually. The total dose rate at each detection point was found through a Sievert summation of the point source contributions. For 137Cs sources with identical activities, a correction factor of 0.965±0.005 was calculated, equal to the ratio of the dose rate of the cylindrical source to that of the sphere. Experimental verification using a Nuclear Associates 67-809 series cylindrical source and an Amersham spherical 137Cs source yielded a correction factor of 0.958±0.016. (author)

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

    International Nuclear Information System (INIS)

    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 cm2 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 kNR 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% over the

  7. 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

  8. Comparison between IAEA/TRS-277 and IAEA/TRS-398 protocols for electron beam dosimetry with cylindrical ionization chambers

    International Nuclear Information System (INIS)

    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)

  9. Search for impurities of counting gases in ionization chambers

    International Nuclear Information System (INIS)

    In order to reach for the gas detectors applied at the ALADIN spectrometer of the GSI an as good as possible and timely remaining gas purity, a study on the kind and effects of impurities in different counting gases was performed. The gas purity was observed via the signal height of an α source after a drift path of the electrons of 50 cm. A steady decrease of the α-signals was measures, the steepness of which decreases slowly as function of the time. The half-life lies in the range of weeks, which lets conclude on a slow outgassing from the materials of the arrangement. By a gas chromatography and mass spectroscopy these impurities could be determined. Beside impurities by polar molecules as water and oxygen from the atmosphere, which are deposed in microscopical capillaries of the chamber materials and then outgassed in the samples after several days so-called softeners could be observed. Because these impurities in the arrangement at the ALADIN spectrometer cannot be avoided, a purification system in the flow-through operation was constructed and its effect tested. The gas quality can by this over several days be kept in the mean constant. In this dynamical process the fluctuations of the signal heights lie at ±0.7%. A ionization chamber as monitor for the gas purity was constructed and tested with different gas mixtures concerning observables like signal height and drift time. By this calibrated monitor in the experiment at the ALADIN spectrometer the gas quality can be independently determined. (orig.)

  10. An EGSnrc investigation of cavity theory for ion chambers measuring air kerma

    International Nuclear Information System (INIS)

    The EGSnrc system is used to compare the response of an aluminum-walled thimble chamber to that of a graphite-walled thimble chamber for a 60Co beam. When compared to previous experimental results, the EGSnrc values of the ratios of chamber response differ by as much as 0.7% from the experiment. However, it is shown that this difference can be more than accounted for by switching from using the graphite mean excitation energy of 78 eV used in dosimetry protocols to the value of 86.8 eV suggested by more recent stopping-power experiments. This suggests that the uncertainty analysis of Monte Carlo results must be done more carefully, by taking into account uncertainties in the underlying basic data such as the electron and photon cross sections. In comparison to Spencer-Attix cavity theory for a thick-walled ion chamber, the Monte Carlo calculated values of the chamber response differ from the expected ones by 0.15% and 0.01% for the graphite and aluminum chambers, respectively, which are comparable to previously reported values for the Spencer-Attix correction factors. EGSnrc is also used to investigate the effect on the chamber response of thin dag layers on the inside of the aluminum wall. There is good agreement between the calculated and measured changes in chamber response versus the thickness of the dag. The results are compared to the predictions of the Almond-Svensson extension of cavity theory and show that the theory does not correctly predict the chamber response in the presence of thin dag layers. This finding is in agreement with previously reported experimental results. It is demonstrated that the values of α, the fraction of ionizations in the gas arising from electrons generated in the dag layer, used in the theory, are not the source of the disagreement

  11. Indoor air pollution by organic emissions from textile floor coverings. Climate chamber studies under dynamic conditions

    Science.gov (United States)

    Sollinger, S.; Levsen, K.; Wünsch, G.

    The time dependence of the emission of organic compounds from a polyamide floor covering with styrene-butadiene-rubber (SBR) backing was studied in three climate chambers (0.03, 1.0 and 38 m 3) at 23°C 5nd 45% RH. While volatile compounds such as toluene reach a maximum concentration in the gas phase within 1 h and decrease in concentration to less than 2% within 60 h, the concentration of less volatile compounds, such as 4-phenylcyclohexene, decreases slowly over a period of months. If the chamber is well mixed and a defined chamber loading is maintained the observed concentrations do not depend on the chamber size, the wall material and air velocity. The concentration of the observed emissions is roughly proportional to the chamber loading. Surprisingly it is not inversely proportional to the air exchange rate. Rather, at high air exchange rates mass transfer from the carpet to the gas phase is enhanced. The "decreasing source models" of Dunn and Tichenor ( Atmospheric Environment22, 885-894, 1988) have been applied to the data. They allow the extrapolation of experimental data beyond the time available for measurement. The model calculations reveal the presence of sink effects. The role of the chamber walls as sinks can be determined more reliably if constant sources of an organic compound are placed into the chamber and their increase in concentration with time is compared with the theoretical predictions neglecting sink effects.

  12. A new mini gas ionization chamber for IBA applications

    International Nuclear Information System (INIS)

    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 129Xe 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 1015 protons per cm2 while the performance of the Si detector clearly started to degrade at 1012 particles per cm2.

  13. Coplanar anode implementation in compressed xenon ionization chambers

    Science.gov (United States)

    Kiff, Scott Douglas

    This dissertation examines the problem of microphonic degradation of high-pressure xenon ionization chambers' energy spectra. A detector design that utilizes coplanar anodes is proposed to mitigate this problem, and an optimization study finds the best geometry given some constraints on the system. A radial position-sensing method is developed from theory and implemented in experiments, demonstrating usefulness in the areas of hardware diagnostics and energy spectrum enhancement. Detailed simulations quantify the effects of various physical processes on the measured energy spectrum; the processes that degrade the photopeak most severely also show promise for improvement via design and operational changes. Simulations show multiple-site events are undesirable due to resolution degradation. A hydrogen cooling admixture is implemented to improve energy resolution after detailed simulations predict advantageous performance changes. The detector linearity is shown to be quite good over the range tested, 80-1330 keV. The best measured energy resolution is 4.2% FWHM at 662 keV, which is near the range that would be considered competitive with the less-rugged detectors employing Frisch grids.

  14. A new mini gas ionization chamber for IBA applications

    Science.gov (United States)

    Müller, A. M.; Cassimi, A.; Döbeli, M.; Mallepell, M.; Monnet, I.; Simon, M. J.; Suter, M.; Synal, H.-A.

    2011-12-01

    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 129Xe 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 15 protons per cm 2 while the performance of the Si detector clearly started to degrade at 10 12 particles per cm 2.

  15. Charge collection efficiency in ionization chambers exposed to electron beams with high dose per pulse.

    Science.gov (United States)

    Laitano, R F; Guerra, A S; Pimpinella, M; Caporali, C; Petrucci, A

    2006-12-21

    The correction for charge recombination was determined for different plane-parallel ionization chambers exposed to clinical electron beams with low and high dose per pulse, respectively. The electron energy was nearly the same (about 7 and 9 MeV) for any of the beams used. Boag's two-voltage analysis (TVA) was used to determine the correction for ion losses, k(s), relevant to each chamber considered. The presence of free electrons in the air of the chamber cavity was accounted for in determining k(s) by TVA. The determination of k(s) was made on the basis of the models for ion recombination proposed in past years by Boag, Hochhäuser and Balk to account for the presence of free electrons. The absorbed dose measurements in both low-dose-per-pulse (less than 0.3 mGy per pulse) and high-dose-per-pulse (20-120 mGy per pulse range) electron beams were compared with ferrous sulphate chemical dosimetry, a method independent of the dose per pulse. The results of the comparison support the conclusion that one of the models is more adequate to correct for ion recombination, even in high-dose-per-pulse conditions, provided that the fraction of free electrons is properly assessed. In this respect the drift velocity and the time constant for attachment of electrons in the air of the chamber cavity are rather critical parameters because of their dependence on chamber dimensions and operational conditions. Finally, a determination of the factor k(s) was also made by zero extrapolation of the 1/Q versus 1/V saturation curves, leading to the conclusion that this method does not provide consistent results in high-dose-per-pulse beams. PMID:17148826

  16. 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

    experimental methods for general recombination correction for LICs are compared and investigated for both pulsed and continuous beams. The experimental methods are all based on one of two approaches: either measurements at two different dose rates (two-dose-rate methods), or measurements at three different LIC...... recommended by the manufacturer of the LICs used, the agreement between the different methods is generally within the experimental uncertainties. For pulsed beams, the agreement between the methods is poor. The inaccuracies found in the results from the three-voltage methods are associated with numerical...... 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...

  17. A modified design of an experimental ionization chamber for gamma-ray dosimetry of spent fuel

    International Nuclear Information System (INIS)

    The lowest values of the theoretical sensitivities of an ionization chamber filled with argon and xenon gases are 1.42x10/sup 13/ and 6.178x 10/sup 15/ A/cm/sup 3/-R/hr respectively. It has been found that the value of the sensitivity increase in the atomic number of the gas. The effect of attenuation in the wall of the detector has been estimated and found to be the lowest at about 1 MeV. For higher and lower energies the attenuation in the wall increases with a corresponding significant decrease in the sensitivity. The chamber has been tested with fission product gamma-rays from spent fuel elements of Pakistan Atomic Energy Research Reactor (PARR-1). The results indicate that the insertion of an electrode at an intermediate position lowers the operating voltage substantially and also reduces the slope in the plateau region. It has also been observed that in three electrode system the initial (columnar) recombination losses are almost absent and very small volume recombination losses are expected at very high exposure. (author)

  18. Measurements of Gas-Wall Partitioning of Oxidized Species in Environmental Smog Chambers and Teflon Sampling Lines

    Science.gov (United States)

    Krechmer, J.; Pagonis, D.; Ziemann, P. J.; Jimenez, J. L.

    2015-12-01

    Environmental "smog" chambers have played an integral role in atmospheric aerosol research for decades. Recently, many works have demonstrated that the loss of gas-phase material to fluorinated ethylene propylene (FEP) chamber walls can have significant effects on secondary organic aerosol (SOA) yield results. The effects of gas-wall partitioning on highly oxidized species is still controversial, however. In this work we performed a series of experiments examining the losses of oxidized gas-phase compounds that were generated in-situ­ in an environmental chamber. The loss of species to the walls was measured using three chemical ionization mass spectrometry techniques: proton-transfer-reaction (PTR), nitrate (NO3-) ion, and iodide (I-). Many oxidized species have wall loss timescales ranging between 15 to 45 minutes and scale according to the molecule's estimated saturation concentration c* and functional groups. By comparing results of the different techniques, and in particular by the use of the "wall-less" NO3- source, we find that measuring species with high chamber wall-loss rates is complicated by the use of a standard ion-molecule reaction (IMR) region, as well as long Teflon sampling lines, which can be important sinks for gas-phase species. This effect is observed even for semi-volatile species and could have significant effects on ambient sampling techniques that make highly time-resolved measurements using long sampling lines, such as eddy covariance measurements.

  19. Radiation dosimetry with plane-parallel ionization chambers: An international (IAEA) code of practice

    International Nuclear Information System (INIS)

    Research on plane-parallel ionization chambers since the IAEA Code of Practice (TRS-277) was published in 1987 has expanded our knowledge on perturbation and other correction factors in ionization chamber dosimeter, and also constructional details of these chambers have been shown to be important. Different national organizations have published, or are in the process of publishing, recommendations on detailed procedures for the calibration and use of plane-parallel ionization chambers. An international working group was formed under the auspices of the IAEA, first to assess the status and validity of IAEA TRS-277, and second to develop an international Code of Practice for the calibration and use of plane-parallel ionization chambers in high-energy electron and photon beams. The purpose of this work is to describe the forthcoming Code of Practice. (author). 39 refs, 3 figs, 2 tabs

  20. Ionization chamber with fast timing properties and good energy resolution for fission fragment detection

    International Nuclear Information System (INIS)

    A twin ionization chamber for fission fragment detection is described. The chamber allows to extract both, fast timing- and energy proportional signals. A time resolution of 1.62 ns FWHM was obtained between two fission fragments detected in the two halves of the chamber. For 241Am α-particles the chamber gave an energy resolution of 1.3 percent. As counting gas methane NTP was used

  1. A calibration method of an ionization chamber for measuring 222Rn concentration

    International Nuclear Information System (INIS)

    When 222Rn concentration is measured with an ionization chamber, the conversion factor of ionization current to 222Rn concentration has been decided in individual case. A flow-type ionization chamber (the effective volume; 18 l) was used for measuring 222Rn concentration in this work. The conversion factor of this ionization chamber was obtained 1.11 (Bq/m3/fA) by the use of RaDEF standard source. From the results of three other literatures and this work, the following formula to calculate the conversion factor (a) was obtained as a function of the effective volume V (m3) of ionization chamber; a = (1.036 x 102-1) / [V·(log V + 6.908)] (Bq/m3/fA). (author)

  2. Practical electron dosimetry: a comparison of different types of ionization chambers

    International Nuclear Information System (INIS)

    Since Markus chambers are no longer recommended in the 1997 DIN 6800-2 version there are uncertainties as to the use of alternative chamber types for electron dosimetry. Therefore, we performed a comparison between different types of ionization chambers. In particular, the widespread Farmer and Roos chambers were compared with the Markus chamber for polarity effect, chamber-to-chamber variation, and deviations of the measured absorbed dose relative to the value obtained with the Roos chamber (which is regarded as an ideal Bragg-Gray-chamber). The perturbation correction factor at 60Co radiation was determined experimentally as 1,029 ± 0,5% (Roos chamber) and 1,018 ± 0,5% (Markus chamber) for the investigated plane-parallel chambers. In addition, we could show that the Roos chambers do not have a larger chamber-to-chamber variation than the Farmer chambers. Likewise, our results suggest that Farmer chambers could be used for electron energies above 6 MeV. (orig.)

  3. Shielding walls against ionizing radiation. Lead bricks

    International Nuclear Information System (INIS)

    The standard contains specifications for the shape and requirements set for lead bricks such that they can be used to construct radiation-shielding walls according to the building kit system. The dimensions of the bricks are selected in such a way as to permit any modification of the length, height and thickness of said shielding walls in units of 50 mm. The narrow side of the lead bricks juxtaposed to one another in a wall construction to shield against radiation have to form prismatic grooves and tongues: in this way, direct penetration by radiation is prevented. Only cuboid bricks (serial nos. 55-60 according to Table 10) do not have prismatic tongues and grooves. (orig.)

  4. On the Frisch-Grid signal in ionization chambers

    Science.gov (United States)

    Al-Adili, A.; Hambsch, F.-J.; Bencardino, R.; Pomp, S.; Oberstedt, S.; Zeynalov, Sh.

    2012-04-01

    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 σ. The measurements were made with fission fragments from Cf(sf)252, using two different grids, with 1 and 2 mm wire distances, leading to the GI values: σ=0.031 and σ=0.083, respectively. The theoretical grid signal was confirmed because the detected grid pulse-height distribution was smaller for the larger σ. 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: Cf(sf)252, U(n,f)235 and U(n,f)234. 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.

  5. On the Frisch–Grid signal in ionization chambers

    International Nuclear Information System (INIS)

    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 σ. The measurements were made with fission fragments from 252Cf(sf), using two different grids, with 1 and 2 mm wire distances, leading to the GI values: σ=0.031 and σ=0.083, respectively. The theoretical grid signal was confirmed because the detected grid pulse-height distribution was smaller for the larger σ. 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: 252Cf(sf), 235U(n,f) and 234U(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. α spectrometer of parallel plate grid ionization chamber of high energy resolution and applied

    International Nuclear Information System (INIS)

    Parallel plate Grid ionization chamber with cathode area of 300 cm2 was developed and applied to detect minimum α-emitters. It consist of a vacuum system, a gas cycle system of the parallel plate grid ionization chamber, electronics (a high voltage supply, a pre-amplifier and a main amplifier) and a computer-multichannel analyzer. The energy resolution is 23 keV FWHM for the 244Cm electrostatic precipitated source. The integral background is typically 10 counts/h between 4 and 6 MeV. The detector efficiency is 50%. The minimum detecting activity is 3 x 10-4 Bq (3σ, 30 hours). This spectrometer is suitable for detecting various samples, such as samples of the soil, water, air, bion, food, structural material, geology, archaeology, α-emitters of afterprocessing and measuring α activity of accounting for and control of nuclear material and monitoring the artificial radioactivity nuclides of environment samples around nuclear facilities. The spectrometer is equipped with apparatus for preparing large area α source by using vacuum deposition or ultrasonic pulverization. The operating program of preparing source is simple. The source thickness can be kept in 40-60 μm/cm2

  7. α spectrometer of parallel plate grid ionization chamber of high energy resolution

    International Nuclear Information System (INIS)

    Parallel plate grid ionization chamber with cathode area of 300 cm2 was developed and applied to detect minimum α-emitters. It consist of a vacuum system, a gas cycle system of the parallel plate grid ionization chamber, electronics (a high voltage supply, a pre-amplifier and a main amplifier) and a computer-multichannel analyzer. The energy resolution is 23 keV FWHM for the 244Cm electrostatic precipitated source. The integral background is typically 10 counts/h between 4 and 6 MeV. The detector efficiency is 50%. The minimum detecting activity is 3 x 10-4 Bq (3σ, 30 hours). This spectrometer is suitable for detecting various samples, such as samples of the soil, water, air, bion, food, structural material, geology, archaeology, α-emitters of after processing and measuring α activity of accounting for and control of nuclear material and monitoring the artificial radioactivity nuclides of environment samples around nuclear facilities. The spectrometer is equipped with apparatus for preparing large area α source by using vacuum deposition or ultrasonic pulverization. The operating program of preparing source is simple. The source thickness can be kept in 40-60 μm/cm2

  8. Dependence of charge collection distributions and dose on the gas type filling the ionization chamber for a p(66)Be(49) clinical neutron beam

    International Nuclear Information System (INIS)

    Measurements of central axis depth charge distributions (CADCD) in a p(66)Be(49) clinical neutron beam using A-150 TE plastic ionization chambers (IC) have shown that these distributions are dependent on the gas type filling the ICs. IC volumes from 0.1 to 8 cm3 and nine different gases were investigated. Off axis ratios and build-up measurements do not seem to be as sensitive to gas type. The gas dosimetry constants given in the AAPM Protocol for Neutron Beam Dosimetry for air and methane based TE gases were tested for consistency in water and in TE solution filled phantoms at depths of 10 cm, when used in conjunction with an IC having 5 mm thick walls of A-150. 29 refs., 7 figs., 1 tab

  9. 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.

  10. Improved energy resolution in an ionization chamber through suppression of the electrical field theory distortions

    International Nuclear Information System (INIS)

    In an ionization chamber the entrance window disturbs the electrical field lines. The resolution is thus affected. This effect is made negligible by an appropriate potential distribution on the Mylar window. (orig.)

  11. Influence on measuring ionization chamber's time response speed with charge integration amplifying circuit

    International Nuclear Information System (INIS)

    The time response speed of measuring amplifier directly influences the research on ionization chamber's time response speed. The reasons why the measuring circuit was designed with charge integration amplifier were presented. The mechanism of emerging stepped current signal of ionization chamber unit irradiated by a stable radiation source was analyzed. The method of studying amplifier time response by measuring the changing process of current signal was proposed. The relationship of the amplifier's time response speed with the detector unit interelectrode capacitance, the amplifier's input protecting resistance and its feedback integral capacitance was studied through experiment. It is concluded that the amplifier's time response speed is concerned with the constant time of ionization chamber unit interelectrode capacitance and protecting resistance. And it is not concerned with the feedback integral capacitance. It provides theoretical guidance on designing ionization chamber and measuring circuit. (authors)

  12. A study of energy resolution in a gridded ionization chamber filled with tetramethylsilane and tetramethylgermanium

    International Nuclear Information System (INIS)

    The energy resolutions of 976 keV conversion electrons from a 207Bi source are measured in a gridded ionization chamber filled with tetramethylsilane (TMS) and tetramethylgermanium (TMG), and are found to be about 5.7 and 5.5% (rms) for TMS and TMG, respectively. We also deduce a simple method of estimating the electron lifetime using a gridded ionization chamber. The electron lifetime, free ion yield and thermalization length for these liquids are measured by this simple method

  13. Construction of an ionization chamber for the measurement of dose of low energy x-rays

    International Nuclear Information System (INIS)

    We designed and constructed the prototype of an ionization chamber to measure the dose of an X-ray tube with Molybdenum anode. This X-ray tube is located in the Physics department at CINVESTAV and is used for medical physics purposes in the imaging area. The ionization chamber is designed to measure doses on biological samples exposed to X-rays and will be applied in radiation protection studies

  14. 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. PMID:27164479

  15. 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.

  16. Cylindrical ionization chamber with a screening grid and xenon under the pressure of 50 atm

    International Nuclear Information System (INIS)

    A design is considered of a cylindrical ionization chamber with a screening grid. The chamber is filled with xenon at 50 atm and has the sensitive volume of 2 l. The main characteristics of the chamber are presented: the energy resolution and detection efficiency for gamma quanta of different energies. It is shown that the chamber energy resolution is 4% for 662 keV at the optimal electric field. The comparative analysis is carried out for this xenon chamber and for the NaI(Tl) standard crystal. 9 refs.; 5 figs

  17. IFE chamber walls: requirements, design options, and synergy with MFE plasma facing components

    International Nuclear Information System (INIS)

    The wall of inertial fusion energy (IFE) chambers faces demanding conditions. IFE operation is cyclic in nature and following each micro-explosion, the chamber wall is subjected to a large flux of photons, energetic particles and neutrons. Key requirements are that: (i) the chamber wall accommodates the cyclic energy deposition while providing the required lifetime, and (ii) that after each shot the chamber is cleared and returned to a quiescent state in preparation for the target injection and the firing of the driver for the subsequent shot. This paper summarizes the IFE operating conditions, discusses their impact on the choice of chamber wall configuration, and identifies the key issues. Particular attention is given to identifying common issues and operating conditions between IFE and magnetic fusion energy (MFE) with the goal of maximizing the synergy between chamber wall design and R and D for MFE and IFE

  18. 33 CFR 183.112 - Flotation material and air chambers.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Flotation material and air... SECURITY (CONTINUED) BOATING SAFETY BOATS AND ASSOCIATED EQUIPMENT Flotation Requirements for Inboard Boats, Inboard/Outdrive Boats, and Airboats § 183.112 Flotation material and air chambers. (a)...

  19. Studies of turbulent liquid sheets for protecting IFE reactor chamber first walls

    International Nuclear Information System (INIS)

    The HYLIFE-II conceptual inertial fusion energy (IFE) reactor design uses stationary and oscillating slab jets, or liquid sheets, to create a protective pocket that allows target injection and driver beam propagation while protecting the chamber first walls from neutrons, X-rays and target debris. Thick liquid wall protection can, therefore, reduce reactor chamber size and increase chamber lifetime in commercial IFE reactors. Minimizing driver beam interference and irradiation of the final focus magnets places stringent requirements upon the surface smoothness of the stationary liquid sheets that shield the heavy-ion driver array. Experiments were carried out to determine how nozzle and flow conditioner design affect surface smoothness in turbulent liquid sheets at Reynolds numbers up to 130000. The free-surface was directly imaged using planar laser-induced fluorescence (PLIF) at downstream distances up to 25 times the sheet thickness at the nozzle exit. The data are processed to determine the probability of finding fluid at any given spatial location. The surface smoothness of sheets of water issuing from nozzles with various contractions and rectangular or nearly elliptical exits into atmospheric pressure air were quantified and compared. The free-surface characteristics of liquid sheets issuing from unblocked and partially blocked (2.5% of total area) but otherwise identical flow conditioners were compared to investigate the robustness of flow conditioning elements over long operation times. These results on nearly prototypical turbulent stationary liquid sheets address a number of technical feasibility issues for thick liquid protection in IFE reactors

  20. 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.

  1. 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)

  2. Heat flows to the combustion chamber walls in detonation and turbulent combustion regimes

    Science.gov (United States)

    Bykovskii, F. A.

    1991-02-01

    Measuremens of heat flows to the walls of an annular combustion chamber under conditions of combustion and continuous detonation are reported for a propane-oxygen mixture. It is shown that specific heat flows to the chamber walls under conditions of detonation are significantly lower than those observed during ordinary combustion. The experimental equipment and details of the experimental procedure are described.

  3. Application of a tandem ionization chamber in a quality control program of X-ray beams, radiotherapy level

    International Nuclear Information System (INIS)

    A tandem ionization chamber, developed at the Instituto de Pesquisas Energeticas e Nucleares (IPEN), for X radiation beams, radiotherapy level, was applied into a quality control program of the Calibration Laboratory of IPEN. This ionization chamber is composed by two ionization chambers, with a volume of 0.6 cm3 each one. Its inner plane-parallel electrodes and guard rings are made of different materials: one is made of aluminum and the other is made of graphite. Because of this difference in materials, the ionization chamber forms a tandem system. The relative response of the calibration factors of both sides of the chamber allows an easy verification of the X-ray beam qualities stability. The ionization chamber was submitted to some tests to verify the stability of its response: leakage current before and after exposure, repeatability and reproducibility. The performance of the ionization chamber was satisfactory. (author)

  4. Investigation of the applicability of a special parallel-plate ionization chamber for x-ray beam dosimetry

    Science.gov (United States)

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

    2014-02-01

    Diagnostic x-rays are the greatest source of exposition to ionizing radiation of the population worldwide. In order to obtain accurate and lower-cost dosimeters for quality control assurance of medical x-ray facilities, a special ionization chamber was designed at the Calibration Laboratory of the IPEN, for dosimetry in diagnostic radiology beams. For the chamber characterization some tests were undertaken. Monte Carlo simulations were proposed to evaluate the distribution of the deposited energy in the sensitive volume of the ionization chamber and the collecting electrode effect on the chamber response. According to the obtained results, this special ionization chamber presents potential use for dosimetry of conventional diagnostic radiology beams.

  5. Determination of the ND,air factor of plane parallel chambers and hm values

    International Nuclear Information System (INIS)

    The use of plane parallel ionization chambers for the dosimetry of electron beams has been recommended by most national and international dosimetry protocols. The International Code of Practice TRS-381 provides recommendations for the calibration and use in reference conditions of plane parallel chambers in radiotherapy electron beams, as well as for relative dose measurements in electron and photon beams. The present investigations focus mainly on two topics: (i) determinations of the ND,air factor for the plane parallel chambers PTW-23343 Markus and PTW-34001 Roos, using different methods proposed in TRS-381; and (ii) experimental determinations of the fluence correction factor hm in PMMA. For the Markus chamber the results show no difference between the ND,air obtained with 60Co in water and the electron beam method. The discrepancies found for the Roos chamber lead us to question the value of pwall for 60Co recommended in TRS-381. The hm values obtained are lower than those in TRS-381 for all the energies measured, and show no difference for the different chambers used. (author)

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

    International Nuclear Information System (INIS)

    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. (author)

  7. 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.

  8. Utilization of ionization chambers of parallel plates for X-radiation detection between 25 and 250 Kv

    International Nuclear Information System (INIS)

    An ionization chamber of parallel plates done in Nuclear and Energetic Research institute Brazil, was tested in X-radiation fields of low and medium energy. The results showed that this type of chamber may be used. The calibration factors were compared to the other ionization chambers of secondary standard. (C.G.C.)

  9. Rapid determination of atmospheric alpha contamination by using the Frisch grid ionization chamber

    International Nuclear Information System (INIS)

    In a radiation emergency situation, the majority of radionuclides is dispersed in the form of aerosols and can be captured on aerosol filters. Alpha-spectrometric analysis is necessary for alpha radionuclides emitting no gamma radiation. A Frisch grid ionization chamber has been tested for this purpose. Three types of filters were tested: Millipore membrane filters, Synpor membrane filters, and glass-fiber Whatman filters. Aerosols from the radon chamber were deposited on the filter by means of an aerosol sampler, the alpha-spectrum was measured and its quality was evaluated. For the next tests, the glass-fiber Whatman filter was chosen. The aim of the experiments that followed was to determine the limits of detection (LDs) for some radionuclides. Outdoor air samples were prepared using filters 10 cm in diameter. The interval between the end of sampling and the start of counting was different for each sample, owing to which the time dependence of the LD levels. The average LD shortly after sampling was about 1.1 Bq/filter and decreased to about 0.5 Bq/filter in 3 hours. (orig.)

  10. Accurate simulation of ionization chamber response with the Monte Carlo code PENELOPE

    Energy Technology Data Exchange (ETDEWEB)

    Sempau, Josep [Technical University of Catalonia (Spain)

    2010-07-01

    Full text. Ionization chambers (IC) are routinely used in hospitals for the dosimetry of the photon and electron beams used for radiotherapy treatments. The determination of absorbed dose to water from the absorbed dose to the air filling the cavity requires the introduction of stopping power ratios and perturbation factors, which account for the disturbance caused by the presence of the chamber. Although this may seem a problem readily amenable to Monte Carlo simulation, the fact is that the accurate determination of IC response has been, during the last 20 years, one of the most important challenges of the simulation of electromagnetic showers. The main difficulty stems from the use of condensed history techniques for electron and positron transport. This approach, which involves grouping a large number of interactions into a single artificial event, is known to produce the so-called interface effects when particles travel across surfaces separating different media. These effects are extremely important when the electron step length is not negligible compared to the size of the region being crossed, as it is the case with the cavity of an IC. The artifact, which becomes apparent when the chamber response shows a marked dependence on the adopted step size, can be palliated with the use of sophisticated electron transport algorithms. These topics will be discussed in the context of the transport model implemented in the Penelope code. The degree of violation of the Fano theorem for a simple, planar geometry, will be used as a measure of the stability of the algorithm with respect to variations of the electron step length, thus assessing the 'quality' of its condensed history scheme. It will be shown that, with a suitable choice of transport parameters, Penelope can simulate IC response with an accuracy of the order of 0.1%. (author)

  11. Accurate simulation of ionization chamber response with the Monte Carlo code PENELOPE

    International Nuclear Information System (INIS)

    Full text. Ionization chambers (IC) are routinely used in hospitals for the dosimetry of the photon and electron beams used for radiotherapy treatments. The determination of absorbed dose to water from the absorbed dose to the air filling the cavity requires the introduction of stopping power ratios and perturbation factors, which account for the disturbance caused by the presence of the chamber. Although this may seem a problem readily amenable to Monte Carlo simulation, the fact is that the accurate determination of IC response has been, during the last 20 years, one of the most important challenges of the simulation of electromagnetic showers. The main difficulty stems from the use of condensed history techniques for electron and positron transport. This approach, which involves grouping a large number of interactions into a single artificial event, is known to produce the so-called interface effects when particles travel across surfaces separating different media. These effects are extremely important when the electron step length is not negligible compared to the size of the region being crossed, as it is the case with the cavity of an IC. The artifact, which becomes apparent when the chamber response shows a marked dependence on the adopted step size, can be palliated with the use of sophisticated electron transport algorithms. These topics will be discussed in the context of the transport model implemented in the Penelope code. The degree of violation of the Fano theorem for a simple, planar geometry, will be used as a measure of the stability of the algorithm with respect to variations of the electron step length, thus assessing the 'quality' of its condensed history scheme. It will be shown that, with a suitable choice of transport parameters, Penelope can simulate IC response with an accuracy of the order of 0.1%. (author)

  12. Sonoluminescence air bubbles as chemical reaction chambers

    CERN Document Server

    Lohse, D; Dupont, T F; Hilgenfeldt, S; Johnston, B; Lohse, Detlef; Brenner, Michael P; Dupont, Todd F; Hilgenfeldt, Sascha; Johnston, Blaine

    1996-01-01

    Sound driven gas bubbles can emit light pulses, a phenomenon called sonoluminescence. Air is found to be one of the most friendly gases towards this phenomenon, but only if it contains 1\\% argon. We suggest a chemical mechanism to account for the strong dependence on the gas mixture, based on the dissociation of nitrogen at high temperatures and reactions which form \\rm{NO}_3^- and \\rm{NH}_4^+, among other ions; the reaction products should be investigated experimentally. Inert gases are crucial for stable sonoluminescence because they do not react with the fluid. Our phase diagram in the concentration vs forcing pressure space is applicable to any gas mixture and in good agreement with latest measurements of the UCLA group.

  13. Tuning Fano resonances with a nano-chamber of air.

    Science.gov (United States)

    Chen, Jianjun; He, Keke; Sun, Chengwei; Wang, Yujia; Li, Hongyun; Gong, Qihuang

    2016-05-15

    By designing a polymer-film-coated asymmetric metallic slit structure that only contains one nanocavity side-coupled with a subwavelength plasmonic waveguide, the Fano resonance is realized in the experiment. The Fano resonance originates from the interference between the narrow resonant spectra of the radiative light from the nanocavity and the broad nonresonant spectra of the directly transmitted light from the slit. The lateral dimension of the asymmetric slit is only 825 nm. Due to the presence of the soft polymer film, a nano-chamber of air is constructed. Based on the opto-thermal effect, the air volume in the nano-chamber is expanded by a laser beam, which blueshifts the Fano resonance. This tunable Fano resonance in such a submicron slit structure with a nano-chamber is of importance in the highly integrated plasmonic circuits. PMID:27176948

  14. Photon quality correction factors for ionization chambers in an epithermal neutron beam

    International Nuclear Information System (INIS)

    The radiation field of a neutron beam optimized for boron neutron capture therapy constitutes of a mixture of a photon and a neutron component. The photon and neutron absorbed dose to tissue have different biological effectiveness, suggesting that they should be determined separately. The thermal neutron absorbed dose component can be determined in phantom materials using activation probes. The photon and the fast neutron component can be determined using ionization chambers. The response of ionization chambers in different photon beams has recently been reported for conventional radiation therapy. Thus far, the beam quality correction factors kQ-factors) for photons for ionization chambers in epithermal neutron beams have been assumed equal to unity or estimated through measurements in accelerator produced photon beams. In the present study the kQγ- factors have been determined for two commercially available detectors in an epithermal neutron beam optimized for BNCT using the Monte Carlo method

  15. 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) .

  16. Virtual Frisch-grid ionization chambers filled with high-pressure Xe

    Science.gov (United States)

    Bolotnikov, Aleksey E.; Austin, Robert; Bolozdynya, Alexander; Richards, John D.

    2004-10-01

    New approaches to the design of high-pressure Xe (HPXe) ionization chambers are described. HPXe ionization chambers represent a well-known technique for detecting gamma rays in the energy range between 50 keV and 3 MeV. Since the HPXe detector is an electron-only carrier device, its commonly accepted design includes a Frisch-grid-a metal mesh employed for the electrostatic shielding from the immobile positive ions. The grid is a key element of the device"s design which provides good energy resolution of the detector, typically 2-3% FWHM at 662 keV. However, the grid makes the design more complex and less rugged, especially for field applications. Recently, we developed several designs of HPXe ionization chambers without shielding grids. The results obtained from the testing of these devices are presented here.

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

    International Nuclear Information System (INIS)

    A novel, segmented, multi-gap, pressurized gas ionization chamber is being developed for optimization of the luminosity of the LHC. The ionization chambers are to be installed in the front quadrupole and zero degree neutral particle absorbers in the high luminosity 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 an SPS external proton beam. Single 300 GeV protons are used to simulate the hadronic/electromagnetic shower produced by the forward collision products from the interaction regions of the LHC. The capability of instrumentations to measure the luminosity of individual bunches in a 40 MHz bunch train is demonstrated

  18. Gamma compensated pulsed ionization chamber wide range neutron/reactor power measurement system

    International Nuclear Information System (INIS)

    An improved method and system of pulsed mode operation of ionization chambers is described in which a single sensor system with gamma compensation is provided by sampling, squaring, automatic gate selector, and differential amplifier circuit means, employed in relation to chambers sensitized to neutron plus gamma and gamma only to subtract out the gamma component, wherein squaring functions circuits, a supplemental high performance pulse rate system, and operational and display mode selection and sampling gate circuits are utilized to provide automatic wide range linear measurement capability for neutron flux and reactor power. Neon is employed as an additive in the ionization chambers to provide independence of ionized gas kinetics temperature effects, and the pulsed mode of operation provide independence of high temperature insulator leakage effects. (auth)

  19. SU-D-19A-01: Can Farmer-Type Ionization Chambers Be Used to Improve the Accuracy of Low-Energy Electron Beam Reference Dosimetry?

    International Nuclear Information System (INIS)

    Purpose: To investigate the use of cylindrical Farmer-type ionization chambers to improve the accuracy of low-energy electron beam calibration. Historically, these chamber types have not been used in beams with incident energies less than 10 MeV (R50 < 4.3 cm) because early investigations suggested large (up to 5 %) fluence perturbation factors in these beams, implying that a significant component of uncertainty would be introduced if used for calibration. More recently, the assumptions used to determine perturbation corrections for cylindrical chambers have been questioned. Methods: Measurements are made with cylindrical chambers in Elekta Precise 4, 8 and 18 MeV electron beams. Several chamber types are investigated that employ graphite walls and aluminum electrodes with very similar specifications (NE2571, NE2505/3, FC65-G). Depth-ionization scans are measured in water in the 8 and 18 MeV beams. To reduce uncertainty from chamber positioning, measurements in the 4 MeV beam are made at the reference depth in Virtual Water™. The variability of perturbation factors is quantified by comparing normalized response of various chambers. Results: Normalized ion chamber response varies by less than 0.7 % for similar chambers at average electron energies corresponding to that at the reference depth from 4 or 6 MeV beams. Similarly, normalized measurements made with similar chambers at the reference depth in the 4 MeV beam vary by less than 0.4 %. Absorbed dose calibration coefficients derived from these results are stable within 0.1 % on average over a period of 6 years. Conclusion: These results indicate that the uncertainty associated with differences in fluence perturbations for cylindrical chambers with similar specifications is only 0.2 %. The excellent long-term stability of these chambers in both photon and electron beams suggests that these chambers might offer the best performance for all reference dosimetry applications

  20. SU-D-19A-01: Can Farmer-Type Ionization Chambers Be Used to Improve the Accuracy of Low-Energy Electron Beam Reference Dosimetry?

    Energy Technology Data Exchange (ETDEWEB)

    Muir, B R; McEwen, M R [Measurement Science and Standards, National Research Council, Ottawa, ON (Canada)

    2014-06-01

    Purpose: To investigate the use of cylindrical Farmer-type ionization chambers to improve the accuracy of low-energy electron beam calibration. Historically, these chamber types have not been used in beams with incident energies less than 10 MeV (R{sub 5} {sub 0} < 4.3 cm) because early investigations suggested large (up to 5 %) fluence perturbation factors in these beams, implying that a significant component of uncertainty would be introduced if used for calibration. More recently, the assumptions used to determine perturbation corrections for cylindrical chambers have been questioned. Methods: Measurements are made with cylindrical chambers in Elekta Precise 4, 8 and 18 MeV electron beams. Several chamber types are investigated that employ graphite walls and aluminum electrodes with very similar specifications (NE2571, NE2505/3, FC65-G). Depth-ionization scans are measured in water in the 8 and 18 MeV beams. To reduce uncertainty from chamber positioning, measurements in the 4 MeV beam are made at the reference depth in Virtual Water™. The variability of perturbation factors is quantified by comparing normalized response of various chambers. Results: Normalized ion chamber response varies by less than 0.7 % for similar chambers at average electron energies corresponding to that at the reference depth from 4 or 6 MeV beams. Similarly, normalized measurements made with similar chambers at the reference depth in the 4 MeV beam vary by less than 0.4 %. Absorbed dose calibration coefficients derived from these results are stable within 0.1 % on average over a period of 6 years. Conclusion: These results indicate that the uncertainty associated with differences in fluence perturbations for cylindrical chambers with similar specifications is only 0.2 %. The excellent long-term stability of these chambers in both photon and electron beams suggests that these chambers might offer the best performance for all reference dosimetry applications.

  1. The characterization of the Advanced Markus ionization chamber for use in reference electron dosimetry in the UK

    International Nuclear Information System (INIS)

    The IPEM Code of Practice (IPEM 2003) for electron dosimetry for radiotherapy beams recommends design requirements for parallel-plate ionization chambers used to determine absorbed dose to water in an electron beam. The Classic Markus design has been found not to meet these requirements. The Advanced Markus ionization chamber has been designed to rectify the problems associated with the Classic Markus ionization chamber. The response of three Advanced Markus ionization chambers was investigated and compared to the designated chamber types. Absorbed dose to water calibration factors were derived at the National Physical Laboratory (NPL) for each ionization chamber at seven electron energies in the range nominally 4-19 MeV. Investigations were carried out into chamber settling, polarity effects, ion recombination and the chamber perturbation. The response of the ionization chambers in a clinical beam was also investigated. In general all three Advanced Markus ionization chambers showed the same energy response. The magnitude of the polarity effect was typically 5% at a nominal energy of 4 MeV. There was discrepancy between the polarity measurements made at the NPL and in the clinic. The recommendation of this study is that this chamber type is not suitable for reference dosimetry in electron beams

  2. Gridded ionization chamber and dual parameter measurement system for fast neutron-induced charged particles emission reaction

    International Nuclear Information System (INIS)

    A twin ionization chamber with a common cathode and grids is described for (n,α), (n,p) studies. The chamber is used to determine the energy spectra and angular distribution of the charged particles emitted from the sample positioned on the cathode by dual parameter measurements of coinciding pulses from the anode and cathode of the ionization chamber. Pu α source is used to test the property of the chamber, an isotropic angular distribution is basically showed and the energy resolution is about 2%. This ionization chamber has already been applied to the studies of the 40Ca(n,α) and 64Zn(n,α) reactions

  3. 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.

  4. New look at displacement factor and point of measurement corrections in ionization chamber dosimetry

    International Nuclear Information System (INIS)

    A new technique is presented for determination of the effective point of measurement when cavity ionization chambers are used to measure the absorbed dose due to ionizing radiation in a dense medium. An algorithm is derived relating the effective point of measurement to the displacement correction factor. This algorithm relates variations of the displacement factor to the radiation field gradient. The technique is applied to derive the magnitudes of the corrections for several chambers in a p(66)Be(49) neutron therapy beam. 30 references, 4 figures, 1 table

  5. Comparison of the half-value layer: ionization chambers vs solid-state meters

    International Nuclear Information System (INIS)

    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)

  6. A multiple sampling time projection ionization chamber for nuclear fragment tracking and charge measurement

    International Nuclear Information System (INIS)

    A detector has been developed for the tracking and charge measurement of the projectile fragment nuclei produced in relativistic nuclear collisions. This device, MUSIC II, is a second generation Multiple Sampling Ionization Chamber (MUSIC), and employs the principles of ionization and time projection chambers. It provides unique charge determination for charges Z≥6, and excellent track position measurement. MUSIC II has been used most recently with the EOS (equation of state) TPC and other EOS collaboration detectors. Earlier it was used with other systems in experiments at the Heavy Ion Superconducting Spectrometer (HISS) facility at Lawrence Berkeley Laboratory and the ALADIN spectrometer at GSI. (orig.)

  7. Experimental data on collection efficiency of ionization chamber in pulsed-swept beam

    Energy Technology Data Exchange (ETDEWEB)

    Scarpa, G.; Milano, F.; Moscati, M.; Renzi, R.

    1991-12-31

    The correction factor accounting for recombination losses of ionization in a chamber becomes quite significant when the instantaneous dose-rate present in the beam is very high, as happens in linear accelerators used for radiation therapy. This is particularly the case of pulsed-swept linacs, where the field homogeneity is obtained by scanning the whole area with a relatively small electron beam. This contribution describes some methods for taking into account recombination effects and presents some experimental results obtained on a pulsed-swept electron beam by using both an ionization chamber and other detectors which are dose-rate independent, such as Fricke solution and thermoluminescent dosemeters (TLD).

  8. Experimental determination of corrections for fission fragment investigations using a Frisch gridded ionization chamber

    International Nuclear Information System (INIS)

    Although the invention of the ionization chamber dates back nearly 50 years the last decade has seen a remarkable revival of this device for charged particle detection. It has become apparent that such a detector has distinct advantages. Not only does the ionization chamber allow measurements of total particle energy with energy resolution far superior to that of surface barrier detectors but also simultaneously the particles' specific ionization density distribution (the socalled Bragg-curve) can be determined. Therefore, besides the particle kinetic energy, mass and angular distribution, also information about the atomic number of the detected ion can be obtained using a double Frisch gridded ionization chamber. This type of detector is in use at CBNM since almost 10 years. It has been substantially improved during this period. The special electronic treatment of the chambers pulses will be described. The necessary corrections to the raw chamber signals will be demonstrated step by step giving typical key-figures and the way they are implemented. An error estimation will be given too. (orig.)

  9. Use of a large gridded ionization chamber for identification of alpha emitters samples

    International Nuclear Information System (INIS)

    This paper refers to a large magnitude gridded ionization chamber with high resolution used in the identification of alpha radioactive samples. Several values of α energy were found which matched perfectly well adjustment curve of the chamber. Many other additional measures using different kinds of adjusted detectors were successfully obtained in order to confirm the results gotten in the experiments, thus leading to the identification of some elements of the 233 U radioactive series. (author). 10 refs., 4 figs., 1 tab

  10. High pressure xenon (HPXe) ionization chamber for γ-ray spectrometry at room temperature

    International Nuclear Information System (INIS)

    High pressure xenon ionization chambers with Frisch grid are promising devices for γ ray spectrometry at room temperature and above because of their good performances (particularly their energy resolution). In this work, the characteristics and typical performances of these detectors are presented. Some improvements of electronics and signal processing are also investigated in the aim of making these chambers even more versatile and performing. (authors)

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

    International Nuclear Information System (INIS)

    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 mm2 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.

  12. Pulse mode readout techniques for use with non-gridded industrial ionization chambers

    Energy Technology Data Exchange (ETDEWEB)

    Popov, Vladimir E. [JLAB; Degtiarenko, Pavel V. [JLAB

    2011-10-01

    Highly sensitive readout technique for precision long-term radiation measurements has been developed and tested in the Radiation Control Department at Jefferson Lab. The new electronics design is used to retrieve ionization data in a pulse mode. The dedicated data acquisition system works with M=Audio Audiophile 192 High-Definition 24-bit/192 kHz audio cards, taking data in continuous waveform recording mode. The on-line data processing algorithms extract signals of the ionization events from the data flow and measure the ionization value for each event. Two different ion chambers are evaluated. The first is a Reuter-Stokes Argon-filled (at 25 atm) High Pressure Ionization Chamber (HPIC), commonly used as a detector part in many GE Reuter-Stokes instruments of the RSS series. The second is a VacuTec Model 70181, 5 atm Xenon-filled ionization chamber. Results for both chambers indicate that the techniques allow using industrial ICs for high sensitivity and precision long-term radiation measurements, while at the same time providing information about spectral characteristics of the radiation fields.

  13. 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.

  14. 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

  15. Ionization Chambers for Monitoring in High-Intensity Charged Particle Beams

    OpenAIRE

    McDonald, J.; Naples, D.; Velissaris, C.; Erwin, A.; Ping, H.; Viren, B.; Diwan, M.

    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.

  16. 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).

  17. Assessment of small volume ionization chambers as reference dosimeters in high-energy photon beams

    Energy Technology Data Exchange (ETDEWEB)

    Le Roy, M; De Carlan, L; Delaunay, F; Donois, M; Fournier, P; Ostrowsky, A; Vouillaume, A; Bordy, J M, E-mail: loic.decarlan@cea.fr [CEA, LIST, Laboratoire National Henri Becquerel, 91191 Gif-sur-Yvette CEDEX (France)

    2011-09-07

    LNE-LNHB is involved in a European project aiming at establishing absorbed dose-to-water standards for photon-radiation fields down to 2 x 2 cm{sup 2}. This requires the calibration of reference ionization chambers of small volume. Twenty-four ionization chambers of eight different types with volume ranging from 0.007 to 0.057 cm{sup 3} were tested in a {sup 60}Co beam. For each chamber, two major characteristics were investigated: (1) the stability of the measured current as a function of the irradiation time under continuous irradiation. At LNE-LNHB, the variation of the current should be less than {+-}0.1% in comparison with its first value (over a 16 h irradiation time); (2) the variation of the ionization current with the applied polarizing voltage and polarity. Leakage currents were also measured. Results show that (1) every tested PTW (31015, 31016 and 31014) and Exradin A1SL chambers demonstrate a satisfying stability under irradiation. Other types of chambers have a stability complying with the stability criterion for some or none of them. (2) IBA CC01, IBA CC04 and Exradin A1SL show a proper response as a function of applied voltage for both polarities. PTW, Exradin A14SL and Exradin A16 do not. Only three types of chambers were deemed suitable as reference chambers according to LNE-LNHB requirements and specifications from McEwen (2010 Med. Phys. 37 2179-93): Exradin A1SL chambers (3/3), IBA CC04 (2/3) and IBA CC01 (1/3). The Exradin A1SL type with an applied polarizing voltage of 150 V was chosen as an LNE-LNHB reference chamber type in 2 x 2 cm{sup 2} radiation fields.

  18. A design study for a 'spiral staircase' ionization chamber for the quality control of electron beams

    International Nuclear Information System (INIS)

    In order to verify that the energies of electron beams used for external beam therapy remain constant, IPEM 81 recommends a constancy check based on the ratio of ionization chamber measurements at two depths along the central axis. Such measurements for a range of electron energies can be a time consuming process. The purpose of this study was to design a device that would use several ion chambers simultaneously to measure electron depth dose curves, and hence the electron energy. A design was developed for a device consisting of ten independent ionization chambers, shaped and arranged in a solid phantom like the steps of a spiral staircase, the axis of the staircase being coincident with the axis of the electron beam. Measurements were carried out to test the design of individual chambers and to optimize the radius of the spiral and both the depth intervals and the lateral spacing between adjacent chambers. For ranges of electron energy from 6-12 MeV and 12-20 MeV the radii of the spirals needed were found to be 36.5 mm and 30.9 mm, the angular separations between edges of the chambers were 52 deg. and 30 deg. and chamber depths were found to be 10, 15, 20, 25, 30, 35, 40, 45, 50, 55 mm and 20, 40, 45, 50, 55, 60, 65, 70, 75, 80 mm, respectively. (note)

  19. Comparative study of ionization chambers of two different sensitive volumes for dose quality control of IMRT

    International Nuclear Information System (INIS)

    The aim of this work is to make a comparative study of ionization chambers with sensitive volume of 0.01 cm3 and 0.13 cm3 to evaluate the dose assurance for IMRT treatment. To perform this study, 20 IMRT planning were selected with small field size, and dose measurements have been performed in a low dose gradient region with both ionization chambers. These measurements were compared with data provided by the planning software. The analysis of measurements showed that both chambers can be used for IMRT quality control, because the variations found not exceed 4,5% of expected value and the chamber with a volume of 0.13 cm3 had better results. In this work, one can conclude that the chamber with sensitive volume of 0.13cm3 despite to have a larger volume, this chamber is more favorable for quality control of absolute dosimetry of IMRT, but no excluding the use of chamber with sensitive volume of 0.01cm3 which obtained satisfactory results. (author)

  20. Results from a continuos control of the stability of standard ionization chambers

    International Nuclear Information System (INIS)

    The results from regular checks of measuring assembly performance constancy carried out in the period 1981-2000 for five Secondary Standard Chambers are presented. The test procedure consisted of 10 consecutive measurements of collected electrical charge for a time of 200 s each. For all chambers the percentage deviations are into the range of ± 1.5 %. For the whole period the average values of deviations are between 0.15 % and 0.14 %. The results for two chambers (2505/A SN 598 and NPL 2651 SN 096) in chronological succession are graph shown. The histograms of deviations for two other chambers (NE 2571 No. 238 and NE 2575 No. 118 are given. The deviations have a random character and due to dominant influence of some of the affecting quantities on given data. According to the international documents, the performance stability of the Secondary Standard ionization chambers is quite satisfactory

  1. 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.

  2. Use of well-type ionization chambers in radioactive metrology

    International Nuclear Information System (INIS)

    A summary is given of the results of our observations and experiments gathered together over a period of 10 years in the Radioelement Measurements Laboratory, concerning the use of well-type chambers in refined metrology. The optimum conditions for obtaining good reproducibility are defined; this is indispensable if improved sensitivity and accuracy are required. For this, we consider, and measure, the effects of: the nature and the shape of the sources and of the containers; the random form of the response and its statistical treatment; the non-linearity and the show drift of the installation. A sound knowledge of the causes of error, the application of adequate correction methods and an exact calculation of the error, all make it possible to carry out measurements under the best conditions for obtaining a good reproducibility. The accuracy can attain 1.5 per cent. (author)

  3. A high resolution gridded ionization chamber for nuclear spectroscopy

    International Nuclear Information System (INIS)

    This paper describes some techniques used in the design of high resolution gridded ionisation chambers for measurements of absolute activity of radionuclides. Details of the geometry of the system and its electrodes are presented; their shape and the spacing between the grid wire was studied with the help of an electrolytic tank. The experimental spectra obtained with an Am 241 source using Ar + 10% methane as a flow gas show a total resolution of 39,07 KeV in very good agreement with the best results available in the literature. An application of the methods developed was used in the design ans construction of a proportional counter provided with three sequential grids disposed in such a way that the pulses from the first stage had their amplitude multiplied by the two further stages. Multiplication factors of the order of 10 sup(3) were obtained but higher values are expected. (author)

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

    International Nuclear Information System (INIS)

    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 4mm3 sensitive volume. The detector was characterized in a plastic phantom with 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 2×2cm2, in which case the linear array offers a much better characterization of the penumbra region. Down to 1×1cm2, 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 technology will be

  5. A dual type gridded ionization chamber as liquid argon purity monitor II

    International Nuclear Information System (INIS)

    The attenuation lengths of electrons in liquid argon purified by molecular sieves, a Ti-Ba getter and an Oxysorb filter was measured by using a dual type gridded ionization chamber. From the electric field dependence of the attenuation length, it is concluded that the type of remaining impurity is not an oxygen type, but N2O type. (author)

  6. Future development of the demands on therapy dosemeters with ionization chambers

    International Nuclear Information System (INIS)

    Only little will change with the introduction of the European internal market with regard to the demands on ionization chamber dosemeters used in radiotherapy, provided that the harmonized standard is aligned with IEC publication 731. Type licences for domestic calibration will be replaced by European Communities licences. (orig.)

  7. ΔE-E telescope with high energy resolution large sensitive area ionization chamber

    International Nuclear Information System (INIS)

    The construction and the performances of ΔE-E telescope with active thick 11 cm and window area 1600 mm2 are described. ΔE detector is a Frisch ionization chamber. The performances of ΔE detector utilizing 239Pu-α source is tested. The optimum ΔE resolution obtained is 4.6%

  8. Reactor oscillator project - Theoretical study; operation problems; choice of the ionization chamber

    International Nuclear Information System (INIS)

    Theoretical study of the reactor operator covers methods of the danger coefficient and the method based on measuring the phase angle. Operation with the reactor oscillator describes measurement of the cross section and resonance integral, measurement of the fissionable materials properties, measurement of impurities in the graphite sample. A separate chapter is devoted to the choice of the appropriate ionization chamber

  9. Determination of 238U nucleus number using grid ionization chamber method and small solid angle method

    International Nuclear Information System (INIS)

    Using the grid ionization chamber method and small solid angle method, the number of 238U nucleus in the highly pure U3O8 sample is determined. Although the ratio of efficiency for the two methods is as high as 484, the results are in good agreement

  10. Calculational-theoretical studies of the system of local automated regulators and lateral ionization chambers

    International Nuclear Information System (INIS)

    Methods of engineering synthesis of the systems for nuclear reactor local automated power regulation and radial-azimuthal energy distribution stabilization operating according to lateral ionization chamber signals are described. Results of calculational-theoretical investigations into the system efficiency and peculiarities of its reaction to some perturbations typical of the RBMK type reactors are considered

  11. Dosimetric application of a special pencil ionization chamber in radiotherapy X-ray beams

    International Nuclear Information System (INIS)

    The aim of this work was to study the performance of a pencil ionization chamber with a sensitive volume of only 1.06 cm3 and a length of 3.0 cm, developed at the Calibration Laboratory of the IPEN, in very low-energy radiotherapy X-ray beams. These beams are still used for certain skin cancer treatments due to their rapid attenuation in tissue. The dosimeter performance was evaluated in some tests proposed by the IEC 60731 standard: short- and long-term stability and linearity of response. For a complete analysis of the dosimeter response, the EGSnrc Monte Carlo simulation was utilized to investigate the influence of its different parts on the ionization chamber response. All results of the tests were in accordance with the recommended limits, and this work shows that it is possible to extend the application of this pencil-type ionization chamber developed at the LCI. - Highlights: ► A special pencil-type ionization chamber was characterized for radiotherapy X-ray beams. ► The results of the characterization tests were within the recommended limits. ► The EGSnrc code was employed to evaluate the components of the dosimeter. ► The simulations showed that this novel configuration is suitable for this application. ► This dosimeter may be used for quality control programs at laboratories and clinics

  12. The uncertainty associated to the position of the ionization chamber

    International Nuclear Information System (INIS)

    This work is about the determination of the components of uncertainties originated for the positioning of 600cm3 camera in a field of radiation for a 137Cs source for a Dosimetry Laboratories. The basic idea is the inverse square of the distance law and its influence on the kerma in air. It was demonstrated that the effect over the uncertainty is negligible, for a 30 cm3 camera the result will be different. (author)

  13. Electronic system for the automation of current measurements produced by ionization chambers

    International Nuclear Information System (INIS)

    Ionization Chambers in current mode operation are usually used in Nuclear Metrology in the determination of radionuclide activity. For this purpose measurements of very low ionization currents, in the range of 10-8 to 10-14 A, are required. Usually, electrometers perform the current integration method under command of signals from an automation system, in order to reduce the measurement uncertainties. In the present work, an automation system, developed for current integration measurements at the Laboratorio de Metrologia Nuclear (LMN) of Instituto de Pesquisas Energeticas e Nucleares (IPEN), is described. This automation system is composed by software (graphic interface and control) and an electronic module connected to a microcomputer, by means of a commercial data acquisition card CAD12/32 (LYNX Tecnologia Eletronica Ltda.). Measurements, using an electrometer Keithley 616 (Keithley Instruments, Inc) and an ionization chamber IG12/A20 (20th Century Electronics Ltd.), were performed in order to check the system and for validating the project. (author)

  14. Automation of the reading of an ionization chamber: study and design of a data transfer system

    International Nuclear Information System (INIS)

    Management of information obtained through ionization chamber, type of detector the most employed in centers or institutions using ionizing radiation machines and radioactive sources, is done manually because data are fed into computers from keyboard. This procedure presents hazards of loss and bad transcription of information. A more practical way of getting over this handicap is the setting up of a system that transfers data from ionization chamber into computer. Thereafter, it will be easier for the user to adjust his data processing software to the system underconsideration. This system, even though not directly designed to process data, that being a specific task of each user, is constituted of an electronic aspect which plays the interface part between them. It takes account parameters having relevance to the quality and the quantity of information put out by the detector

  15. 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.

  16. 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)

  17. 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.

  18. A special ionization chamber performance for the quality control in radiotherapy

    International Nuclear Information System (INIS)

    A special double-faced plane parallel ionization chamber, with inner electrodes of different materials was developed. Its use will be in quality control programs of X-rays equipment, radiotherapy level. This chamber was tested and calibrated in accordance with international recommendations, and it showed a satisfactory level of performance, mainly with regard to its use: the formation of a Tandem system for confirmation of half-value layers and effective energies in X-radiation beams, previously determined by the conventional method. In this developed system absorbers or any special set-ups are not necessary. The main advantages of this type of chamber are simple and quick measurements, that enable higher frequency of quality control tests. Moreover, the Tandem chamber presents low cost, and can be used with any commercial available electrometer. (author)

  19. Long Term Stability Of Farmer Type Ionization Chamber Calibration Coefficient belonging To Local Radiotherapy Centres In Malaysia

    International Nuclear Information System (INIS)

    The accuracy of the ionization chambers calibration coefficient is one of the factors that would contribute to efficient radiotherapy treatment. The IAEA therefore has recommended that an ionization chamber be calibrated every year, with a condition that the deviations between the previous and new calibration coefficients ND,w should not differ by ±1.5 %. It has been identified that Farmer type ionization chambers is the most popular ionization chamber among the radiotherapy centres in Malaysia. For this reason, the purpose of this work is to evaluate the calibration coefficients long term stability of the Farmer type ionization chambers. A total of 33 Farmer type ionization chambers were studied and the mean μ of the ND,w deviation together with its standard error SE were calculated. This μ ±SE will be used to measure stability of ND,w. Our results showed that most chambers have μ ±SE lies within the ±1.5 %. It is thus concluded that most of the Farmer type ionization chamber were stable in their ND,w and safe to be used for radiotherapy treatment. (author)

  20. A dual type gridded ionization chamber as purity monitor of liquid argon

    International Nuclear Information System (INIS)

    The liquid argon time projection chamber (LATPC) is currently developed for detecting solar neutrons or proton decays. A dual type gripped ionization chamber with different drift distances of liberated electrons is constructed to measure the purity of liquid argon. A purification system of gaseous argon for LATPC with a drift space of about 150 cm is also constructed. The performances of both the dual type gripped ionization chamber and the purifier are tested seeking to develop a large scale LATPC. It is demonstrated that the attenuation length of electrons and also the impurity level in liquid argon can be well determined in the dual type gripped ionization chamber. In the case of the purifier, there still remains unknown low-level impurities in purified liquid argon. The results are compared with UCI data which were obtained with liquid argon mixed with water vapor. the same tendency is found in the attenuation length of their data as in the present results. This seems to suggest the dominant impurity remaining in the purifier is still water. The present apparatus was previously tested with liquid argon purified by other purification system of Ti-Ba getters. The attenuation length obtained by those tests was almost 100 cm. (N.K.)

  1. The effect of waterproofing sleeves on the response of FARMER like ionization chambers

    International Nuclear Information System (INIS)

    According to most recent dosimetry protocols, the determination of the absorbed dose to water for photon and electron beams should be performed with non-water-proof ionization chamber along with plastic waterproofing sleeves whose thickness should be less than 1 mm. In these protocols, the correction for the waterproofing sleeve is incorporated in the equation of the perturbation factor pwall. Many SSDLs and hospitals were previously provided with thicker sleeves and are probably still using them for routine calibrations. The objective of the work presented in this paper is to investigate the effect of the waterproofing sleeves on the response of a WELLHOFER IC 70 ionization chambers in a 60Co and two high energy X-ray beams, 6MV and 18 MV. This chamber is inherently waterproof, thus, the ionisation current obtained with sleeves of different thickness is compared to the current obtained without sleeve. The results are improved by performing, for each thickness, at least two series of measurements with and without sleeve. The results show that with 60Co, the ionization response increases from 0.08% to 0.47% for sleeves from 0.75 mm to 1.75 mm. For 6 MV and 18 MV X-rays, the signal decreases respectively by 0.8% and 1%. When taking into account the perturbation correction factor including the waterproofing sleeve component, the ratio R/Ro , where R is the product of the chamber signal and the perturbation factor (the subscript is for the response without sleeve) is increasing from 0.14% to 0.55% for 60Co. For X-rays, this ratio decreases up to 0.75% and 0.59% respectively for 6 MV and for 18 MV. Similar results are obtained with FARMER like ionization chambers

  2. Beam quality conversion factors for parallel-plate ionization chambers in MV photon beams

    Energy Technology Data Exchange (ETDEWEB)

    Muir, B. R.; McEwen, M. R.; Rogers, D. W. O. [Carleton Laboratory for Radiotherapy Physics, Physics Department, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6 (Canada); Institute for National Measurement Standards, National Research Council of Canada, Ottawa, Ontario K1A 0R6 (Canada); Carleton Laboratory for Radiotherapy Physics, Physics Department, Carleton University, 1125 Colonel By Drive, Ottawa, Ontario K1S 5B6 (Canada)

    2012-03-15

    Purpose: To investigate the behavior of plane-parallel ion chambers in high-energy photon beams through measurements and Monte Carlo simulations. Methods: Ten plane-parallel ion chamber types were obtained from the major ion chamber manufacturers. Absorbed dose-to-water calibration coefficients are measured for these chambers and k{sub Q} factors are determined. In the process, the behaviors of the chambers are characterized through measurements of leakage currents, chamber settling in cobalt-60, polarity and ion recombination behavior, and long-term stability. Monte Carlo calculations of the absorbed dose to the air in the ion chamber and absorbed dose to water are obtained to calculate k{sub Q} factors. Systematic uncertainties in Monte Carlo calculated k{sub Q} factors are investigated by varying material properties and chamber dimensions. Results: Chamber behavior was variable in MV photon beams, especially with regard to chamber leakage and ion recombination. The plane-parallel chambers did not perform as well as cylindrical chambers. Significant differences up to 1.5% were observed in calibration coefficients after a period of eight months although k{sub Q} factors were consistent on average within 0.17%. Chamber-to-chamber variations in k{sub Q} factors for chambers of the same type were at the 0.2% level. Systematic uncertainties in Monte Carlo calculated k{sub Q} factors ranged between 0.34% and 0.50% depending on the chamber type. Average percent differences between measured and calculated k{sub Q} factors were - 0.02%, 0.18%, and - 0.16% for 6, 10, and 25 MV beams, respectively. Conclusions: Excellent agreement is observed on average at the 0.2% level between measured and Monte Carlo calculated k{sub Q} factors. Measurements indicate that the behavior of these chambers is not adequate for their use for reference dosimetry of high-energy photon beams without a more extensive QA program than currently used for cylindrical reference-class ion chambers.

  3. Beam quality conversion factors for parallel-plate ionization chambers in MV photon beams

    International Nuclear Information System (INIS)

    Purpose: To investigate the behavior of plane-parallel ion chambers in high-energy photon beams through measurements and Monte Carlo simulations. Methods: Ten plane-parallel ion chamber types were obtained from the major ion chamber manufacturers. Absorbed dose-to-water calibration coefficients are measured for these chambers and kQ factors are determined. In the process, the behaviors of the chambers are characterized through measurements of leakage currents, chamber settling in cobalt-60, polarity and ion recombination behavior, and long-term stability. Monte Carlo calculations of the absorbed dose to the air in the ion chamber and absorbed dose to water are obtained to calculate kQ factors. Systematic uncertainties in Monte Carlo calculated kQ factors are investigated by varying material properties and chamber dimensions. Results: Chamber behavior was variable in MV photon beams, especially with regard to chamber leakage and ion recombination. The plane-parallel chambers did not perform as well as cylindrical chambers. Significant differences up to 1.5% were observed in calibration coefficients after a period of eight months although kQ factors were consistent on average within 0.17%. Chamber-to-chamber variations in kQ factors for chambers of the same type were at the 0.2% level. Systematic uncertainties in Monte Carlo calculated kQ factors ranged between 0.34% and 0.50% depending on the chamber type. Average percent differences between measured and calculated kQ factors were - 0.02%, 0.18%, and - 0.16% for 6, 10, and 25 MV beams, respectively. Conclusions: Excellent agreement is observed on average at the 0.2% level between measured and Monte Carlo calculated kQ factors. Measurements indicate that the behavior of these chambers is not adequate for their use for reference dosimetry of high-energy photon beams without a more extensive QA program than currently used for cylindrical reference-class ion chambers.

  4. Dosimetric evaluation of a 2D pixel ionization chamber for implementation in clinical routine

    International Nuclear Information System (INIS)

    In this paper we present the results of a dosimetric evaluation of a 2D ionization chamber array with the objective of its implementation for quality assurance in clinical routine. The pixel ionization chamber MatriXX (Scanditronix Wellhofer, Germany) consists of 32 x 32 chambers with a distance of 7.6 mm between chamber centres. The effective depth of measurement under the surface of the detector was determined. The dose and energy dependence, the behaviour of the device during its initial phase and its time stability as well as the lateral response of a single chamber of the detector in cross-plane and diagonal directions were analysed. It could be shown, that the detector's response is linear with dose and energy independent. Taking the lateral response into account, two different dose profiles, for a pyramidal and an IMRT dose distribution, were applied to compare the data generated by a treatment planning system with measurements. From these investigations it can be concluded that the detector is a suitable device for quality assurance and 2D dose verifications

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

    International Nuclear Information System (INIS)

    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 cm3. 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 cm2 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 cm2 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.

  6. Gridded ionization chamber for detection of x-ray wave activity in tokamak plasmas

    International Nuclear Information System (INIS)

    In order to carry out x-ray observations of magnetohydrodynamic wave activity of the plasma during DD and DT (deuterium-beam-heated deuterium and tritium plasmas, respectively) operation of the Tokamak Fusion Test Reactor (TFTR), we will need detectors not susceptible to nuclear radiation damage. We have investigated the use of gridded ionization chambers as fast nondamageable x-ray detectors. A prototype chamber is described which was tested on the PDX tokamak. These tests and laboratory tests with a pulsed x-ray source suggest that the detector has sufficient sensitivity and speed for the required measurements

  7. Gridded ionization chamber for detecion of x-ray wave activity in tokamak plasmas

    International Nuclear Information System (INIS)

    In order to carry out X-ray observations of magnetohydrodynamic wave activity of the plasma during DD and DT (deuterium-beam-heated deuterium and tritium plasmas, respectively) operation of the Tokamak Fusion Test Reactor (TFTR), we will need detectors not susceptible to nuclear radiation damage. We have investigated the use of gridded ionization chambers as fast nondamageable X-ray detectors. A prototype chamber is described, which was tested on the PDX tokamak. These tests and laboratory tests with a pulsed X-ray source suggest that the detector has sufficient sensitivity and speed for the required measurements

  8. Set-up on the basis of multiwire proportional and ionization chambers for radioactive beam experiments

    International Nuclear Information System (INIS)

    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 6He on a CH2 target are presented

  9. Design, construction and tests of well type ionization chamber for beta and gamma radiation detection

    International Nuclear Information System (INIS)

    This paper describes the design, construction and tests of well type ionization chamber, with parallel plate electrodes, which is used in the measurements of radiopharmacous activities, by means of beta and/or gamma radiations detection. Its response was studied utilizing Tc-99, I-131, Co-60, Am-241 and Sr-90 sources. The results obtained show that, due to to the very low leakage current from the chamber and the linearity of response, its possible to measure activities in the range from 20KBq up to 10GBq, whith a precision better than 1%. (author)

  10. A study of the response of ionization chambers to mammography beams

    International Nuclear Information System (INIS)

    Some simulated mammography radiation beams have been established at the BIPM using a low-energy x-ray tube with a tungsten anode and molybdenum as a filter. The response of two ionization chambers of different types to these beams is compared with that obtained in mammography beams at the PTB and the NMi which were produced with x-ray tubes with molybdenum anodes and molybdenum filters. The relative differences between the chamber responses to these two different types of beams were less than 7 x 10-3 which implies the uncertainty for the transfer of a calibration from one type of beam to the other. (authors)

  11. Validation of the neutron and gamma fields in the JSI TRIGA reactor using in-core fission and ionization chambers.

    Science.gov (United States)

    Žerovnik, Gašper; Kaiba, Tanja; Radulović, Vladimir; Jazbec, Anže; Rupnik, Sebastjan; Barbot, Loïc; Fourmentel, Damien; Snoj, Luka

    2015-02-01

    CEA developed fission chambers and ionization chambers were utilized at the JSI TRIGA reactor to measure neutron and gamma fields. The measured axial fission rate distributions in the reactor core are generally in good agreement with the calculated values using the Monte Carlo model of the reactor thus verifying both the computational model and the fission chambers. In future, multiple absolutely calibrated fission chambers could be used for more accurate online reactor thermal power monitoring. PMID:25479432

  12. Calibration methods of plane-parallel ionization chambers used in electron dosimetry

    International Nuclear Information System (INIS)

    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 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)

  13. Application of LabVIEW on Ionization Chamber to Measurement Radiation

    International Nuclear Information System (INIS)

    The purpose of this research was to apply LabVIEW program to control an ionization chamber. LabVIEW was used to compose a block diagram and front panel. The block diagram was programmed to be controlled by the front panel. Radiation dose of Cs -137 at 1.00, 1.50, 2.00, 2.50, 3.00 and 4.00 meter were compared from LabViEW and manual system. The results show that the different percentages of Pb filter of thickness 0, 20 and 39 mm are 0.68, 0.68 and 0.48, respectively. This experiment results indicated that the LabVIEW can be used in assisting radiation measurement. Furthermore, by controlling the ionization chamber by LabVIEW, the radiation dose received by operator is reduced.

  14. Simulations of ^12C Break Up In A Twin Ionization Chamber

    Science.gov (United States)

    Segal, C. B.; Patel, N. R.; Greife, U.; Rehm, K. E.; Deibel, C. M.; Greene, J.; Henderson, D.; Jiang, C. L.; Kay, B. P.; Lee, H. Y.; Pardo, R.; Notani, M.; Marley, S. T.; Tang, X. D.

    2008-10-01

    In stellar explosions the triple α decay process is key to forming the life-giving ^12C . This experiment is to further investigate the energy region in ^12C around 10 MeV where a theoretically predicted 2^+ state has yet to be observed. The motivation for studying this is to better understand the ^12C nucleosynthesis process that occurs in red giant stars where the short lived ^8Be interacts with alphas at extreme temperature and pressure scenarios which then in turn creates ^12C. We study the particle-unbound states by implanting ^12B into a twin Frisch grid ionization chamber and following the decay into ^12C and subsequently into three α particles. The response of this ionization chamber to the detection of multiple α particles was studied using various simulation programs. Results of these simulations and limits for the predicted 2^+ state will be presented.

  15. 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.

  16. Development of a 300 cm2 parallel plate α grid ionization chamber

    International Nuclear Information System (INIS)

    The structure and characteristics of a parallel plate α grid ionization chamber with a cathode area of 300cm2 are presented in this paper. The counting gas mixture of the ionization chamber is P-10 gas (90%Ar + 10%CH4) with a pressure of 1.8 x 105 Pa. It can ensure long time (48h) stable work when the gas flow rate is more than 25 mL/min. Its main specifications are: energy resolution is 36 keV for Φ239Pu electrodeposition sources; background count rate 12.6 counts/h in the range of 4 to 6 MeV; minimal detectable limit 2 x 10-4Bq (3σ,27h); detection efficiency 44% for 232Th source with a diameter of 190 mm

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

    International Nuclear Information System (INIS)

    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

  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. 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.

  20. Calculation of the energy dependent efficiency of gridded 3He fast neutron ionization chambers

    International Nuclear Information System (INIS)

    The relative efficiency function for total energy events in a 3He fast neutron ionization chamber has been calculated with a Monte Carlo approach. It is shown that the efficiency function applicable to a point isotropic source located near the surface of the spectrometer differs significantly from that obtained in standard calibration procedures using neutrons from the 7Li(p,n)7Be reaction for Esub(n) > 1.5 MeV. (orig.)

  1. A cylindrical xenon ionization chamber detector for high resolution, room temperature gamma radiation spectroscopy

    International Nuclear Information System (INIS)

    A 0.75 l gridded cylindrical ionization chamber gamma radiation detector using highly purified xenon near the critical point as the detection medium is described. The detector operates at room temperature with a noise subtracted intrinsic energy resolution of 1.8% at 662 keV. The detector design and performance variables are discussed in comparison to previous planar and cylindrical xenon detectors. (orig.)

  2. High efficiency charged-particle spectrometer using gridded ionization chamber for fast-neutron induced reactions

    International Nuclear Information System (INIS)

    A high efficiency charged particle spectrometer for fast neutron induced reactions has been developed using a gridded-ionization chamber taking advantage of its large solid angle and capability of energy-angle determination. It is characterized by high stopping-power and low background to be applicable for alpha-particles emitted by 15 MeV neutrons and protons for MeV incident neutrons. The spectrometer has been applied successfully for (n, alpha) and (n, p) reactions. (orig.)

  3. Measurement of atom numbers of compound α source by using a gridded ionization chamber

    International Nuclear Information System (INIS)

    Atom numbers of the isotopes of a compound α source are measured by using a gridded ionization chamber (GIC). Make full use of the characteristics of the GIC, the self-absorption and scattering effects are corrected, and the precise results are derived. The study establishes the basis of the further experiment of the light nuclei (n, α) reaction. The method can also be used in measuring the weak α source. (authors)

  4. Application of the Shockley-Ramo theorem on the grid inefficiency of Frisch grid ionization chambers

    Science.gov (United States)

    Göök, A.; Hambsch, F.-J.; Oberstedt, A.; Oberstedt, S.

    2012-02-01

    The concept of grid inefficiency in Frisch grid ionization chambers and its influence on the anode pulse shape is explained in terms of the Shockley-Ramo theorem for induced charges. The grid inefficiency correction is deduced from numerically calculated weighting potentials. A method to determine the correction factor experimentally is also presented. Experimental and calculated values of the correction factor are shown to be in good agreement.

  5. A high dynamic Micro Strips Ionization Chamber featuring Embedded Multi DSP Processing

    OpenAIRE

    Voltolina, Francesco; Menk, Ralf H.; Carrato, Sergio

    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 cus...

  6. Application of the Shockley-Ramo theorem on the grid inefficiency of Frisch grid ionization chambers

    International Nuclear Information System (INIS)

    The concept of grid inefficiency in Frisch grid ionization chambers and its influence on the anode pulse shape is explained in terms of the Shockley-Ramo theorem for induced charges. The grid inefficiency correction is deduced from numerically calculated weighting potentials. A method to determine the correction factor experimentally is also presented. Experimental and calculated values of the correction factor are shown to be in good agreement.

  7. Determination of correction factor ksat for recombination losses in ionization chambers using dual-voltage method

    International Nuclear Information System (INIS)

    A review is presented of determining the saturation correction factor ksat of ionization chambers using a dual-voltage method. Basic relations are listed for the calculation of the correction factor for continuous, pulsed, and pulsed swept radiation, and the methods are presented of solving the relations. The computer code, graphs and tables are listed for determination of the saturation factor on the basis of measurements. The feasibility of the method for practical measurements is discussed. (author). 3 figs., 2 tabs., 10 refs

  8. A study of the response of a gas ionization chamber to different sources of ionizing radiation

    International Nuclear Information System (INIS)

    The response of the TAMU Forward Hadron Calorimeter Chambers to neutrons from a 239Pu-Be source was investigated in hope of developing a strategy to reduce the effects of the background events called /open quotes/Texas towers/close quotes/ in the CDF trigger for the next run. The response to a standard (55Fe γ-ray) energy source was also studied and found to be similar to that of the chambers installed at CDF. In addition, the effects of different sampling gases and intermediate absorbers on the rate of large energy pulses were investigated. The neutron data were compared with the energy spectrum measured in CDF and that simulated using Monte Carlo techniques. It was found that the large energy pulse frequency can be reduced by as much as 50% if a non-hydrogenous sampling gas is used in conjunction with a neutron moderator

  9. Operating characteristics of a double ionization chamber and on-line tritium production rate measurement in a fusion blanket

    International Nuclear Information System (INIS)

    A double ionization chamber supporting a layer of 6LiF on a central cathod, is fabricated for on-line measurement of the tritium production in fusion blankets. The charged particles accompanying the 6Li(n,α)t reaction are detected by two separate tiny parallel plate ionization chambers held on either side of the common central cathod. The operating characteristics, tritium production measured with a double ionization chamber and comparison with the results obtained by LSM are presented in this paper. (author)

  10. 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.

  11. 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.

  12. An ionization chamber with Frisch grids for studies of high-energy neutron-induced fission

    Science.gov (United States)

    Tutin, G. A.; Ryzhov, I. V.; Eismont, V. P.; Kireev, A. V.; Condé, H.; Elmgren, K.; Olsson, N.; Renberg, P.-U.

    2001-01-01

    A gridded ionization chamber for fission fragment detection is described. The chamber has been specially designed for use at the quasi-monoenergetic 7Li(p, n) neutron source at the The Svedberg Laboratory, Uppsala, Sweden. The detector permits measurements of fission fragment energy and emission angle for two targets with diameter of up to 10 cm. The time response of the chamber (⩽5 ns FWHM) is adequate to apply time-of-flight discrimination against background events induced by non-peak neutrons. Results of angular anisotropy measurements for the 232Th (n, f) and 238U(n, f) reactions in the 20-160 MeV energy range are given.

  13. Alpha spectrometric ionization chamber with 2 m2 working area and its application

    International Nuclear Information System (INIS)

    A grid ionization chamber with cylindrical configuration was constructed for the measurement of the alpha spectra of very low level samples, which makes possible the measurement of radiation sources with an area of up to 2 m2. The chamber has a volume of 400 l and is filled with technical argon with 5% addition of methane. Energy resolution of the detection system is 85 keV at 5.5 MeV, detection efficiency is 37% and the background at a range of 200 keV at 5.5 MeV is 10 cph. The detection limit is 1 mBq. The chamber may be used for measuring half-life of alpha-emitting rare earths, for dating sediments using the 210Pb-210Po method and geological samples using the U-Th method, for determining the composition and concentration of natural and technogenic alpha sources in natural samples. (J.P.)

  14. The thin-wall tube drift chamber operating in vacuum (prototype)

    International Nuclear Information System (INIS)

    The goal of this work was to design drift tubes and a chamber operating in vacuum, and to develop technologies for tubes independent assembly and mounting in the chamber. These design and technology were tested on the prototype. The main features of the chamber are the following: the drift tubes are made of flexible mylar film (wall thickness 36 μm, diameter 9.80 mm, length 2160 mm) using ultrasonic welding along the generatrix; the welding device and methods were developed at JINR. Drift tubes with end plugs, anode wires and spacers were completely assembled outside the chamber. “Self-centering” spacers and bushes were used for precise setting of the anode wires and tubes. The assembled tubes were sealed with O-rings in their seats in the chamber which simplified the chamber assembling. Moreover the tube assembly and the chamber manufacture can be performed independently and in parallel; this sufficiently reduces the total time of chamber manufacture and assembling, its cost and allows tubes to be tested outside the chamber. The technology of independent tube assembling is suitable for a chamber of any shape but a round chamber is preferable for operation in vacuum. Single channel amplifier-discriminator boards which are more stable against cross talks were used for testing the tubes. Independently assembled tubes were mounted into the chamber prototype and its performance characteristic measured under the vacuum conditions. The results showed that both the structure and the tubes themselves normally operate. They are suitable for making a full-scale drift chamber for vacuum

  15. The thin-wall tube drift chamber operating in vacuum (prototype)

    Science.gov (United States)

    Alexeev, G. D.; Glonti, L. N.; Kekelidze, V. D.; Malyshev, V. L.; Piskun, A. A.; Potrbenikov, Yu. K.; Rodionov, V. K.; Samsonov, V. A.; Tokmenin, V. V.; Shkarovskiy, S. N.

    2013-08-01

    The goal of this work was to design drift tubes and a chamber operating in vacuum, and to develop technologies for tubes independent assembly and mounting in the chamber. These design and technology were tested on the prototype. The main features of the chamber are the following: the drift tubes are made of flexible mylar film (wall thickness 36 μm, diameter 9.80 mm, length 2160 mm) using ultrasonic welding along the generatrix; the welding device and methods were developed at JINR. Drift tubes with end plugs, anode wires and spacers were completely assembled outside the chamber. "Self-centering" spacers and bushes were used for precise setting of the anode wires and tubes. The assembled tubes were sealed with O-rings in their seats in the chamber which simplified the chamber assembling. Moreover the tube assembly and the chamber manufacture can be performed independently and in parallel; this sufficiently reduces the total time of chamber manufacture and assembling, its cost and allows tubes to be tested outside the chamber. The technology of independent tube assembling is suitable for a chamber of any shape but a round chamber is preferable for operation in vacuum. Single channel amplifier-discriminator boards which are more stable against cross talks were used for testing the tubes. Independently assembled tubes were mounted into the chamber prototype and its performance characteristic measured under the vacuum conditions. The results showed that both the structure and the tubes themselves normally operate. They are suitable for making a full-scale drift chamber for vacuum.

  16. 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.

  17. 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.

  18. 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.

  19. Characteristics of A-150 plastic-equivalent gas in A-150 plastic ionization chambers for p(66)Be(49) neutrons

    International Nuclear Information System (INIS)

    The evaluation of a gas mixture having an atomic composition similar to that of A-150 TE-plastic has been extended to a high energy neutron therapy beam. A-150 gas, air and methane-based TE gas were each flowed through A-150 plastic-walled ion chambers of different sizes and irradiated with p(66)Be(49) neutrons. A tentative value for anti W(A-150) of 27.3 +- 0.5 J C-1 was derived for this beam. The anti W value of the A-150 gas mixture is compared to those of methane-based TE gas and of air for the p(66)Be(49) neutron beam as well as to corresponding values found in similar experiments using 14.8 MeV monoenergetic neutrons. 17 references, 3 figures, 3 tables

  20. Field Ionization of Cold Atoms near the Wall of a Single Carbon Nanotube

    International Nuclear Information System (INIS)

    We observe the capture and field ionization of individual atoms near the side wall of a single suspended nanotube. Extremely large cross sections for ionization from an atomic beam are observed at modest voltages due to the nanotube's small radius and extended length. The effects of the field strength on both the atomic capture and the ionization process are clearly distinguished in the data, as are prompt and delayed ionizations related to the locations at which they occur. Efficient and sensitive neutral atom detectors can be based on the nanotube capture and wall ionization processes.

  1. Field Ionization of Cold Atoms near the Wall of a Single Carbon Nanotube

    CERN Document Server

    Goodsell, Anne; Golovchenko, J A; Hau, Lene Vestergaard; 10.1103/PhysRevLett.104.133002

    2010-01-01

    We observe the capture and field ionization of individual atoms near the side wall of a single suspended nanotube. Extremely large cross sections for ionization from an atomic beam are observed at modest voltages due to the nanotube's small radius and extended length. The effects of the field strength on both the atomic capture and the ionization process are clearly distinguished in the data, as are prompt and delayed ionizations related to the locations at which they occur. Efficient and sensitive neutral atom detectors can be based on the nanotube capture and wall ionization processes.

  2. Establishment of a new calibration method of pencil ionization chamber for dosimetry in computed tomography

    International Nuclear Information System (INIS)

    Pencil ionization chambers are used for beam dosimetry in computed tomography equipment (CT). In this study, a new calibration methodology was established, in order to make the Calibration Laboratory of Instituto de Pesquisas Energeticas e Nucleares (LCI) suitable to international metrological standards, dealing with specific procedures for calibration of these chambers used in CT. Firstly, the setup for the new RQT radiation qualities was mounted, in agreement with IEC61267 from the International Electrotechnical Commission (IEC). After the establishment of these radiation qualities, a specific calibration methodology for pencil ionization chambers was set, according to Technical Report Series No. 457, from the International Atomic Energy Agency (IAEA), which describes particularities of the procedure to be followed by the Secondary Standard Dosimetry Laboratories (SSDL's), concerning to collimation and positioning related to the radiation beam. Initially, PPV (kV) measurements and the determination of copper additional filtrations were carried out, measuring the half value layers (HVL) recommended by the IEC 61267 standard, after that the RQT 8, RQT 9 and RQT 10 radiation quality references were established. For additional filters, aluminum and copper of high purity (around 99.9%) were used. RQT's in thickness of copper filters equivalent to the set 'RQR (Al) + Additional Filtration (Cu)' was directly found by an alternative methodology used to determine additional filtrations, which is a good option when RQR's have not the possibility of be setting up. With the establishment of this new methodology for the ionization pencil chambers calibration, the LCI is ready to calibrate these instruments according to the most recent international standards. Therefore, an improvement in calibration traceability, as well as in metrological services offered by IPEN to all Brazil is achieved. (author)

  3. Wall loss of atomic nitrogen determined by ionization threshold mass spectrometry

    International Nuclear Information System (INIS)

    In the afterglow of an inductively coupled N2 plasma, relative N atom densities are measured by ionization threshold mass spectrometry as a function of time in order to determine the wall loss time twN from the exponential decay curves. The procedure is performed with two mass spectrometers on different positions in the plasma chamber. twN is determined for various pressures, i.e., for 3.0, 5.0, 7.5, and 10 Pa. For this conditions also the internal plasma parameters electron density ne and electron temperature Te are determined with the Langmuir probe and the rotational temperature TrotN2 of N2 is determined with the optical emission spectroscopy. For TrotN2, a procedure is presented to evaluate the spectrum of the transition υ′=0→υ″=2 of the second positive system (C3Πu→B3Πg) of N2. With this method, a gas temperature of 610 K is determined. For both mass spectrometers, an increase of the wall loss times of atomic nitrogen with increasing pressure is observed. The wall loss time measured with the first mass spectrometer in the radial center of the cylindrical plasma vessel increases linearly from 0.31 ms for 3 Pa to 0.82 ms for 10 Pa. The wall loss time measured with the second mass spectrometer (further away from the discharge) is about 4 times higher. A model is applied to describe the measured twN. The main loss mechanism of atomic nitrogen for the considered pressure is diffusion to the wall. The surface loss probability βN of atomic nitrogen on stainless steel was derived from twN and is found to be 1 for the present conditions. The difference in wall loss times measured with the mass spectrometers on different positions in the plasma chamber is attributed to the different diffusion lengths

  4. Characteristics of A-150 plastic equivalent gas in A-150 plastic ionization chambers for p(66)Be(49) neutrons

    International Nuclear Information System (INIS)

    The average energy necessary to produce an electron-ion pair (anti W) of a gas mixture having an atomic composition very close to that of A-150 plastic has been studied through use in different size ionization chambers made of that plastic in a p(66)Be(49) neutron therapy beam. A tentative value for anti W(A-150-gas) of 27.3 +/ -0.5 J C-1 was derived. The anti W value of the A-150 equivalent gas mixture is compared to those of methane-based tissue-equivalent gas and of air for the p(66)Be(49) neutron beam as well as to corresponding values found in similar experiments using 14.8 MeV monoenergetic neutrons

  5. Test of a dual-type gridded ionization chamber using liquid xenon

    International Nuclear Information System (INIS)

    A liquid xenon dual-type gridded ionization chamber designed as a gamma-ray spectrometer was constructed and some tests for gamma-rays were made by using highly purified xenon gas. The energy resolution of 8.6% at fwhm was obtained for collimated gamma-rays of 662 keV. The resolutions at fwhm for non-collimated gamma-rays were (9.6 +- 0.4)% at 662 keV, (6.5 +- 0.3)% at 1332 keV and (4.5 +- 0.3)% at 2614 keV. These results show that, for gamma-ray energies above 1600 keV, the energy resolution for the liquid xenon ionization chamber is better than that for a conventionally available 1 3/4'' diameter x 2'' NaI(Tl) crystal. This characteristic of the chamber was kept nearly constant for more than 24 h. The resolution obtained experimentally were compared with the theoretical values and the causes of the differences between them are discussed. (orig.)

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

    Science.gov (United States)

    Fourmentel, D.; Filliatre, P.; Villard, J. F.; Lyoussi, A.; Reynard-Carette, C.; Carcreff, H.

    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-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.

  7. 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.

  8. 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

  9. 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. PMID:26724022

  10. 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.

  11. Adjustment of high-pressure twin gridded ionization chamber and preliminary measurement of 58Ni(n,p) reaction

    International Nuclear Information System (INIS)

    A high-pressure twin gridded ionization chamber is introduced. After some adjustments, the chamber was used to measure the 58Ni(n,p) reaction. The results show that the current system and method are suitable for the research of (n,p) reactions

  12. Ignition Characteristics of Premixed Methane/air in Micro Chamber

    International Nuclear Information System (INIS)

    The ignition process of premixed methane/air in a micro-scale chamber is simulated with the combination of surface chemistry and gas-phase reactions. The effect of different parameters on the ignition characteristics are analyzed in detail and the sensitive analysis is performed on main elementary reactions. It is found that the ignition of the mixture is inhibited by surface reaction, which mainly depends on the sticking ability of the surface on CH3 radical. The ignition inhibition can be reduced by increasing the initial temperature and pressure. The increase of equivalence ratio has small impact on ignition delay time when it is larger than stoichiometric ratio. The ignition delay time would increase significantly with surface-area-to- volume ratio. The product of sticking coefficient and surface-area-to-volume ratio can be used to measure the intensity of surface reaction. The larger the product is, the stronger the inhibition of the surface reaction on ignition has

  13. Clinical applications of a high speed matrix ionization chamber portal imaging system

    International Nuclear Information System (INIS)

    A main disadvantage of the present matrix ionization chamber system for electronic portal imaging is its relatively slow image acquisition of 6 s at full resolution. We have solved this problem by modifying the read-out electronics in two ways: First, faster high voltage switches are applied which work with a higher voltage; Second, faster read-out amplifiers are applied which have reduced cross-talk. With these improvements circuit noise is no longer dominant at typical radiotherapy dose rates. Because the quantum noise level in the matrix ionization chamber system is purely determined by signal integration in the liquid medium, the image scan can now be reduced to as short as 0.55 s with little loss of image quality. However, there is some loss of resolution at readout speed faster than 1.5 s due to speed limitations of the read-out amplifiers. One of the applications of the new device is double exposures for larynx fields. At a reduced dose rate of 125 MU/min, only about 5 MUs are required for a single frame on a 4 MV ABB Dynaray accelerator. Other applications which benefit from the reduced image scan time are time lapse movies. Typically 15 frames per field are made during one fraction. The movies offer both information on patient motion and improved image quality by averaging the frames. Finally, on-line analysis of the images can be performed more easily and has been included in the software package. In can be concluded that the higher speed of the new matrix ionization chamber system is an important improvement for several clinical applications

  14. Ambiguities in the grid-inefficiency correction for Frisch-Grid Ionization Chambers

    Science.gov (United States)

    Al-Adili, A.; Hambsch, F.-J.; Bencardino, R.; Oberstedt, S.; Pomp, S.

    2012-05-01

    Ionization chambers with Frisch grids have been very successfully applied to neutron-induced fission-fragment studies during the past 20 years. They are radiation resistant and can be easily adapted to the experimental conditions. The use of Frisch grids has the advantage to remove the angular dependency from the charge induced on the anode plate. However, due to the Grid Inefficiency (GI) in shielding the charges, the anode signal remains slightly angular dependent. The correction for the GI is, however, essential to determine the correct energy of the ionizing particles. GI corrections can amount to a few percent of the anode signal. Presently, two contradicting correction methods are considered in literature. The first method adding the angular-dependent part of the signal to the signal pulse height; the second method subtracting the former from the latter. Both additive and subtractive approaches were investigated in an experiment where a Twin Frisch-Grid Ionization Chamber (TFGIC) was employed to detect the spontaneous fission fragments (FF) emitted by a 252Cf source. Two parallel-wire grids with different wire spacing (1 and 2 mm, respectively), were used individually, in the same chamber side. All the other experimental conditions were unchanged. The 2 mm grid featured more than double the GI of the 1 mm grid. The induced charge on the anode in both measurements was compared, before and after GI correction. Before GI correction, the 2 mm grid resulted in a lower pulse-height distribution than the 1 mm grid. After applying both GI corrections to both measurements only the additive approach led to consistent grid independent pulse-height distributions. The application of the subtractive correction on the contrary led to inconsistent, grid-dependent results. It is also shown that the impact of either of the correction methods is small on the FF mass distributions of 235U(nth, f).

  15. Ambiguities in the grid-inefficiency correction for Frisch-Grid Ionization Chambers

    International Nuclear Information System (INIS)

    Ionization chambers with Frisch grids have been very successfully applied to neutron-induced fission-fragment studies during the past 20 years. They are radiation resistant and can be easily adapted to the experimental conditions. The use of Frisch grids has the advantage to remove the angular dependency from the charge induced on the anode plate. However, due to the Grid Inefficiency (GI) in shielding the charges, the anode signal remains slightly angular dependent. The correction for the GI is, however, essential to determine the correct energy of the ionizing particles. GI corrections can amount to a few percent of the anode signal. Presently, two contradicting correction methods are considered in literature. The first method adding the angular-dependent part of the signal to the signal pulse height; the second method subtracting the former from the latter. Both additive and subtractive approaches were investigated in an experiment where a Twin Frisch-Grid Ionization Chamber (TFGIC) was employed to detect the spontaneous fission fragments (FF) emitted by a 252Cf source. Two parallel-wire grids with different wire spacing (1 and 2 mm, respectively), were used individually, in the same chamber side. All the other experimental conditions were unchanged. The 2 mm grid featured more than double the GI of the 1 mm grid. The induced charge on the anode in both measurements was compared, before and after GI correction. Before GI correction, the 2 mm grid resulted in a lower pulse-height distribution than the 1 mm grid. After applying both GI corrections to both measurements only the additive approach led to consistent grid independent pulse-height distributions. The application of the subtractive correction on the contrary led to inconsistent, grid-dependent results. It is also shown that the impact of either of the correction methods is small on the FF mass distributions of 235U(nth, f).

  16. Quantification of Gas-Wall Partitioning in Teflon Environmental Chambers Using Rapid Bursts of Low-Volatility Oxidized Species Generated in Situ.

    Science.gov (United States)

    Krechmer, Jordan E; Pagonis, Demetrios; Ziemann, Paul J; Jimenez, Jose L

    2016-06-01

    Partitioning of gas-phase organic compounds to the walls of Teflon environmental chambers is a recently reported phenomenon than can affect the yields of reaction products and secondary organic aerosol (SOA) measured in laboratory experiments. Reported time scales for reaching gas-wall partitioning (GWP) equilibrium (τGWE) differ by up to 3 orders of magnitude, however, leading to predicted effects that vary from substantial to negligible. A new technique is demonstrated here in which semi- and low-volatility oxidized organic compounds (saturation concentration c* < 100 μg m(-3)) were photochemically generated in rapid bursts in situ in an 8 m(3) environmental chamber, and then their decay in the absence of aerosol was measured using a high-resolution chemical ionization mass spectrometer (CIMS) equipped with an "inlet-less" NO3(-) ion source. Measured τGWE were 7-13 min (rel. std. dev. 33%) for all compounds. The fraction of each compound that partitioned to the walls at equilibrium follows absorptive partitioning theory with an equivalent wall mass concentration in the range 0.3-10 mg m(-3). Measurements using a CIMS equipped with a standard ion-molecule reaction region showed large biases due to the contact of compounds with walls. On the basis of these results, a set of parameters is proposed for modeling GWP in chamber experiments. PMID:27138683

  17. Development of gamma compensated boron lined ionization chamber with intermediate range monitor for reactor applications

    International Nuclear Information System (INIS)

    Gamma compensated boron lined ionization chamber with indigenously developed 40.5% enriched boron-10 and polyetheretherketone insulating spacers has been developed. The detector has an overall diameter of 85 mm and overall length of 315 mm. Tests on the chamber with intermediate range monitor have been conducted in both gamma and neutron fields. The detector has good saturation characteristics, adequate neutron sensitivity and required gamma compensation. The linearity of response of the detector at various reactor power levels was also found to be within the required limits. The Log P signal output variation due to change in amplifier temperature of IRM, was found to be within limits for temperature variations from 25℃ to 30.13℃ thus indicating stable output against changes in temperature of IRM amplifier at steady reactor power operation. (author)

  18. 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.

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

    International Nuclear Information System (INIS)

    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

  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. An experimental setup for the study of the steady air flow in a diesel engine chamber

    OpenAIRE

    Montanero José María; Marcos Alberto; Castilla Alejandro; Vega Emilio José; Fernández Joaquín; Barrio Raúl

    2012-01-01

    We present an experimental setup for studying the steady air flow in a diesel engine chamber. An engine block containing the inlet manifold was placed on a test bench. A steady air stream crossed the inlet manifold and entered a glass chamber driven by a fan. A PIV system was set up around the bench to measure the in-chamber flow. An air spray gun was used as seed generator to producing sub-millimeter droplets, easily dragged by the air stream. Images of the in-flow chamber were acquired in t...

  2. A method to measure the activity of sealed gamma sources by means of ionization chambers

    International Nuclear Information System (INIS)

    The paper contains a recommendation concerning the propagation of the activity unit for sealed gamma sources from the normals of the national metrological authorities of the USSR (VNIM) and the GDR (ASMW) to normals of lower order. Propagation of the activity unit is provided by comparative measurements with ionization chambers. The recommendation implies cases in which the source contains impurities as well as cases in which the design of the sources to be compared is different. Furthermore, the recommendation includes the method of error evaluation. (author)

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

    International Nuclear Information System (INIS)

    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)

  4. Measurement of neutron-induced charged-particle-emission reaction cross section using gridded ionization chamber

    International Nuclear Information System (INIS)

    A gridded ionization chamber (GIC) having large geometrical efficiency, ∼2π, has been developed for measurements of neutron-induced charged-particle emission cross sections. Test experiments proved the proper operation of GIC with complete charge collection even if the gas pressure was over 10 atm.. GIC was applied successfully to proton and α emission cross section measurements for nickel at the several MeV and 15 MeV incident neutron energies with the results in good agreement with the previous data and evaluations. The construction of GIC and the experimental technique are presented in this paper. (author)

  5. (n,α) cross section measurement of gaseous sample using gridded ionization chamber. Cross section determination

    International Nuclear Information System (INIS)

    We are developing a method of (n,α) 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 12C(n,α0)9Be measurement. We applied this method to the 16O(n,α)13C cross section around 14.1 MeV. (author)

  6. (n, α) Cross-section measurement using a gaseous sample and a gridded ionization chamber

    International Nuclear Information System (INIS)

    We developed a method of (n, α) cross-section measurement using a gaseous sample in a gridded ionization chamber (GIC). This method enables us to measure the cross section of gaseous samples, such as C, O and N, with very large solid angle close to 4π without distortion due to energy loss in the sample. The detection efficiency, which is difficult to estimate for gaseous samples, was estimated by using GIC signals and tight neutron collimation. This method was verified through the 12C(n, α0)9Be cross-section measurement for 14.1 MeV neutrons

  7. (n, α) cross section measurement of light nuclei using gridded ionization chamber and gaseous sample

    International Nuclear Information System (INIS)

    We have developed a measuring method of (n, α) cross section by using gaseous sample in a gridded ionization chamber. In this study, we measured the 12C(n, α0) and the 16O(n, α0), (n, α123) cross sections for En=11.5 and 12.8 MeV neutrons. We also deduced the 12C(n, xα) spectrum and analyzed the data by a kinematic calculation combined with the reaction data of the 12C(n, n'3α). (author)

  8. Laboratory of routine alpha-spectrometry based on gridded ionization chambers

    International Nuclear Information System (INIS)

    A laboratory of routine alpha spectrometry based on gridded ionization chambers (80 cm2, 500 cm2 and 20,000 cm2 of source area) was built for direct measurement of samples with low specific activity. They allow direct spectrometry of as low as 6.7 mBq.g-1, 2.5 mBq.g-1, and 0.18 mBq.g-1, respectively. Simple quantitative physical methods of large-area source preparation are described. The system was used to measure the concentration of alpha emitters in environmental samples. (author). 3 figs., 1 tab., 7 refs

  9. Circuitry for monitoring a high direct current voltage supply for an ionization chamber

    International Nuclear Information System (INIS)

    An arrangement to measure the voltage of the supply and a switching means controlled by this is described. The voltage measurer consists of first and second signal coupling means, the input of the second (connected to the voltage supply) is connected in series with the output of the first. An ionization chamber with this circuitry may be used to monitor the radiation output of a particle accelerator more accurately. Faulty measurements of the dose output, caused by voltages in the earth circuit, are avoided. (U.K.)

  10. Study and application of dual parameter spectrometer based on a gridded ionization chamber

    International Nuclear Information System (INIS)

    A dual parameter spectrometer is developed with which the anode and cathode signals of the gridded ionization chamber are recorded simultaneously, a computer program is designed to collect, display and store the two dimensional spectra. Alpha sources are measured with the spectrometer and the angle distribution of alpha particles are calculated. It is discussed how to correct the effects of back scattering and self absorption in the measurement of activity with the angle distribution and it is pointed out that the resolution of the energy spectra can be improved by using the angle distribution as well

  11. Study of 241 Am alpha spectra resolution using a ionization chamber with different grid types

    International Nuclear Information System (INIS)

    This paper describes some techniques used in the design of high resolution gridded ionization chambers for measurements of absolute activity of radionuclides. Details of the geometry of the system and its electrodes are presented; their shape and the spacing between the grid wire were studied. The experimental spectra obtained with an 241 Am source using 90% Ar and 10% C H4 as a flow gas show a total resolution of 39 KeV in very good agreement with best results available in the literature. (author). 17 refs., 2 figs., 3 tabs

  12. Investigation of 234U(n,f) with a Frisch-grid ionization chamber

    OpenAIRE

    Al-Adili, Ali

    2011-01-01

    This work treats three topics. The main topic concerns neutron-induced fission of 234U. The main goal is to investigate the fission-fragments properties  as a function of the incident neutron energy. The study was carried out using a twin Frisch-grid ionization chamber. The first fluctuations on fragment properties are presented, in terms of strong angular anisotropy oscillation. The second part of the work treats the data-acquisition systems in use, particularly for neutron-induced fission e...

  13. Signal processing system for parallel plate ionization chamber at test beam of BEPC II

    International Nuclear Information System (INIS)

    A signal processing system has been designed in order to read out the electrode signals of 2D parallel plate ionization chamber at test beam facility of BEPC II. The system mainly includes that charge sensitive pre-amplifier, main-amplifier, analog to digital convertor and personal computer. Digital signals were recorded and displayed real time in histograms using data acquirement program based on Linux operating system. This signal processing system can be operated easily and has lower electronic noise and stable performance. (authors)

  14. New assembly of ionization chambers for the RBMK reactor control systems

    International Nuclear Information System (INIS)

    A new assembly consisting of ionization chambers (IC) and cables is developed for the RBMK reactor control systems (RCS). The assembly together with the channel of RCS ensures reliable power control in the range from 10-10 to 1.5 nominal power and measuring the neutron flux density in the reactor core height. The design of the assembly with IC is presented. Tests showed that the new IC assembly provides high sensitivity of measurements and RCS channel noise immunity in all range of reactor power variation

  15. Investigation of power distribution nonuniformity effect on readings of out-of-pile ionization chambers

    International Nuclear Information System (INIS)

    Taking as an example South-Ukrainian WWER-1000 type NPP the problems related to the possibility of obtaining integral characteristics of power distribution by readings of out of-pile ionization chambers (IC) are considered. The regression dependence of IC readings on axial offset (AO)-characteristic of peak- power distribution along the core length is investigated. This dependence proved to be linear. For power evaluation linear combination of IC readings is used. Simultaneously by the readings of two IC located at different core length the evaluation of AO values can be performed

  16. (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)

  17. 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%.

  18. (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)

  19. Experimental study on the influence of the central electrode in Farmer-type ionization chambers

    International Nuclear Information System (INIS)

    In the IAEA TRS-381 protocol, kcel and pcel account for the central electrode perturbation during the air kerma chamber calibration and the in-phantom measurements. The values of these correction factors are based mainly on Monte Carlo simulations. In the present work experimental data on kcel and pcel for the NE-2571 chamber is provided, relative to a graphite electrode. In addition, the relative influence of the 3 mm diameter A-150 central electrode of the NE-2581 chamber is studied. The experimentally determined value of kcel for a 1 mm aluminium electrode is 1.008±0.2%, and of pcel in photon and electron beams 0.993±0.2% and 0.997±0.2% respectively. The experimental data and the Monte Carlo simulations agree to within 0.2%. No significant influence of the A-150 central electrode diameter on the absorbed dose determination is shown. (author)

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

    International Nuclear Information System (INIS)

    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

  1. Theoretical investigations of a double ionization chamber for on-line monitoring of tritium production in fusion blankets

    International Nuclear Information System (INIS)

    This paper reports that a double ionization chamber employing a thin coating of enriched 6LiF radiating material offers an effective means of identifying a 6Li(n, α)t reaction. The concept is based on the detection of ionization caused by alpha particles and tritons. The charged particles emitted in opposite directions can be detected by a double parallel plate ionization chamber configuration. This method can therefore be employed to directly measure tritium breeding rates inside the fusion blankets. Complete details of the parameters that govern the response of such a detector system are described. A Monte Carlo scheme is developed to determine the direction and energy lost by the particles in traversing various media, and the detector response is calculated from the energy deposited in the ionization region of each chamber. The calculations are performed for the entire energy range of neutrons available in the fusion blankets

  2. 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

  3. 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.

  4. Correction factors for photon beam quality for cylindrical ionization chambers: Monte Carlo calculations by using the PENELOPE code

    International Nuclear Information System (INIS)

    Were directly determined correction factors depending on the type camera beam quality, k, Q, and kQ, Qo, instead of the product (w, air p) Q, for three type cylindrical ionization chambers Pinpoint and divergent monoenergetic beams of photons in a wide range of energies (4-20 MV). The method of calculation used dispenses with the approaches taken in the classic procedure considered independent of braking power ratios and the factors disturbance of the camera. A detailed description of the geometry and materials chambers were supplied by the manufacturer and used as data input for the system 2006 of PENELOPE Monte Carlo calculation using a User code that includes correlated sampling, and forced interactions division of particles. We used a photon beam Co-60 as beam reference for calculating the correction factors for beam quality. No data exist for the cameras PTW 31014, 31015 and 31016 in the TRS-398 at they do not compare the results with data calculated or determined experimentally by other authors. (author)

  5. 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...

  6. 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.

  7. Performance, at ambient temperature, of ionization chambers filled with a liquid dielectric

    International Nuclear Information System (INIS)

    The authors describe the performance characteristics of ionization chambers filled with carefully purified normal hexane. A detailed study of the background of a detector of this type enabled them to define the conditions in which it is possible to stabilize this background and to reduce it to about 10-14 A/cm2, for a uniform electric field of 8000 V/cm. Under irradiation with alpha or gamma rays, and at laboratory temperature, the current which passes through the chamber is a linear function of the applied electric field, up to a critical field value which is a function of the degree of purity of the liquid. Above that critical value, a process of ion-multiplication takes place, somewhat, similar to that which takes place in gases. The change in the ionization current then becomes exponential. In that area of multiplication the authors detected impulses created by the passage of individual alpha particles. The low mobility of the ions in the hexane and their extensive recombination considerably limits the amplitude of the impulses, which can easily be confused with the amplifier's background if a certain number of precautions are not taken. Impulses were recorded with amplitudes varying between 2.5 x 10-5 and 25 x 10-5 V, and with growth-times between 2 and 20 μs in electric fields of 21600 to 65600 V/cm. A number of preliminary results for other liquid fillings are given. (author)

  8. The standard facility for nuclide activity measurement by 4πγ high pressure ionization chamber

    International Nuclear Information System (INIS)

    The standard consists of 4πγ pressurized ionization chambers (IC/2C(1.0 MPa) and IG12/A20(2.0 MPa), small current measurement system, standard bottles, one set of long-live reference sources (226Ra), and lead shields. It has the following advantages: 1) long-term stability less than 0.1% per year; 2) fast speed for activity measurement; 3) Do allowing the direct measurement activity of solutions in ampoules; 4) permit measurement over a long range of activity (104-1010 Bq). For short-live nuclides, it is necessary to know the efficiency of the ionization chamber. The calibration factors can be calculated according to the efficiency curve and the probability of γ-ray emission. The calibration factors of some nuclides are calculated and the deviation of the calculation factors from experiment is less than +-3%. The half-life of 99Tcm is measured, the result is 6.0053 +- 0.0018 h

  9. Features of ionization of atmospheric air at radioactive pollution

    International Nuclear Information System (INIS)

    One studied the peculiarities of heterogeneous ionization at radioactive contamination of the atmosphere lower layers. When analyzing the radiochemical conversion of the atmosphere one determined that at rather high 0.1-1 MPa pressures the ranges with high concentration of ionized particles, so-called tracks of high-energy corpuscular (protons, α- and β-particles) emissions might be formed in the air. A model of the atmosphere track ionization taking account of the elementary processes within the tracks that was: kinetics, molecular diffusion and ion drift within the electrical field, was proposed. Paper presents all basic elementary ion-molecular processes in the ionized troposphere and determines the application limits of the mentioned model

  10. Technical Note: Experimental determination of the effective point of measurement of two cylindrical ionization chambers in a clinical proton beam

    Energy Technology Data Exchange (ETDEWEB)

    Sugama, Yuya, E-mail: yuya.sugama@gmail.com [Proton Therapy Center, Aizawa Hospital, Nagano 390-0821, Japan and Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi 409-3898 (Japan); Nishio, Teiji [Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima 734-8551 (Japan); Onishi, Hiroshi [Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Yamanashi 409-3898 (Japan)

    2015-07-15

    Purpose: IAEA TRS-398 notes that cylindrical ionization chambers are preferred for reference proton dosimetry. If a cylindrical ionization chamber is used in a phantom to measure the dose as a function of depth, the effective point of measurement (EPOM) must be taken into account. IAEA TRS-398 recommends a displacement of 0.75 times the inner cavity radius (0.75R) for heavy ion beams. Theoretical models by Palmans and by Bhullar and Watchman confirmed this value. However, the experimental results vary from author to author. The purpose of this study is to accurately measure the displacement and explain the past experimental discrepancies. Methods: In this work, we measured the EPOM of cylindrical ionization chambers with high accuracy by comparing the Bragg-peak position obtained with cylindrical ionization chambers (PTW 30013, PTW 31016) to that obtained using a plane-parallel ionization chamber (PTW 34045). Results: The EPOMs of PTW 30013 and 31016 were shifted by 0.92 ± 0.07 R with R = 3.05 mm and 0.90 ± 0.14 R with R = 1.45 mm, respectively, from the reference point toward the source. Conclusions: The EPOMs obtained were greater than the value of 0.75R proposed by the IAEA TRS-398 and the analytical results.

  11. Development of electrometer and DAS for ionization chamber for Indus-2, RRCAT

    International Nuclear Information System (INIS)

    Ionization Chambers (ICs) are widely used for the measurement of the ionizing radiations in the Synchrotron Radiation Source (SRS) beam lines. Its output current depends on the chamber design, radiation dose and applied voltage. Commercially available electrometers have some restriction in tailor-made applications. To overcome these limitations in measurement of ionization current or charge in the range of few pA to μA, we have indigenously developed an electrometer and associated Data Acquisition system for Indus-2 applications. To make uniform interface and portability across ICs of various size and geometry, a universal DAS is developed which consists of an embedded controller and internal programmable HV supply (0 - 2.0 kV) to bias IC, which caters the dynamic range of 120 dB for current measurement. To handle large dynamic range, two independent channels of amplifiers are interfaced which are controlled by micro controller. Channel one uses gated integrator based charge amplifier for low current signal i.e. 10 pA-100 nA and channel two is used as trans-impedance amplifier for 100 nA to 10 μA range. Micro controller selects the modes, the programmable gains (1, 10 and 100), integration time from 1-1000 ms and HV from 0-2.0 kV. Micro controller also digitizes the analog signal. The unit can be used as standalone mode or remotely with optical fiber based serial communications for data logging and networking. The developed unit was calibrated using keithley source 6220 and is further rigorously tested with laboratory based PW 3830 X-ray generator source. The developed system has leakage current of <10 pA. Further an indigenously developed IC was also used to test the developed electrometer at the saturation voltage of 990 V. The linearity of the electrometer is better than 1%. (author)

  12. Electrical conductivities of air ionized by shock-waves (1961)

    International Nuclear Information System (INIS)

    Results are given of measurements made using electrodes of the conductivity of air ionized by shock-waves in a shock-tube. For low and high wave velocities, two very different conductivity profiles behind the wave are obtained, The measured conductivities are then compared with the theoretical values. (author)

  13. Intercomparison of ionization chambers in standard X-ray beams, at radiotherapy, diagnostic radiology and radioprotection levels

    International Nuclear Information System (INIS)

    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: 67Ga, 201Tl and 99mTc; 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)

  14. Calculation of Electric Field Distortion Rate due to Potential Difference between Guard Electrode and Collection Electrode using Simulator in Parallel Plate Ionization Chamber

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han Soo; Kim, Yong Kyun; Park, Se Hwan; Kang, Sang Mook; Ha, Jang Ho; Chung, Jong Eun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2005-07-01

    Ionization chamber is still widely used in radiation detection field because that gives absolute dose, hardness for radiation damage and simplicity of operation in somewhat. Parallel plate ionization chamber for proton beam calibration was designed and fabricated in KAERI. Fabricated ionization chamber includes guard electrode that may cause distortion of electric field due to potential difference between guard electrode and collection electrode. To calculate this distortion rate Maxwell and Garfield simulator was incorporated.

  15. A grid-ionization chamber and a ΔE-E particle telescope detection set-up

    International Nuclear Information System (INIS)

    A detection set-up, composed of a typical grid-ionization chamber and a ΔE-E particle telescope, was constructed to study the charge distributions of fragments in spontaneous fission of 252Cf. The fission fragment energy and the emission angle corresponding to the symmetrical axis were measured by the grid-ionization chamber, the ΔE-E particle telescope in which a thin grid-ionization chamber was served as the ΔE-section and a surface barrier detector as the E-section was employed to determined the charge of the complementary fragment. Four parameter measurements of 252Cf spontaneous fission were performed by this set-up, the results show that the charge resolution of Z/ΔZ>40:1 can be obtained by this detector system. (authors)

  16. Setup and characterization of a Frisch grid ionization chamber for the spectroscopy of low specific activities

    International Nuclear Information System (INIS)

    The realization of this work was the usage of a Frisch grid ionization chamber for measuring the lowest specific alpha activity. In the practical case the detector should be used to remeasure the half life of 144Nd. Only very thin targets can be used, due to the extreme long half life and the very short range of alpha particles in matter. The area of the samples must be big enough to get the required activity. In comparison gridded ionization chambers are the most practical devices. The chamber was realized in that way, that two gridded chambers shares a common anode. This could be used to minimize the detector background. The charge, which was induced in the detector electrodes, is acquired by an analog to digital converter. The full analysis of the data is done after the measurement. With the pulse form analysis it is possible to extract information about every event occurring in the detector. It is also possible to correct the grid inefficiency and the correlated angle dependence of the pulse height. This improves the energy resolution. A resolution of 0.86 % at 5.1 MeV is possible. The characterization of the events is also used for the suppression of the detector background. Due to different conditions for an assumed alpha event the majority of the events which disturbs the measurement could be removed. So it is possible to suppress the background in the range between 1 MeV to 2.2 MeV of 435 events per day without the characterization to 21.6 events per day with characterization, which is a factor of roughly 20. The detection efficiency is not noticeably effected. For sufficiently long measurements a lowest limit of detection of 10 counts per day is expectable. For a target geometry which can be used with this setup, about 50 alpha decays of 144Nd per day will occur. With a detection efficiency a bit below 50 % the measurement on 144Nd should be possible.

  17. Measurements of double-differential α-particle production cross sections of Fe and Ni using gridded ionization chamber

    International Nuclear Information System (INIS)

    Double-differential α-particle production cross sections of Fe and Ni were measured for neutron energy region between 4 and 14 MeV using a gridded ionization chamber. The method applied in this work enables us to measure the double-differential cross sections at various incident neutron energies because of the high efficiency and background suppression capability of the gridded ionization chamber. The double-differential cross sections, the energy-differential cross sections and the excitation functions were obtained for the (n,xα) reactions of Fe and Ni and are compared with the previous experiments and evaluated data. (author)

  18. Range-Energy Relations for Heavy Charged Particles in Gases Using the Double-Gridded Ionization Chamber

    International Nuclear Information System (INIS)

    The application of the double-gridded pulse ionization chamber to measuring the range-energy relations for alpha particles, protons, and heavy recoils is discussed. Range-energy values for recoil protons and alpha particles in a gas mixture of Argon plus 10% Methane are presented to confirm the method. The chamber described has been designed primarily for the measurement of proton ranges in a tissue equivalent gas mixture of CO2 , CH4 and N, and for fast neutron spectroscopy. (author)

  19. Chamber wall interactions with HBr/Cl{sub 2}/O{sub 2} plasmas

    Energy Technology Data Exchange (ETDEWEB)

    Srivastava, Ashutosh K.; Ohashi, Tomohiro; Donnelly, Vincent M., E-mail: vmdonnelly@uh.edu [Department of Chemical and Biomolecular Engineering, University of Houston, Houston, Texas 77204-4004 (United States)

    2015-07-15

    The authors have studied the interaction of HBr/Cl{sub 2}/O{sub 2} inductively coupled plasmas with reactor chamber wall deposits, with and without Si etching, using the “spinning wall” technique. The spinning wall is part of the reactor chamber walls, allowing near-real-time analysis of the composition of surface layers via Auger electron spectrometry and determination of species desorbing off the walls by mass spectrometry. In HBr plasmas with no bias voltage on the Si substrate, and hence no Si etching, HBr is ∼30% dissociated, and H{sub 2} and Br{sub 2} form in the plasma. Layers deposited on the reactor chamber contained little if any Br under these conditions. Adding O{sub 2} to an HBr plasma leads to formation of H{sub 2}O and increased Br{sub 2} (compared to a pure HBr plasma) products that desorb from the spinning wall. H{sub 2}O has a very long residence time on the surface. With bias voltage applied to the Si substrate in an HBr plasma, mass spectrometer signals are prominent for SiBr and SiBr{sub 3}, and weaker for SiBr{sub 2}, SiBr{sub 4}, Si{sub 2}Br{sub 4}, Si{sub 2}Br{sub 5}, and Si{sub 2}OBr{sub 5}. Under these conditions, a SiO{sub x}Br{sub y} layer deposits on the spinning wall. Adding 20% O{sub 2} to HBr stops etching and eliminates Br from the surface layer, indicating that Br on the reactor walls is a result of SiBr{sub x} impingement and not from bromination by impinging Br. With HBr/Cl{sub 2} plasmas and no bias on the stage, a SiO{sub x}Cl{sub y} layer deposits, and no Br is detected. HCl, BrCl, and Br{sub 2} were detected in the line-of-sight leak, around the spinning wall, of a HBr/Cl{sub 2} (1:1) gas mixture in the absence of a plasma. Residence time analysis of species in the chamber and a change in the product distribution with a change in the composition of the layer deposited on the chamber wall suggest that reactions forming these products in the absence of a plasma occur on the reactor walls. With a plasma and bias on the Si

  20. 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

  1. Development of gridded ionization chamber for measuring atomic number of fission fragments

    International Nuclear Information System (INIS)

    In order to investigate the mechanism of asymmetric mass division in low energy fission of actinides, the detector for measuring an atomic number (Z) for fission fragments has been developed. Because the atomic number is closely related to energy losses of fragments, the gridded ionization chamber with divided anode is useful for this purpose. The detector was designed and optical conditions such as the distance and electric potential between electrodes were searched using alpha particles from 252Cf. The total energy and energy losses of fission fragments from 252Cf were measured under the obtained conditions. It was found that fission fragments lost most of the kinetic energy in the beginning of their range. This behavior agrees qualitatively with results of simulation by TRIM code. In the presentation, the results of energy measurements under various conditions will be shown and discussed. (author)

  2. The mass dependence of the signal peak height of a Bragg-curve ionization chamber

    International Nuclear Information System (INIS)

    The Bragg-curve detector of the parallel plate ionization chamber type generates a signal that is a distorted replica of the original Bragg-curve. In result of this distortion, the signal peak height is not only a function of the atomic number of the heavy ion, as it is often stated, but also of the particle mass. This mass effect was studied with the aid of computer simulation, and it was found to be dependent on the Frisch grid to anode gap width and on the detector gas. The charge resolution of the detector is affected very significantly by this mass dependence of the signal peak height. Therefore, a careful selection of the detector gas and the grid to anode gap width is necessary, if good charge resolution over a wide range of heavy ions is required. (orig.)

  3. Particle emission angle determination in Frisch grid ionization chambers by electron drift-time measurements

    Science.gov (United States)

    Göök, A.; Chernykh, M.; Enders, J.; Oberstedt, A.; Oberstedt, S.

    2010-09-01

    The double kinetic energy measurement of fission fragments with a double-sided Frisch grid ionization chamber allows a careful determination of the emission angle, which is essential in order to apply appropriate energy-loss corrections. We present a drift-time method, which uses the time that free electrons need to drift from the location of their creation, e.g. by a fission fragment in the counting gas, to the grid, before inducing a signal on the anode. Such a measurement leaves energy and angular information fully decoupled. We demonstrate the applicability of the drift-time method for the example of the 234,238U (γ,f) reactions performed at the superconducting Darmstadt electron linear accelerator. The angular resolutions achieved with this method are comparable to those obtained with other methods.

  4. The mass dependence of the signal peak height of a Bragg-curve ionization chamber

    Science.gov (United States)

    Shenhav, N. J.; Stelzer, H.

    1985-01-01

    The Bragg-curve detector of the parallel plate ionization chamber type generates a signal that is a distorted replica of the original Bragg-curve. In result of this distortion, the signal peak height is not only a function of the atomic number of the heavy ion, as it is often stated, but also of the particle mass. This mass effect was studied with the aid of computer simulation, and it was found to be dependent on the Frisch grid to anode gap width and on the detector gas. The charge resolution of the detector is affected very significantly by this mass dependence of the signal peak height. Therefore, a careful selection of the detector gas and the grid to anode gap width is necessary, if good charge resolution over a wide range of heavy ions is required.

  5. On the neutron spatial distribution in ionization chamber channels of the WWER type reactors

    International Nuclear Information System (INIS)

    Results of experimental and calculational studies permitting to estimate the neutron flux spatial distribution in ionization chamber channels of the commercial WWER-1000 and WWER-440 reactors and also of the WWER-440 reactor with water biological shield are presented. The integral neutron flux density distribution along the channel cross section approximately at height of the core middle and the corresponding thermal and fast neutron flux density distributions are measured by the activation detectors. It is shown that the difference in fast neutron flux density exceeds that of thermal neutrons. The commercial WWER-1000 type reactor the fast neutron flux density is decreased by the factor of 1.7, and thermal neutron flux density - by the factor of 1.2, for the commercial WWER-440 reactor these values are 1.37 and 1.18, and for the WWER-440 one with water shield - 1.5 and 1.18

  6. Particle emission angle determination in Frisch grid ionization chambers by electron drift-time measurements

    International Nuclear Information System (INIS)

    The double kinetic energy measurement of fission fragments with a double-sided Frisch grid ionization chamber allows a careful determination of the emission angle, which is essential in order to apply appropriate energy-loss corrections. We present a drift-time method, which uses the time that free electrons need to drift from the location of their creation, e.g. by a fission fragment in the counting gas, to the grid, before inducing a signal on the anode. Such a measurement leaves energy and angular information fully decoupled. We demonstrate the applicability of the drift-time method for the example of the 234,238U (γ,f) reactions performed at the superconducting Darmstadt electron linear accelerator. The angular resolutions achieved with this method are comparable to those obtained with other methods.

  7. 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.

  8. Ionization chamber array for patient specific VMAT, Tomotherapy and IMRT QA

    International Nuclear Information System (INIS)

    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

  9. Energy resolution of gas ionization chamber for high-energy heavy ions

    Science.gov (United States)

    Sato, Yuki; Taketani, Atsushi; Fukuda, Naoki; Takeda, Hiroyuki; Kameda, Daisuke; Suzuki, Hiroshi; Shimizu, Yohei; Nishimura, Daiki; Fukuda, Mitsunori; Inabe, Naohito; Murakami, Hiroyuki; Yoshida, Koichi; Kubo, Toshiyuki

    2014-01-01

    The energy resolution is reported for high-energy heavy ions with energies of nearly 340 MeV/nucleon and was measured using a gas ionization chamber filled with a 90%Ar/10%CH4 gas mixture. We observed that the energy resolution is proportional to the inverse of the atomic number of incident ions and to the inverse-square-root of the gas thickness. These results are consistent with the Bethe-Bloch formula for the energy loss of charged particles and the Bohr expression for heavy ion energy straggling. In addition, the influence of high-energy δ-rays generated in the detector on the energy deposition is discussed.

  10. Radial force on the vacuum chamber wall during thermal quench in tokamaks

    Energy Technology Data Exchange (ETDEWEB)

    Pustovitov, V. D., E-mail: pustovitov-vd@nrcki.ru [National Research Centre Kurchatov Institute (Russian Federation)

    2015-12-15

    The radial force balance during a thermal quench in tokamaks is analyzed. As a rule, the duration τ{sub tp} of such events is much shorter than the resistive time τ{sub w} of the vacuum chamber wall. Therefore, the perturbations of the magnetic field B produced by the evolving plasma cannot penetrate the wall, which makes different the magnetic pressures on its inner and outer sides. The goal of this work is the analytical estimation of the resulting integral radial force on the wall. The plasma is considered axially symmetric; for the description of radial forces on the wall, the results of V.D. Shafranov’s classical work [J. Nucl. Energy C 5, 251 (1963)] are used. Developed for tokamaks, the standard equilibrium theory considers three interacting systems: plasma, poloidal field coils, and toroidal field coils. Here, the wall is additionally incorporated with currents driven by ∂B/∂t≠0 accompanying the fast loss of the plasma thermal energy. It is shown that they essentially affect the force redistribution, thereby leading to large loads on the wall. The estimates prove that these loads have to be accounted for in the disruptive scenarios in large tokamaks.

  11. Quality assurance of proton beams using a multilayer ionization chamber system

    International Nuclear Information System (INIS)

    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

  12. Simulation study of the photon quality correction factors of ionization chambers for FiR 1 epithermal neutron beam

    International Nuclear Information System (INIS)

    At FiR 1 BNCT facility in Finland, neutron-insensitive Mg(Ar) ionization chambers are used for photon dose measurements in an epithermal neutron beam. Previously, photon sensitivity factors for the chamber for the measurements in a water phantom in FiR 1 beam have been determined experimentally from measurements in 60Co gamma and in a 6 MV clinical accelerator photon beams. However, the response of the ionization chamber in a water phantom depends on energy spectrum and angle of the photons and the secondary electrons created inside the phantom and may differ depending on type of the irradiation source (accelerator vs. an epithermal neutron beam). Also, the experimental sensitivity factor does not take into account the possible perturbations in the photon production in phantom caused by the ionization chamber materials. Therefore, it is necessary to determine the photon quality correction factors (kQγ) for the Mg(Ar) chamber at the FiR 1 beam through computer simulations. In this study, the kQγ factors have been determined for Mg(Ar) chamber from Monte Carlo calculations of absorbed photon dose at two depths in a water phantom using MCNP code. The kqγ factors obtained with this method are compared to the sensitivity factors determined with measurements in an accelerator photon beam and to the kQγ factors published previously. (author)

  13. SU-D-213-04: Accounting for Volume Averaging and Material Composition Effects in An Ionization Chamber Array for Patient Specific QA

    International Nuclear Information System (INIS)

    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

  14. 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

  15. 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.

  16. Alpha spectroscopy with ionization chamber to determine uranium and thorium in environmental samples

    International Nuclear Information System (INIS)

    A high-resolution, parallel Frisch ionization chamber with an efficient area of 320 cm2 was developed and applied as an alpha spectrometer. The resolution of the spectrum is approximatelly 40 KeV fwhm (full width half maximum) for 233U point source. The spectrum is recorded by a 1024 channels pulse-height analyser. The counting gas is commercial available mixture of argon and methane. The counting efficiency for 233U energy-window selected is in order of 42% for a calibration source placed on the cathode axis. No radial dependence of this efficiency was observed. The chamber was used for counting the activity of uranium and thorium isotopes on large area stainless steel planchets. The large area thin sources were prepared extracting the uranium and thorium isotopes from 1M HNO3- aqueous solution with polymeric membranes containing tri-n-octyl-phosphine oxide adhered on the surface of the 314 cm2 planchet. The integral back-ground is typically 7 counts/min between 4 and 6 MeV. The sensitivity of the procedure used ofr 238U is about 30 Bq/1 based on 3S of back-ground, 1 liter sample volume and 30 min counting time. (Author)

  17. A multiple sampling ionization chamber (MUSIC) for measuring the charge of relativistic heavy ions

    International Nuclear Information System (INIS)

    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 40Ar and 0.30e fwhm for 1.08 GeV/nucleon 139La and 139La 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 σ≅100 μm. (orig.)

  18. A gridded ionization chamber with a movable cathode for precise measurements of W-values in highly purified rare gases

    International Nuclear Information System (INIS)

    A single gridded ionization chamber with a movable cathode was constructed in order to measure W-values in highly purified rare gases without ambiguity. The chamber gases were continuously purified with a purifier filled with many pellets of titanium-barium getter. The purifier proved to be so powerful as to reduce impurities in rare gases to the level of 1 ppb or less. Performance tests of the chamber were made by measurements of W-values of argon-methane mixtures relative to that of argon. The measurements were made with a precision of ±0.14%. (orig.)

  19. Verification of the absorbed dose values determined with plane parallel ionization chambers in therapeutic electron beams using ferrous sulfate dosimetry

    International Nuclear Information System (INIS)

    Absolute and relative dosimetry measurements in clinical electron beams using different detectors were performed at a Philips SL18 accelerator. For absolute dosimetry, ionization chamber measurements with the PTW Markus and PTW Roos plane parallel chambers were performed in water following the recommendations of the TRS-381 Code of Practice, using different options for chamber calibration. The dose results obtained with these ionization chambers using the electron beam calibration method were compared with the dose response of the ferrous sulphate (Fricke) chemical dosimeter. The influence of the choice of detector type on the determination of physical quantities necessary for absolute dose determination was investigated and discussed. Results for dmax, R50 and Rp were in agreement within statistical uncertainties when using a diode, diamond or plane parallel chamber. The effective point of measurement for the Markus chamber is found to be shifted 0.5 mm from the front surface of the cavity. Fluence correction factors, hm, for dose determination in electron beams using a PMMA phantom were determined experimentally for both plane parallel chamber types. (author)

  20. Review of data and methods recommended in the international code of practice for dosimetry IAEA Technical Reports Series No. 381, The Use of Plane Parallel Ionization Chambers in High Energy Electron and Photon beams. Final report of the co-ordinated research project on dose determination with plane parallel ionization chambers in therapeutic electron and photon beams

    International Nuclear Information System (INIS)

    In 1987 the IAEA published a Code of Practice entitled ''Absorbed Dose Determination in Photon and Electron Beams: An International Code of Practice'' (IAEA Technical Reports Series No. 277), to advise users on how to obtain the absorbed dose in water from measurements made with an ionization chamber, calibrated in terms of air kerma. The Code of Practice described procedures and provided data for the use of ionization chambers to obtain the absorbed dose in high energy photon and electron beams. It was so designed that a variety of cylindrical chambers could be used, which represented the existing conditions worldwide. However, most national and international dosimetry protocols recognized the advantages of plane parallel ionization chambers, explicitly for electron beams and especially for low energy electron beams (below 10 MeV). Although this was acknowledged in TRS-277, recommended procedures for the calibration and use of these chambers were not fully developed. Another Code of Practice entitled ''The Use of Plane Parallel Ionization Chambers in High Energy Electron and Photon Beams: An International Code of Practice for Dosimetry'' (IAEA Technical Reports Series No. 381) was published in 1997 to update TRS-277 and complement it with respect to the area of parallel plate ionization chambers. TRS-381 describes options on how to calibrate plane parallel chambers, against air kerma or absorbed dose to water standards at 60Co gamma ray energies, in order to determine the absorbed dose to water in reference conditions. The use of these chambers to calibrate therapy electron beams, as well as to perform relative dose measurements for photon and electron beams, is included in the Code of Practice which also updates some of the data and concepts in TRS-277. It is considered that the Code of Practice TRS-381 fills the gaps that existed in TRS-277 with respect to plane parallel chambers and will result in improved accuracy in radiotherapy dosimetry when these chambers

  1. Development of improved free-air ionisation chamber as absolute dosimetry standard for low-energy X rays in INER

    International Nuclear Information System (INIS)

    The National Radiation Standard Laboratory of the Inst. 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 Inst. of Advanced Industrial Science and Technology (AIST) experimental results comparison using a transfer chamber yielded a difference <1.0% at the 95% confidence level in calibration factors. The overall uncertainty for the X-ray measurement in terms of air kerma was <0.6% at the 95% confidence level. These results indicated that the improved FAC is capable of serving as a primary standard as well as a trace standard in low-energy X-ray calibration services in Taiwan and even forming a basis for the future mammography X-ray air-kerma primary standard. (authors)

  2. Angular distribution and cross section measurements for the reaction 40Ca(n,α)37Ar using gridded ionization chamber

    International Nuclear Information System (INIS)

    A new-type double gridded ionization chamber (GIC) with a multi-parameters data acquisition and processing system has been established for the study of fast-neutron-induced (n,p) and (n,α) reactions. The system has been applied to measurements of angular distribution, energy spectra and differential cross section of the 40Ca(n,α)37Ar reaction

  3. Fabrication process of ionization chamber multidetector and multidetector got by this process. Procede de fabrication d'un multidetecteur a chambres d'ionisation et multidetecteur obtenu par ce procede

    Energy Technology Data Exchange (ETDEWEB)

    Tirelli, M.; Lecolant, R.; Hecquet, R.

    1986-06-20

    The multidetector ionization chamber walls are fixed one related to the others and carried together with a tool above a resin bath to polymerize. After resin hardening, the detector includes resin basis. To contain the resin bath, the realization of a mould cut in a massive resin block are been provided for. This allows for its manutention all along the process without any deterioration risk.

  4. Design and performance of a heavy ion detector using a gridded ionization chamber with helical position-sensitive proportional counter

    International Nuclear Information System (INIS)

    A counter specifically designed for heavy ions and low-energy helium ions has been constructed for use in the focal plane of a Q3D spectrometer. The counter utilizes a gridded ionization chamber to measure energy loss and total energy of the particles incident on the detector and a helical proportional chamber to establish the position and hence the momentum along the focal plane. The ionization chamber information is used to establish the mass and charge of the incident particle with high precision and under low background conditions. The helix provides excellent spatial resolution along with high counting rate performance and a resolution independent of the angle at which the particles enter the detector

  5. Identification and spectrometry of low-energy charged particles by means of ionization chamber with two grids

    International Nuclear Information System (INIS)

    The method of using an ionization chamber with two grids for identification and spectrometry of low-energy charged particles with the close energy, but different product of their mass and charge is described. The method enables to carry out multidimensional measurements of coincident pulses from the cathode and anode of ionization chamber. The selection circuit provides for relizble identification of different sorts of charged particles with close energy and essentially improves the raio of the effect and background at low energy resolution due to a radioactive target in the chamber. The method was used in investigation of reactions (n,p) on slow neutrons for radioactive targets 7Be, 36Cl, 88Y

  6. Simulation of the Interaction of X-rays with a Gas in an Ionization Chamber by the Monte Carlo Method

    International Nuclear Information System (INIS)

    The final objective of any ionization chamber is the measurement of the energy amount or radiation dose absorbed by the gas into the chamber. The final value depends on the composition of the gas, its density and temperature, the ionization chamber geometry, and type and intensity of the radiation. We describe a Monte Carlo simulation method, which allows one to compute the dose absorbed by the gas for a X-ray beam. Verification of model has been carried out by simulating the attenuation of standard X-ray radiation through the half value layers established in the ISO 4037 report, while assuming a Weibull type energy distribution for the incident photons. (Author) 6 refs

  7. 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

  8. 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.

  9. High resolution multiple sampling ionization chamber (MUSIC) sensitive to position coordinates

    International Nuclear Information System (INIS)

    A new type of MUSIC sensitive to position coordinates is reported. The development of the first version of this type of chamber is based on the principles presented by Badhwar in 1973. The present detector will be used in experiments on fusion by using radioactive beams. This chamber due to the high resolution is suitable to identification and tracking of low Z particles. One of our goals, when we started this work, was to reduce as much as possible the Z value of particles that can be 'seen' by an ionization chamber. The resolution of the chamber was significantly improved by connecting the preamplifiers directly to the MUSIC's pads. These preamplifiers are able to work in vacuum and very low gas pressure. In this way the value of signal to noise ratio was increased by a factor of ∼10. The detector is of Frisch grid type, with the anode split into 10 active pads. It is the first model of a MUSIC with the field shared between the position grid and the anode pads. The Frisch grid was necessary because the detector is originally designed for very accurate energy measurements and particle identification. A drawing of this detector is shown. The detector itself consists of four main parts. The first one is the constant field-gradient cage, sandwiched in between the cathode and the Frisch grid. The second is the Frisch grid. The third is the position grid located under the Frisch grid. The last one is the plate with the anode pads. The cage is made of 100 μm Cu-Be wires. Every wire was tensioned with a weight representing half of its breaking limit. The Frisch grid was done on an aluminium frame, on which 20 μm W wires spaced 0.3 mm, were wound. For the position grid, 10 groups of 20 μm gold plated W wires have been used. Each group consisted of 5 wires spaced 0.9 mm and connected in parallel. The anode pads 7.8 x 60 mm2 were perpendicular to the beam direction. Each pad and each of the position wire groups were connected to a preamplifier. The energy resolution

  10. Fusion cross sections of carbon isotopes obtained with an ionization chamber in active target mode

    International Nuclear Information System (INIS)

    Carbon fusion has provided questions to both physicists and astronomers for at least the last 50 years. From fundamental nuclear structure to recent discoveries in stellar phenomena there are still open topics. Fusion in the 12C + 12C system show oscillations that are not present in neighboring systems and are yet not completely understood. Unexplained behavior in the threshold between 1p and 2s1d shells is seen as fusion cross sections show significant changes in systems which differ by only a nucleon. A new type of stellar explosions, called super bursts, in X-ray binaries were recently observed and are thought to require fusion of radioactive carbon isotopes for an explanation, opening new paths for stellar nucleosynthesis. These are a few interesting examples that motivated the development of a new measurement technique, which comprises a Multi Sampling Ionization Chamber (Music) operated in active target mode, with methane gas (C H4) as both counting gas and reaction target. This offers a high efficiency detection method where excitation functions can be sampled, using a single beam energy, in a range determined by the ionization gas pressure. This is a great advantage since it drastically reduces the measurement time and the data are automatically normalized. The high efficiency of the detector makes it ideal for experiments where the reaction cross section and/or the beam intensity are low, i.e. for processes involving radioactive nuclei. Using the Music, fusion cross sections in systems with carbon isotopes of mass numbers A = 10, 12, 13, 14, 15 impinging on a carbon-12 target have been measured. Beam energies of about 3 MeV/A were used for obtaining fusion excitation functions in the center of mass energy range between 10 and 20 MeV. In this contribution, the operation principle of the Music is discussed. Then, the experimental excitation functions are presented and compared with previous data (3when available) and different theoretical models

  11. Construction of an ionization chamber for buildup measurements in megavoltage X-ray beams

    International Nuclear Information System (INIS)

    The design and construction of a simple homemade ion chamber for brildup measurements in megavoltage beams is described. Tests indicate that the performance of the chamber is superior in some respects to a commercially available chamber. Results obtained using the chamber in a 6 MV beam are presented. (Author)

  12. Air kerma strength calibration of 0.6 cc Farmer chamber for 192Ir HDR source

    International Nuclear Information System (INIS)

    One of the methods adopted by hospitals for the calibration of the HDR 192Ir source, in terms of Air Kerma Strength (AKS) is to use 0.6cc chamber at short source to chamber distances for measuring the air kerma rate at the chamber position and then compute the AKS using the appropriate correction factors. However, the 0.6 cc Farmer type chambers purchased by the users for the calibration of the HDR 192Ir source, are not generally provided with an HDR 192Ir calibration factor. With the result, many hospitals that have purchased the Farmer type chamber for the calibration of 192Ir HDR sources, use the 60Co calibration factor for this purpose. The use of 60Co calibration factor for the 192Ir HDR source would unnecessarily increase the uncertainty of the measured AKS. Again, because of the low chamber sensitivity, hospitals often use, source to chamber distances as small as a few cm for calibrating the 192Ir HDR source. In the absence of a rigid source-chamber positioning system, this can lead to several percent errors in AKS determination. Also, hospitals often don't take into account corrections for the room scatter or the fluence non-uniformity across the chamber, which further increase the uncertainty of the measured AKS

  13. Patient specific IMRT quality assurance with film, ionization chamber and detector arrays: Our institutional experience

    International Nuclear Information System (INIS)

    -value>0.05). Conclusions: Among the TPSs, Tomoplan and Corvus had the best agreement with the point dose measurement. Based on anatomical location of treatment site, head and neck cancers had the lowest gamma value for the patients treated and brain sites had the highest gamma value. However, the values are not significantly different. TomoTherapy machines continue to have the best overall gamma values as compared to CLINAC machines. - Highlights: • IMRT QA methods performed at our institution were analyzed retrospectively. • IMRT QA using film & ionization chamber was compared with 2D array of ion chambers. • Dosimetric measurements were compared against the plan based on multiple criteria. • Criteria included TPS, anatomic site, Linac type, number of control points, arcs or beams. • Average dose differences and Gamma analysis were estimated to exceed passing criteria

  14. Design and building of an extrapolation ionization chamber for beta dosimetry

    International Nuclear Information System (INIS)

    An extrapolation chamber was designed and built to be used in beta dosimetry. The basic characteristics of an extrapolation chamber are discussed, together with fundamental principle of the dosimetric method used. Details of the chamber's design and properties of materials employed are presented. A full evaluation of extrapolation chamber under irradiation from two 90Sr + 90Y beta sources is done. The geometric parameters of the chamber, leakage current and ion collection efficiency are determined. (Author)

  15. The control system of the multi-strip ionization chamber for the HIMM

    International Nuclear Information System (INIS)

    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

  16. Investigation of fission layers for precise fission cross-section measurements with a gridded ionization chamber

    International Nuclear Information System (INIS)

    An ionization chamber with a Frisch grid is used to determine both the energy (E) of the charged particles emitted from the source positioned coplanar with the cathode, and the cosine of the emission angle (/sigma phi/) with respect to the normal of the cathode. In the plane determined by the variables cos/sigma phi/ and E, it is possible to identify an area that is unaffected by backscattering and self-absorption. Events belonging to this area show an isotropic angular distribution for alpha particles and also for fragments of fission induced by thermal neutrons, which, extrapolated to 90 deg, yields the absolute number of events. The capabilities of this technique are demonstrated by the investigation of four evaporated 235 UF4 layers and one suspension-sprayed 235U3O8 layer. For the UF4 layers, the alpha-particle source strengths were determined, and agreement was found within 0.3% with values independently measured by low-geometry alpha counting. The same method was also applied to fission events induced by thermal neutrons. The determination of the total number of fission events is determined to an accuracy of better than 0.5%. The longstanding doubts on the magnitudes of fragment absorption and scattering are, in principle, circumvented by the present method, and therefore no assumptions on fragment ranges and scattering cross sections are needed. It is emphasized that the present method, within reasonable limits, is insensitive to source shape and homogeneity in its thickness

  17. Measurement of differential (n,xα) cross section using 4π gridded ionization chamber

    International Nuclear Information System (INIS)

    We carried out the measurements of high resolution α emission spectra of 58Ni and natNi between 4.5 and 6.5 MeV, and 12C(n,xα) cross section using a 4π 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 (55Fe). These results were compared with another direct measurement and statistical model calculations. In 12C measurement, GIC was applied for (n,xα) reactions of light nuclei. This application is difficult to (n,xα) 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 12C(n,xα) reaction at En=14.1 MeV. In our experiment, the 12C(n,α0)9Be angular differential cross section and 12C(n,n'3α) cross section were obtained. (author)

  18. Investigation of fission layers for precise fission cross section measurements with a gridded ionization chamber

    International Nuclear Information System (INIS)

    An ionization chamber with Frisch-grid is used to determine both the energy (E) of the charged particles emitted from the source positioned coplanar with the cathode, and the cosine of the emission angle (theta) with respect to the normal of the cathode. In the plane determined by the variables cos theta and E it is possible to identify an area which is unaffected by backscattering and selfabsorption. Events belonging to this area show an isotropic angular distribution for alpha particles and also for fission fragments induced by thermal neutrons, which, extrapolated to 90 deg., yields the absolute number of events. The capabilities of this technique are demonstrated by the investigation of four evaporated 235UF4 layers and one suspension sprayed 235U3O8 layer. For the UF4 layers the alpha particle source strengths were determined, and agreement was found within 0.3% with values independently measured by low geometry alpha counting. The same method was applied also to fission events induced by thermal neutrons. An accuracy for the determination of the total number of fission events of better than 0.5% is reached. The longstanding doubts on the magnitudes of fragment absorption and scattering are in principle circumvented by the present method and therefore no assumptions on fragment ranges and scattering cross-sections are needed. It is also emphasized that the present method, within reasonable limits, is intensive to source shape and thickness homogeneity. (author)

  19. Assaying of targets for nuclear measurements with a gridded ionization chamber

    International Nuclear Information System (INIS)

    An ionization chamber with a Frisch grid is used to determine both the energy (E) of the charged particles emitted from the sample positioned coplanar with the cathode, and the cosine of the emission angle (theta) with respect to the normal of the cathode. Using the combined information on costheta and E, problems in particle counting due to sample absorption and scattering effects can be circumvented and sample source strengths are readily determined to an accuracy of 0.3%. However, it is emphasized that the source strength can be determined from the particles emitted in a large solid angle close to 2 π sr, which means a considerable higher efficiency than for the conventional low geometry counting technique. Moreover the present method, within reasonable limit is intensive to source shape and thickness homogeneity. The technique will be illustrated by measurements of alpha particles and fission fragments emitted from a set of four vacuum evaporated UF4, three electrodeposited and one suspension-sprayed 235U3O8 layers. The energy and angular distributions of alpha particles and of the heavy alpha recoils emitted from a self transferred 224Ra source will be discussed. The low energetic alpha recoils might be useful as probes for the investigation of ultrathin (< 400 A) layers. (orig.)

  20. Assaying of 235U fission layers for nuclear measurements with a gridded ionization chamber

    International Nuclear Information System (INIS)

    An ionization chamber with a Frisch grid is used to determine both the energy (E) of the charged particles emitted from the sample positioned coplanar with the cathode, and the cosine of the emission angle (theta) with respect to the normal of the cathode. Using the combined information on cos theta and E, problems in particle counting due to sample absorption and scattering effects can be circumvented and sample source strengths are readily determined to an accuracy of 0.3%. However, it is emphasized that the source strength can be determined from the particles emitted in a large solid angle close to 2π steradian, which means a considerable higher efficiency than for the conventional low geometry counting techniques. Moreover the present method, within reasonable limits is insensitive to source shape and thickness homogeneity. The technique will be illustrated by measurements of alpha particles and fission fragments emitted from a set of four vacuum evaporated UF4, three electrodeposited and one suspension-sprayed 235U3O8 layers. (author)

  1. Annual change in calibration constant of ionization chamber used in diagnostic radiology

    International Nuclear Information System (INIS)

    Committee on Radiological Protection of Japan Radiological Society (JRS) is making a database on patient doses for typical radiographies for introducing the guidance levels in Japan. The Committee reported necessity of a protocol on dosimetry in diagnostic radiology for introducing the guidance levels. Although a protocol on dosimetry in radiation therapy is established, there is no protocol on dosimetry in diagnostic radiology in Japan. Then, as a first step to establish a protocol on dosimetry in diagnostic radiology, annual changes in a calibration constant of an ionization chamber as a practical standard dosimeter has been investigated for 4 years. Changes in calibration constants for 4 years are within 2% for X-rays with effective energies than 32 keV. From these results, practical frequencies of calibrations for practical standard dosimeters are discussed for maintain of their precision. If an accuracy of practical standard dosimeters is 5% for diagnostic radiology, frequencies of their calibrations may be once in a year or two years. (author)

  2. Assaying of targets for nuclear measurements with a gridded ionization chamber

    Science.gov (United States)

    Budtz-Jørgensen, C.; Knitter, H. H.; Bortels, G.

    1985-06-01

    An ionization chamber with a Frisch grid is used to determine both the energy ( E) of the charge particles emitted from the sample positioned coplanar with the cathode, and the cosine of the emission angle (ϑ) with respect to the normal of the cathode Using the combined information on cosϑ and E, problems in particle counting due to sample absoprtion and scattering effect can be circumvented and sample source strengths are readily determined to an accurary of 0.3%. However, it is emphasized that the source strength can be determined from the particles emitted in a large solid angle close to 2τ sr, which means a considerable higher efficiency than for the conventional low geometry counting techniques. Moreover the present method, within reasonable limits is insensitive to source shape and thickness homogeneity. The technique will be illustrated by measurements of alpha particles and fission fragments emitted from a set of four vacuum evaporated UF 4, three electrodeposited and one suspension-sprayed 235U 3O 8 layers. The energy and angular distributions of alpha particles and of the heavy alpha recoils emitted from a self transferred 224Ra source will be discussed. The low energetic alpha recoils might be useful as probes for the investigation of ultrathin ( < 400 Å) layers.

  3. 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...

  4. 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...

  5. 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. PMID:26979835

  6. 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.

  7. 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.

  8. Space-charge effects of the proportional counters in a multiple-ionization chamber

    International Nuclear Information System (INIS)

    At the ALADIN spectrometer of the GSI in october 1991 for the first time the new multiple ionization chamber was applied, in the two anode planes of which are additional multiwire-proportional counters. The proportional counters are required in order to make the detection of light fragments (Z4 gold projectiles per second by these positive space charges the homogeneous electric field of the MUSIC is disturbed. This effect is especially strong in the beam plane. As consequence of the space charge additionally electrons are focused on the proportional counter so that their amplitudes in dependence on the beam intensity increase up to the 2.5-fold. Furthermore the y coordinate is falsified, because the electrons are diverted to the medium plane. On the measurement of the x coordinate this diversion has with maximally 0.1% only a small influence. These space-charge effects can be qualitatively described by a schematic model, which assumes a stationary positive space charge. Additionally for the proportional counters, which are not in the beam plane, their resolution was determined. In these counters the space-charge effects are small, because essentially fewer particles are registrated than in the medium MWPC's. By this charges of fragments with Z<10 could be separated. The charge resolution amounted at lithium 0.8 charge units. The position resolution of the proportional counters in y direction was determined to less than 8 mm. The detection probability of the fragments amounts for lithium 90% and from boron all fragments are detected

  9. Feasibility study for the development of a Dose Calibrator with a well ionization chamber

    International Nuclear Information System (INIS)

    Dose calibrators are intended for the metrological assurance of medical diagnostic studies in which radiopharmaceuticals are used. It is the final link in the national system of standards to ensure quality control and the radiation safety of the dose administered to patients while using these nuclear techniques. The wide utilization of radiopharmaceuticals in our country in several modules of nuclear medicine and other laboratories where radio-isotopic preparations are used, as well as the existence of the National Center of Isotopes to produce them determine the necessity of national production of dose calibration equipment. In this paper, it is presented the result of a feasibility study to develop a dose calibrator with a well-type ionization chamber for nuclear medicine services of the National Health System with gamma camera. It is specifically intended to contribute to monitor and control the activity of the prepared samples to be administered to patients under studies with gamma cameras to ensure compliance with the current requirements of quality and radiation safety. (Author)

  10. 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)

  11. Comparison of theoretical and experimental determinations of calibration factors for cylindrical and parallel plates ionization chambers

    International Nuclear Information System (INIS)

    The Ionizing Radiation Dosimetry Section of CNEA is the National Laboratory of Dosimeter Reference, having been designated by the National Institute of Industrial Technology (INTI, deposit taker by Law 19,511/72 of the national standards for metrology) for the safekeeping and operation of the national standards for dosimetry (Agreement INTI - CNEA, February 2004). From their creation, the CRRD provides, among other services, the calibration of dosemeters used in radiotherapy, in terms of Kerma in air, and since year 2002 provides calibration in terms of absorbed dose in water. In this work, those elements appear whereupon it counts the laboratory and that they tend to consolidate the securing of the quality of the results obtained in the calibrations of dosemeters. (author)

  12. Alpha-spectrometric determination of low activities of Th, U, and Pu with semiconductor and grid ionization chamber

    International Nuclear Information System (INIS)

    The direct preparation of alpha-containing counter layers from TOPO extracts by vaporization on the counter planchet is described. For a typical surface density of 2 μl/cm2 the half-widths of the peaks in the semiconductor and grid ionization chamber (GIK) are mostly in the range of 50 keV. However, 20 times more material can be prepared on the large surface of the GIK counter planchets than in the semiconductor chamber. Alpha emitters of a few mBq can be detected in the GIK within a measuring time of 1 d, depending on their position in the spectrum. (orig.)

  13. Determination of the recombination correction for the BIPM parallel-plate ionization chamber type in a pulsed photon beam

    International Nuclear Information System (INIS)

    The correction factor for recombination losses ks 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-1 at 100 Hz)

  14. 33 CFR 183.222 - Flotation material and air chambers.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 2 2010-07-01 2010-07-01 false Flotation material and air... SECURITY (CONTINUED) BOATING SAFETY BOATS AND ASSOCIATED EQUIPMENT Flotation Requirements for Outboard Boats Rated for Engines of More Than 2 Horsepower General § 183.222 Flotation material and air...

  15. 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...

  16. The use of plane parallel ionization chambers in high energy electron and photon beams. An international code of practice for dosimetry

    International Nuclear Information System (INIS)

    Research on plane-parallel ionization chambers since the IAEA code of practice (TRS-277) was published in 1987 has explained our knowledge on perturbation and other correction factors in ionization chamber, and also constructional details of these chambers have been shown to be important. Different countries have published, or are in the process of publishing, dosimetry recommendations which include specific procedures for the use of plan parallel ionization chambers. An international working group was formed under the auspieces of the IAEA, first to review the status and the actual validity of the code of practice and second to develop an international code of practice of the use of plane parallel ionization chambers in high energy electron and photon beams used in radiotherapy. This document fulfills the second taste. 153 refs, 21 figs, 18 tabs

  17. Combination of emulsion chamber and air shower array at Mt. Chacaltaya

    International Nuclear Information System (INIS)

    Data of 34 familes with the accompanying air showers, observed by the combination of emulsion chamber and air shower array at Mt. Chacaltaya, are presented. Comparison with the simulation calculation concludes that a change is necessary in the characteristics of hadron interactions in E0≥1015 eV

  18. Analytic And Monte Carlo Study Of The Perturbation Factor kp For A Standard Of Dw Through An Ka Standard Ionization Chamber BEV-CC01

    International Nuclear Information System (INIS)

    To characterize an ionization chamber BEV-CC01 as a standard of absorbed dose to water Dw at SSDL-Mexico, the approach developed by the BIPM for 60Co gamma radiation, has been chosen. This requires the estimation of a factor kp, which stems from the perturbation introduced by the presence of the ionization chamber in the water phantom, and due to finite size of the cavity. This factor is the product of four terms: ψw,c (μen/ρ)w,c (1 + μ'.y-bar)w,c and kcav. Two independent determinations are accomplished using a combination of the Monte Carlo code MCNP4C in ITS mode [2,3] and analytic methods: one kp parallel =1.1626 ± uc=: 0.90% for the chamber axis parallel to the beam axis; and another kp =1.1079± uc=0.89% for the chamber axis perpendicular to the beam axis. The variance reduction techniques: splitting-Russian roulette, source biasing and forced photon collisions are employed in the simulations to improve the calculation efficiency. The energy fluence for the 60Co housing-source Picker C/9 is obtained by realistic Monte Carlo (MC) simulation, it is verified by comparison of MC calculated and measured beam output air kerma factors, and percent depth dose curves in water, PDD. This spectrum is considered as input energy for a point source (74% is from primary photons and the rest 26% is from scattered radiation) in the determination of the kp factors. Details of the calculations are given together with the theoretical basis of the ionometric standard employed

  19. A charged particle telescope with a gas ionization chamber ΔE detector with axial charge collection

    International Nuclear Information System (INIS)

    A charged particle telescope with a gas ionization in which no frisch grid is used has been set-up. The three basic parts of this telescope are: (1) the window assembly, (2) the gas cell and (3) the E detctor assembly. These parts are described. The active length of the ionization chamber can be changed easily according to the need. The field configuration is axial. Using a gas mixture of 90 per cent argon and 10 per cent methane, and alpha-sources 241Am and 239Pu, the performance of the detector was tested in a vacuum chamber at various pressures and various anode voltages for gas length of 3 cm. It is observed that energy resolution is 185 keV at 1.2 kg/cm2 gas pressure and the suitable range of operating anode voltage is 300 to 600 v. (M.G.B)

  20. Discovery of multiple, ionization-created CS2 anions and a new mode of operation for drift chambers

    International Nuclear Information System (INIS)

    This paper focuses on the surprising discovery of multiple species of ionization-created CS2 anions in gas mixtures containing electronegative CS2 and O2, identified by their slightly different drift velocities. Data are presented to understand the formation mechanism and identity of these new anions. Regardless of the micro-physics, however, this discovery offers a new, trigger-less mode of operation for the drift chambers. A demonstration of trigger-less operation is presented

  1. Large area neutron detector based on Li6 ionization chamber with integrated body-moderator of high density polyethylene

    International Nuclear Information System (INIS)

    A detector was developed and funded by DHS to be a lower cost alternative to 3He detectors. A 6Li foil-lined ionization chamber was prepared with fill gas at one atmosphere and pulse mode operation. The high-density polyethylene (HOPE) body serves also as a neutron moderator. All electrodes, including high voltage bias supply, are hermetically sealed within the plastic slabs.

  2. Automated system with LabVIEW for the obtention of voltage plateau, graphic of sensitivity and operation voltage in an ionization chamber

    International Nuclear Information System (INIS)

    The work developed for the Laguna Verde Nuclear Power Central allows to obtain the voltage plateau, graphic of sensitivity and operation voltage of three types of ionization chambers which are used in their monitoring systems of process radiation. The automated system is based in a personal computer (Pc) for controlling and acquiring data from the different instruments used, its programming was realized with virtual instruments (LabVIEW, National Instruments software). The system also realizes a diagnosis of the ionization chamber and determine whether the parameters obtained are inside of the manufacturer specifications, that is to say, it determines when the ionization chamber must be replaced. (Author)

  3. Metrology of the radon in air volume activity at the italian radon reference chamber

    International Nuclear Information System (INIS)

    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 222Rn 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 m3. 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)

  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. The stability of liquid-filled matrix ionization chamber electronic portal imaging devices for dosimetry purposes

    International Nuclear Information System (INIS)

    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

  6. Poster — Thur Eve — 21: Off-axis dose perturbation effects in water in a 5 × 5 cm2 18 MV photon beam for the PTW microLion and Exradin A1SL ionization chambers

    International Nuclear Information System (INIS)

    A PTW microLion liquid ionization chamber and an Exradin A1SL air-filled ionization chamber have been modeled using the egs-chamber user code of the EGSnrc system to determine their perturbation effects in water in a 5 × 5 cm2 18 MV photon beam. A model of the Varian CL21EX linear accelerator was constructed using the BEAMnrc Monte Carlo code, and was validated by comparing measured PDDs and profiles from the microLion and A1SL chambers to calculated results that included chamber models. Measured PDDs for a 5 × 5 cm2 field for the microLion chamber agreed with calculations to within 1.5% beyond a depth of 0.5 cm, and the A1SL PDDs agreed within 1.0% beyond 1.0 cm. Measured and calculated profiles at 10 cm depth agreed within 1.0% for both chambers inside the field, and within 4.0% near the field edge. Local percent differences increased up to 15% at 4 cm outside the field. The ratio of dose to water in the absence of the chamber relative to dose in the chamber's active volume as a function of off-axis distance was calculated using the egs-chamber correlated sampling technique. The dose ratio was nearly constant inside the field and consistent with the stopping power ratios of water to detector material, but varied up to 3.3% near the field edge and 5.2% at 4 cm outside the field. Once these perturbation effects are fully characterized for more field sizes and detectors, they could be applied to clinical water tank measurements for improved dosimetric accuracy

  7. 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.

  8. Main Chamber Plasma-Wall Interaction Studies in DIII-D in Support of ITER

    International Nuclear Information System (INIS)

    Full text: Recent experiments in DIII-D examined heat and particle flux profiles to main chamber regions that are of particular concern for the design of ITER's first wall. The first of these are at the midplane where ITER is expected to limit plasmas during the rampup and rampdown phases of discharge. The scrapeoff layer (SOL) power flux density e-folding length, λq, is a critical design parameter for limiters. Scans of the plasma current, density, and input power were performed in DIII-D to test the modified divertor L-mode scaling of λq used for ITER. During inner wall limited (IWL) L-mode discharges λq is on average ∼ 2.5 times larger than in diverted and upper outer wall limited plasmas, in agreement with the assumptions used in the ITER limiter design. The measured values of λq are in reasonable agreement with ITER scaling, constituting the first direct test of this scaling in limited plasmas and confirming assumed strong dependence of λq on the device size. However, scaling dependencies of λq on individual discharge parameters could not be confirmed. The other concern for main chamber interactions in ITER is at the top of the vessel where a secondary divertor is expected to handle both steady state and edge localized mode (ELM) levels of particles and energy. The IRTV-measured secondary divertor heat flux exhibits an overall decrease for smaller ELM regimes (higher density) and magnetic configurations with a greater distance (drsep) between the primary and secondary separatrices. During ELMs, fast IRTV line scan shows a multi-peaked surface temperature profile and IRTV image data shows multi-peaked spiral patterns. Steady-state IRTV heat flux patterns show an exponential decay length, λq, near the secondary strike point similar to thermocouple time averaged heat flux profiles and 4 times larger than typical primary divertor cases. Thermocouple heat flux profiles were determined from fast response thermocouples placed 1 cm deep in the main graphite

  9. Determination of the diaphragm correction factor of the LNE-LNHB free-air chambers for low and medium energy X-rays

    International Nuclear Information System (INIS)

    Until recently, in the establishment of the French LNE-LNHB national reference in terms of air kerma for low and medium energy X-rays, the effect of the diaphragm located at the entrance of the free-air ionization chambers was not sufficiently taken into account. This report describes the different Monte Carlo computations made in 2010-2011 with the PENELOPE Monte Carlo code to determine a correction factor (kdia) describing the influence of the different incident photon interactions taking place into the diaphragm on the deposited energy in the collecting volume. (author)

  10. CFD SIMULATION OF AIR ION REGIME IN WORK AREAS AT CONDITION OF ARTIFICIAL AIR IONIZATION

    Directory of Open Access Journals (Sweden)

    M. M. Biliaiev

    2016-04-01

    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

  11. Ionization detector

    International Nuclear Information System (INIS)

    The objects of the invention are, first, to provide an ionization detector having a three chamber structure characterised by a built-in feedback path that regeneratively stabilizes the operating point of the detector. Secondly, to provide a specially designed chamber construction including electrodes shaped so as to enhance the efficiency of the chamber and reduce ion recombination. The ionization chamber described has a chamber structure with a first closed chamber and a second chamber able to receive gases from outside. These two chambers have a common boundary including a common electrode. One electrode associated with the second chamber, and one within the first chamber, define a third chamber within the first chamber allowing an ionization path between. A radioactive source provides ionizing radiation for all three chambers and establishes an ionization current. There is a detector coupled to the common electrode for detecting changes in this current. (U.K.)

  12. A charged particle telescope with a gas ionization chamber ΔE detector with axial charge collection

    International Nuclear Information System (INIS)

    An ionization chamber as ΔE detector with axial field configuration has been set up. No frisch grid is required. The detector is backed by a surface barrier E detector. The thin aluminized mylar entrance window acts as anode on which positive voltage is applied. A charged particle telescope with the above ionization chamber has been fabricated. It consists of three parts, the window assembly, the gas cell and the E detector assembly. These are described. The performance of the detector was tested in a vacuum chamber using 241Am and 239Pu α-sources at various pressures and anode voltages using a gas length of 3 cm. The gas mixture used was 90 per cent argon and 10 per cent methane. The measurements showed that operating anode voltage in the range of 300 to 600V and the pressure range from 0.1 to 0.9 kg/cm2 were suitable for heavy ions. (M.G.B.)

  13. Influence of size of the ionization chamber in determination of the quality of an X-ray field of references

    International Nuclear Information System (INIS)

    The quality of an X-ray field of reference can be evaluated with the determination of the values of the first and second half-value layer - 1st and 2nd CSR, from measurements carried out with appropriate ionisation chambers. The acceptance criteria of ISO 4037-1 states that the values of 1st and 2nd CSR may not differ by more than -5% of the reference values. Procedures have been developed on X-ray equipment PANTAK, model HF160, adjusted to produce a field of 48 keV X-ray, to investigate the determination of the values of 1st and 2nd CSR with the use of different ionization chambers of varying volumes. The initial results indicate that the values of 1st and 2nd CSR are influenced by the size of the ionization chamber used, which suggests the determination of algorithm for the determination of a single value of 1st and 2nd CSR

  14. Use of an Ionization Chamber and Tritiated Oil for Continuous Measurement of the Oil Consumption of an Internal Combustion Engine

    International Nuclear Information System (INIS)

    By adding tritiated squalene to the lubricating oil and passing some of the exhaust gases through an ionization chamber kept at 150°C to avoid water vapour condensation, it was possible to carry out continuous measurement of the oil consumption of an internal combustion engine. The sensitivity of the chamber is of the order of 0.015 μCi of tritiated water per litre of exhaust gas. The specific activities used were of the order of 0.3 Ci per litre of oil; this value is considerably higher than that used when measuring the samples by liquid scintillation, but this disadvangage is largely offset by the continuity of the measurements. Owing to the intense ionization of the exhaust gases, it was necessary to placc an ion trap before the chamber. The method has been used on an engine test bench for two years and has now reached a stage suiiable for practical development. By making further improvements, which have not yet been tackled, it seems likely that this method can be applied to a vehicle in normal operation. (author)

  15. Charge trapping in aligned single-walled carbon nanotube arrays induced by ionizing radiation exposure

    Energy Technology Data Exchange (ETDEWEB)

    Esqueda, Ivan S., E-mail: isanchez@isi.edu [Information Sciences Institute, University of Southern California, Arlington, Virginia 22203 (United States); Cress, Cory D. [Electronics Science and Technology Division, Naval Research Laboratory, Washington, DC 20375 (United States); Che, Yuchi; Cao, Yu; Zhou, Chongwu [Department of Electrical Engineering, University of Southern California, Los Angeles, California 90089 (United States)

    2014-02-07

    The effects of near-interfacial trapping induced by ionizing radiation exposure of aligned single-walled carbon nanotube (SWCNT) arrays are investigated via measurements of gate hysteresis in the transfer characteristics of aligned SWCNT field-effect transistors. Gate hysteresis is attributed to charge injection (i.e., trapping) from the SWCNTs into radiation-induced traps in regions near the SWCNT/dielectric interface. Self-consistent calculations of surface-potential, carrier density, and trapped charge are used to describe hysteresis as a function of ionizing radiation exposure. Hysteresis width (h) and its dependence on gate sweep range are investigated analytically. The effects of non-uniform trap energy distributions on the relationship between hysteresis, gate sweep range, and total ionizing dose are demonstrated with simulations and verified experimentally.

  16. A study of the linear behaviour of a three electrode ionization chamber for N-16 gamma-rays

    International Nuclear Information System (INIS)

    The (I,V) characteristics of a locally designed three electrode ionization chamber filled with argon gas at 180 psi and Xe at 95 psi have been studied for high energy gamma rays from /sup 16/N produced in a Pakistan Research Reactor-1 (PARR-1). The reactor was operated at four different power levels i.e. 1 MW, 3 MW, 6 Mw and 9 MW. It is observed that the measured ionization current increase linearly with reactor power for both gases. The plateau region is reached above 1 kV for all the rector powers used in this work. The detector operating voltage is found to be 2 kV. It is observed that in the plateau region the slope increases with an increase in the exposure rate. The (1/I,1/V) and (I,1/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. Both these losses is slightly greater than that of the initial recombination losses. The linearity behavior of the chamber is also observed. It is also observed that in case of Xe, ionization current is about three time greater than for the case of Ar. (author)

  17. Power measurement in the 7A2 configuration of the RP-0 reactor using the neutron noise technique connected to a compensated ionized chamber

    International Nuclear Information System (INIS)

    Results of the neutron noise measurements carried out in the 7A2 configuration of the RP-0 reactor using the BC3 rod to reach criticality are presented. These measurements were carried out using a compensated ionized chamber (CIC) located at E2 position. Finally, potential calibration of the march chamber 4 from the reactor instrumentation is presented

  18. Calibration of diffusion chambers for measuring of 222Rn in air

    International Nuclear Information System (INIS)

    This paper describes the calibration of plastic and metal diffusion chambers by an experimental set-up installed in the 'Dosimetry and Radiation Protection' laboratory of the Faculty of Physics of the University of Sofia 'St. Kliment Okhridski'. The metal diffusion chamber consists of tin can with a tin cap and few holes on the side wall of the chamber. The holes are covered with polyethylene foil from the inner side and piece of fabric between the foil and the holes in order to protect the foil from piercing by the swarfs around the holes. At the inner side of the cap is attached cross-like holder which purpose is to hold the SSNTD. It can be anticipated that the metal diffusion chambers have several advantages compared to the plastic ones.The calibration factors k were determined for three track-counting modes for both the metal and the plastic diffusion chambers with uncertainty less than 10% at the level of one standard deviation. A good correspondence was shown between the two programs for automatic counting (the calibration factors k do not differ within one standard deviation for both type of diffusion chambers). It. was also shown that using automatic instead of visual counting mode would not significantly worsen the sensitivity of the method and it is preferable because of its high productivity. (authors)

  19. New standards for ionizing radiation measurements

    International Nuclear Information System (INIS)

    The Ionizing Radiation Division has developed new national standards for mammographic X rays and for brachytherapy sources, such as iodine-125. The Attix chamber, a variable volume free-air ionization chamber, has been established as the primary national standard for mammographic X rays. The Attix chamber resides in the newly developed NIST Mammography Calibration Range and will be used to perform routine calibrations. The wide-angle free-air ionization chamber utilizes a large volume and a novel electric field configuration in order to circumvent the limitations of conventional free-air chambers. Seventeen beam qualities for X rays from molybdenum (Mo) and rhodium (Rh) anodes have been parameterized for the calibration of mammographic ionization chambers. The beam qualities available include anode/filter combinations of Mo/Mo, Mo/Rh and Rh/Rh. The mammography range was developed in collaborations with the U.S. Food and Drug Administration's (FDA) Center for Devices and Radiological Health, the implementors of the Mammography Quality Standards Act (MQSA) of 1992. The wide-angle free-air ionization chamber has been used to measure the output of two types of iodine-125 seeds, those with resin balls and those with silver wire. Both free-air chambers have been intercompared with the Ritz parallel-plate free-air ionization chamber

  20. A micro-gap, air-filled ionisation chamber as a detector for criticality accident dosimetry

    International Nuclear Information System (INIS)

    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. Air-filled ionisation chamber with very small gap is a simple dosemeter, which fulfills the most desired properties of criticality accident dosemeters. Short ion collection time is achieved by combination of small gap and relatively high polarising voltage. For the same reason, parasitic recombination of ions in the chamber is negligibly small even at high dose rates. The difference between neutron and gamma sensitivity is small for tissue-equivalent chamber and is expected to become practically negligible when the chamber electrodes are made of polypropylene. Additional capacitor provides a broad measuring range from ∼0.1 Gy up to ∼25 Gy; however, leakage of electrical charge from polarising capacitor has to be observed and taken into account. Periodical re-charging of the device is necessary. Obviously, final test of the device in conditions simulating criticality accident is needed and will be performed as soon as available. (authors)

  1. Direct measurement of absorbed dose to water in HDR 192Ir brachytherapy: Water calorimetry, ionization chamber, Gafchromic film, and TG-43

    International Nuclear Information System (INIS)

    Purpose: Gafchromic film and ionometric calibration procedures for HDR 192Ir brachytherapy sources in terms of dose rate to water are presented and the experimental results are compared to the TG-43 protocol as well as with the absolute dose measurement results from a water calorimetry-based primary standard. Methods: EBT-1 Gafchromic films, an A1SL Exradin miniature Shonka thimble type chamber, and an SI HDR 1000 Plus well-type chamber (Standard Imaging, Inc., Middleton, WI) with an ADCL traceable Sk calibration coefficient (following the AAPM TG-43 protocol) were used. The Farmer chamber and Gafchromic film measurements were performed directly in water. All results were compared to direct and absolute absorbed dose to water measurements from a 4 deg. C stagnant water calorimeter. Results: Based on water calorimetry, the authors measured the dose rate to water to be 361±7 μGy/(h U) at a 55 mm source-to-detector separation. The dose rate normalized to air-kerma strength for all the techniques agree with the water calorimetry results to within 0.83%. The overall 1-sigma uncertainty on water calorimetry, ionization chamber, Gafchromic film, and TG-43 dose rate measurement amounts to 1.90%, 1.44%, 1.78%, and 2.50%, respectively. Conclusions: This work allows us to build a more realistic uncertainty estimate for absorbed dose to water determination using the TG-43 protocol. Furthermore, it provides the framework necessary for a shift from indirect HDR 192Ir brachytherapy dosimetry to a more accurate, direct, and absolute measurement of absorbed dose to water.

  2. Fusion energy research with lasers, direct drive targets, and dry wall chambers

    International Nuclear Information System (INIS)

    We are carrying out a coordinated, focused effort to develop Laser Inertial Fusion Energy. The key components are developed in concert with one another and the science and engineering issues are addressed concurrently. Significant progress has been made in this program: We are evaluating target designs that show it could be possible to achieve the high gains (>100) needed for a practical fusion system. These have a low density CH foam that is wicked with solid DT, and over coated with a thin high-Z layer. Significant advances have been made with the two types of laser are being developed: Krypton Fluoride (KrF) gas lasers and Diode Pumped Solid State Lasers (DPPSL). Both have the potential to meet the fusion energy requirements for rep-rate, efficiency, durability and cost. This paper also presents the advances in development of chamber operating windows (target survival plus no wall erosion), final optics (aluminum at grazing incidence has high reflectivity and exceeds required laser damage threshold), target fabrication (advanced foams and high Z overcoats), and target injection (new facility for target injection and tracking studies). (author)

  3. Calibration of a 4π-γ well-type ionization chamber system for measuring of the radionuclides activity

    International Nuclear Information System (INIS)

    The calibration of a 4π well-type ionization Chamber System installed at the Laboratorio de Metrologia Nuclear, of the Instituto de Energia Atomica of Sao Paulo used for of the activity determination of radioactive solutions is descrided. The determination can be performed by two methods: 1) Direct Method, comparing the ionization Chamber response for solutions of unknown activity against that obtained with a solution which is standardized by the Absolute 4πβγ Coincidence Method. By this method the following radionuclides are standardized: 241Am, 139Ce, 198Au, 22Na, 134Cs, 54Mn, 60Co, 42K, 24Na. In this case, the accuracy achieved is about 0.2 to 0,4%. 2) Indirect Method, by means of curves of relative beta or gama efficiency, which were determined in this work. This method can be applied for those radionuclides not included in the direct method. In this case, the accuracy depends on the gama energy range of the curves and on the accuracy of the absolute gama intensities, taken from the literature. In general the uncertainty is greater than the direct method, but values of 0,2% can be achieved in favourable cases. The upper and lower limits of Activity that can be measured depend on the radionuclide. These limits are from a few micro-curies to many mili-curies, which are satisfactory for most purposes. The sample preparation is simple and the time spent in the measurement is, in general, restricted to a few minutes. These are some of the advantages of this ionization Chamber System in comparison with other systems

  4. 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.

  5. Description of the XXXIV ARCAL Project Repairing and calibration of electrometers and ionization chambers used in radiotherapy

    International Nuclear Information System (INIS)

    The technological tools from what the humanity has for the illnesses diagnosis and the cancer treatment, are based in great extent in the use of ionizing radiations. This situation worries to the International Atomic Energy Agency (IAEA), which has implemented technical cooperation programs for protecting the human health. In Latin America the ARCAL program (Regional Agreement of Cooperation for Promotion of Nuclear Science and Technology in Latina America and the Caribbean was created. The Project ARCAL XXXIV has as objective to establish three regional centers of repairing, maintenance and electric calibration of clinical dosemeters, equipment made up for an ionization chamber and an electrometer which is used in radiotherapy to generate calibration procedures, personnel training, establishment of an intercomparison net for the electrometers control used as standards and designing current intensity sources which serve as work standards for each one of the participant countries, Mexico is one of them. (Author)

  6. Measurements of neutron-induced proton and α-particle production cross sections using gridded ionization chamber

    International Nuclear Information System (INIS)

    A gridded ionization chamber for measurements of the neutron induced charged-particle production cross sections has been developed and applied to the measurements of (n,p) and (n,α) cross sections for Ni and Cu at incident neutron energies of 4.3 ∼ 6.5 MeV and 14.1 MeV. This technique is very effective owing to its large geometrical efficiency. The energy- and angular-differential cross sections and reaction cross sections were deduced and compared with previous experimental and evaluated data. (author)

  7. Study on the realization of a minimum ionizing particle detector: development of a PPAC (Parallel-plate Avalanche Chamber)

    International Nuclear Information System (INIS)

    Parallel-Plate Avalanche Chamber (PPAC) detectors are used currently to observe nuclear disintegrations in nuclear physics. The work that has been done here shows PPAC can be used in high energy physics under certain conditions to detect minimum ionizing particles. Their advantage is to join good time resolution with low matter density. A PPAC prototype has been made with 90% efficiency, 3 NS jitter, 2 NS rise time, 20 mg/cm2 mass, 1.5 mm spatial accuracy. The parameters studied were electrodes design, choice of gas filling, electronics and anode strips. The detector is to be used as a hodoscope with high flux of particles

  8. 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.

  9. Calibration of plane-parallel chambers and determination of pwall for the NACP and Roos chambers for 60Co γ-ray beams

    International Nuclear Information System (INIS)

    Procedures for the calibration and use of plane-parallel ionization chambers in high-energy electron and photon beams have been given in the international code of practice IAEA TRS-381. In the present work, plane-parallel ionization chambers of the type PTW-34001 Roos and Scanditronix NACP02 have been calibrated using two NK-based procedures. For the NACP chamber the difference between the ND,air chamber factors determined in an electron beam and in a 60Co γ-ray beam, respectively, is of the same magnitude as the experimental uncertainty. Results for the PTW Roos chambers, however, do not agree, in accordance with recent findings of other authors. The value determined in a 60Co γ-ray beam is questioned and the reason for the discrepancy assigned to the correction factor for the perturbation due to the chamber wall, pwall . New values of pwall have been experimentally determined by comparing absorbed dose measurements based on air-kerma and absorbed dose to water calibration procedures. A new pwall factor for the Roos chamber in 60Co γ-ray beams in water (1.009±0.6%) was derived as the weighted average of the different determinations. The value is not significantly higher than the pwall factor given in TRS-381 (1.003±1.5%), but the combined standard uncertainty is reduced. The chamber to chamber variation for six commercial PTW Roos chambers and a Roos prototype was found to be very small. (author)

  10. Testing the accuracy of electron transport in the Monte Carlo code FLUKA for calculation of ion chamber wall perturbation factors

    International Nuclear Information System (INIS)

    A reliable Monte Carlo based investigation of ion chambers in medical physics problems depends on the accuracy of the charged particle transport and implementations of the condensed history technique. Improper handling of media interfaces can lead to anomalous results or 'interface artefacts'. This work presents a rigorous investigation of the electron transport algorithm in the general purpose Monte Carlo (MC) code FLUKA (2008.3b.1). A 'Fano test' was implemented in order to benchmark the accuracy of the algorithm. Furthermore, the calculation of wall perturbation factors pwall of a Roos type chamber irradiated by electrons were performed and compared with values based on the EGSnrc MC code

  11. Modeling SOA formation from alkanes and alkenes in chamber experiments: effect of gas/wall partitioning of organic vapors.

    Science.gov (United States)

    Stéphanie La, Yuyi; Camredon, Marie; Ziemann, Paul; Ouzebidour, Farida; Valorso, Richard; Madronich, Sasha; Lee-Taylor, Julia; Hodzic, Alma; Aumont, Bernard

    2014-05-01

    Oxidation products of Intermediate Volatility Organic Compounds (IVOC) are expected to be the major precursors of secondary organic aerosols (SOA). Laboratory experiments were conducted this last decade in the Riverside APRC chamber to study IVOC oxidative mechanisms and SOA formation processes for a large set of linear, branched and cyclic aliphatic hydrocarbons (Ziemann, 2011). This dataset are used here to assess the explicit oxidation model GECKO-A (Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere) (Aumont et al., 2005). The simulated SOA yields agree with the general trends observed in the chamber experiments. They are (i) increasing with the increasing carbon number; (ii) decreasing with increasing methyl branch number; and (iii) increasing for cyclic compounds compared to their corresponding linear analogues. However, simulated SOA yields are systematically overestimated regardless of the precursors, suggesting missing processes in the model. In this study, we assess whether gas-to-wall partitioning of organic vapors can explain these model/observation mismatches (Matsunaga and Ziemann, 2010). First results show that GECKO-A outputs better match the observations when wall uptake of organic vapors is taken into account. Effects of gas/wall partitioning on SOA yields and composition will be presented. Preliminary results suggest that wall uptake is a major process influencing SOA production in the Teflon chambers. References Aumont, B., Szopa, S., Madronich, S.: Modelling the evolution of organic carbon during its gas-phase tropospheric oxidation: development of an explicit model based on a self generating approach. Atmos.Chem.Phys., 5, 2497-2517 (2005). P. J. Ziemann: Effects of molecular structure on the chemistry of aerosol formation from the OH-radical-initiated oxidation of alkanes and alkenes, Int. Rev.Phys.Chem., 30:2, 161-195 (2011). Matsunaga, A., Ziemann, P. J.: Gas-wall partitioning of organic compounds in a Teflon film

  12. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    OpenAIRE

    Y. S. La; Camredon, M; Ziemann, P. J.; R. Valorso; Matsunaga, A; V. Lannuque; Lee-Taylor, J.; Hodzic, A.; S. Madronich; B. Aumont

    2015-01-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kineti...

  13. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    OpenAIRE

    Y. S. La; Camredon, M; Ziemann, P. J.; R. Valorso; Matsunaga, A; V. Lannuque; Lee-Taylor, J.; Hodzic, A.; S. Madronich; B. Aumont

    2016-01-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kineti...

  14. Characterization and wall compatibility testing of a 40K pound thrust class swirl-coaxial injector and calorimeter combustion chamber

    Science.gov (United States)

    Petersen, E. L.; Rozelle, R.; Borgel, P. J.

    1991-01-01

    Subscale injector-combustor tests under the NASA Space Transportation Engine Thrust Chamber Technology program measured characteristic velocity (c-asterisk) efficiencies and wall heat fluxes for the pressure range 1710 psia to 2360 psia and for the overall O2/H2 mixture ratio range 5.5 to 6.4. Tests involving radially-uniform mixture ratio profiles produced c-asterisk efficiencies above 99 percent; nonuniform profiles associated with wall durability-enhancement schemes resulted in lower efficiencies. Though all three wall protection methods proved successful at reducing wall heat flux, scarfing of the outer-row, swirl-coaxial injection elements was the technique which resulted in the least debit in c-asterisk per unit reduction in heat flux.

  15. Numerical investigations of cooling holes system role in the protection of the walls of a gas turbine combustion chamber

    Energy Technology Data Exchange (ETDEWEB)

    Ben Sik Ali, Ahlem; Kriaa, Wassim; Mhiri, Hatem [Ecole Nationale D' Ingenieurs de Monastir, Unite de Thermique et Thermodynamique des Procedes industriels, Monastir (Tunisia); Bournot, Philippe [IUSTI, UMR CNRS 6595, Marseille (France)

    2012-05-15

    Numerical simulations in a gas turbine Swirl stabilized combustor were conducted to investigate the effectiveness of a cooling system in the protection of combustor walls. The studied combustion chamber has a high degree of geometrical complexity related to the injection system as well as the cooling system based on a big distribution of small holes (about 3,390 holes) bored on the flame tube walls. Two cases were considered respectively the flame tube without and with its cooling system. The calculations were carried out using the industrial CFD code FLUENT 6.2. The various simulations made it possible to highlight the role of cooling holes in the protection of the flame tube walls against the high temperatures of the combustion products. In fact, the comparison between the results of the two studied cases demonstrated that the walls temperature can be reduced by about 800 C by the mean of cooling holes technique. (orig.)

  16. Multiple sampling ionization chamber (MUSIC) for investigation of fusion induced by halo nuclei

    International Nuclear Information System (INIS)

    A high resolution MUSIC for low and medium energy ions up to ∼ 20 AMeV, for investigation of fusion processes induced by halo nuclei, has been achieved. The chamber was used in the first experiments, aiming at investigating fusion processes induced by 9,11 Li with light targets. In these experiments MUSIC was used for the identification of the inclusive evaporation residues produced in the Si detector target, mounted inside the chamber. By using MUSIC it was possible to separate the inclusive spectra corresponding to the fusion processes, from the background due to the energy degraded beam particles. In principle such a chamber could be also used for investigation of particular fusion channels produced in the entrance window. In this case one could obtain the fusion product trajectory angle with the horizontal plane, by coupling each anode pad to a TDC. The chamber was also provided by a position grid, mounted between the Frisch grid and the anode pads. The energy loss distribution widths were measured using α particles. The chamber was filled with P-10 gas at pressures between 200 and 300 torr. The obtained resolution corresponding to a single pad, is close to the limit derived from the theory of Badhwar. (authors)

  17. Dosimetric parameters for small field sizes using Fricke xylenol gel, thermoluminescent and film dosimeters, and an ionization chamber

    International Nuclear Information System (INIS)

    Dosimetric measurements in small therapeutic x-ray beam field sizes, such as those used in radiosurgery, that have dimensions comparable to or smaller than the build-up depth, require special care to avoid incorrect interpretation of measurements in regions of high gradients and electronic disequilibrium. These regions occur at the edges of any collimated field, and can extend to the centre of small fields. An inappropriate dosimeter can result in an underestimation, which would lead to an overdose to the patient. We have performed a study of square and circular small field sizes of 6 MV photons using a thermoluminescent dosimeter (TLD), Fricke xylenol gel (FXG) and film dosimeters. PMMA phantoms were employed to measure lateral beam profiles (1 x 1, 3 x 3 and 5 x 5 cm2 for square fields and 1, 2 and 4 cm diameter circular fields), the percentage depth dose, the tissue maximum ratio and the output factor. An ionization chamber (IC) was used for calibration and comparison. Our results demonstrate that high resolution FXG, TLD and film dosimeters agree with each other, and that an ionization chamber, with low lateral resolution, underestimates the absorbed dose. Our results show that, when planning small field radiotherapy, dosimeters with adequate lateral spatial resolution and tissue equivalence are required to provide an accurate basic beam data set to correctly calculate the absorbed dose in regions of electronic disequilibrium

  18. 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

  19. Alpha-particle spectrometry of large-area samples using an open-flow pulse ionisation chamber

    International Nuclear Information System (INIS)

    Ionization chambers are established and well known detectors of ionizing radiation. Current-mode chambers are in frequent use in such fields as dosimetry, environmental surveillance and radiation protection, while pulse-mode, Frisch-grid, chambers used to be used for spectrometry and have largely been replaced by scintillation and semiconducting-diode detectors. Dealing specifically with low-level alpha-particle spectrometry, the surface-barrier or ion-implanted semiconducting detectors are the standard choice, but in some applications where radiochemical treatment and production of small electroplated samples are impossible or inconvenient, pulse-ionization chambers are still in use. For breath and air-radon samples scintillation cells dominate, but pulse ionization chambers are utilized as high-standard laboratory instruments. For continuous measurements of radon concentration in air, a multiwire-electrode ionization chamber has been described. A commercial radon-in-air system, based on a pulse ionization chamber is described. (author)

  20. 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.

  1. 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.

  2. Investigation and performance tests of a new parallel plate ionization chamber with double sensitive volume for measuring diagnostic X-rays

    International Nuclear Information System (INIS)

    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

  3. 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

    2006-03-01

    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. PMID:16481690

  4. Investigation of air bipolar ionization effects in cheese and kajmak craft production

    International Nuclear Information System (INIS)

    Milk and dairy products are sustainable to the development of numerous microorganisms, especially pathogens. Therewith, it is necessary to achieve a high level of hygiene in dairy plants, in order to get safe and high quality products. Based on that, modern food production implies application of different air treatments. Microbiological status of air and working surfaces in the cheese and kajmak craft production, before and after air treatment by bipolar ionization, was investigated. It is concluded that bipolar ionization may be considered as an efficient method for improving of microbiological status of air, as well as surfaces that are in contact with the air

  5. Performance study of the primary standard ionization chamber for deployment of the diagnostic radiology qualities

    International Nuclear Information System (INIS)

    Activities radiotherapy, diagnostic radiology and radiation protection, require knowledge of physical and dosimetric parameters, to be applied safely. Aiming to meet demand in Brazil, the National Laboratory of Metrology of Ionising Radiation - LNMRI - is deploying the primary standard for the calibration of secondary standard chambers, used in quality control in hospitals, clinics and industries. (author)

  6. Quality assurance for radon exposure chambers at the National Air and Radiation Environmental Laboratory, Montgomery, Alabama

    International Nuclear Information System (INIS)

    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

  7. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    Science.gov (United States)

    La, Y. S.; Camredon, M.; Ziemann, P. J.; Valorso, R.; Matsunaga, A.; Lannuque, V.; Lee-Taylor, J.; Hodzic, A.; Madronich, S.; Aumont, B.

    2016-02-01

    Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA) formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A) modeling tool, which explicitly represents SOA formation and gas-wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms) under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas-wall mass transfer, the vapor pressure of the species and the duration of the experiments. This work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.

  8. Breakdown voltage reduction by field emission in multi-walled carbon nanotubes based ionization gas sensor

    International Nuclear Information System (INIS)

    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

  9. Effect of Ionization Saturation and Duct Shape on Losses Near Walls

    International Nuclear Information System (INIS)

    In ducts where there is a large Hall effect the distribution of the current density is known to be very irregular near the walls which support the electrodes. These irregularities are due to the boundary conditions imposed on the surface of the electrode, which is an equipotential, and also on the surface of the intermediate insulating layer, which does not allow of a normal current component. These losses are a matter for concern in an opencycle conversion ducts since they give rise to the need for considerable electrode subdivision, which is liable to be expensive. They are disastrous in the case of closed-cycle gas systems, when an electron heating effect is involved. A very elementary analysis shows that it is possible to make the current distribution almost completely regular along the electrodes, due to the low resistivity of the gas parallel to B, by simply inclining the wall in relation to the magnetic field. An equally simple analysis indicates that inclining the wall cuts out the inter-electrode ''short-circuit'' effects because the current component which is perpendicular to B and u is no longer zero along the insulator. This is equivalent to increasing the apparent resistivity parallel to u. It is almost impossible to. establish the correct formulae because of the tridimensionality of the field, but the very approximate formulae obtained indicate that an inclination of 45° is perfectly adequate. It seems reasonable to suppose, therefore, that by breaking down the walls of the electrode into elementary planes inclined in relation to B, the supplementary distortion losses caused by the Hall effect will disappear. In the specific case where the electron heating effect considerably aggravates the ''short-circuit'' effect, another type of remedy might be possible: the seeding concentration could be adjusted so as to achieve almost complete ionization of the atoms in the normal operation of the duct. The conductivity investigations reported at the Paris

  10. 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.

  11. Chamber Bioaerosol Study: Outdoor Air and Human Occupants as Sources of Indoor Airborne Microbes

    OpenAIRE

    Adams, RI; Bhangar, S; Pasut, W; Arens, EA; Taylor, JW; Lindow, SE; Nazaroff, WW; Bruns, TD

    2015-01-01

    © 2015 Adams et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. 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 o...

  12. Monte Carlo study of the depth-dependent fluence perturbation in parallel-plate ionization chambers in electron beams

    Energy Technology Data Exchange (ETDEWEB)

    Zink, K., E-mail: klemens.zink@kmub.thm.de [Institute of Medical Physics and Radiation Protection (IMPS), University of Applied Sciences Giessen, Giessen D-35390, Germany and Department of Radiotherapy and Radiooncology, University Medical Center Giessen-Marburg, Marburg D-35043 (Germany); Czarnecki, D.; Voigts-Rhetz, P. von [Institute of Medical Physics and Radiation Protection (IMPS), University of Applied Sciences Giessen, Giessen D-35390 (Germany); Looe, H. K. [Clinic for Radiation Therapy, Pius-Hospital, Oldenburg D-26129, Germany and WG Medical Radiation Physics, Carl von Ossietzky University, Oldenburg D-26129 (Germany); Harder, D. [Prof. em., Medical Physics and Biophysics, Georg August University, Göttingen D-37073 (Germany)

    2014-11-01

    Purpose: The electron fluence inside a parallel-plate ionization chamber positioned in a water phantom and exposed to a clinical electron beam deviates from the unperturbed fluence in water in absence of the chamber. One reason for the fluence perturbation is the well-known “inscattering effect,” whose physical cause is the lack of electron scattering in the gas-filled cavity. Correction factors determined to correct for this effect have long been recommended. However, more recent Monte Carlo calculations have led to some doubt about the range of validity of these corrections. Therefore, the aim of the present study is to reanalyze the development of the fluence perturbation with depth and to review the function of the guard rings. Methods: Spatially resolved Monte Carlo simulations of the dose profiles within gas-filled cavities with various radii in clinical electron beams have been performed in order to determine the radial variation of the fluence perturbation in a coin-shaped cavity, to study the influences of the radius of the collecting electrode and of the width of the guard ring upon the indicated value of the ionization chamber formed by the cavity, and to investigate the development of the perturbation as a function of the depth in an electron-irradiated phantom. The simulations were performed for a primary electron energy of 6 MeV. Results: The Monte Carlo simulations clearly demonstrated a surprisingly large in- and outward electron transport across the lateral cavity boundary. This results in a strong influence of the depth-dependent development of the electron field in the surrounding medium upon the chamber reading. In the buildup region of the depth-dose curve, the in–out balance of the electron fluence is positive and shows the well-known dose oscillation near the cavity/water boundary. At the depth of the dose maximum the in–out balance is equilibrated, and in the falling part of the depth-dose curve it is negative, as shown here the

  13. 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.

  14. A halo event observed with an emulsion chamber and air shower array at Mt Chacaltaya

    International Nuclear Information System (INIS)

    A hybrid experiment to operate simultaneously an air shower array, a hadron calorimeter and an emulsion chamber is under way at Mt Chacaltaya (5200 m, Bolivia). An event with a halo, a blackened area of ∼1 cm on x-ray film of the emulsion chamber, was observed with the experiment. Information about the halo (Ehalo = 850 TeV) and on high energy particles of electromagnetic and hadronic components outside the halo (ΣEγ = 632.5 TeV and ΣE(γ)h = 278.8 TeV with a detection threshold of 2 TeV) was obtained from emulsion chamber data. Details about low energy hadrons were determined from the hadron calorimeter data, and characteristics of the accompanying air shower (Ne = 7.0 x 107, s = 0.59) were determined by the air shower array. We reconstruct the event, based on the observed data. The event is compared with simulated events, which supports the conclusion that nuclear interactions change their characteristics in the high energy region so as to result in stronger energy subdivision

  15. Hybrid experiments with air-shower array and emulsion chamber at high mountains

    International Nuclear Information System (INIS)

    Characteristics of air-shower-triggered atmospheric families detected in the hybrid experiments together with emulsion chamber and AS-array at high mountains are compared with those of simulations. The analysis of families accompanied by air-showers with Ne≥107 shows that the experimental family-energy distribution favors a proton-dominant chemical composition of primary cosmic-rays but the lateral distribution favors a heavy-dominant composition. Thus no simulations can describe the overall characteristics of the data of hybrid experiments.

  16. Hybrid experiments with air-shower array and emulsion chamber at high mountains

    Energy Technology Data Exchange (ETDEWEB)

    Besshapov, S.P.; Cherdintseva, K.V.; Chubenko, A.P.; Nesterova, N.M.; Nikolskaya, N.M.; Pavluchenko, V.P.; Shaulov, S.B. [P.N.Lebedev Physical Institute, Leninsky prospect 53, 119991 Moscow (Russian Federation); Nam, R.A.; Piskal, V.V.; Vildanov, N.G.; Vildanova, L.I. [Tien-Shan highmountain CR station, Mitina 3, 480021 Almaty (Kazakhstan); Janseitova, J.K. [Jezkazgan University, Jezkazgan, Republic Kazakhstan (Kazakhstan); Aoki, H. [Faculty of Science, Soka University, Hachijoji, Tokyo, 192-8577 (Japan); Honda, K. [Faculty of Engineering, University of Yamanashi, Kofu, 400-8511 (Japan); Inoue, N. [Faculty of Science, Saitama University, Saitama, 388-8570 (Japan); Kawasumi, N. [Faculty of Education, University of Yamanashi, Kofu, 400-8510 (Japan); Martinic, N. [Insitute de Investigaciones Fisicas, Universidad Mayor de San Andres, La Paz (Bolivia, Plurinational State of); Ochi, N. [General Education, Yonago National College of Technology, Yonago, 683-8502 (Japan); Ohmori, N. [Faculty of Science, Kochi University, Kochi, 780-8520 (Japan); Ohsawa, A. [Institute for Cosmic Ray Research, University of Tokyo, Kashiwa, 277-8582 (Japan)

    2009-12-15

    Characteristics of air-shower-triggered atmospheric families detected in the hybrid experiments together with emulsion chamber and AS-array at high mountains are compared with those of simulations. The analysis of families accompanied by air-showers with N{sub e}>=10{sup 7} shows that the experimental family-energy distribution favors a proton-dominant chemical composition of primary cosmic-rays but the lateral distribution favors a heavy-dominant composition. Thus no simulations can describe the overall characteristics of the data of hybrid experiments.

  17. Method for determining correction factors induced by irradiation of ionization chamber cables in large radiation field

    International Nuclear Information System (INIS)

    A simple method was developed to be suggested to hospital physicists in order to be followed during large radiation field dosimetry, to evaluate the effects of cables, connectors and extension cables irradiation and to determine correction factors for each system or geometry. All quality control tests were performed according to the International Electrotechnical Commission for three clinical dosimeters. Photon and electron irradiation effects for cables, connectors and extention cables were investigated under different experimental conditions by means of measurements of chamber sensitivity to a standard radiation source of 90Sr. The radiation induced leakage current was also measured for cables, connectors and extension cables irradiated by photons and electrons. All measurements were performed at standard dosimetry conditions. Finally, measurements were performed in large fields. Cable factors and leakage factors were determined by the relation between chamber responses for irradiated and unirradiated cables. (author)

  18. Double ionization chamber as neutron flux monitor and for tritium breeding studies in fusion blanket experiments

    International Nuclear Information System (INIS)

    A new method for direct determination of tritium breeding, specially suited to thermal blankets is presented. The method can provide true tritium events even in the presence of a reasonable fraction of high energy neutrons. There exists no transfer or recovery losses and also the method exhibits good efficiency, in addition to being an on-line one. The detector consist of two identical chambers separated by a common earthing ring which supports a thin nickel foil loaded with Li6F covered with a thin gold layer acting as a conducting electrode. Two nickel discs are held symmetrically on either side of the central electrode as charge collectors. The chambers can be filled with a suitable inert gas. The system response to thermal neutrons was calculated by both analytical as well Monte Carlo method and is in good agreement with experimental results

  19. Multiple sampling ionization chamber (MUSIC) for fusion induced by halo nuclei investigation

    International Nuclear Information System (INIS)

    A high resolution MUSIC, for low and medium energy ion, has been developed. The high pulse height resolution was obtained by coupling the preamplifiers directly to the anode pads. The pulse height measurements were performed by using a 241 Am alpha source. The energy loss distribution widths measured in P-10 gas at pressures between 200 and 300 torr are in agreement with the theory of Badhwar. The achieved resolution of the chamber is closed to the statistical limit. MUSIC was used for fusion investigation by using 11 Li radioactive beam and Si and C targets. It was found to be very useful in eliminating the energy degraded and parasitic beam admixtures. It was expected that this type of chamber could be used also for isotopes of light elements identification, in Accelerator Mass Spectrometry applications. (authors)

  20. A novel convolution-based approach to address ionization chamber volume averaging effect in model-based treatment planning systems

    International Nuclear Information System (INIS)

    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