Liquid ionization chambers for LET determination

DEFF Research Database (Denmark)

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

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

Liquid-filled ionization chamber temperature dependence

Energy Technology Data Exchange (ETDEWEB)

Franco, L. [Dpto. de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, Campus Sur S/N, 15782 Santiago de Compostela (Spain)]. E-mail: luciaff@usc.es; Gomez, F. [Dpto. de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, Campus Sur S/N, 15782 Santiago de Compostela (Spain); Iglesias, A. [Dpto. de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, Campus Sur S/N, 15782 Santiago de Compostela (Spain); Pardo, J. [Dpto. de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, Campus Sur S/N, 15782 Santiago de Compostela (Spain); Pazos, A. [Dpto. de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, Campus Sur S/N, 15782 Santiago de Compostela (Spain); Pena, J. [Dpto. de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, Campus Sur S/N, 15782 Santiago de Compostela (Spain); Zapata, M. [Dpto. de Fisica de Particulas, Facultade de Fisica, Universidade de Santiago, Campus Sur S/N, 15782 Santiago de Compostela (Spain)

2006-05-10

Temperature and pressure corrections of the read-out signal of ionization chambers have a crucial importance in order to perform high-precision absolute dose measurements. In the present work the temperature and pressure dependences of a sealed liquid isooctane filled ionization chamber (previously developed by the authors) for radiotherapy applications have been studied. We have analyzed the thermal response of the liquid ionization chamber in a {approx}20 deg. C interval around room temperature. The temperature dependence of the signal can be considered linear, with a slope that depends on the chamber collection electric field. For example, a relative signal slope of 0.27x10{sup -2}K{sup -1} for an operation electric field of 1.67x10{sup 6}Vm{sup -1} has been measured in our detector. On the other hand, ambient pressure dependence has been found negligible, as expected for liquid-filled chambers. The thermal dependence of the liquid ionization chamber signal can be parametrized within the Onsager theory on initial recombination. Considering that changes with temperature of the detector response are due to variations in the free ion yield, a parametrization of this dependence has been obtained. There is a good agreement between the experimental data and the theoretical model from the Onsager framework.

Gridded Ionization Chamber

International Nuclear Information System (INIS)

Manero Amoros, F.

1962-01-01

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

Ionization chamber for smoke detector and the like

International Nuclear Information System (INIS)

Rork, G.D.; Thorp, E.J.; Zegarski, R.J.

1985-01-01

This invention relates to detectors of the ionization type for detecting airborne particulate matter and, in particular, to the construction of an ionization chamber for such a detector. This invention may be used for detecting a variety of materials, such as dust, fog and the like, but is particularly useful for detecting combustion products such as smoke. The smoke detector ionization chamber has two electrodes connected to a source of electric power; means defining access openings for enabling air flow into and out of the chamber; and means for causing ionization within the chamber. It has control structure means within the chamber in the path of the airflow cooperating with the electrodes to establish within the chamber an electric field having a higher intensity close to the access openings and a lower intensity in the remainder of the chamber without significantly impairing the flow of neutral particles into the chamber. The control structure reduces airflow velocity within the chamber without adversely affecting the access of airborne particles to the chamber

Improvements in ionization chambers

International Nuclear Information System (INIS)

Whetten, N.R.; Zubal, C.

1980-01-01

A method of reducing mechanical vibrations transmitted to the parallel plate electrodes of ionization chamber x-ray detectors, commonly used in computerized x-ray axial tomography systems, is described. The metal plate cathodes and anodes are mounted in the ionizable gas on dielectric sheet insulators consisting of a composite of silicone resin and glass fibres. (UK)

An ionization chamber with magnetic levitated electrodes

CERN Document Server

Kawaguchi, T

1999-01-01

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

Numerical solutions of differential equations of an ionization chamber

International Nuclear Information System (INIS)

Novkovic, D.; Tomasevic, M.; Subotic, K.; Manic, S.

1998-01-01

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 CO 2 were also in good agreement with the experimental data of Moriuchi et al (author)

Ionization chambers for LET determination

DEFF Research Database (Denmark)

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

2010-01-01

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

Calibration of working standard ionization chambers and dose standardization

International Nuclear Information System (INIS)

Abd Elmahoud, A. A. B.

2011-01-01

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

Calibration of ionization chambers used in LDR brachytherapy

International Nuclear Information System (INIS)

Alvarez, Oscar T.B.; Caldas, Linda V.E.

2005-01-01

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%

A liquid ionization chamber using tetramethylsilane

International Nuclear Information System (INIS)

Engler, J.; Keim, H.

1983-12-01

First results with a liquid ionization chamber using tetramethylsilane (TMS) are presented. A stack of iron plates was tested with cosmic ray muons and the charge output for minimum ionizing particles was measured. (orig.) [de

Making MUSIC: A multiple sampling ionization chamber

International Nuclear Information System (INIS)

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

2007-01-01

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. 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

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.

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.

Determination of non-uniformity correction factors for cylindrical ionization chambers close to 192Ir brachytherapy sources

International Nuclear Information System (INIS)

Toelli, H.; Bielajew, A. F.; Mattsson, O.; Sernbo, G.

1995-01-01

When ionization chambers are used in brachytherapy dosimetry, the measurements must be corrected for the non-uniformity of the incident photon fluence. The theory for determination of non-uniformity correction factors, developed by Kondo and Randolph (Rad. Res. 1960) assumes that the electron fluence within the air cavity is isotropic and does not take into account material differences in the chamber wall. The theory was extended by Bielajew (PMB 1990) using an anisotropic electron angular fluence in the cavity. In contrast to the theory by Kondo and Randolph, the anisotropic theory predicts a wall material dependence in the non-uniformity correction factors. This work presents experimental determination of non-uniformity correction factors at distances between 10 and 140 mm from an Ir-192 source. The experimental work makes use of a PTW23331-chamber and Farmer-type chambers (NE2571 and NE2581) with different materials in the walls. The results of the experiments agree well with the anisotropic theory. Due to the geometrical shape of the NE-type chambers, it is shown that the full length of the these chambers, 24.1mm, is not an appropriate input parameter when theoretical non-uniformity correction factors are evaluated

Research on insulating material affecting the property of gas ionization chamber

International Nuclear Information System (INIS)

Wang Liqiang; Wang Zhentao; Zheng Jian

2014-01-01

The insulating material in ionization chamber affects the internal gas pressure and ionic pulse shape in the research process of the ion drift velocity in high pressure gas ionization chamber. It will affect the ion drift velocity measurement. It is required to isolate by insulating material between electrode to electrode and between electrodes to the shell of gas ionization chamber. Insulating material in gas ionization chamber is indispensable. Therefore it needs to carefully study the insulating material affecting the performance of gas ionization chamber. First of all, it is found that Teflon can slowly adsorb the working gas in ionization chamber, and the gas pressure in it is reduced when we measure the sensitivity of gas ionization chamber over time. It is verified by experiment that insulating materials absorbing and releasing gas is dynamically reversible process. Then the adsorbing gas property of 95% aluminium oxide ceramic and Teflon is studied through experimental comparision. Gas adsorption equilibrium time of ceramic material is faster, generally it is about a few hours, and the gas adsorption capacity is relatively less. Gas adsorption equilibrium time of Teflon is slower, it is about a few days, and the gas adsorption capacity is relatively more. It is found that Teflon will release part of the gas at higher temperature through experimental research on the influence of Teflon adsorbing gas. Finally it is studied that the distribution of insulation in ionization chamber affects the time response speed of ionization chamber by measuring the signal pulse shape of ionization chamber under the pulse X-ray. Through these experimental research, it is presented that it need to pay attention to select insulation material and to design the internal structure and arrangement of insulating material when we design gas ionization chamber. (authors)

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.

Pencil-shaped radiation detection ionization chamber

International Nuclear Information System (INIS)

Suzuki, A.

1979-01-01

A radiation detection ionization chamber is described. It consists of an elongated cylindrical pencil-shaped tubing forming an outer wall of the chamber and a center electrode disposed along the major axis of the tubing. The length of the chamber is substantially greater than the diameter. A cable connecting portion at one end of the chamber is provided for connecting the chamber to a triaxial cable. An end support portion is connected at the other end of the chamber for supporting and tensioning the center electrode. 17 claims

Evaluation of the operational characteristics of a CT ionization chamber

International Nuclear Information System (INIS)

Maia, Ana F.; Caldas, Linda V.E.

2006-01-01

The most common ionization chamber used in computed tomography dosimetry is the 'pencil ionization chamber'. It is a special cylindrical dosimeter developed for attending computed tomography beams particularities. In this study, a Victoreen pencil ionization chamber was submitted to a set of tests for a detailed evaluation of its operational characteristics. Such as many kinds of detectors, especially field instruments, this ionization chamber had originally a preamplifier to keep it electrically more stable. In this study, the performance of the chamber was analyzed with the original preamplifier and after its removal, and the results were compared. The objective of the preamplifier removal was to enable connecting the chamber to other kinds of electrometers available in laboratories. The behavior of the pencil ionization chamber before and after the removal of the preamplifier was very similar, and the results obtained were always within the limits of international recommendations. The results obtained in both situations allow, if necessary, the preamplifier removal of the system without lack of precision in the measurements

Improving the accuracy of ionization chamber dosimetry in small megavoltage x-ray fields

Science.gov (United States)

McNiven, Andrea L.

The dosimetry of small x-ray fields is difficult, but important, in many radiation therapy delivery methods. The accuracy of ion chambers for small field applications, however, is limited due to the relatively large size of the chamber with respect to the field size, leading to partial volume effects, lateral electronic disequilibrium and calibration difficulties. The goal of this dissertation was to investigate the use of ionization chambers for the purpose of dosimetry in small megavoltage photon beams with the aim of improving clinical dose measurements in stereotactic radiotherapy and helical tomotherapy. A new method for the direct determination of the sensitive volume of small-volume ion chambers using micro computed tomography (muCT) was investigated using four nominally identical small-volume (0.56 cm3) cylindrical ion chambers. Agreement between their measured relative volume and ionization measurements (within 2%) demonstrated the feasibility of volume determination through muCT. Cavity-gas calibration coefficients were also determined, demonstrating the promise for accurate ion chamber calibration based partially on muCT. The accuracy of relative dose factor measurements in 6MV stereotactic x-ray fields (5 to 40mm diameter) was investigated using a set of prototype plane-parallel ionization chambers (diameters of 2, 4, 10 and 20mm). Chamber and field size specific correction factors ( CSFQ ), that account for perturbation of the secondary electron fluence, were calculated using Monte Carlo simulation methods (BEAM/EGSnrc simulations). These correction factors (e.g. CSFQ = 1.76 (2mm chamber, 5mm field) allow for accurate relative dose factor (RDF) measurement when applied to ionization readings, under conditions of electronic disequilibrium. With respect to the dosimetry of helical tomotherapy, a novel application of the ion chambers was developed to characterize the fan beam size and effective dose rate. Characterization was based on an adaptation of the

Saturation curves of Tandem ionization chambers for Hp(10) measurement

International Nuclear Information System (INIS)

Vivolo, Vitor; Caldas, Linda V.E.

2005-01-01

It is very important that the radiation detectors measure doses with high precision and accuracy. The verification of the standard dosemeters such as ionization chambers is a very important step in quality control programs of calibration laboratories and in radioprotection procedures. In this work the polarity effect and ionic recombination of two ionization chambers were studied. Saturation curves were obtained using two identical in shape, parallel-plate ionization chambers developed at IPEN (radioprotection level), with collecting electrodes made of different materials (to obtain different energy dependences of their responses) in standard X radiation beams of low and medium energies. The tests were performed following international standard recommendations (IEC 60731). The results show that both ionization chambers were approved in the tests; the variation on the readings were lower than 1%, for bias voltage between - 400V and + 400V. The results of the polarity tests of the ionization chambers show that the response variation is within the standard IEC 60731 limits. The determined ionic recombination agrees with the recommendation of IAEA (TRS 398). Therefore, the ionization chambers tested in this work were approved. (author)

Calibration of ionization chamber survey meter

International Nuclear Information System (INIS)

Kadhim, A.K.; Kadni, T.B.

2016-01-01

Radiation measuring devices need to process calibration which lose their sensitivity and the extent of the response and the amount of stability under a changing conditions from time to time and this period depends on the nature and use of field in which used devices. A comparison study was done toa (45 I P) ( ionization chamber survey meter) and this showed the variation factor in five different years. This study also displayed the concept of radiation instrument calibration and necessity of every year calibration of them.In this project we used the five years calibration data for ionization chamber survey meter model Inspector (1/C F). the value deviation (∆ %) of Cfs for four years of calibration in comparison of C F for the year 2007 are very high and the device under research is not good to use in field and reliable because the ionization chamber is very sensitive to humidity and must calibrate a year or less, or due ing every two years and must maintain carefully to reduce the discarded effects the measurements.

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

International Nuclear Information System (INIS)

Yoshizumi, Maira Tiemi

2010-01-01

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)

Ionization chamber correction factors for MR-linacs.

Science.gov (United States)

Pojtinger, Stefan; Dohm, Oliver Steffen; Kapsch, Ralf-Peter; Thorwarth, Daniela

2018-06-07

Previously, readings of air-filled ionization chambers have been described as being influenced by magnetic fields. To use these chambers for dosimetry in magnetic resonance guided radiotherapy (MRgRT), this effect must be taken into account by introducing a correction factor k B . The purpose of this study is to systematically investigate k B for a typical reference setup for commercially available ionization chambers with different magnetic field strengths. The Monte Carlo simulation tool EGSnrc was used to simulate eight commercially available ionization chambers in magnetic fields whose magnetic flux density was in the range of 0-2.5 T. To validate the simulation, the influence of the magnetic field was experimentally determined for a PTW30013 Farmer-type chamber for magnetic flux densities between 0 and 1.425 T. Changes in the detector response of up to 8% depending on the magnetic flux density, on the chamber geometry and on the chamber orientation were obtained. In the experimental setup, a maximum deviation of less than 2% was observed when comparing measured values with simulated values. Dedicated values for two MR-linac systems (ViewRay MRIdian, ViewRay Inc, Cleveland, United States, 0.35 T/ 6 MV and Elekta Unity, Elekta AB, Stockholm, Sweden, 1.5 T/7 MV) were determined for future use in reference dosimetry. Simulated values for thimble-type chambers are in good agreement with experiments as well as with the results of previous publications. After further experimental validation, the results can be considered for definition of standard protocols for purposes of reference dosimetry in MRgRT.

Ionization chamber correction factors for MR-linacs

Science.gov (United States)

Pojtinger, Stefan; Steffen Dohm, Oliver; Kapsch, Ralf-Peter; Thorwarth, Daniela

2018-06-01

Previously, readings of air-filled ionization chambers have been described as being influenced by magnetic fields. To use these chambers for dosimetry in magnetic resonance guided radiotherapy (MRgRT), this effect must be taken into account by introducing a correction factor k B. The purpose of this study is to systematically investigate k B for a typical reference setup for commercially available ionization chambers with different magnetic field strengths. The Monte Carlo simulation tool EGSnrc was used to simulate eight commercially available ionization chambers in magnetic fields whose magnetic flux density was in the range of 0–2.5 T. To validate the simulation, the influence of the magnetic field was experimentally determined for a PTW30013 Farmer-type chamber for magnetic flux densities between 0 and 1.425 T. Changes in the detector response of up to 8% depending on the magnetic flux density, on the chamber geometry and on the chamber orientation were obtained. In the experimental setup, a maximum deviation of less than 2% was observed when comparing measured values with simulated values. Dedicated values for two MR-linac systems (ViewRay MRIdian, ViewRay Inc, Cleveland, United States, 0.35 T/ 6 MV and Elekta Unity, Elekta AB, Stockholm, Sweden, 1.5 T/7 MV) were determined for future use in reference dosimetry. Simulated values for thimble-type chambers are in good agreement with experiments as well as with the results of previous publications. After further experimental validation, the results can be considered for definition of standard protocols for purposes of reference dosimetry in MRgRT.

Multiple chamber ionization detector

International Nuclear Information System (INIS)

Solomon, E.E.

1982-01-01

An ionization smoke detector employs a single radiation source in a construction comprising at least two chambers with a center or node electrode. The radioactive source is associated with this central electrode, and its positioning may be adjusted relative to the electrode to alter the proportion of the source that protrudes into each chamber. The source may also be mounted in the plane of the central electrode, and positioned relative to the center of the electrode. The central electrode or source may be made tiltable relative to the body of the detector

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

International Nuclear Information System (INIS)

Silva, Jonas Oliveira da

2013-01-01

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)

Study on time response properties of ionization chamber in profile gauge

International Nuclear Information System (INIS)

Wang Zhentao; Shen Yixiong; Wang Liqiang; Hao Pengfei

2011-01-01

The drift time of ions in the ionization chamber was measured by means of using a shortly pulsed X-ray device and through analyzing the voltage signals on the load resistor of the chamber recorded by a digital oscilloscope. By using this method, the time response properties of the ionization chamber in the profile gauge were studied, results of ion drift time for ionization chambers with different internal structures, different voltages and different gas pressures were introduced and the sources of error were discussed. The experiment results show that the time response of ionization chamber in profile gauge meets the requirement of on-line hot strip measuring. (authors)

Industrial development of neutron detectors, fission chambers, self powered detectors, ionization chambers

International Nuclear Information System (INIS)

Constans, H.; Coville, P.; Guerre, J.

1975-01-01

Reactor control requires the determination of neutron flux at all times. The needed characteristics lead to use of several types of detectors: boron lined counters, boron lined ionization chambers, fission ionization chambers and self powered detectors. The principle of the reaction involved the fabrication requirements, the different modes of utilization and the characteristics obtained are examined for each detector. The problem of electric connections in the active area has been solved by developing ''integrated cables'' [fr

Time expansion chamber and single ionization cluster measurement

International Nuclear Information System (INIS)

Walenta, A.H.

1978-10-01

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

Establishment of a tandem ionization chamber system in standard mammography beams

International Nuclear Information System (INIS)

Silva, Jonas O. da; Caldas, L.V.E.

2011-01-01

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

Development of standard ionization chamber counting system for activity measurements

International Nuclear Information System (INIS)

Pyun, Woong Beom; Lee, Hyun Koo; Lee, Hai Yong; Park, Tae Soon

1998-01-01

This study is to set up the activity measuring system using a 4π γ 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 4π γ ionization chamber is about 0.02% and the background current is 0.054±0.024 pA. this 4π γ ionization chamber is calibrated by 6 standard gamma emitting radionuclides from KRISS. According to the result of this study, it is revealed that this 4π γ ionization chamber counting system can be used as a secondary standard instrument for radioactivity measurement

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.

Cylindrical ionization chamber with compressed krypton

International Nuclear Information System (INIS)

Kuz'minov, V.V.; Novikov, V.M.; Pomanskii, A.A.; Pritychenko, B.V.; Viyar, J.; Garcia, E.; Morales, A.; Morales, J.; Nunes-Lagos, R.; Puimedon, J.; Saens, K.; Salinas, A.; Sarsa, M.

1993-01-01

A cylindrical ionization chamber with a grid is used to search for double positron decay and atomic electron conversion to a positron in 78 Kr. 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 88 Y) when the chamber is filled with a mixture of Kr+0.2% H 2 under a pressure of 25 atm

Characteristics of Noble Gas-filled Ionization Chambers for a Low Dose Rate Monitoring

International Nuclear Information System (INIS)

Kim, Han Soo; Park, Se Hwan; Ha, Jan Ho; Lee, Jae Hyung; Lee, Nam Ho; Kim, Jung Bok; Kim, Yong Kyun; Kim, Do Hyun; Cho, Seung Yeon

2007-01-01

An ionization chamber is still widely used in fields such as an environmental radiation monitoring, a Radiation Monitoring System (RMS) in nuclear facilities, and an industrial application due to its operational stability for a long period and its designs for its applications. Ionization chambers for RMS and an environmental radiation monitoring are requested to detect a low dose rate at as low as 10-2 mR/h and several 3R/h, respectively. Filling gas and its pressure are two of the important factors for an ionization chamber development to use it in these fields, because these can increase the sensitivity of an ionization chamber. We developed cylindrical and spherical ionization chambers for a low dose rate monitoring. Response of a cylindrical ionization chamber, which has a 1 L active volume, was compared when it was filled with Air, Ar, and Xe gas respectively. Response of a spherical ionization chamber was also compared in the case of 9 atm and 25 atm filling-pressures. An inter-comparison with a commercially available high pressure Ar ionization chamber and a fabricated ionization chamber was also performed. A High Pressure Xenon (HPXe) ionization chamber, which was configured with a shielding mesh to eliminate an induced charge of positive ions, was fabricated both for the measurement of an environmental dose rate and for the measurement of an energy spectrum

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)

Plaetsen, A. van der; Thierens, H.; Palmans, H.

2000-01-01

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 d max , R 50 and R p 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, h m , for dose determination in electron beams using a PMMA phantom were determined experimentally for both plane parallel chamber types. (author)

Pressurized air ionization chamber with aluminium walls for radiometric dosimetry

International Nuclear Information System (INIS)

Rodrigues, R.G.S.; Pela, C.A.; Netto, T.G.

1996-01-01

A pressurized air ionization chamber with 23 cm 3 and aluminium walls is evaluated concerning its sensitiveness in low exposure rate. Considering conventional ionization chambers, this chamber shows a better performance since the air pressure of 2500 kPa minimizes the energy dependence to less than 5% between 40 and 1.250 keV

Physical aspects on the neutron irradiation. 4. Dosimetry with ionization chamber

International Nuclear Information System (INIS)

Hiraoka, Takeshi; Takada, Masashi

2008-01-01

Absolute measurements of the absorbed dose for irradiation are generally made using ionization chambers, which should be calibrated by the standard radiation source. The neutron dose measurements are not simple since gamma rays always contaminate the neutron flux and a variety of charged particles are induced by neutrons. Following subjects are described: (1) The method by ICRU 45 to estimate total dose of neutrons and gamma ray, (2) The method to measure the neutron dose and the gamma ray dose separately using paired ionization-chambers, and (3) The calibration of ionization chambers. The stability of the standard ionization-chambers is also presented. (K.Y.)

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.

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

International Nuclear Information System (INIS)

Stoyanov, D G

2007-01-01

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

Effects of air humidity on ionization chamber response

International Nuclear Information System (INIS)

Meger, C.; DeLuca, P.M. Jr.; Pearson, D.W.; Venci, R.

1983-01-01

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

Performance of a pencil ionization chamber in various radiation beams

International Nuclear Information System (INIS)

Maia, A.F.; Caldas, L.V.E.

2003-01-01

Pencil ionization chambers were recommended for use exclusively in the computed tomography (CT) dosimetry, and, from the start, they were developed only with this application in view. In this work, we studied the behavior of a pencil ionization chamber in various radiation beams with the objective of extending its application. Stability tests were performed, and calibration coefficients were obtained for several standard radiation qualities of the therapeutical and diagnostic levels. The results show that the pencil ionization chamber can be used in several radiation beams other than those used in CT

Computational evaluation of a pencil ionization chamber in a standard diagnostic radiology beam

International Nuclear Information System (INIS)

Mendonca, Dalila Souza Costa; Neves, Lucio Pereira; Perini, Ana Paula; Belinato, Walmir

2016-01-01

In this work a pencil ionization chamber was evaluated. This evaluation consisted in the determination of the influence of the ionization chamber components in its response. For this purpose, the Monte Carlo simulations and the spectrum of the standard diagnostic radiology beam (RQR5) were utilized. The results obtained, showed that the influence of the ionization chamber components presented no significant influence on the chamber response. Therefore, this ionization chamber is a good alternative for dosimetry in diagnostic radiology. (author)

Amplifier Design for Proportional Ionization Chambers

Energy Technology Data Exchange (ETDEWEB)

Baker, W. H.

1950-08-24

This paper presents the requirements of a nuclear amplifier of short resolving time, designed to accept pulses of widely varying amplitudes. Data are given which show that a proportional ionization chamber loaded with a 1,000-ohm resistor develops pulses of 0.5 microsecond duration and several volts amplitude. Results indicate that seven basic requirements are imposed on the amplifier when counting soft beta and gamma radiation in the presence of alpha particles, without absorbers. It should, (1) have a fast recovery time, (2) have a relatively good low frequency response, (3) accept pulses of widely varying heights without developing spurious pulsed, (4) have a limiting output stage, (5) preserve the inherently short rise time of the chamber, (6) minimize pulse integration, and (7) have sufficient gain to detect the weak pulses well below the chamber voltage at which continuous discharge takes place. The results obtained with an amplifier which meets these requirements is described. A formula is derived which indicates that redesign of the proportional ionization chamber might eliminate the need for an amplifier. This may be possible if the radioactive particles are collimated parallel to the collecting electrode.

Study of the replacement correction factors for ionization chamber dosimetry by Monte Carlo simulations

Science.gov (United States)

Wang, Lilie

In ionization chamber radiation dosimetry, the introduction of the ion chamber into medium will unavoidably distort the radiation field near the chamber because the chamber cavity material (air) is different from the medium. A replacement correction factor, Prepl was introduced in order to correct the chamber readings to give an accurate radiation dose in the medium without the presence of the chamber. Generally it is very hard to measure the values of Prepl since they are intertwined with the chamber wall effect. In addition, the P repl values always come together with the stopping-power ratio of the two media involved. This makes the problem of determining the P repl values even more complicated. Monte Carlo simulation is an ideal method to investigate the replacement correction factors. In this study, four different methods of calculating the values of Prepl by Monte Carlo simulation are discussed. Two of the methods are designated as 'direct' methods in the sense that the evaluation of the stopping-power ratio is not necessary. The systematic uncertainties of the two direct methods are estimated to be about 0.1-0.2% which comes from the ambiguous definition of the energy cutoff Delta used in the Spencer-Attix cavity theory. The two direct methods are used to calculate the values of P repl for both plane-parallel chambers and cylindrical thimble chambers in either electron beams or photon beams. The calculation results are compared to measurements. For electron beams, good agreements are obtained. For thimble chambers in photon beams, significant discrepancies are observed between calculations and measurements. The experiments are thus investigated and the procedures are simulated by the Monte Carlo method. It is found that the interpretation of the measured data as the replacement correction factors in dosimetry protocols are not correct. In applying the calculation to the BIPM graphite chamber in a 60Co beam, the calculated values of P repl differ from those

Development and characterization of special ionization chambers for computed tomography beams

International Nuclear Information System (INIS)

Castro, Maysa Costa de

2016-01-01

The use of computed tomography (CT) for imaging procedures is growing due to advances in the CT equipment technology, because they allow the obtention of images with better resolution than through other techniques. Therefore, they are responsible for increasing the dose radiation of patients during the procedure. This fact led to a greater concern about the doses received by patients who undergo this type of examination. To perform the dosimetry in CT beams, the most widely used instrument is the pencil type ionization chamber, because this dosimeter has a uniform response to the incident radiation beam for all angles. The conventional ionization chamber, which is available on the market, has a sensitive volume length of 10 cm; however, some studies have shown that this dosimeter has underestimated the dose values. Therefore, in this study two ionization chambers with sensitive volume lengths of 10 cm and 30 cm, making use of low cost national materials, were developed at the Calibration Laboratory of Instruments (LCI-IPEN/CNEN). The characterization of these chambers was performed, and the results were obtained within the international recommended limits. As an application, the developed ionization chambers and a commercial chamber were tested in a clinical tomograph. The developed ionization chambers were analyzed in a complete way for their possible uses. (author)

Radiation damage to tetramethylsilane and tetramethylgermanium ionization chambers

International Nuclear Information System (INIS)

Hoshi, Y.; Higuchi, M.; Oyama, K.

1994-01-01

Two detector media suitable for a warm liquid, ionization chamber filled with tetramethylsilane (TMS) and tetramethylgermanium (TMG) were exposed to γ radiation form a 60 Co source up to dose 579 Gray and 902 Gray, respectively. The electron lifetimes and the free ion yields were measured as a function of accumulated radiation dose. A similar behavior of the electron lifetimes and the free ion yields with increasing radiation does was observed between the TMS and TMG ionization chambers

α spectrometry grid ionization chamber: improvement of the characteristics

International Nuclear Information System (INIS)

Le Du, R.; Miltenberger, B.

1968-01-01

The rise time of the signals obtained with a grid ionization chamber depends on the orientation in the chamber and on the mobility of the ionization components. Our grid chambers are fitted with an electronic system which analyses the signals due to the electronic ionization components which are collected on the plate and on the source holder. By obtaining coincidence between these two signals, it is possible to select paths of any given orientation. Using this principle we have built an electronic collimator which does not have the disadvantages of a mechanical collimator for alpha spectra studies, and which, further, considerably reduces the background of the chamber. Simultaneously with the study of the improvement of a spectra with our device, we have been able to dissociate the contributions of back-diffusion and of self-absorption phenomena to the activity of an alpha source; some results will be presented. (authors) [fr

Stability of reference class ionization chambers used for radiotherapy dosimetry: IAEA experience

International Nuclear Information System (INIS)

Czap, L.; Meghzifene, A.; Shortt, K.R.; Andreo, P.

2002-01-01

The IAEA calibrates ionization chambers, used in radiotherapy, for its Member States. The calibrations are either for Secondary Standards Dosimetry Laboratories (SSDLs) or hospitals from countries without a SSDL. For that purpose, the IAEA calibrates mainly reference class instruments that are in turn used to cross-calibrate field class instruments at the hospital. Typically, the IAEA calibrates about 30-40 ionization chambers per year, of which about half are new chambers purchased by the IAEA for its Member States using Technical Cooperation funds. The IAEA database includes the calibration coefficients of 189 reference class ionization chambers of the following types: NE-2561/2611, NE-2571, W-30001/W-30010. The results of the calibrations and recalibrations of the ionization chambers in terms of air kerma and absorbed dose to water are presented and discussed. The ratio of 60 Co calibration coefficients N D,w /N K , labelled C K , was determined for all chambers. The use of C K as a chamber dependent parameter and quality control indicator to check the results of the routine IAEA calibrations is discussed. In the process of its routine calibrations, the IAEA identified a specific problem related to the W- 30001 ionization chambers. The stability of these chambers was found to exceed the 0.5% tolerance limit set by the International IEC standard. Other SSDLs reported similar findings. The manufacturer stopped the production of these W-30001 chambers to investigate the reasons for this anomalous behaviour. After identifying and correcting the problem, the manufacturer produced a new type of ionization chamber. Five of these chambers were tested at the IAEA and found to be within the tolerance limit

Ionization chamber for high dose measurements

International Nuclear Information System (INIS)

Rodrigues Junior, Ary de Araujo

2005-01-01

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 60 Co 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 cm 3 has been developed for high-doses real-time monitoring, during the sample irradiation at a static position in a 60 Co 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

Angular dependence of the parallel plate ionization chambers of Ipen

International Nuclear Information System (INIS)

Albuquerque, M. da P.P.; Caldas, L.

1989-08-01

The ionization chambers with parallel plates designed and constructed at IPEN for the dosimetry of soft X-radiation fields were studied in relation to thein angular dependence between O and +- 90 0 . The objective of this study is to verify the chambers response variation for small positioning errors during the field dosimetry used in Radiotherapy. The results were compared with those of commercial parallel plate ionization chambers used as secondary and testiary standards. (author) [pt

A magnetically levitated electrode ionization chamber of the noncontact measurement type

International Nuclear Information System (INIS)

Kawaguchi, Toshiro; Yoshimura, Atsushi

2002-01-01

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

A magnetically levitated electrode ionization chamber of the noncontact measurement type

CERN Document Server

Kawaguchi, T

2002-01-01

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

Spherical ionization chamber of 14 liter for precise measurement of environmental radiation dose rate

International Nuclear Information System (INIS)

Nagaoka, Toshi; Saito, Kimiaki; Moriuchi, Shigeru

1991-05-01

A spherical ionization chamber of 14 liter filled with 1 atm. nitrogen gas was arranged aiming at precise measurement of dose rate due to environmental gamma rays and cosmic rays. Ionization current-dose rate conversion factor for this ionization chamber was derived from careful consideration taking into account the attenuation by chamber wall, ionization current due to alpha particles and so on. Experiments at calibrated gamma ray fields and intercomparison with NaI(Tl) scintillation detector were also performed, which confirmed this ionization chamber using the conversion factor can measure the dose rate with an error of only a few percent. This ionization chamber will be used for measurement of environmental gamma ray and cosmic ray dose rate. (author)

Performance of ionization chambers in X radiation beams, radioprotection level

International Nuclear Information System (INIS)

Bessa, Ana C.M.; Potiens, Maria da Penha A.; Caldas, Linda V.E.

2005-01-01

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 90 Sr + 90 Y. 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%

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

International Nuclear Information System (INIS)

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

2010-01-01

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

Automatic control system for measuring currents produced by ionization chambers

International Nuclear Information System (INIS)

Brancaccio, Franco

2002-01-01

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 18 F and 153 Sm were obtained, making possible to determine activities of these radionuclides. (author)

Determination of absorbed dose to water from a miniature kilovoltage x-ray source using a parallel-plate ionization chamber

Science.gov (United States)

Watson, Peter G. F.; Popovic, Marija; Seuntjens, Jan

2018-01-01

Electronic brachytherapy sources are widely accepted as alternatives to radionuclide-based systems. Yet, formal dosimetry standards for these devices to independently complement the dose protocol provided by the manufacturer are lacking. This article presents a formalism for calculating and independently verifying the absorbed dose to water from a kV x-ray source (The INTRABEAM System) measured in a water phantom with an ionization chamber calibrated in terms of air-kerma. This formalism uses a Monte Carlo (MC) calculated chamber conversion factor, CQ , to convert air-kerma in a reference beam to absorbed dose to water in the measurement beam. In this work CQ was determined for a PTW 34013 parallel-plate ionization chamber. Our results show that CQ was sensitive to the chamber plate separation tolerance, with differences of up to 15%. CQ was also found to have a depth dependence which varied with chamber plate separation (0 to 10% variation for the smallest and largest cavity height, over 3 to 30 mm depth). However for all chamber dimensions investigated, CQ was found to be significantly larger than the manufacturer reported value, suggesting that the manufacturer recommended method of dose calculation could be underestimating the dose to water.

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

International Nuclear Information System (INIS)

Wang, Zhentao; Shen, Yixiong; An, Jigang

2012-01-01

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

Evaluation of the energy dependence of ionization chambers pencil type calibrated beam tomography standards

International Nuclear Information System (INIS)

Fontes, Ladyjane Pereira; Potiens, Maria da Penha A.

2015-01-01

The Instrument Calibration Laboratory of IPEN (LCI - IPEN) performs calibrations of pencil-type ionization chambers (IC) used in measures of dosimetric survey on clinical systems of Computed Tomography (CT). Many users make mistakes when using a calibrated ionization chamber in their CT dosimetry systems. In this work a methodology for determination of factors of correction for quality (Kq) through the calibration curve that is specific for each ionization chamber was established. Furthermore, it was possible to demonstrate the energy dependence on an pencil-type Ionization Chamber(IC) calibrated at the LCI - IPEN. (author)

Pressurized ionization chamber dose ratemeter for enviromental radiation measaurement

Energy Technology Data Exchange (ETDEWEB)

Qingyu, Yue; Hua, Jin; Youling, Jiang

1986-01-01

The dose ratemeter, mainly used for measuring absorbed doserate of environmental gamma radiation and the charged particle components of cosmic-rays in /sup f/ree-air/sup ,/ consists of an energy compensated spherical pressurized ionization chamber, a MOS electrometer and a digital voltmeter. The flat energy response of the pressurized ionization chamber ranges from 60 keV to 1250 keV. It has good stability and higher sensitivity, and weights 6 kg.

Simulation of the saturation curve of the ionization chamber in overlapping pulsed radiation

International Nuclear Information System (INIS)

Park, Se Hwan; Kim, Yong Kyun; Kim, Han Soo; Kang, Sang Mook; Ha, Jang Ho

2006-01-01

Procedures for determination of collection efficiency in ionization chambers have been studied by numerous investigators. If the theoretical approach for air-filled ionization chambers exposed to continuous radiation is considered, the result in the near-saturation region is a linear relationship between ) (1/I(V) vs 1/V 2 , where I(V) is the current measured with the ionization chamber at a given polarization voltage V . For pulsed radiation beams, Boag developed a model and the resulted in a linear relationship between ) (1/I(V) and 1/V when the collection efficiency, f , is larger than 0.9. The assumption of the linear relationship of ) (1/I(V) with 1/V or 1/V 2 in the near-saturation region makes the determination of the saturation current simple, since the linear relationship may be determined with only two measured data points. The above discussion of the collection efficiency of the ionization chamber exposed to the pulsed radiation is valid only if each pulse is cleared before the next one occurs. The transit times of the ions in the chamber must be shorter than the time interval between the radiation pulses. Most of the previous works concerning the characteristics of the saturation curve of an ionization chamber in the pulsed beam were done for the case where the transit times of the ions were shorter than the interval between the radiation pulses. However, the experimental data for the intermediate case, where the ion transit time was comparable to the interval between the radiation pulses or the ion transit time was slightly longer than the interval between the radiation pulses, were rare. The saturation curves of the ionization chambers in the pulsed radiation were measured with the pulse beamed electron accelerator at the Korea Atomic Energy Research Institute (KAERI), where the ion transit times in the ionization chambers were longer than the time interval between the radiation pulses. We used two ionization chambers: one was a commercial thimble

Characteristics of the saturation curve of the ionization chambers in overlapping pulsed beams

International Nuclear Information System (INIS)

Park, S.H.; Kim, Y.K.; Kim, H.S.; Kang, S.M.; Ha, J.H.

2006-01-01

When a pulsed radiation is incident on an air-filled ionization chamber wherein the primary electrons are rapidly absorbed to become negative ions, it is known that the reciprocal of the ionizing current is linearly proportional to the reciprocal of the polarization voltage in the near saturation region. However, the relationship between the reciprocal of the ionizing current and the reciprocal of the polarization voltage will deviate from a simple linearity when the ion transit time in the ionization chamber is longer than the interval between the radiation pulses. Two thimble-type ionization chambers, one of which was designed and fabricated by us, were employed to measure the saturation curves of the ionization chambers in a pulsed Bremsstrahlung X-ray, which was generated with an electron accelerator. A model was developed to explain the shape of the measured saturation curves in the overlapping pulsed radiation, and the results of it were compared with the measured ones. The dependency of the shape of the saturation curve on the geometrical design of the ionization chambers in the pulsed radiation was discussed

A multi purpose 4 π counter spherical ionization chamber type

International Nuclear Information System (INIS)

Calin, Marian Romeo; Calin, Adrian Cantemir

2004-01-01

A pressurized ionization chamber detector able to measure radioactive sources in internal 2π or 4π geometry was built in order to characterize alpha and beta radioactive sources, i.e. to calibrate these sources by relative method and to test the behavior of gas mixtures in pressurized-gas radiation detectors. The detector we made is of spherical shape and works by collecting in a uniform electric field the ionization charges resulting from the interaction of ionizing radiation with gas in the sensitive volume of the chamber. An ionizing current proportional to the activity of the radioactive source to be measured is obtained. In this paper a gas counter with a spherical symmetry is described. This detector can work in a very satisfactory manner, either as a flow counter or as a ionization chamber reaching in the latter case a good α pulse height resolution, even with large emitting sources. Calculations are made in order to find the dependence of the pulse shape on the direction of emission of an α-particle by a point source in the chamber (finite track). A good agreement is found between these calculations and the experimental tests performed, which show that this dependence can be employed in high efficiency measurements of angular α-γ correlations. (authors)

Evaluation of a special pencil ionization chamber by the Monte Carlo method

International Nuclear Information System (INIS)

Mendonca, Dalila; Neves, Lucio P.; Perini, Ana P.

2015-01-01

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

Study of Low Work Function Materials for Hot Cavity Resonance Ionization Laser Ion Sources

CERN Document Server

Catherall, R; Fedosseev, V; Marsh, B; Mattolat, C; Menna, Mariano; Österdahl, F; Raeder, S; Schwellnus, F; Stora, T; Wendt, K; CERN. Geneva. AB Department

2008-01-01

The selectivity of a hot cavity resonance ionization laser ion source (RILIS) is most often limited by contributions from competing surface ionization on the hot walls of the ionization cavity. In this article we present investigations on the properties of designated high-temperature, low-work function materials regarding their performance and suitability as cavity material for RILIS. Tungsten test cavities, impregnated with a mixture of barium oxide and strontium oxide (BaOSrO on W), or alternatively gadolinium hexaboride (GdB6) were studied in comparison to a standard tungsten RILIS cavity as being routinely used for hot cavity laser ionization at ISOLDE. Measurement campaigns took place at the off-line mass separators at ISOLDE / CERN, Geneva and RISIKO / University of Mainz.

Study of low work function materials for hot cavity resonance ionization laser ion sources

CERN Document Server

Schwellnus, F; Crepieux, B; Fedosseev, V N; Marsh, B A; Mattolat, Ch; Menna, M; Österdahl, F K; Raeder, S; Stora, T; Wendta, K

2009-01-01

The selectivity of a hot cavity resonance ionization laser ion source (RILIS) is most often limited by contributions from competing surface ionization of the hot walls of the ionization cavity. In this article we present investigations on the properties of designated high temperature, low work function materials regarding their performance and suitability as cavity material for RILIS. Tungsten test cavities, impregnated with a mixture of barium oxide and strontium oxide (BaOSrO on W), or alternatively gadolinium hexaboride (GdB6) were studied in comparison to a standard tungsten RILIS cavity as being routinely used for hot cavity laser ionization at ISOLDE. Measurement campaigns took place at the off-line mass separators at ISOLDE/CERN, Geneva and RISIKO/University of Mainz.

Calibration of ionization chamber and GM counter survey meters, (1)

International Nuclear Information System (INIS)

Bingo, Kazuyoshi; Kajimoto, Yoichi; Suga, Shin-ichi

1978-01-01

Three types of ionization chamber survey meters and a type of GM counter survey meter were calibrated for measuring the β-ray absorbed dose rate in a working area. To estimate the β-ray absorbed dose rate, a survey meter was used without and with a filter. A reading of survey meter's indicator measured with the filter was subtracted from a reading measured without the filter, and then the absorbed dose rate was obtained by multiplying this remainder by a conversion coefficient. The conversion coefficients were roughly constant with distance more than 8 cm (ionization chamber survey meters) and with distance more than 5 cm (GM counter survey meter). The conversion coefficient was dependent on β-ray energies. In order to measure the absorbed dose rate of tissue whose epidermal thickness is 40 mg/cm 2 , the constant value, 4 (mrad/h)/(mR/h), was chosen independently of β-ray energies as the conversion coefficient of three types of ionization chamber survey meters. The conversion coefficient of the GM counter survey meter was more energy dependent than that of every type of ionization chamber survey meter. (author)

Design and construction of a radiation monitor with ionization chamber

International Nuclear Information System (INIS)

Ramirez J, F.J.

1994-01-01

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)

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

International Nuclear Information System (INIS)

Mohammed, K. T. A.

2013-07-01

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)

High concentration tritium gas measurement with small volume ionization chambers for fusion fuel gas monitors

International Nuclear Information System (INIS)

Uda, Tatsuhiko; Okuno, Kenji; Matsuda, Yuji; Naruse, Yuji

1991-01-01

To apply ionization chambers to fusion fuel gas processing systems, high concentration tritium gas was experimentally measured with small volume 0.16 and 21.6 cm 3 ionization chambers. From plateau curves, the optimum electric field strength was obtained as 100∼200 V/cm. Detection efficiency was confirmed as dependent on the ionization ability of the filled gas, and moreover on its stopping power, because when the range of the β-rays was shortened, the probability of energy loss by collisions with the electrode and chamber wall increased. Loss of ions by recombination was prevented by using a small volume ionization chamber. For example the 0.16 cm 3 ionization chamber gave measurement with linearity to above 40% tritium gas. After the tritium gas measurements, the concentration levels inside the chamber were estimated from their memory currents. Although more than 1/4,000 of the maximum, current was observed as a memory effect, the smaller ionization chamber gave a smaller memory effect. (author)

Study on time response character for high pressure gas ionization chamber of krypton and xenon

International Nuclear Information System (INIS)

Tan Chunming; Wu Haifeng; Qing Shangyu; Wang Liqiang

2006-01-01

The time response character for Kr and Xe high pressure gas ionization chamber is analyzed and deduced. Compared with the measure data of pulse rising time for three gas-filled ionization chambers, the calculated and experimental results are equal to each other. The rising time less than 10 ms for this kind of ionization chamber can be achieved, so this ionization chamber is able to meet the requirement for imaging detection. (authors)

A pressurized ionization chamber dose ratemeter for enviromental radiation measaurement

International Nuclear Information System (INIS)

Yue Qingyu; Jin Hua

1986-01-01

The dose ratemeter, mainly used for measuring absorbed doserate of environmental gamma radiation and the charged particle components of cosmic-rays in f ree-air , consists of an energy compensated spherical pressurized ionization chamber, a MOS electrometer and a digital voltmeter. The flat energy response of the pressurized ionization chamber ranges from 60 keV to 1250 keV. It has good stability and higher sensitivity, and weights 6 kg

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

International Nuclear Information System (INIS)

Andreo, P.

1996-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Andreo, P [Lunds Hospital, Lund (Sweden). Radiophysics Dept.; Almond, P R [J.G. Brown Cancer Center, Univ. of Lousville, Lousville, KY (United States). Dept. of Radiation Oncology; Mattsson, O [Sahlgrenska Hospital, Gothenburg (Sweden). Dept. of Radiation Physics; Nahum, A E [Royal Marsden Hospital, Sutton (United Kingdom). Joint Dept. of Physics; Roos, M [Physikalisch-Technische Bundesanstalt, Braunschweig (Germany)

1996-08-01

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.

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

International Nuclear Information System (INIS)

Perini, Ana Paula; Neves, Lucio Pereira; Santos, William de Souza; Caldas, Linda V.E.

2014-01-01

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

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

International Nuclear Information System (INIS)

Silva, Natalia F.; Xavier, Marcos; Vivolo, Vitor; Caldas, Linda V.E.

2015-01-01

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)

Comments on evaluation of energy of partial discharges in ionization chambers

International Nuclear Information System (INIS)

Lechowski, Z.

1980-01-01

A method of evaluation of energy of partial discharges in ionization chambers which are intended for investigation on electric strength of insulating materials is presented. It is demonstrated that an ionization chamber must be considered as a set of discharge sources and that for energy evaluation an amplitude analysis of apparent charge of discharges is useful. (author)

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

International Nuclear Information System (INIS)

Cardoso, J.; Oliveira, C.; Carvalho, A.F.

2005-01-01

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, H p (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 137 Cs and 60 Co. 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)

Laboratory implantation for well type ionization chambers calibration

International Nuclear Information System (INIS)

Vianello, E.A.; Dias, D.J.; Almeida, C.E. de

1998-01-01

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)

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

International Nuclear Information System (INIS)

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

2017-01-01

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

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

International Nuclear Information System (INIS)

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

2012-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

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

2014-07-01

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

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

International Nuclear Information System (INIS)

Perini, Ana Paula; Neves, Lucio Pereira; Santos, William de Souza; Caldas, Linda V.E.; Frimaio, Audrew; Costa, Paulo R.

2014-01-01

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

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

International Nuclear Information System (INIS)

Perini, Ana Paula

2013-01-01

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)

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

International Nuclear Information System (INIS)

Sempau, Josep

2010-01-01

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)

Reasonable selection of automatic exposure density compensation of ionization chamber

International Nuclear Information System (INIS)

Tian Fuqiang; Nie Shikun; Wang Zhihong; Zeng Jianhua; Cheng Guanxun; Xiang Qian

2000-01-01

Objective: To introduce and discuss the methods of reasonable selection of the automatic exposure density compensation of ionization chamber to provide important references for clinic radiograph and improve the quality of images. Methods: X-ray machines with ionization chamber automatic exposure control system were used in this study. Compared with the standard baseline of the normal density of the object radio-graphed, the reasonable ionization chamber density compensation (IDC) was chosen and compared with the radiograph without IDC through a water model test and density measurement. Results: There was no significant difference between two groups (100 films each) which were randomly divided to the group with or without IDC, but there was statistically significant difference in the special groups. Conclusion: To select suitable IDC is very important for guaranteeing radiographic quality, moreover, to establish a suitable kV is also necessary, usually it is 10 to 20 kV higher than the optioned kV. The relative factors must be fixed relatively and be matched correctly

Proton-therapy and hadron-therapy ionization chambers

International Nuclear Information System (INIS)

Boissonnat, Guillaume

2015-01-01

In the framework of the ARCHADE project (Advanced Resource Center for Hadron-therapy in Europe), a research project in Carbone ion beam therapy and clinical Proton-therapy, this work investigates the beam monitoring and dosimetry aspects of ion beam therapy. The main goal, here, is to understand the operating mode of air ionization chambers, the detectors used for such applications. This study starts at a very fundamental level as the involved physical and chemical parameters of air were measured in various electric field conditions with dedicated setups and used to produce a simulation tools aiming at reproducing the operating response in high intensity PBS (Pencil Beam Scanning) coming from IBA's (Ion Beam Applications) next generation of proton beam accelerators. In addition, an ionization chamber-based dosimetry equipment was developed, DOSION III, for radiobiology studies conducted at GANIL under the supervision of the CIMAP laboratory. (author)

Design of the free-air ionization chamber, FAC-IR-150, for X-ray dosimetry

Science.gov (United States)

Mohammadi, Seyed Mostafa; Tavakoli-Anbaran, Hossein

2018-03-01

The primary standard for X-ray dosimetry is based on the free-air ionization chamber (FAC). Therefore, the Atomic Energy Organization of Iran (AEOI) designed the free-air ionization chamber, FAC-IR-150, for low and medium energy X-ray dosimetry. The purpose of this work is the study of the free-air ionization chamber characteristics and the design of the FAC-IR-150. The FAC-IR-150 dosimeter has two parallel plates, a high voltage plate and a collector plate. A guard electrode surrounds the collector and is separated by an air gap. A group of guard strips is used between up and down electrodes to produce a uniform electric field in all the ion chamber volume. This design involves introducing the correction factors and determining the exact dimensions of the ionization chamber by using Monte Carlo simulation.

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

Energy Technology Data Exchange (ETDEWEB)

Laitano, R F [Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA Centro Ricerche Casaccia, c.p. 2400 Rome (Italy); Guerra, A S [Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA Centro Ricerche Casaccia, c.p. 2400 Rome (Italy); Pimpinella, M [Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA Centro Ricerche Casaccia, c.p. 2400 Rome (Italy); Caporali, C [Istituto Nazionale di Metrologia delle Radiazioni Ionizzanti, ENEA Centro Ricerche Casaccia, c.p. 2400 Rome (Italy); Petrucci, A [A.C.O. S. Filippo Neri, U.O. Fisica Sanitaria, Rome (Italy)

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{sub s}, relevant to each chamber considered. The presence of free electrons in the air of the chamber cavity was accounted for in determining k{sub s} by TVA. The determination of k{sub s} was made on the basis of the models for ion recombination proposed in past years by Boag, Hochhaeuser 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{sub 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.

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

International Nuclear Information System (INIS)

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

2014-01-01

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. - Highlights: • An ionization chamber with a novel design was characterized for x-ray beam dosimetry. • This ionization chamber was evaluated in diagnostic radiology qualities. • The characterization tests results were within the recommended limits. • Monte Carlo simulations were employed to evaluate the design of the dosimeter. • The developed prototype is a good alternative for calibration laboratories and clinics

Performance of a parallel plate ionization chamber in beta radiation dosimetry

International Nuclear Information System (INIS)

Antonio, Patricia L.; Caldas, Linda V.E.

2011-01-01

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)

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)

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

International Nuclear Information System (INIS)

Ghilardi, A.J.P.

1988-01-01

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 BF 3 ionization chamber and that new technologies for deposition of the boron layer will produce higher efficiency detectors. (author). 102 refs, 32 fig, 10 tabs

Gridded Ionization Chamber; Camara de ionizacion con reja

Energy Technology Data Exchange (ETDEWEB)

Manero Amoros, F

1962-07-01

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

INVESTIGATION OF THE HUMIDITY EFFECT ON THE FAC-IR-300 IONIZATION CHAMBER RESPONSE.

Science.gov (United States)

Mohammadi, Seyed Mostafa; Tavakoli-Anbaran, Hossein

2018-02-01

The free-air ionization chamber is communicating with the ambient air, therefore, the atmospheric parameters such as temperature, pressure and humidity effect on the ionization chamber performance. The free-air ionization chamber, entitled as FAC-IR-300, that design at the Atomic Energy Organization of Iran, AEOI, is required the atmospheric correction factors for correct the chamber reading. In this article, the effect of humidity on the ionization chamber response was investigated. For this reason, was introduced the humidity correction factor, kh. In this article, the Monte Carlo simulation was used to determine the kh factor. The simulation results show in relative humidities between 30% to 80%, the kh factor is equal 0.9970 at 20°C and 0.9975 at 22°C. From the simulation results, at low energy the energy dependence of the kh factor is significant and with increasing energy this dependence is negligible. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

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

International Nuclear Information System (INIS)

Yoshizumi, Maira T.; Caldas, Linda V.E.

2008-01-01

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 cm 3 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)

Circuit for current measures from ionization chambers

International Nuclear Information System (INIS)

Mello, F.L.V. de; Oliveira, A.H. de; Rezende, R.S.

1992-01-01

The design and the specifications of an ammeters of low cost for small current, IOE-14 Ampere, from ionization chambers or others transducers used in nuclear instrumentation are described. Special attention is given to the integrated electronic components, available in the brazilian market. (C.G.C.)

More realistic simulation of the response of an ionization chamber

International Nuclear Information System (INIS)

Torii, T.; Nozaki, T.; Ando, H.

1994-01-01

In order to study the consequence of geometrical modeling of a finger tip ionization chamber and the difference of the calculated results using two Monte Carlo codes EGS4 and ITS3.0, the energy responses of an ionization chamber have been calculated. In the EGS4 calculation, it has been developed a versatile user code PRESTA-CG to calculate the response of radiation detectors with more complicated geometrical design by the combinatorial geometry (CG) method. This paper presents comparisons of the energy responses between these codes. (author)

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

International Nuclear Information System (INIS)

Mukhtar, A.M.; Samat, S.B.; Mohd Taufik Dolah

2014-01-01

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 N D,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 N D,w deviation together with its standard error SE were calculated. This μ ±SE will be used to measure stability of N D,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 N D,w and safe to be used for radiotherapy treatment. (author)

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

International Nuclear Information System (INIS)

Ellis, W.H.

1975-01-01

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)

Characterization of ionization chambers in double face for X-ray detection systems

International Nuclear Information System (INIS)

Costa, Alessandro M. da; Caldas, Linda V.O.

2000-01-01

Two identical parallel-plate ionization chambers with collecting electrodes of different materials (in order to obtain different energy dependences), developed at Instituto de Pesquisas Energeticas e Nucleares, were tested in low energy X-radiation beams, simulating a special ionization chamber, of double face, in a Tandem system. The purpose of this work is to justify a project of a double face detection system utilizing ionization chambers in Tandem. In relation to conventional methods, this kind of system will provide more efficient and precise absorbed dose in air measurements and radiation effective energy determinations. The results obtained in relation to characteristics of short- and long-term stabilities and angular and energy dependence show that the project is feasible and very appropriate. (author)

The Effects of Ionizing Radiation on the Oral Cavity.

Science.gov (United States)

de Barros da Cunha, Sandra Ribeiro; Ramos, Pedro Augusto Mendes; Nesrallah, Ana Cristina Aló; Parahyba, Cláudia Joffily; Fregnani, Eduardo Rodrigues; Aranha, Ana Cecília Corrêa

2015-08-01

The aim of this study is to present a literature review on the effects of the ionizing radiation from radiotherapy treatment on dental tissues. Among the effects of increasing global life expectancy and longevity of the teeth in the oral cavity, increasing rates of neoplastic diseases have been observed. One of the important treatment modalities for head and neck neoplastic diseases is radiotherapy, which uses ionizing radiation as the main mechanism of action. Therefore, it is essential for dentists to be aware of the changes in oral and dental tissues caused by ionizing radiation, and to develop treatment and prevention strategies. In general, there is still controversy about the effects of ionizing radiation on dental structures. However, qualitative and quantitative changes in saliva and oral microbiota, presence of oral mucositis and radiation-related caries are expected, as they represent the well-known side effects of treatment with ionizing radiation. Points that still remain unclear are the effects of radiotherapy on enamel and dentin, and on their mechanisms of bonding to contemporary adhesive materials. Ionizing radiation has shown important interaction with organic tissues, since more deleterious effects have been shown on the oral mucosa, salivary glands and dentin, than on enamel. With the increasing number of patients with cancer seeking dental treatment before and after head and neck radiotherapy, it is important for dentists to be aware of the effects of ionizing radiation on the oral cavity.

A novel micro liquid ionization chamber for clinical dosimetry

International Nuclear Information System (INIS)

Stewart, K.J.; Seuntjens, J.P.

2002-01-01

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 60 Co beam. The factor k Q 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 mm 3 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 cm 3 RMI Solid Water phantom at 10 cm depth with a 10x10 cm 2 field at the phantom surface. Absorbed dose was determined using an Exradin A12 chamber with an absorbed-dose to water calibration factor for 60 Co established at a

Environmental gamma radiation monitoring system with a large volume air ionization chamber

International Nuclear Information System (INIS)

Duftschmid, K.E.; Strachotinsky, C.; Witzani, J.

1986-01-01

An improved environmental monitoring system has been designed and tested consisting of an ionization chamber with 120 l sensitive volume, operated at atmospheric pressure, and a commercial electrometer amplifier with digital voltmeter. The system is controlled by a desk calculator with printer for automated operation and calculation of dose and doserate. The ionization chamber provides superior dosimetric performance as compared to usual GM-counters and high pressure chambers. The system has been field-tested during the 'European Intercomparison Programme for Environmental Monitoring Instruments' organized by the Commission of the European Communities. (Author)

Ionization chamber circuit arrangement for counterbalancing long-term aging processes

International Nuclear Information System (INIS)

Fischer, H.; Goeldner, R.; Grosse, H.J.; Reinhardt, K.

1985-01-01

The described circuit arrangement changes the amplification of the output signal during the lifetime of the ionization chamber in such a way that the sensitivity of the detector becomes independent of the decreasing activity of the radiation source. It is suitable for ionization flue gas detectors

Characterisation of an ionization chamber of the radioisotope metrology laboratory

International Nuclear Information System (INIS)

Bocca, Gabriel R.; Iglicki, Flora A.

1999-01-01

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)

Air filled ionization chambers and their response to high LET radiation

DEFF Research Database (Denmark)

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

Background Air filled ionization chambers (ICs) are widely used for absolute dosimetry, not only in photon beams but also in beams of heavy charged particles. Within the IC, electron hole pairs are generated by the energy deposition originating from incoming radiation. High-LET particles create......-plate ionization chamber exposed to heavy ions Phys. Med. Biol. 43 3549–58, 1998. ELSAESSER, T. et al.: Impact of track structure on biological treatment planning ion ion radiotherapy. New Journal pf Physics 10. 075005, 2008...

Ionization chamber gradient effects in nonstandard beam configurations

International Nuclear Information System (INIS)

Bouchard, Hugo; Seuntjens, Jan; Carrier, Jean-Francois; Kawrakow, Iwan

2009-01-01

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., P wall , P stem , and P cel ) 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

Fire-detection device with an ionization chamber

Energy Technology Data Exchange (ETDEWEB)

Conforti, F J; Ogden, W L

1974-10-14

The invention fire-detector in which a detecting circuit of adjustable sensitivity is connected to an ionization chamber sensitive to combustion products. An appropriate circuit is adapted to check the operation and to determine if: the apparatus is duly fed with power; the detector is working; and the apparatus is working at the appropriate sensitivity.

Properties of electret ionization chambers for routine dosimetry in photon radiation fields

International Nuclear Information System (INIS)

Doerschel, B.; Pretzsch, G.

1985-01-01

The main properties of photon routine dosemeters are their energy and angular dependence as well as their measuring range and accuracy. The determination of radiation exposure from dosemeter response is based on the choice of an appropriate conversion factor taking into account the influence of body backscattering on the dosemeter response. Measuring range and accuracy of an electret ionization chamber first of all depend on electret stability, methods of charge measurement, and geometry of the chamber. The dosemeter performance is described for an electret ionization chamber which was designed for application to routine monitoring of radiation workers. (author)

Performance tests of a special ionization chamber for X-rays in mammography energy range

Energy Technology Data Exchange (ETDEWEB)

Silva, J.O., E-mail: jonas.silva@ufg.br [Universidade Federal de Goiás (UFG), Goiânia (Brazil). Instituto de Física; Caldas, L.V.E. [Instituto de Pesquisas Energéticas e Nucleares (IPEN-CNEN/SP), São Paulo, SP (Brazil). Centro de Metrologia das Radiações

2017-07-01

A special mammography homemade ionization chamber was developed to be applied for mammography energy range dosimetry. This chamber has a total sensitive volume of 6 cm{sup 3} and is made of a PMMA body and graphite coated collecting electrode. Performance tests as saturation, ion collection efficiency, linearity of chamber response versus air kerma rate and energy dependence were determined. The results obtained with this special homemade ionization chamber are within the limits stated in international recommendations. This chamber can be used in quality control programs of mammography energy range. All measurements were carried out at the Calibration Laboratory of IPEN. (author)

Determination of the Kwall correction factor for a cylindrical ionization chamber to measure air-kerma in 60Co gamma beams

International Nuclear Information System (INIS)

Laitano, R.F.; Toni, M.P.; Pimpinella, M.; Bovi, M.

2002-01-01

The factor K wall to correct for photon attenuation and scatter in the wall of ionization chambers for 60 Co air-kerma measurement has been traditionally determined by a procedure based on a linear extrapolation of the chamber current to zero wall thickness. Monte Carlo calculations by Rogers and Bielajew (1990 Phys. Med. Biol. 35 1065-78) provided evidence, mostly for chambers of cylindrical and spherical geometry, of appreciable deviations between the calculated values of K wall and those obtained by the traditional extrapolation procedure. In the present work an experimental method other than the traditional extrapolation procedure was used to determine the K wall factor. In this method the dependence of the ionization current in a cylindrical chamber was analysed as a function of an effective wall thickness in place of the physical (radial) wall thickness traditionally considered in this type of measurement. To this end the chamber wall was ideally divided into distinct regions and for each region an effective thickness to which the chamber current correlates was determined. A Monte Carlo calculation of attenuation and scatter effects in the different regions of the chamber wall was also made to compare calculation to measurement results. The K wall values experimentally determined in this work agree within 0.2% with the Monte Carlo calculation. The agreement between these independent methods and the appreciable deviation (up to about 1%) between the results of both these methods and those obtained by the traditional extrapolation procedure support the conclusion that the two independent methods providing comparable results are correct and the traditional extrapolation procedure is likely to be wrong. The numerical results of the present study refer to a cylindrical cavity chamber like that adopted as the Italian national air-kerma standard at INMRI-ENEA (Italy). The method used in this study applies, however, to any other chamber of the same type. (author)

Beam tests of ionization chambers for the NuMI neutrino beam

Energy Technology Data Exchange (ETDEWEB)

Robert M. Zwaska et al.

2003-09-25

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

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

International Nuclear Information System (INIS)

Chen Yingtang; Qi Huiquan; Chen Zemin

1995-01-01

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 40 Ca(n,α) and 64 Zn(n,α) reactions

The high-sensitive magnetic levitated electrode ionization chamber of the noncontacting type

International Nuclear Information System (INIS)

Kawaguchi, Toshiro; Yoshimura, Atsushi

1999-01-01

There are two types of ionization chamber using magnetically levitated electrode: one is that by Tanaka et al. and the other, by authors'. The latter lacks the sensitivity relative to the former and thereby to solve the problem, authors made an improvement so that the electrode charge could be readout by noncontact after the leviated electrode was electrified by noncontact for an interval. This new type ionization chamber made it possible to measure the quite low dose radiation with stability and high sensitivity. Actually, the electrode was suspended by the teflon thread fixed on the steel cup levitated magnetically in the ionization chamber of which wall was covered by Al and equipped with an electrostatic charger for the electrode by noncontact. After measurement, the electrode was moved in the Faraday cage placed under the chamber to readout the voltage. For operation conditions of the apparatus, observation was done on the relationship between ionization current by 137 Cs and the applied voltage. For actual measurement, ionizations by low dose γ ray derived from KCl which containing 40 K in a small amount and by Rn at the fine and rainy days were measured. The exposure rate by KCl (500 g bottle) was found to be 12.7 x 10 -10 C/kg·h with the background value of 9.8 x 10 -10 . Rn concentrations in the air were 112.3 and 18.34 Bq/m 3 for 1 hr in the rainy and fine day, respectively, in Fukuoka City. (K.H.)

Dosimetry in VMAT for prostate using ionization chambers of different volumes

International Nuclear Information System (INIS)

Groppo, Daniela P.; Anderson, Ernani; Pavan, Guilherme A.; Caldas, Linda V.E.

2016-01-01

The volumetric modulated arc therapy is one of the most modern radiotherapy techniques. The advents of this modality in the dose delivery can also contribute to errors during the execution of the treatment, therefore various types of quality control are carried out. The individual assessment of dose delivered to the patient is also an important quality control test and required by the current regulations. The objective of this study was to evaluate the use of different volume ionization chambers for dosimetry of VMAT treatments for prostate cancer. Three ionization chambers were evaluated and all of them showed satisfactory results. (author)

Design of an ionization diffusion chamber detector

International Nuclear Information System (INIS)

Sugiarto, S.

1976-01-01

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 (CO 2 solid) temperature is used. This detector is ready for seeing alpha and beta particle tracks. (author)

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

International Nuclear Information System (INIS)

Dohm, O.S.; Christ, G.

2002-01-01

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 60 Co 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.) [de

The physics and chemistry of room-temperature liquid-filled ionization chambers

International Nuclear Information System (INIS)

Holroyd, R.A.

1985-01-01

The properties of excess electrons in non-polar liquids, such as tetramethylsilane and 2,2,4,4-tetramethylpentane, which are suitable for room-temperature liquid-filled ionization chambers are reviewed. Such properties as mobility, ionization yield, conduction band energy, trapping, and the influence of the electric field are considered. (orig.)

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

International Nuclear Information System (INIS)

Kuahara, L.T.; Correa, E.L.; Potiens, M.P.A.

2015-01-01

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

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

International Nuclear Information System (INIS)

Bessa, Ana Carolina Moreira de

2007-01-01

Since the calibration of radiation measurement instruments and the knowledge of their major characteristics are very important subjects, several different types of ionization chambers were inter compared 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: 67 Ga, 201 Tl and 99m Tc; the results obtained were all within the requirements of the national standard CNEN-NE-3.05. In order to complete the range of radiation qualities of the Calibration Laboratory of IPEN, standard radiation beam qualities, radiation protection and low energy radiation therapy levels, were established, according international recommendations. Three methodologies for the calibration of unsealed ionization chambers in X-ray beams were studied and compared. A set of Victoreen ionization chambers, specially designed for use in laboratorial intercomparisons, was submitted to characterization tests. The performance of these Victoreen ionization chambers showed that they are suitable for use in radioprotection beams, because the results obtained agree with international recommendations. However, these Victoreen ionization chambers can be used in radiotherapy and diagnostic radiology beams only with some considerations, since their performance in these beams, especially in relation to the energy dependence and stabilization time tests, did not agree with the international recommendations for dosimeters used in radiotherapy and diagnostic radiology beams. This work presents data on the performance of several types of ionization chambers in different X-ray beams, that may be useful for choosing the appropriate instrument for measurements in ionizing radiation beams. (author)

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

International Nuclear Information System (INIS)

Bessa, Ana Carolina Moreira de

2006-01-01

Since the calibration of radiation measurement instruments and the knowledge of their major characteristics are very important subjects, several different types of ionization chambers were intercompared in terms of their calibration coefficients and their energy dependence, in radiotherapy, diagnostic radiology and radioprotection standard beams. An intercomparison of radionuclide calibrators for nuclear medicine was performed, using three radionuclides: 67 Ga, 201 Tl and 99m Tc; the results obtained were all within the requirements of the national standard CNEN-NE-3.05. In order to complete the range of radiation qualities of the Calibration Laboratory of IPEN, standard radiation beam qualities, radiation protection and low energy radiation therapy levels, were established, according international recommendations. Three methodologies for the calibration of unsealed ionization chambers in X-ray beams were studied and compared. A set of Victoreen ionization chambers, specially designed for use in laboratorial intercomparisons, was submitted to characterization tests. The performance of these Victoreen ionization chambers showed that they are suitable for use in radioprotection beams, because the results obtained agree with international recommendations. However, these Victoreen ionization chambers can be used in radiotherapy and diagnostic radiology beams only with some considerations, since their performance in these beams, especially in relation to the energy dependence and stabilization time tests, did not agree with the international recommendations for dosimeters used in radiotherapy and diagnostic radiology beams. This work presents data on the performance of several types of ionization chambers in different X-ray beams, that may be useful for choosing the appropriate instrument for measurements in ionizing radiation beams. (author)

Application of LabVIEW on Ionization Chamber to Measurement Radiation

International Nuclear Information System (INIS)

Kerdchockchai, P.; Soodprasert, T.; Hoonnivathana, E.; Naemchnthara, P.; Limsuwan, P.; Naemchanthara, K.

2014-01-01

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.

Project, construction and calibration of parallel plate ionization chambers for x-radiation

International Nuclear Information System (INIS)

Albuquerque, M.P.P.

1989-01-01

Two pairs of parallel-plate ionization chambers were projected and constructed. In each pair one of the chambers has a collecting electrode and a guard ring made of graphite and the other, of aluminium. The difference between both pairs is that in only one case screws were used to fix the chamber components. The chambers are made of Lucite with aluminized Mylar entrance windows; they have circular form and are unsealed. All chamber components are easily available. The main chamber characteristics were determined, applying the tests of current leakage, repetitively and long term stability. The energy and angular dependence, and the polarity effect were also studied, obtaining the saturation curves and determining the build-up effect for gamma radiation detection. The chambers were calibrated with low and intermediate energy X-radiation, gamma radiation of sup(60)Co an sup(137)Cs, and beta radiation of sup(90)Sr + sup(90)Y. The obtained results show the viability of utilization of these chambers in radiation dosimetry and the results were compared with those of imported commercial ionization chambers of the secondary standard type. The great difference between the energy dependence of the chambers according to the collecting electrode material, allowed the formation of a Tandem system (constituted by a chamber pair A, C), for the determination of the effective energy and the exposure rate in air of unknown X-radiation fields, in the case of low intermediate energy ranges. (author)

Ion collection efficiency of ionization chambers in electron beams

International Nuclear Information System (INIS)

Garcia, S.; Cecatti, E.R.

1984-01-01

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) [pt

General cavity theory in the dosimetry of X-rays. Experimental study with a high-pressure chamber

International Nuclear Information System (INIS)

Janssens, A.; Eggermont, G.; Jacobs, R.

1978-01-01

Consistent models have been constructed for the calculation of the stopping power ratio in the limiting cases of small and large cavity sizes. The direct application of this theory is inhibited by the lack of data on isotropic backscatter coefficients and the uncertainty in the appropriate interpolation procedure between the limiting cases. An experimental arrangement has been set up to yield confirmation of the theory and to provide the missing information. Measurements have been made of the ionization density in a parallel-plate chamber with gold walls, filled with air pressurized from 1 to 25 atm. The plate separation is 4 mm and the effective energy of the heavily filtered X-rays is 170 keV, such that quite a large of cavity sizes is covered, from about one tenth of the average electron range to about the maximum range. The collecting plate of the chamber consists of a 10 cm dia. collecting electrode surrounded by a 5 cm guard ring, such that no side wall effects occur. Through attenuation of the X-rays in the walls of the pressure vessel, the air mass and the gold foils, a large fluence of secondary photons is produced, which has been calculated with great accuracy. The experimental data and the calculated values of the stopping power ratio (air to gold) show good agreement, within the limits of confidence of the energy absorption coefficients. Further analysis of the data shows the need to use a 24% smaller value for the ratio of absorption coefficients (air to gold), and determines the energy backscatter coefficient of gold (bsub(en)=0.49) and the interpolation procedure. The consequences of applying cavity theory in dosimetry are discussed. (author)

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

CERN Document Server

Nakagawa, A; Yoshida, T

2003-01-01

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

Ionization chambers for monitoring in high-intensity charged particle beams

CERN Document Server

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

2003-01-01

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

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

International Nuclear Information System (INIS)

Andersson, Jonas; Toelli, Heikki

2011-01-01

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

Determination of dose components in mixed gamma neutron fields by use of high pressure ionization chambers

International Nuclear Information System (INIS)

Golnik, N.; Pliszczynski, T.; Wysocka, A.; Zielczynski, M.

1985-01-01

The two ionization chamber method for determination of dose components in mixed γ-neutron field has been improved by increasing gas pressure in the chambers up to some milions pascals. Advantages of high pressure gas filling are the followings: 1) significant reduction of the ratio of neutron-to gamma sensitivity for the hydrogen-free chamber, 2) possibility of sensitivity correction for both chambers by application of appropriate voltage, 3) high sensitivity for small detectors. High-pressure, pen-like ionization chambers have been examined in fields of different neutron sources: a TE-chamber, filled with 0.2 MPa of quasi-TE-gas and a conductive PTFE chamber, filled with 3.1 MPa of CO 2 . The ratio of neutron-to-gamma sensitivity for the PTFE chamber, operated at electrical field strength below 100 V/cm, has not exceeded 0.01 for neutrons with energy below 8 MeV. Formula is presented for calculation of this ratio for any high-pressure, CO 2 -filled ionization chamber. Contribution of gamma component to total tissue dose in the field of typical neutron sources has been found to be 3 to 70%

Pencil beam proton radiography using a multilayer ionization chamber

NARCIS (Netherlands)

Farace, Paolo; Righetto, Roberto; Meijers, Arturs

2016-01-01

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

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.

Optimization of electret ionization chambers for dosimetry in mixed neutron-gamma fields

International Nuclear Information System (INIS)

Doerschel, B.; Pretzsch, G.

1984-01-01

The properties of combination dosemeters consisting of two air-filled electret ionization chambers in mixed neutron-gamma fields have been investigated. The first chamber, polyethylene-walled, is sensitive to neutrons and gamma rays, the second, having walls of teflon, is sensitive to gamma rays only. The properties of the dosemeters are determined by the resulting errors and the measuring range. As both properties depend on the dimensions of the electret ionization chambers they have been taken into account in optimizing the dimensions. The results show that with the use of the dosemeters the effective dose equivalent in mixed neutron-gamma fields can be determined nearly independently of the spectra. The lower detection limit is less than 1 mSv and the maximum uncertainty of dose measurements about 12%. (author)

Ionization chamber for measurements of high-level tritium gas

International Nuclear Information System (INIS)

Carstens, D.H.W.; David, W.R.

1980-01-01

The construction and calibration of a simple ionization-chamber apparatus for measurement of high level tritium gas is described. The apparatus uses an easily constructed but rugged chamber containing the unknown gas and an inexpensive digital multimeter for measuring the ion current. The equipment after calibration is suitable for measuring 0.01 to 100% tritium gas in hydrogen-helium mixes with an accuracy of a few percent. At both the high and low limits of measurements deviations from the predicted theoretical current are observed. These are briefly discussed

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

International Nuclear Information System (INIS)

Pereira, L.C.S.; Navarro, V.C.C.; Navarro, M.V.T.; Macedo, E.M.

2015-01-01

Generally, the half value layer (HVL) is determined by using ionization chambers and aluminum filters. However, some solid-state dosimeters allow simultaneous measurements of X-ray's parameters, among which the HVL. The main objective of this study was to compare the HVL's values indicated by four different solid-state dosimeters, whose values were measured by ionization chambers. The maximum difference found between the two methods was 11.42%, one the solid-state dosimeters, showing that the use these instruments to determine CSR in industrial X-ray should be subject to a more thorough evaluation. (author)

Study on the ionization chamber for thickness measurement

International Nuclear Information System (INIS)

Xue Shili; Miao Qiangwen

1988-01-01

The principle, construction and performances of ionization chambers for measuring the thickness of metal and nonmetal materials are introduced. With them the thickness of thin materials (thickness ranging from 10 to 6000 g/m 2 ), the surface layer thickness of composed materials and the thickness of steel plate (thickness ranging from 0 to 32 kg/m 2 ) are measured effectively

Characterization and Simulation of a New Design Parallel-Plate Ionization Chamber for CT Dosimetry at Calibration Laboratories

Science.gov (United States)

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

2013-12-01

In this work, a new extended-length parallel-plate ionization chamber was tested in the standard radiation qualities for computed tomography established according to the half-value layers defined at the IEC 61267 standard, at the Calibration Laboratory of the Instituto de Pesquisas Energéticas e Nucleares (IPEN). The experimental characterization was made following the IEC 61674 standard recommendations. The experimental results obtained with the ionization chamber studied in this work were compared to those obtained with a commercial pencil ionization chamber, showing a good agreement. With the use of the PENELOPE Monte Carlo code, simulations were undertaken to evaluate the influence of the cables, insulator, PMMA body, collecting electrode, guard ring, screws, as well as different materials and geometrical arrangements, on the energy deposited on the ionization chamber sensitive volume. The maximum influence observed was 13.3% for the collecting electrode, and regarding the use of different materials and design, the substitutions showed that the original project presented the most suitable configuration. The experimental and simulated results obtained in this work show that this ionization chamber has appropriate characteristics to be used at calibration laboratories, for dosimetry in standard computed tomography and diagnostic radiology quality beams.

Collection efficiency of charges in ionization chambers in presence of constant or variable radiation intensity

International Nuclear Information System (INIS)

Decuyper, J.

1970-01-01

The theoretical and experimental study of the collection of carriers built up by ionization in standard chambers, is made by varying the value of different acting parameters. In the presence of constant ionization intensity and under a D.C. and A.C. voltage, the effect of geometry, recombination, diffusion and attachment is analyzed. The compensation of thermal neutron D.C. chambers is equally considered. Under a time dependent ionization intensity and D.C. voltage, is then studied the effect of recombination on current response, and on the collection efficiency of all formed charges. (author) [fr

SU-F-T-310: Does a Head-Mounted Ionization Chamber Detect IMRT Errors?

International Nuclear Information System (INIS)

Wegener, S; Herzog, B; Sauer, O

2016-01-01

Purpose: The conventional plan verification strategy is delivering a plan to a QA-phantom before the first treatment. Monitoring each fraction of the patient treatment in real-time would improve patient safety. We evaluated how well a new detector, the IQM (iRT Systems, Germany), is capable of detecting errors we induced into IMRT plans of three different treatment regions. Results were compared to an established phantom. Methods: Clinical plans of a brain, prostate and head-and-neck patient were modified in the Pinnacle planning system, such that they resulted in either several percent lower prescribed doses to the target volume or several percent higher doses to relevant organs at risk. Unaltered plans were measured on three days, modified plans once, each with the IQM at an Elekta Synergy with an Agility MLC. All plans were also measured with the ArcCHECK with the cavity plug and a PTW semiflex 31010 ionization chamber inserted. Measurements were evaluated with SNC patient software. Results: Repeated IQM measurements of the original plans were reproducible, such that a 1% deviation from the mean as warning and 3% as action level as suggested by the manufacturer seemed reasonable. The IQM detected most of the simulated errors including wrong energy, a faulty leaf, wrong trial exported and a 2 mm shift of one leaf bank. Detection limits were reached for two plans - a 2 mm field position error and a leaf bank offset combined with an MU change. ArcCHECK evaluation according to our current standards also left undetected errors. Ionization chamber evaluation alone would leave most errors undetected. Conclusion: The IQM detected most errors and performed as well as currently established phantoms with the advantage that it can be used throughout the whole treatment. Drawback is that it does not indicate the source of the error.

SU-F-T-310: Does a Head-Mounted Ionization Chamber Detect IMRT Errors?

Energy Technology Data Exchange (ETDEWEB)

Wegener, S; Herzog, B; Sauer, O [University of Wuerzburg, Wuerzburg (Germany)

2016-06-15

Purpose: The conventional plan verification strategy is delivering a plan to a QA-phantom before the first treatment. Monitoring each fraction of the patient treatment in real-time would improve patient safety. We evaluated how well a new detector, the IQM (iRT Systems, Germany), is capable of detecting errors we induced into IMRT plans of three different treatment regions. Results were compared to an established phantom. Methods: Clinical plans of a brain, prostate and head-and-neck patient were modified in the Pinnacle planning system, such that they resulted in either several percent lower prescribed doses to the target volume or several percent higher doses to relevant organs at risk. Unaltered plans were measured on three days, modified plans once, each with the IQM at an Elekta Synergy with an Agility MLC. All plans were also measured with the ArcCHECK with the cavity plug and a PTW semiflex 31010 ionization chamber inserted. Measurements were evaluated with SNC patient software. Results: Repeated IQM measurements of the original plans were reproducible, such that a 1% deviation from the mean as warning and 3% as action level as suggested by the manufacturer seemed reasonable. The IQM detected most of the simulated errors including wrong energy, a faulty leaf, wrong trial exported and a 2 mm shift of one leaf bank. Detection limits were reached for two plans - a 2 mm field position error and a leaf bank offset combined with an MU change. ArcCHECK evaluation according to our current standards also left undetected errors. Ionization chamber evaluation alone would leave most errors undetected. Conclusion: The IQM detected most errors and performed as well as currently established phantoms with the advantage that it can be used throughout the whole treatment. Drawback is that it does not indicate the source of the error.

Characteristics of ionization chambers for intense pulsed x-rays and Co-60 #betta#-rays, (2)

International Nuclear Information System (INIS)

Kanazawa, Tamotsu; Okabe, Shigeru; Fukuda, Kyue; Furuta, Junichiro; Fujino, Takahiro

1981-01-01

Mean ionization currents and pulse figures of parallel plate ionization chambers enclosed with various gases were measured when they were exposed to intense pulsed X-rays and continuous #betta#-rays. Relation between the measured ionization current and the intensity of X-rays was obtained at the applied voltage of 1000 V. In the case of intense pulsed X-rays, ionization current was smaller in comparison with the case of continuous #betta#-rays, under the X-rays of equal intensity. Pulse figures were observed with chambers which were filled with the gases of air and O 2 and they are considered to be caused by the free electrons of these gases. In these cases, polarity effects of the electric field on the pulse figures were not recognized. Various figures and their changes were also observed from chambers filled with He, Ne, N 2 , Ar, kr, and Xe, respectively. Polarity effects were recognized on those pulse figures. (author)

2D convolution kernels of ionization chambers used for photon-beam dosimetry in magnetic fields: the advantage of small over large chamber dimensions

Science.gov (United States)

Khee Looe, Hui; Delfs, Björn; Poppinga, Daniela; Harder, Dietrich; Poppe, Björn

2018-04-01

This study aims at developing an optimization strategy for photon-beam dosimetry in magnetic fields using ionization chambers. Similar to the familiar case in the absence of a magnetic field, detectors should be selected under the criterion that their measured 2D signal profiles M(x,y) approximate the absorbed dose to water profiles D(x,y) as closely as possible. Since the conversion of D(x,y) into M(x,y) is known as the convolution with the ‘lateral dose response function’ K(x-ξ, y-η) of the detector, the ideal detector would be characterized by a vanishing magnetic field dependence of this convolution kernel (Looe et al 2017b Phys. Med. Biol. 62 5131–48). The idea of the present study is to find out, by Monte Carlo simulation of two commercial ionization chambers of different size, whether the smaller chamber dimensions would be instrumental to approach this aim. As typical examples, the lateral dose response functions in the presence and absence of a magnetic field have been Monte-Carlo modeled for the new commercial ionization chambers PTW 31021 (‘Semiflex 3D’, internal radius 2.4 mm) and PTW 31022 (‘PinPoint 3D’, internal radius 1.45 mm), which are both available with calibration factors. The Monte-Carlo model of the ionization chambers has been adjusted to account for the presence of the non-collecting part of the air volume near the guard ring. The Monte-Carlo results allow a comparison between the widths of the magnetic field dependent photon fluence response function K M(x-ξ, y-η) and of the lateral dose response function K(x-ξ, y-η) of the two chambers with the width of the dose deposition kernel K D(x-ξ, y-η). The simulated dose and chamber signal profiles show that in small photon fields and in the presence of a 1.5 T field the distortion of the chamber signal profile compared with the true dose profile is weakest for the smaller chamber. The dose responses of both chambers at large field size are shown to be altered by not

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

International Nuclear Information System (INIS)

Datte, P.; Beche, J.-F.; Haguenauer, M.; Manfredi, P.F.; Manghisoni, M.; Millaud, J.; Placidi, M.; Ratti, L.; Riot, V.; Schmickler, H.; Speziali, V.; Turner, W.

2002-01-01

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

Large magnitude gridded ionization chamber for impurity identification in alpha emitting radioactive samples

International Nuclear Information System (INIS)

Santos, R.N. dos.

1992-01-01

This paper refers to a large magnitude gridded ionization chamber with high resolution used in the identification of α radioactive samples. The chamber and the electrode have been described in terms of their geometry and dimensions, as well as the best results listed accordingly. Several α emitting radioactive samples were used with a gas mixture of 90% Argon plus 10% Methane. We got α energy spectrum with resolution around 22,14 KeV in agreement to the best results available in the literature. The spectrum of α energy related to 92 U 233 was gotten using the ionization chamber mentioned in this work; several values 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 92 U 233 radioactive series. Such results show the possibility of using the chamber mentioned for measurements of α low activity contamination. (author)

Response to 'Comments on 'Ionization chamber volume determination and quality assurance using micro-CT imaging''

International Nuclear Information System (INIS)

McNiven, Andrea L; Holdsworth, David W; Battista, Jerry J; Umoh, Joseph; Kron, Tomas

2009-01-01

Air ionization chamber dosimetry plays a crucial role in international dose calibration for the radiotherapy clinical environment. Micro-CT images of ion chambers can play an important role in quality assurance of these devices by detecting internal geometry, materials and defects non-invasively, as we demonstrated (McNiven et al 2008 Phys. Med. Biol. 53 5029-43). We also suggested that electric-field simulation based upon these accurate chamber-specific 3D images rather than manufacturer blueprints could be valuable in assessing ionometric sensitivity. As recently performed by Ross et al these electric field simulations play a vital role in understanding key components that contribute to the chamber sensitive volume and ionization calibration coefficients. (letter to the editor)

Specification and tests of three prototypes from tissue-equivalent ionization chamber

International Nuclear Information System (INIS)

Teixeira, D.L.; Cardoso, D.O.; Pereira, O.S.; Nobre Filho, L.S.; Cabral, T.S.

1992-01-01

Three prototypes of tissue-equivalent ionization chamber are specified and tested. The results obtained by these prototypes are presented, aiming the determination of operation parameters, defined by IEC 395 standard. (C.G.C.)

Effects of ionization chamber construction on dose measurements in a heterogeneity

International Nuclear Information System (INIS)

Mauceri, T.; Kase, K.

1987-01-01

Traditionally, measurements have been made in heterogeneous phantoms to determine the factors which should be applied to dose calculations, when calculating a dose to a heterogeneous medium. Almost all measurements have relied on relatively thin-walled ion chambers, with no attempt to match ion chamber wall material to the measuring medium. The recent AAPM dosimetry protocol has established that a mismatch between ion chamber wall and phantom material can have an effect on dose measurement. To investigate the affect of this mismatch of ion chamber wall material to phantom material, two parallel-plate ion chambers were constructed. One ion chamber from solid water, for measurements in a solid water phantom and the other from plastic lung material, for measurements in a plastic lung material phantom. Correction factors measured by matching ion chamber to media were compared to correction factors measured by using a thin-walled cavity ion chamber with no regard for matching wall and media for cobalt-60, 6-, 10- and 20-MV photon beams. The results demonstrated that the matching of ion chamber to measuring media can be ignored, provided that a small, approximately tissue-equivalent, thin-walled ion chamber is used for measuring the correction factors

Radiation monitoring in a synchrotron light source facility using magnetically levitated electrode ionization chambers

International Nuclear Information System (INIS)

Ichiki, Hirofumi; Kawaguchi, Toshirou; Utsunomiya, Yoshitomo; Ishibashi, Kenji; Ikeda, Nobuo; Korenaga, Kazuhito

2009-01-01

We developed a highly accurate differential-type automatic radiation dosimeter to measure very low radiation doses. The dosimeter had two ionization chambers, each of which had a magnetically levitated electrode and it was operated in a repetitive-time integration mode. We first installed the differential-type automatic radiation dosimeter with MALICs at a high-energy electron accelerator facility (Kyushu Synchrotron Light Research Center Facility) and measured the background and ionizing radiations in the facility as well as the gaseous radiation in air. In the background dose measurements, the accuracy of the repetitive-time integration-type dosimeter was three times better than that of a commercial ionization chamber. When the radiation dose increased momentarily at the electron injection from the linac to the operating storage ring, the dosimeter with repetitive-time integral mode gave a successful response to the actual dose variation. The gaseous radiation dose in the facility was at the same level as that in Fukuoka City. We confirmed that the dosimeter with magnetically levitated electrode ionization chambers was usable in the accelerator facility, in spite of its limited response when operated in the repetitive-time integration mode. (author)

Track reconstruction in liquid hydrogen ionization chamber

International Nuclear Information System (INIS)

Balbekov, V.I.; Baranov, A.M.; Krasnokutski, R.N.; Perelygin, V.P.; Rasuvaev, E.A.; Shuvalov, R.S.; Zhigunov, V.P.; Lebedenko, V.N.; Stern, B.E.

1979-01-01

It is shown that particle track parameters can be reconstructed by the currents in the anode cells of the ionization chamber. The calculations are carried out for the chamber with 10 cm anode-cathode gap width. For simplicity a two-dimensional chamber model is used. To make the calculations simpler the charge density along the track is considered to be constant and equal to 10 4 electrons/mm. The drift velocity of electrons is assumed to be 5x10 6 cm/s. The anode is devided into cells 2 cm in width. The events in the chamber is defined with the coordinates X and Z of the event vertex, polar angles THETA of each track and track length l. The coordinates x, y and track angle THETA are reconstructed by currents with errors of up to millimetre and milliradian. The reconstruction errors are proportional to noise levels of electronics and also depend on the track geometry and argon purification. The energy resolution of the chamber is calculated for high energy electrons by means of computer program based on a Monter-Carlo method. The conclusion is made that the energy resolution depends on the gap width as a square root. Two ways to solve the track reconstruction problem are considered: 1. the initial charge density is determined by measuring the charges induced in anode strips at some discrete moments of time; 2. the evaluation of the parameters ia made by traditional minimization technique. The second method is applicable only for a not very large number of hypothesis, but it is less time consuming

Design of data acquisition system for 2D-ARRAY ionization chamber detector

International Nuclear Information System (INIS)

He Chaohui; Xing Guilai; Wu Zhifang; Wang Zhentao

2012-01-01

The introduction is given on the design and development of data acquisition system for 2D-ARRAY ionization chamber detector, which is used for dose verification of tumor radiotherapy. The paper describes the structure and the principle of the 2D-ARRAY ionization chamber detector system in detail, and focuses on the discussion on the design process of the detector's data acquisition system and the development of data acquisition system which is constituted by preamplifier, preamplifier control board and data acquisition board. The client can setup the parameters of the detector system via TCP/IP and do data processing such as high speed data collection and acquisition, further operation and so on. (authors)

Alkali suppression within laser ion-source cavities and time structure of the laser ionized ion-bunches

CERN Document Server

Lettry, Jacques; Köster, U; Georg, U; Jonsson, O; Marzari, S; Fedosseev, V

2003-01-01

The chemical selectivity of the target and ion-source production system is an asset for Radioactive Ion-Beam (RIB) facilities equipped with mass separators. Ionization via laser induced multiple resonant steps Ionization has such selectivity. However, the selectivity of the ISOLDE Resonant Ionization Laser Ion-Source (RILIS), where ionization takes place within high temperature refractory metal cavities, suffers from unwanted surface ionization of low ionization potential alkalis. In order to reduce this type of isobaric contaminant, surface ionization within the target vessel was used. On-line measurements of the efficiency of this method is reported, suppression factors of alkalis up to an order of magnitude were measured as a function of their ionization potential. The time distribution of the ion bunches produced with the RILIS was measured for a variety of elements and high temperature cavity materials. While all ions are produced within a few nanoseconds, the ion bunch sometimes spreads over more than 1...

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...

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

International Nuclear Information System (INIS)

Brancaccio, Franco; Dias, Mauro da Silva

2002-01-01

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 (20 th Century Electronics Ltd.), were performed in order to check the system and for validating the project. (author)

Evaluation of functioning of an extrapolation chamber using Monte Carlo method

International Nuclear Information System (INIS)

Oramas Polo, I.; Alfonso Laguardia, R.

2015-01-01

The extrapolation chamber is a parallel plate chamber and variable volume based on the Braff-Gray theory. It determines in absolute mode, with high accuracy the dose absorbed by the extrapolation of the ionization current measured for a null distance between the electrodes. This camera is used for dosimetry of external beta rays for radiation protection. This paper presents a simulation for evaluating the functioning of an extrapolation chamber type 23392 of PTW, using the MCNPX Monte Carlo method. In the simulation, the fluence in the air collector cavity of the chamber was obtained. The influence of the materials that compose the camera on its response against beta radiation beam was also analysed. A comparison of the contribution of primary and secondary radiation was performed. The energy deposition in the air collector cavity for different depths was calculated. The component with the higher energy deposition is the Polymethyl methacrylate block. The energy deposition in the air collector cavity for chamber depth 2500 μm is greater with a value of 9.708E-07 MeV. The fluence in the air collector cavity decreases with depth. It's value is 1.758E-04 1/cm 2 for chamber depth 500 μm. The values reported are for individual electron and photon histories. The graphics of simulated parameters are presented in the paper. (Author)

Status of ionization chambers calibration for radiation therapy in Brazil

Science.gov (United States)

Gonçalves, M.; Joana, G.; Leal, P.; Vasconcelos, R.; do Couto, N.; Teixeira, F. C.; Soares, A. D.; Santini, E. S.; Salata, C.

2018-03-01

CNEN makes a constant effort to keep updated with international standards and national needs to strengthen the radiological protection status of the country. The guidelines related to radiation treatment facilities have been revised in the last five years in order to take in consideration the most relevant aspects of the growing technology as well as to mitigate the accidents or incidents observed in practice. Hence, clinical dosimeters have gained special importance as significant items in Brazilian regulation. In the present work we discuss the importance of inspections from the point of view of equipment dosimetry and instruments quality control. The dosimeter sets based on thimble and well ionization chambers need periodic calibration, and this calibration becomes a fundamental task in order to guarantee the dose prescribed-delivered to patients. Thus Brazilian guidelines enforce the need of at least two sets of clinical dosimeters with thimble chambers calibrated and one set of electrometer with well ionization chamber for hdr equipment. We call attention to the fact that inspections are a very valuable tool in order to enforce the application of guidelines around the country both by enlightening the weaker aspects of facilities concerning radiological protection and by stating in loco that reasons which lead the regulatory body to enforce such guidelines items.

Individual dosemeter with ionization chamber for intervention

International Nuclear Information System (INIS)

Prigent, M.

1982-01-01

The altogether intervention ratemeter-dosemeter is a device for work condition control and for dosimetry of intervention gang in hostile medium. A portable irradiation marker with ionization chamber either carried by staff, either put at the work post, delivers an information function of the surrounding irradiation field in which moves the intervention staff. The information is processed so as the absorbed dose rate and the absorbed dose are given simultaneously. The connection between the marker and the process device is made by a cable (up to 100m) or by radio link [fr

Ionization of H2O molecules through second order collisions in an argon-filled flow ionization chamber

International Nuclear Information System (INIS)

Leonhardt, J.

1976-01-01

In an argon-filled ionization chamber with a constant radionuclide radiation source, the ionization of H 2 O through second order collisions with 3sub(p) 2 states of argon excited by field-accelerated electrons is considered within the range of discharge caused by external potentials under atmospheric pressure. It is found that the logarithm of the change of ionization current is proportional to power 3/2 of the electric field strength. Possible formation mechanisms are discussed. Most probable is the ionization of H 2 O through collision with Ar 2 argon dimers originating from excited metastable atoms as a result of triple collision. The production cross section for H 2 O + has been estimated to be sigmasub(H 2 O) approximately 5x10 -15 . (author)

Prototype development or multi-cavity ion chamber for depth dose measurement

International Nuclear Information System (INIS)

Nayak, M.K.; Sahu, T.K.; Haridas, G.; Bandyopadhyay, Tapas; Tripathi, R.M.; Nandedkar, R.V.

2016-01-01

In high energy electron accelerators, when the electrons interact with vacuum chamber or surrounding structural material, Bremsstrahlung x-rays are produced. It is having a broad spectrum extending up to the electron energies. Dose measured as a function of depth due to electromagnetic cascade will give rise to depth dose curve. To measure the online depth dose profile in an absorber medium, when high energy electron or Bremsstrahlung is incident, a prototype Multi-Cavity Ion Chamber (MCIC) detector is developed. The paper describes the design and development of the MCIC for measurement of depth dose profile

Comparison between AAPM TG-51 and IAEA TRS-398 for plane parallel ionization chambers irradiated by clinical electron beams

International Nuclear Information System (INIS)

Mahmoud, M.A.

2005-01-01

We compared the results of absorbed dose determined at reference conditions according to AAPM T G-51 and IAEA TRS-398 using plane parallel ionization chambers. The study showed agreement between the two protocols for Holt ,Exradin P11, NACP, Attix RMI 449 and Roos ionization chambers. For Markus ionization chambers the absorbed dose calculated using AAPM TG-51 is higher than that calculated using IAEA TRS-398 by 1.8 % for R 5 0 =2 cm and decrease with increased R 5 0 to reach 1.2 % for R 5 0 =20 cm. For Capintec PS-033 ionization chambers the absorbed dose calculated using AAPM TG-51 is constantly higher than that calculated by IAEA TRS-398 by 1.5 %. A theoretical explanation was introduced for these results

Alarm radiation dosimeter with improved integrating pulse ionization chamber and high voltage supply

International Nuclear Information System (INIS)

Borkowski, C.J.; Rochelle, J.M.

1975-01-01

An alarm dosimeter is described which features an improved integrating pulse ionization chamber of the type containing an hermetically sealed gas diode. Improved operation and miniaturization of the chamber are made possible by a ringing choke converter high voltage supply having a ripple-type output that insures discharge of the gas diode. (author)

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

DEFF Research Database (Denmark)

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

2012-01-01

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

RF, Thermal and Structural Analysis of the 201.25 MHz Muon Ionization Cooling Cavity

International Nuclear Information System (INIS)

Virostek, S.; Li, D.

2005-01-01

A finite element analysis has been carried out to characterize the RF, thermal and structural behavior of the prototype 201.25 MHz cavity for a muon ionization cooling channel. A single ANSYS model has been developed to perform all of the calculations in a multi-step process. The high-gradient closed-cell cavity is currently being fabricated for the MICE (international Muon Ionization Cooling Experiment) and MUCOOL experiments. The 1200 mm diameter cavity is constructed of 6 mm thick copper sheet and incorporates a rounded pillbox-like profile with an open beam iris terminated by 420 mm diameter, 0.38 mm thick curved beryllium foils. Tuning is accomplished through elastic deformation of the cavity, and cooling is provided by external water passages. Details of the analysis methodology will be presented including a description of the ANSYS macro that computes the heat loads from the RF solution and applies them directly to the thermal model. The process and results of a calculation to determine the resulting frequency shift due to thermal and structural distortion of the cavity will also be presented

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

International Nuclear Information System (INIS)

Hara, H.; Ohnuma, H.; Hoshi, Y.; Yuta, H.; Abe, K.; Suekane, F.; Neichi, M.; Nakajima, T.; Masuda, K.

1998-01-01

The energy resolutions of 976 keV conversion electrons from a 207 Bi 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

Backscattered radiation into a transmission ionization chamber: Measurement and Monte Carlo simulation

International Nuclear Information System (INIS)

Yoshizumi, Maira T.; Yoriyaz, Helio; Caldas, Linda V.E.

2010-01-01

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

Fitting methods for constructing energy-dependent efficiency curves and their application to ionization chamber measurements

International Nuclear Information System (INIS)

Svec, A.; Schrader, H.

2002-01-01

An ionization chamber without and with an iron liner (absorber) was calibrated by a set of radionuclide activity standards of the Physikalisch-Technische Bundesanstalt (PTB). The ionization chamber is used as a secondary standard measuring system for activity at the Slovak Institute of Metrology (SMU). Energy-dependent photon-efficiency curves were established for the ionization chamber in defined measurement geometry without and with the liner, and radionuclide efficiencies were calculated. Programmed calculation with an analytical efficiency function and a nonlinear regression algorithm of Microsoft (MS) Excel for fitting was used. Efficiencies from bremsstrahlung of pure beta-particle emitters were calibrated achieving a 10% accuracy level. Such efficiency components are added to obtain the total radionuclide efficiency of photon emitters after beta decay. The method yields differences of experimental and calculated radionuclide efficiencies for most of the photon-emitting radionuclides in the order of a few percent

SCALP: Scintillating ionization chamber for ALPha particle production in neutron induced reactions

Science.gov (United States)

Galhaut, B.; Durand, D.; Lecolley, F. R.; Ledoux, X.; Lehaut, G.; Manduci, L.; Mary, P.

2017-09-01

The SCALP collaboration has the ambition to build a scintillating ionization chamber in order to study and measure the cross section of the α-particle production in neutron induced reactions. More specifically on 16O and 19F targets. Using the deposited energy (ionization) and the time of flight measurement (scintillation) with a great accuracy, all the nuclear reaction taking part on this project will be identify.

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

Science.gov (United States)

Unterweger, M P; Fitzgerald, R

2014-05-01

As reported at the ICRM 2011, it was discovered that the source holder used for calibrations in the NIST 4πγ ionization chamber (IC) was not stable. This has affected a large number of half-life measurement results previously reported and used in compilations of nuclear data. Corrections have been made on all of the half-life data based on the assumption that the changes to the ionization chamber response were gradual. The corrections are energy dependent and therefore radionuclide specific. This presentation will review our results and present the recommended changes in half-life values and/or uncertainties. © 2013 Published by Elsevier Ltd.

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)

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)

1997-01-01

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

Neutron-sensitive ionization chamber

International Nuclear Information System (INIS)

Mayer, W.

1978-01-01

The neutron-sensitive ionization chamber which is to be applied for BWRs consists of a cylindrical outer electrode, closed at the ends, and a concentrically arranged inner electrode. It is designed as a hollow tube and coated with uranium on the outside. The reaction space lies between the two electrodes. The electrical connection is obtained through a coaxial cable whose nickel helix is properly intorduced into the inner electrode made of titanium or nickel. The sheathing respectively external conductor of the cable has got the same diameter as the outer electrode and is butt-welded to it. Between the cable helix and the sheathing there is filled Al 2 O 3 powder. The reaction space is sealed against the cable by means of a little tube pushed over the internal conductor resp. the helix. It consists of Ni resp. Al 2 O 3 which is coated on the outside at first by a layer of Al 2 O 3 and a layer of Ni resp. by a metal layer on the inside and on the outside. (DG) [de

Comparison between two pencil-type ionization chambers with sensitive volume length of 30 cm

International Nuclear Information System (INIS)

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

2016-01-01

Computed tomography (CT) for imaging procedures has been growing due to advances in the equipment technology, providing a higher dose to the patient, in relation to other diagnostic radiology tests, resulting in a concern for the patients. The dosimetry in CT is carried out with a pencil-type ionization chamber with sensitive volume length of 10 cm. Studies have shown the underestimation of the dose values. In this work two ionization chambers with the sensitive volume length of 30 cm were developed. They were submitted to the main characterization tests; the results showed to be within the international recommended limits. (author)

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

International Nuclear Information System (INIS)

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

2015-01-01

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

Energy dependence of an ionization chamber with parallel plates in standard gamma and x-radiation fields

International Nuclear Information System (INIS)

Batistella, M.A.; Caldas, L.V.E.

1988-09-01

The characteristics of low energy X-radiation standard fields were determined and the energy dependence of a ionization chamber of the superficial type, with parallel plates and fixed volume, normally utilized in the dosimetry at the Radiotherapy level was studied. The possibility of adaptation of this chamber type for use in gamma radiation dosimetry was verified. Different thickness Lucite build-up caps, from 2.0 up to 5.5 mm, were produced and tested in 60 Co and 137 Cs gamma radiation fields. This type of detector, with the adequate build-up cap, presented a performance comparable to that of the thimble type ionization chamber. It was concluded that it is not necessary to use different kinds of chambers for each high and mean energy interval. The superficial chamber, specially produced to detect low energy X-radiation, may be adapted to detect gamma radiation. (author) [pt

High energy photon reference for radiation protection: technical design of the LINAC beam and ionization chambers; and calculation of monoenergetic conversion coefficients

Directory of Open Access Journals (Sweden)

Dusciac D.

2016-01-01

Full Text Available In this work, we present the results of the first part of a research project aimed at offering a complete response to dosimeters providers and nuclear physicists’ demands for high-energy (6 – 9 MeV photon beams for radiation protection purposes. Classical facilities allowing the production of high-energy photonic radiation (proton accelerators, nuclear reactors are very rare and need large investment for development and use. A novel solution is proposed, consisting in the use of a medical linear accelerator, allowing a significant decrease of all costs.Using Monte Carlo simulations (MCNP5 and PENELOPE codes, a specifically designed electron-photon conversion target allowing for obtaining a high energy photon beam (with an average energy weighted by fluence of about 6 MeV has been built for radiation protection purposes. Due to the specific design of the target, this “realistic” radiation protection high-energy photon beam presents a uniform distribution of air kerma rate at a distance of 1 m, over a 30 × 30 cm2 surface. Two graphite cavity ionizing chambers for ionometric measurements have been built. For one of these chambers, the charge collection volume has been measured allowing for its use as a primary standard. The second ionizing chamber is used as a transfer standard; as such it has been calibrated in a 60Co beam, and in the high energy photon beam for radiation protection.The measurements with these ionizing chambers allowed for an evaluation of the air kerma rate in the LINAC based high-energy photon beam for radiation protection: the values cover a range between 36 mGy/h and 210 mGy/h, compatible with radiation protection purposes.Finally, using Monte Carlo simulations, conversion coefficients from air kerma to dose equivalent quantities have been calculated in the range between 10 keV and 22.4 MeV, for the spectral distribution of the fluence corresponding to the beam produced by the linear accelerator of the LNE-LNHB.

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.

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

Energy Technology Data Exchange (ETDEWEB)

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

2015-11-21

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

Multiple chamber ionization detector

International Nuclear Information System (INIS)

Solomon, E.E.

1980-01-01

A multi-chambered ionisation detector enables the amount of radiation entering each chamber from a single radioactive, eg β, source to be varied by altering the proportion of the source protruding into each chamber. Electrodes define chambers and an extended radioactive source is movable to alter the source length in each chamber. Alternatively, the source is fixed relative to outer electrodes but the central electrode may be adjusted by an attached support altering the chamber dimensions and hence the length of source in each. Also disclosed are a centrally mounted source tiltable towards one or other chamber and a central electrode tiltable to alter chamber dimensions. (U.K.)

Characterization of reticulated vitreous carbon foam using a frisch-grid parallel-plate ionization chamber

Science.gov (United States)

Edwards, Nathaniel S.; Conley, Jerrod C.; Reichenberger, Michael A.; Nelson, Kyle A.; Tiner, Christopher N.; Hinson, Niklas J.; Ugorowski, Philip B.; Fronk, Ryan G.; McGregor, Douglas S.

2018-06-01

The propagation of electrons through several linear pore densities of reticulated vitreous carbon (RVC) foam was studied using a Frisch-grid parallel-plate ionization chamber pressurized to 1 psig of P-10 proportional gas. The operating voltages of the electrodes contained within the Frisch-grid parallel-plate ionization chamber were defined by measuring counting curves using a collimated 241Am alpha-particle source with and without a Frisch grid. RVC foam samples with linear pore densities of 5, 10, 20, 30, 45, 80, and 100 pores per linear inch were separately positioned between the cathode and anode. Pulse-height spectra and count rates from a collimated 241Am alpha-particle source positioned between the cathode and each RVC foam sample were measured and compared to a measurement without an RVC foam sample. The Frisch grid was positioned in between the RVC foam sample and the anode. The measured pulse-height spectra were indiscernible from background and resulted in negligible net count rates for all RVC foam samples. The Frisch grid parallel-plate ionization chamber measurement results indicate that electrons do not traverse the bulk of RVC foam and consequently do not produce a pulse.

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

International Nuclear Information System (INIS)

Bauer, G.; Bieser, F.; Brady, F.P.; Chance, J.C.; Christie, W.F.; Gilkes, M.; Lindenstruth, V.; Lynen, U.; Mueller, W.F.J.; Romero, J.L.; Sann, H.; Tull, C.E.; Warren, P.

1997-01-01

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.)

A multiple sampling ionization chamber for the External Target Facility

International Nuclear Information System (INIS)

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

2015-01-01

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

Experimental determination of the beam quality dependence factors, kQ, for ionization chambers used in photon and electron dosimetry

International Nuclear Information System (INIS)

Guerra, A.S.; Laitano, R.F.; Pimpinella, M.

1995-01-01

Dosimetry in radiotherapy with ionization chambers calibrated in 60 Co gamma beams in terms of absorbed dose to water, D W , can be performed if a factor conventionally denoted as k Q is known. The factor k Q depends on the beam quality and the chamber characteristics. Calculated values of the k Q factors for many types of ionization chamber have been recently published. In this work the experimental determination of the k Q factors for various ionization chambers was performed for 6 MV and 15 MV photon beams and for a 14 MeV electron beam. The k Q factors were determined by a procedure based on relative measurements performed with the ionization chamber and ferrous sulphate solution in 60 Co gamma radiation and accelerator beams, respectively. The experimental k Q values are compared with the calculated values so far published. Theoretical and experimental k Q values are in fairly good agreement. The uncertainty in the experimental k Q factors determined in this work is less than about 1%, that is, appreciably smaller than the uncertainty of about 1.5% reported for the calculated values. (Author)

Determination of the air attenuation and electronic loss for the free air concentric cylinders ionization chamber

International Nuclear Information System (INIS)

Oliveira, Hebert Pinto Silveira de

2010-01-01

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 e ) and air attenuation (k 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)

Stability of A-150 plastic ionization chamber response over a ∼30 year period

International Nuclear Information System (INIS)

Kroc, Thomas K.; Lennox, Arlene J.

2007-01-01

At the NIU Institute for Neutron Therapy at Fermilab, the clinical tissue-equivalent ionization chamber response is measured every treatment day using a cesium source that was configured to match readings obtained at the National Bureau of Standards. Daily measurements are performed in air using the air-to-tissue dose conversion factors given in AAPM Report no. 7. The measured exposure calibration factors have been tabulated and graphed as a function of time from 1978 to present. For A-150 plastic ionization chambers, these factors exhibit a sinusoidal variation with a period of approximately one year and amplitude of ± 1%. This variation, attributable to the hygroscopic nature of A-150 plastic, is correlated with the relative humidity of the facility, and is greater than the humidity corrections for gas described in the literature. Our data suggest that chamber calibration should be performed at least weekly to accommodate these variations

Fabrication of the prototype 201.25 MHZ cavity for a muon ionization cooling experiment

International Nuclear Information System (INIS)

Rimmer, R.A.; Manning, S.; Manus, R.; Phillips, L.; Stirbet, M.; Worland, K.; Wu, G.; Li, D.; MacGill, R.; Staples, J.; Virostek, S.; Zisman, M.S.; Taminger, K.; Hafley, R.; Martin, R.; Summers, D.; Reep, M.

2005-01-01

We describe the fabrication and assembly of the first prototype 201. 25 MHz copper cavity for the muon ionization cooling experiment (MICE). This cavity was developed by the US MUCOOL collaboration and will be tested in the new MUCOOL Test Area at Fermilab. We outline the component and subassembly fabrication steps and the various metal forming and joining methods used to produce the final cavity shape. These include spinning, brazing, TIG welding, electron beam welding, electron beam annealing and deep drawing. Some of the methods developed for this cavity are novel and offer significant cost savings over conventional methods

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

Science.gov (United States)

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

2017-02-01

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

Development of an ionization chamber based high sensitivity detector for the measurement of radiation dose from X-ray whole body scanners

International Nuclear Information System (INIS)

Singh, Sunil K.; Tripathi, S.M.; LijiShaiju; Sathian, V.; Kulkarni, M.S.

2016-01-01

Using walk through metal detectors and undergoing frisking for personals at airports, seaports, railway stations and other sensitive places no longer meets proper security requirements. Now a days use of plastic explosives, drug trafficking or illegal carriage of dangerous items concealed under cloths or body cavities has increased many folds which in many cases is not possible to detect by conventional methods. One of the systems which are capable to overcome the above mentioned difficulties is the use of X-ray based whole body scanners, either transmission type or backscatter type, depending upon the nature of requirement. While using these whole body scanners the person being scanned possesses a radiation risk whose safety aspects can be monitored by following international standards (recommending certain dose limits). In order to check the compliance of these dose limits, the dose per scan received by the person (from these whole body scanners) needs to be measured. A very high sensitive ionization chamber has been designed and fabricated for measuring these extremely low X- ray fields ( few μR) produced by a scanning X-ray beam over a large area. A methodology has been developed to measure exposure per scan using large volume ionization chambers. This value of exposure was used to calculate whole body dose as per the recommendations of ANSI standard for its compliance

Study on dosimetric characteristics of ionizing chambers with an electrostatic relay

International Nuclear Information System (INIS)

Yuryatin, E.N.; Fominykh, V.I.; Shumshurov, V.I.; Tel'tsov, M.V.

1979-01-01

The metrologic characteristics of the ionization integral-pulse dosimeters with the electrostatic relay, IC-5B and IC-14 (ionization chambers) are investigated. The dosimeter sizes are as followi IC-5ng 6B -m diameter, 80 mm height; IC-14 - 42 mm diameter, 67 mm height. The ionization volume is filled with argon. The electrostatic relay converts the charge (or current) of the ionization chamber into the succession of electric pulses and so the charge (or current) measurement comes to the calculation of the pulse number. The dosimeter stability is investigated in the beam of 137 Cs γ-radiation source. Distribution of results of operation for 8 hours does not exceed 3 and 1.2%, for 6 days - 1.5 and 2% respectively for IC-5B and IC-14. Sensitivity rate at the dosimeter rotation about the symmetry axis does not exceed +-2.5% at various effective energies of 137 Cs and 60 Co γ-radiations. At the dosimeter rotation about the axis, perpendicular to the symmetry axis, the dosage sensitivity twice as much at the radiation energy lower than 10O keV. The dosimeter sensitivity in the power range of exposure doze of 0.56-195 R/h changes not more than over 5%. The dosimeter dosage sensitivity to the X-ray radiation with the effective energy of 40 keV exceeds approximately 10 times the dosage sensitivity to 137 Cs γ-radiation. The obtained results are useful at the data analysis on the radiation situation of different cosmic devices

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

International Nuclear Information System (INIS)

Yoshizumi, Maira T.; Caldas, Linda V.E.

2011-01-01

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

Evaluation of a new pencil-type ionization chamber for dosimetry in computerized tomography beams

International Nuclear Information System (INIS)

Castro, Maysa C. de; Neves, Lucio P.; Silva, Natalia F. da; Santos, William de S.; Caldas, Linda V.E.

2014-01-01

For performing dosimetry in computed tomography beams (CT), use is made of a pencil-type ionization chamber, since this has a uniform response to this type of beam. The common commercial chambers in Brazil have a sensitive volume length of 10 cm. Several studies of prototypes of this type of ionization chamber have been conducted, using different materials and geometric configurations, in the Calibration Laboratory Instruments of the Institute of Nuclear and Energy Research (LCI) and these showed results within internationally acceptable limits. These ion chambers of 10 cm are widely used nowadays, however studies have revealed that they have underestimated the dose values. In order to solve this problem, we developed a chamber with sensitive volume length of 30 cm. As these are not yet very common and no study has yet been performed on LCI conditions on their behavior, is important that the characteristics of these dosemeters are known, and the influence of its various components. For your review, we will use the Monte Carlo code Penelope, freely distributed by the IAEA. This method has revealed results consistent with other codes. The results for this new prototype can be used in dosimetry of the CT of the hospitals and calibration laboratories as the LCI

Pre-irradiation effects on ionization chambers used in radiation therapy

International Nuclear Information System (INIS)

McCaffrey, J P; Downton, B; Shen, H; Niven, D; McEwen, M

2005-01-01

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)

A New Approach on Output Current Calculation for Thimble-type Ionization Chamber with Variation of Gamma-ray Irradiation Angle

International Nuclear Information System (INIS)

Kim, Jae Cheon; Kim, Soon Young; Kim, Yong Kyun; Kim, Jong Kyung

2006-01-01

The output current of an ionization chamber is directly connected with the size of the active volume and ion-pair distribution in air volume. Their accurate assessments are significantly important in order to analyze the design characteristics of an ionization chamber and interpret the measurements with it. It has been generally assumed that ion-pairs are generated uniformly in air volume for simplicity although they are not uniformly distributed due to various source and geometry conditions. Ion-pair distribution is mainly dependent on the irradiation source conditions, while active volume is deeply related to the ionization chamber design. Therefore, such assumption should be examined if the ion-pair distribution affects real output current of the active volume defined by electric field. A new analytical approach considering both electric field and ion-pair nonuniformity has been proposed to analyze accurately the design characteristics of an ionization chamber and interpretation of measurements with it. The angular dependence analysis was carried out to validate the new concept for calculation of output current

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

International Nuclear Information System (INIS)

Unterweger, M.P.; Fitzgerald, R.

2014-01-01

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

Recommendations for ionization chamber smoke detectors for commercial and industrial fire protection systems (1988)

International Nuclear Information System (INIS)

1989-01-01

Ionization chamber smoke detectors (ICSDs) utilising a radioactive substance as the source of ionization are used to detect the presence of smoke and hence give early warning of a fire. These recommendations are intended to ensure that the use of ICSDs incorporating radium-226 and americium-241 in commercial/industrial fire protection systems does not give rise to any unnecessary radiation exposure

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

International Nuclear Information System (INIS)

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

2012-01-01

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 252 Cf 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 235 U(n th , f).

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

International Nuclear Information System (INIS)

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

2017-01-01

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

Investigating the contamination of accelerated radioactive beams with an ionization chamber at MINIBALL

CERN Document Server

Zidarova, Radostina

2017-01-01

My summer student project involved the operation and calibration of an ionization chamber, which was used at MINIBALL for investigating and determining the contamination in post-accelerated radioactive beams used for Coulomb excitation and transfer reaction experiments.

Electron equilibrium for parallel plate ionization chambers in gamma radiation fields

International Nuclear Information System (INIS)

Caldas, L.; Albuquerque, M. da P.P.

1989-08-01

Parallel plate ionization chambers, designed and constructed for use in low energy X-radiation fields, were tested in gamma radiation beams ( 6 Co and 137 Cs) of two different Calibration Laboratories, in order to study the electron equilibrium occurrence and to verify the possibility of their use for the detection of the kind of radiation too. (author) [pt

Ionization detector

International Nuclear Information System (INIS)

Solomon, E.E.

1980-01-01

A safe and reliable apparatus for detecting products of combustion and aerosols in the atmosphere was developed which uses a beta source. It is easy to adjust for optimum performance. The ionization detector comprises a double chamber; one of the chambers is the basic sensing chamber. The sensing chamber is ported to both the secondary chambers to account for slow ambient changes in the atmosphere outside of the chamber. The voltages from the ionization chamber are adjusted with electrodes in each chamber. The ionization chamber contains baffles to direct the air to be sensed as well as an electrostatic screen. A unique electronic circuit provides an inexpensive and reliable means for detecting the signal change which occurs in the ionization chamber. The decision level of the alarm circuit can be adjusted to allow for any desired sensitivity. (D.N.)

A study of the response of ionization chambers to mammography beams

International Nuclear Information System (INIS)

Kessler, G.; Burns, D.T.; Buermann, L.; Prez, L.A. de

2007-03-01

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)

Investigation of thermal and temporal responses of ionization chambers in radiation dosimetry.

Science.gov (United States)

AlMasri, Hussein; Funyu, Akira; Kakinohana, Yasumasa; Murayama, Sadayuki

2012-07-01

The ionization chamber is a primary dosimeter that is used in radiation dosimetry. Generally, the ion chamber response requires temperature/pressure correction according to the ideal gas law. However, this correction does not consider the thermal volume effect of chambers. The temporal and thermal volume effects of various chambers (CC01, CC13, NACP parallel-plate, PTW) with different wall and electrode materials have been studied in a water phantom. Measurements were done after heating the water with a suitable heating system, and chambers were submerged for a sufficient time to allow for temperature equilibrium. Temporal results show that all chambers equilibrate quickly in water. The equilibration time was between 3 and 5 min for all chambers. Thermal results show that all chambers expanded in response to heating except for the PTW, which contracted. This might be explained by the differences in the volumes of all chambers and also by the difference in wall material composition of PTW from the other chambers. It was found that the smallest chamber, CC01, showed the greatest expansion. The magnitude of the expansion was ~1, 0.8, and 0.9% for CC01, CC13, and parallel-plate chambers, respectively, in the temperature range of 295-320 K. The magnitude of the detected contraction was <0.3% for PTW in the same temperature range. For absolute dosimetry, it is necessary to make corrections for the ion chamber response, especially for small ion chambers like the CC01. Otherwise, room and water phantom temperatures should remain within a close range.

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

International Nuclear Information System (INIS)

Herk, M. van; Gilhuijs, K.; Dalen, A. van; Ven, P. van de; Fencl, W.

1995-01-01

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

Characterization of an extrapolation chamber for low-energy X-rays: Experimental and Monte Carlo preliminary results

Energy Technology Data Exchange (ETDEWEB)

Neves, Lucio P., E-mail: lpneves@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000 Sao Paulo, SP (Brazil); Silva, Eric A.B., E-mail: ebrito@usp.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000 Sao Paulo, SP (Brazil); Perini, Ana P., E-mail: aperini@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000 Sao Paulo, SP (Brazil); Maidana, Nora L., E-mail: nmaidana@if.usp.br [Universidade de Sao Paulo, Instituto de Fisica, Travessa R 187, 05508-900 Sao Paulo, SP (Brazil); Caldas, Linda V.E., E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN), Comissao Nacional de Energia Nuclear, Av. Prof. Lineu Prestes 2242, 05508-000 Sao Paulo, SP (Brazil)

2012-07-15

The extrapolation chamber is a parallel-plate ionization chamber that allows variation of its air-cavity volume. In this work, an experimental study and MCNP-4C Monte Carlo code simulations of an ionization chamber designed and constructed at the Calibration Laboratory at IPEN to be used as a secondary dosimetry standard for low-energy X-rays are reported. The results obtained were within the international recommendations, and the simulations showed that the components of the extrapolation chamber may influence its response up to 11.0%. - Highlights: Black-Right-Pointing-Pointer A homemade extrapolation chamber was studied experimentally and with Monte Carlo. Black-Right-Pointing-Pointer It was characterized as a secondary dosimetry standard, for low energy X-rays. Black-Right-Pointing-Pointer Several characterization tests were performed and the results were satisfactory. Black-Right-Pointing-Pointer Simulation showed that its components may influence the response up to 11.0%. Black-Right-Pointing-Pointer This chamber may be used as a secondary standard at our laboratory.

Response dependence of a ring ionization chamber response on the size of the X radiation field

International Nuclear Information System (INIS)

Yoshizumi, Maira T.; Caldas, Linda V.E.

2009-01-01

A ring monitor ionization chamber was developed at the IPEN-Sao Paulo, Brazil, fixed on a system of collimators which determine the dimension of the radiation field size. This work verified that the ring chamber response depends on the exponential form with the size of de radiation field

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

International Nuclear Information System (INIS)

Koivunoro, H.; Uusi-Simola, J.; Savolainen, S.; Kotiluoto, P.; Auterinen, I.; Kosunen, A.

2006-01-01

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 60 Co 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 (k Qγ ) for the Mg(Ar) chamber at the FiR 1 beam through computer simulations. In this study, the k Qγ 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 k qγ factors obtained with this method are compared to the sensitivity factors determined with measurements in an accelerator photon beam and to the k Qγ factors published previously. (author)

Specific patient verification of IMRT plans using two-dimensional array of ionization chambers.)

International Nuclear Information System (INIS)

Rodriguez Zayas, Michael; Perez Guevara, Adrian; Reyes Gonzalez, Tommy; Gonzalez Perez, Yelina; Sola Rodriguez, Yeline; Caballero, Roberto; Lopez Lopez, Alberto; Castro Crespo, Diosdado

2009-01-01

The most common procedures to validate treatments with IMRT combine planning and administration which introduces the specific patient approach. IMRT is being introduced in Cuba, so it is a study to use as verification for each IMRT treatment plan with the collapsed beam method (Collapsed beams). We present three case studies to look at different situations and presentation of data. The treatment beam and collapsed obtained with an Elekta Precise linear accelerator and TPS PrecisePLAN respectively. The system used to measure a two-dimensional array of ionization chambers and VeriSoft system, both of the firm PTW. Dummy is used as solid sheets of water. The dose difference is evaluated using the gamma index applied to dose map resulting of the comparison between measured and simulated projections. Also the dose absolute is measured using a cylindrical chamber with United electrometer, which is compare with the results of the TPS. In the cases studied are shown along two perpendicular profiles. Tolerance is taken as the gamma index (5%, 5 mm). The method of collapsed beams under two- dimensional beam ionization chambers has been accepted for verification of IMRT treatments at the Radiotherapy Service of the Hospital Hermanos Ameijeiras. (Author)

Ionizing chamber smoke detectors in implementation of radiation protection standards

International Nuclear Information System (INIS)

1977-01-01

In 1977 the NEA Steering Committee adopted a series of Recommendations for Ionizing Chamber Smoke Detectors (ICSDs) in Implementation of Radiation Protection Standards. The purpose of these recommendations is to permit adoption of a harmonized policy by the competent national authorities concerning the issue of licenses for the manufacture, import, use and disposal of ICSDs while insuring that individual and collective exposure doses are kept as low as is reasonably achievable [fr

Scattering study at free air ionization chamber diaphragm

International Nuclear Information System (INIS)

Santos, Alexandre Lo Bianco dos

2011-01-01

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

An open-flow pulse ionization chamber for alpha spectrometry of large-area samples

International Nuclear Information System (INIS)

Johansson, L.; Roos, B.; Samuelsson, C.

1992-01-01

The presented open-flow pulse ionization chamber was developed to make alpha spectrometry on large-area surfaces easy. One side of the chamber is left open, where the sample is to be placed. The sample acts as a chamber wall and therby defeins the detector volume. The sample area can be as large as 400 cm 2 . To prevent air from entering the volume there is a constant gas flow through the detector, coming in at the bottom of the chamber and leaking at the sides of the sample. The method results in good energy resolution and has considerable applicability in the retrospective radon research. Alpha spectra obtained in the retrospective measurements descend from 210 Po, built up in the sample from the radon daughters recoiled into a glass surface. (au)

Measurement of absorbed dose with a bone-equivalent extrapolation chamber

International Nuclear Information System (INIS)

DeBlois, Francois; Abdel-Rahman, Wamied; Seuntjens, Jan P.; Podgorsak, Ervin B.

2002-01-01

A hybrid phantom-embedded extrapolation chamber (PEEC) made of Solid Water trade mark sign and bone-equivalent material was used for determining absorbed dose in a bone-equivalent phantom irradiated with clinical radiation beams (cobalt-60 gamma rays; 6 and 18 MV x rays; and 9 and 15 MeV electrons). The dose was determined with the Spencer-Attix cavity theory, using ionization gradient measurements and an indirect determination of the chamber air-mass through measurements of chamber capacitance. The collected charge was corrected for ionic recombination and diffusion in the chamber air volume following the standard two-voltage technique. Due to the hybrid chamber design, correction factors accounting for scatter deficit and electrode composition were determined and applied in the dose equation to obtain absorbed dose in bone for the equivalent homogeneous bone phantom. Correction factors for graphite electrodes were calculated with Monte Carlo techniques and the calculated results were verified through relative air cavity dose measurements for three different polarizing electrode materials: graphite, steel, and brass in conjunction with a graphite collecting electrode. Scatter deficit, due mainly to loss of lateral scatter in the hybrid chamber, reduces the dose to the air cavity in the hybrid PEEC in comparison with full bone PEEC by 0.7% to ∼2% depending on beam quality and energy. In megavoltage photon and electron beams, graphite electrodes do not affect the dose measurement in the Solid Water trade mark sign PEEC but decrease the cavity dose by up to 5% in the bone-equivalent PEEC even for very thin graphite electrodes (<0.0025 cm). In conjunction with appropriate correction factors determined with Monte Carlo techniques, the uncalibrated hybrid PEEC can be used for measuring absorbed dose in bone material to within 2% for high-energy photon and electron beams

Double ionization chamber survey meter for the separate measurement of penetrating and non-penetrating dose

International Nuclear Information System (INIS)

Lucas, A.C.

1987-01-01

The full capabilities of an advanced 8-bit microprocessor have been utilized in construction of a wide range, multiplexing survey meter based on dual electrometers and ionization chambers. The ionization chambers are constructed of modular conducting and non-conducting parts in such a way that the angular dependence for measurement of beta radiation is controlled by design. Display functions for the high range instrument include logarithmic or linear analog display, digital display of rate or dose, SI or English units, optionally for either total, penetrating, or non-penetrating dose. The instrument is presently configured to operate in the range 0.1 R/hr to 50,000 R/hr in support of the requirements of Regulatory Guide 19.7

Study of cavity effect in micro-Pirani gauge chamber with improved sensitivity for high vacuum regime

Directory of Open Access Journals (Sweden)

Guohe Zhang

2018-05-01

Full Text Available Ultra-low pressure application of Pirani gauge needs significant improvement of sensitivity and expansion of measureable low pressure limit. However, the performance of Pirani gauge in high vacuum regime remains critical concerns since gaseous thermal conduction with high percentage is essential requirement. In this work, the heat transfer mechanism of micro-Pirani gauge packaged in a non-hermetic chamber was investigated and analyzed compared with the one before wafer-level packaging. The cavity effect, extremely important for the efficient detection of low pressure, was numerically and experimentally analyzed considering the influence of the pressure, the temperature and the effective heat transfer area in micro-Pirani gauge chamber. The thermal conduction model is validated by experiment data of MEMS Pirani gauges with and without capping. It is found that nature gaseous convection in chamber, determined by the Rayleigh number, should be taken into consideration. The experiment and model calculated results show that thermal resistance increases in the molecule regime, and further increases after capping due to the suppression of gaseous convection. The gaseous thermal conduction accounts for an increasing percentage of thermal conduction at low pressure while little changes at high pressure after capping because of the existence of cavity effect improving the sensitivity of cavity-effect-influenced Pirani gauge for high vacuum regime.

The proper calibration and use of pocket ionization chamber in personnel radiation monitoring

International Nuclear Information System (INIS)

Mollah, A.S.

1993-01-01

The PIC (pocket ionization chambers) has often been criticized for its lack of precision and accuracy and its tendency to produce false readings. The direct-reading PICs and other dosimeters have numerous characteristics which influence the dosimetric response in a radiation environment

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)

Cruz E, P.

2001-01-01

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)

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

International Nuclear Information System (INIS)

Oliveira, C.T.; Vivolo, V.; Potiens, M.P.A.

2015-01-01

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

Development of Tandem ionization chambers for use in quality control programs in radiotherapy and diagnostic radiology

International Nuclear Information System (INIS)

Costa, Alessandro Martins da

2003-01-01

A quality control program of X-ray equipment used in diagnostic radiology and radiotherapy requires the check of the beam qualities constancy in terms of the half-value layers. In this work, two special double-faced parallel-plate ionization chambers were developed with inner electrodes of different materials, in tandem system. The different energy response of the two faces of each chamber allowed the development of tandem systems useful for the check of beam qualities constancy. The main application of these ionization chambers will be in quality control programs of diagnostic and therapeutic X-ray equipment for confirmation of half-value layers previously determined by the conventional method. Moreover, the tandem chambers may also be utilized for measurements of air kerma values (and air kerma rates) in kilo voltage X-radiation fields used for diagnostic and therapeutic procedures. The chambers were studied in relation to their operational characteristics, and they were calibrated in X-ray beams in accordance to international recommendations. They presented a very good level of performance. In this developed system no absorbers or special set-ups are necessary. A methodology of use of the chambers in the quality control of diagnostic and therapeutic X-ray systems was established, with the elaboration of the respective procedures. (author)

Potential for the application of compact ionization chambers in AMS at energies below 1 MeV/amu

International Nuclear Information System (INIS)

Forstner, O.; Golser, R.; Kutschera, W.; Michlmayr, L.; Priller, A.; Steier, P.; Wallner, A.

2007-01-01

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. The main challenge in AMS is the detection of rare isotope species in the presence of strong isotopic and isobaric interferences. The task of the ionization chamber is the suppression of the unwanted isobar by separating the ions via their different stopping powers. Results of 3 6C l exposure dating measurements at VERA showed an achieved suppression of the unwanted stable isobar 36 S of 3 x 10 -4 . 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 Δ E and E res . An identification of the incident particles is therefore possible via their different energy loss in the two regions of the chamber. 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. The development of such thin foils with their small energy loss allows the use of gas ionization chambers at energies below 1 MeV per nucleon. To minimize the electronic noise the preamplifiers are mounted directly next to the anodes inside the active detector volume. In this work the setup of the detector will be presented. The performance of the ionization chamber in comparison to other previously used techniques for measuring long-lived AMS-relevant radionuclides including 10 Be, 36 Cl and 41 Ca as well as the use of the detector in the search for the live supernova remnant 244 Pu at VERA will be shown. By the example of

Comparison of ionization chamber calibration for mimeographs in W/Mo and W/Al qualities

International Nuclear Information System (INIS)

Pereira, Lara; Macedo, Eric; Navarro, Marcus; Ferreira, Mario; Garcia, Igor; Pires, Evandro; Leite, Handerson; Navarro, Valeria

2016-01-01

The calibration of ionization chambers for mammography laboratories seek to keep pace with technological advancement of manufacturers who have used new combinations anode/filter in mammography beyond the classic combinations of molybdenum and rhodium. This paper proposes to investigate the equivalence between calibrations of chambers different using the combinations W/Mo and W/Al at LABPROSAUD. The results showed a variation less than 1% on relationship between the calibration coefficients obtained in the evaluated combinations anode/filter for an uncertainty of 2.4%. The excellent performance of the chambers suggests a new possibility of calibration in the mammography quality at LABPROSAUD. (author)

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

International Nuclear Information System (INIS)

RANDRIAMAHOLISOA, C.O.

1999-01-01

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 [fr

Development of a mcirocontroller to the positioning control of an ionization chamber

International Nuclear Information System (INIS)

Manfrini, Francisco A.L.; Rocha, Cristina S.C.; Reis, Renato J.; Oliveira, Arno Heeren de

2007-01-01

It was developed a microcontroller to positioning of ionization chamber with high precision. Considering the high sensitivity of intensity of radiation with the distance source-detector is necessary to develop an eletronics able to control position the detector with high precision. The project was based on microcontroller AT 89S8252 of Atmel company. (author)

SU-E-T-623: Polarity Effects for Small Volume Ionization Chambers in Cobalt-60 Beams

Energy Technology Data Exchange (ETDEWEB)

Xu, Y; Bhatnagar, J; Huq, M Saiful [Department of Radiation Oncology, University of Pittsburgh Cancer Institute and UPMC Cancer Center, Pittsburgh, PA (United States)

2015-06-15

Purpose: To investigate the polarity effects for small volume ionization chambers in {sup 60}Co gamma-ray beams using the Leksell Gamma Knife Perfexion. Methods: Measurements were made for 7 small volume ionization chambers (a PTW 31016, an Exradin A14, 2 Capintec PR0-5P, and 3 Exradin A16) using a PTW UNIDOSwebline Universal Dosemeter and an ELEKTA solid water phantom with proper inserts. For each ion chamber, the temperature/pressure corrected electric charge readings were obtained for 16 voltage values (±50V, ±100V, ±200V, ±300V, ±400V, ±500V, ±600V, ±700V). For each voltage, a five-minute leakage charge reading and a series of 2-minute readings were continuously taken during irradiation until 5 stable signals (less than 0.05% variation) were obtained. The average of the 5 reading was then used for the calculation of the polarity corrections at the voltage and for generating the saturation curves. Results: The polarity effects are more pronounced at high or low voltages than at the medium voltages for all chambers studied. The voltage dependence of the 3 Exradin A16 chambers is similar in shape. The polarity corrections for the Exradin A16 chambers changes rapidly from about 1 at 500V to about 0.98 at 700V. The polarity corrections for the 7 ion chambers at 300V are in the range from 0.9925 (for the PTW31016) to 1.0035 (for an Exradin A16). Conclusion: The polarity corrections for certain micro-chambers are large even at normal operating voltage.

Development of gas ionization chambers with coplanar electrodes for alpha-ray spectrometry

International Nuclear Information System (INIS)

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

2016-01-01

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

On the use of unshielded cables in ionization chamber dosimetry for total-skin electron therapy

International Nuclear Information System (INIS)

Zhe Chen; Agostinelli, Alfred; Nath, Ravinder

1998-01-01

The dosimetry of total-skin electron therapy (TSET) usually requires ionization chamber measurements in a large electron beam (up to 120cmx200cm). Exposing the chamber's electric cable, its connector and part of the extension cable to the large electron beam will introduce unwanted electronic signals that may lead to inaccurate dosimetry results. While the best strategy to minimize the cable-induced electronic signal is to shield the cables and its connector from the primary electrons, as has been recommended by the AAPM Task Group Report 23 on TSET, cables without additional shielding are often used in TSET dosimetry measurements for logistic reasons, for example when an automatic scanning dosimetry is used. This paper systematically investigates the consequences and the acceptability of using an unshielded cable in ionization chamber dosimetry in a large TSET electron beam. In this paper, we separate cable-induced signals into two types. The type-I signal includes all charges induced which do not change sign upon switching the chamber polarity, and type II includes all those that do. The type-I signal is easily cancelled by the polarity averaging method. The type-II cable-induced signal is independent of the depth of the chamber in a phantom and its magnitude relative to the true signal determines the acceptability of a cable for use under unshielded conditions. Three different cables were evaluated in two different TSET beams in this investigation. For dosimetry near the depth of maximum buildup, the cable-induced dosimetry error was found to be less than 0.2% when the two-polarity averaging technique was applied. At greater depths, the relative dosimetry error was found to increase at a rate approximately equal to the inverse of the electron depth dose. Since the application of the two-polarity averaging technique requires a constant-irradiation condition, it was demonstrated that an additional error of up to 4% could be introduced if the unshielded cable

Influence of ambient humidity on the current delivered by air-vented ionization chambers revisited

International Nuclear Information System (INIS)

Poirier, Aurelie; Douysset, Guilhem

2006-01-01

The influence of ambient humidity on the current delivered by a vented ionization chamber has been re-investigated. A Nucletron 077.091 well-type chamber together with a 192 Ir HDR brachytherapy source was enclosed in a climatic test chamber and the current was recorded for various humidity values. Great care has been taken for the design of the experimental setup in order to obtain reliable measurements of currents and humidity values inside the chamber active volume. A ±0.35% linear variation of the measured currents has been observed over a common range of humidities. This result is larger than the expected variation. No formal explanation of such a discrepancy has been found yet, however the present results could lead to a set of recommendations

Influence of ambient humidity on the current delivered by air-vented ionization chambers revisited

Energy Technology Data Exchange (ETDEWEB)

Poirier, Aurelie; Douysset, Guilhem [Laboratoire National Henri Becquerel-LNE, CEA Saclay 91191 Gif-sur-Yvette (France)

2006-10-07

The influence of ambient humidity on the current delivered by a vented ionization chamber has been re-investigated. A Nucletron 077.091 well-type chamber together with a {sup 192}Ir HDR brachytherapy source was enclosed in a climatic test chamber and the current was recorded for various humidity values. Great care has been taken for the design of the experimental setup in order to obtain reliable measurements of currents and humidity values inside the chamber active volume. A {+-}0.35% linear variation of the measured currents has been observed over a common range of humidities. This result is larger than the expected variation. No formal explanation of such a discrepancy has been found yet, however the present results could lead to a set of recommendations.

DOSIS: a computer program for the calculation of absorbed dose in photon and electron beams from ionization measurements in a phantom

Energy Technology Data Exchange (ETDEWEB)

Andreo, P [Kungliga Karolinska Mediko-Kirurgiska Inst., Stockholm (Sweden). Radiofysiska Institutionen; Zaragoza Univ. (Spain). Dept. de Radiologia)

1983-06-15

A computer program has been developed to facilitate the calculation of the absorbed dose in photon and electron beams from measurements with an ionization chamber in a phantom. The generalized Bragg-Gray theory, introduced in the latest recommendations of the Nordic Association of Clinical Physics (NACP), is used throughout the code, including more updated parameter values than those included in the NACP protocol. The calibration factor of the ionization chamber in units of absorbed dose in the air of the cavity can be derived for most of the chambers available today by using experimental data or fitted relations to Monte Carlo results.

The influence of air humidity on an unsealed ionization chamber in a linear accelerator

International Nuclear Information System (INIS)

Blad, B.; Nilsson, P.; Knoeoes, T.

1996-01-01

The safe and accurate delivery of the prescribed absorbed dose is the central function of the dose monitoring and beam stabilization system in a medical linear accelerator. The absorbed dose delivered to the patient during radiotherapy is often monitored by a transmission ionization chamber. Therefore it is of utmost importance that the chamber behaves correctly. We have noticed that the sensitivity of an unsealed chamber in a Philips SL linear accelerator changes significantly, especially during and after the summer season. The reason for this is probably a corrosion effect of the conductive plates in the chamber due to the increased relative humidity during hot periods. We have found that the responses of the different ion chamber plates change with variations in air humidity and that they do not return to their original values when the air humidity is returned to ambient conditions. (author)

Development of a standard operating procedure for mammography equipment used in calibration of ionized chambers

International Nuclear Information System (INIS)

Rodrigues, Yklys Santos; Potiens, Maria da Penha Albuquerque

2011-01-01

Mammography is one widely used technique in the detection of breast cancer. In order to optimize the results achieving better images with lower dose rates, a quality assurance programme must be applied to the equipment. Some control tests use ionization chambers to measure air kerma and other quantities. These tests can only be reliable if the ionization chambers used on them are correctly calibrated. In the present work, it was developed a standard operating procedure (SOP) for quality control tests in a commercial mammography equipment installed in the Calibration Laboratory (LCI) at IPEN - Brazilian Institute for energy and nuclear research). Seven tests were performed in the equipment: Tube voltage and exposition time accuracy and reproducibility, linearity and reproducibility of Air kerma and Half Value Layer (HVL). Then, it was made a measurement of the air kerma in the mammography equipment, using a reference ionization chamber with traceability to a primary laboratory in Germany (Physikalisch-Technische Bundesanstalt - PTB), that was later compared with the air kerma measured in an industrial irradiator. This industrial X-ray generator was recently used in the implementation of X-radiation Standards beams, mammography level, following the Standard IEC 61267. The HVL values varied from 0.36 (25kV) to 0.41 mmA1 (35kV), and the measured air kerma rates were between 9.78 and 17.97 mGy/min. (author)

Calibration and consistency of results of an ionization-chamber secondary standard measuring system for activity

International Nuclear Information System (INIS)

Schrader, Heinrich

2000-01-01

Calibration in terms of activity of the ionization-chamber secondary standard measuring systems at the PTB is described. The measurement results of a Centronic IG12/A20, a Vinten ISOCAL IV and a radionuclide calibrator chamber for nuclear medicine applications are discussed, their energy-dependent efficiency curves established and the consistency checked using recently evaluated radionuclide decay data. Criteria for evaluating and transferring calibration factors (or efficiencies) are given

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

International Nuclear Information System (INIS)

Lolic, B.; Markovic, V.

1961-01-01

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

Analysis of the effective point of measurement of a thimble chamber dosimeter set parallel to the X-ray beam axis

International Nuclear Information System (INIS)

Shimono, Tetsunori; Nanbu, Hidekazu; Koshida, Kichiro; Kikuchi, Yuzo

2007-01-01

To measure the narrow beam used in stereotactic irradiation, installation of the ionization chamber parallel to the X-ray beam axis has been used instead of perpendicular installation. However, the definition of the effective point is a major problem in the parallel installation. In this study, we analyzed the effective point in parallel installation, and considered the prediction and evaluation of measurement point displacement. Relative dosimetry was carried out by installing the thimble ionization chamber in both perpendicular and parallel configurations. We then searched for the measurement point that coincided with the percentage depth dose (PDD) of the perpendicular installation by using the displacement of the measurement point of the parallel installation. We found that the effective point of measurement for relative photon beam dosimetry depends on every detail of the chamber design, including the cavity length and the cavity radius. Moreover, the effective point of measurement also depends on the beam quality and the field size. The amount of effective point displacement for the parallel installation was quantified with the linear expression of tissue peak ratio (TPR) 20, 10 . Our results showed that the amount of effective point displacement can be estimated by the ionization volume of the dosimeter and the energy used. (author)

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)

Hilgers, G.; Bahar-Gogani, J.; Wickman, G.

2002-01-01

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 137 Cs and 60 Co 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

Application of the correction factor for radiation qualityKq in dosimetry with pencil-type ionization chambers using a Tandem system

International Nuclear Information System (INIS)

Fontes, Ladyjane Pereira; Potiens, Maria da Penha Albuquerque

2017-01-01

The pencil-type ionization chamber widely used in computed tomography (CT) dosimetry, is a measuring instrument that has a cylindrical shape and provides uniform response independent of the angle of incidence of ionizing radiation. Calibration and measurements performed with the pencil-type ionization chamber are done in terms of Kerma product in air-length (P k,l ) and values are given in Gy.cm. To obtain the values of (P k,l ) during clinical measurements, the readings performed with the ionization chamber are multiplied by the calibration coefficient (N k,l ) and the correction factor C for quality (K q ) which are given in Calibration certificates of the chambers. The application of the correction factor for radiation quality K q is done as a function of the effective energy of the beam that is determined by the Half Value layer (HVL) calculation. In order to estimate the HVL values in this work, a Tandem system made up of cylindrical aluminum and PMMA absorber layers was used as a low cost and easy to apply method. From the Tandem curve, it was possible to construct the calibration curve and obtain the appropriate K q to the beam of the computed tomography equipment studied. (author)

Flatness of two-dimensional beam profile measured with an ionization chamber array

International Nuclear Information System (INIS)

Stefanovski, Z.

2006-01-01

Open beam profiles are basic dosimetric characteristics for the formation of the dose calculation algorithms parameters and for determination of beam quality. One characteristic of the beam profiles as a measure for the beam quality is the field flatness defined as ratio of the difference of maximum and minimum dose in central 80% of the field to the sum of these doses in the part of the field. The measurements, instead with an ordinary ionization chamber, were performed with a chamber array in two depths (1.6 cm and 10 cm) in water phantom. Nominal photon beam energy was 6 MV and field size was 25 cm x 25 cm on the water surface. Field flatness was in the range of 1-2 % which is in accordance with the data acquired during the acceptance testing and commissioning of the accelerators. with the array chamber the beam profiles can be performed quickly and preciously. These features recommend a chamber array as an excellent tool for periodic quality control of beam profiles. (Author)

Stability of special ionizing chambers for using in programs of quality control in radiotherapy and radiodiagnostic

International Nuclear Information System (INIS)

Afonso, Luciana C.; Caldas, Linda V.E.; Costa, Alessandro M. da

2004-01-01

In this work the response stability of two special parallel-plate ionization chambers, developed at the Calibration Laboratory of IPEN, were tested. The chambers are face doubled, with internal collecting electrodes of different materials (graphite and aluminium), in tandem system, and with air volumes of 0.6 cm 3 and 2.5 cm 3 , for radiotherapy and diagnostic radiology levels, respectively. The results showed that the chambers kept constant their metrological characteristics presenting their usefulness for quality control programs in radiotherapy and diagnostic radiology. (author)

Water calorimetry and ionization chamber dosimetry in an 85-MeV clinical proton beam.

Science.gov (United States)

Palmans, H; Seuntjens, J; Verhaegen, F; Denis, J M; Vynckier, S; Thierens, H

1996-05-01

In recent years, the increased use of proton beams for clinical purposes has enhanced the demand for accurate absolute dosimetry for protons. As calorimetry is the most direct way to establish the absorbed dose and because water has recently been accepted as standard material for this type of beam, the importance of water calorimetry is obvious. In this work we report water calorimeter operation in an 85-MeV proton beam and a comparison of the absorbed dose to water measured by ionometry with the dose resulting from water calorimetric measurements. To ensure a proper understanding of the heat defect for defined impurities in water for this type of radiation, a relative response study was first done in comparison with theoretical calculations of the heat defect. The results showed that pure hypoxic water and hydrogen-saturated water yielded the same response with practically zero heat defect, in agreement with the model calculations. The absorbed dose inferred from these measurements was then compared with the dose derived from ionometry by applying the European Charged Heavy Particle Dosimetry (ECHED) protocol. Restricting the comparison to chambers recommended in the protocol, the calorimeter dose was found to be 2.6% +/- 0.9% lower than the average ionometry dose. In order to estimate the significance of chamber-dependent effects in this deviation, measurements were performed using a set of ten ionization chambers of five different types. The maximum internal deviation in the ionometry results amounted to 1.1%. We detected no systematic chamber volume dependence, but observed a small but systematic effect of the chamber wall thickness. The observed deviation between calorimetry and ionometry can be attributed to a combination of the value of (Wair/e)p for protons, adopted in the ECHED protocol, the mass stopping power ratios of water to air for protons, and possibly small ionization chamber wall effects.

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

International Nuclear Information System (INIS)

Grau Carles, A.; Garcia Gomez-Tejedor, G.

2001-01-01

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

A study to assess the long-term stability of the ionization chamber reference system in the LNMRI

Science.gov (United States)

Trindade Filho, O. L.; Conceição, D. A.; da Silva, C. J.; Delgado, J. U.; de Oliveira, A. E.; Iwahara, A.; Tauhata, L.

2018-03-01

Ionization chambers are used as secondary standard in order to maintain the calibration factors of radionuclides in the activity measurements in metrology laboratories. Used as radionuclide calibrator in nuclear medicine clinics to control dose in patients, its long-term performance is not evaluated systematically. A methodology for long-term evaluation for its stability is monitored and checked. Historical data produced monthly of 2012 until 2017, by an ionization chamber, electrometer and 226Ra, were analyzed via control chart, aiming to follow the long-term performance. Monitoring systematic errors were consistent within the limits of control, demonstrating the quality of measurements in compliance with ISO17025.

A study to assess the long-term stability of the ionization chamber reference system in the LNMRI

Energy Technology Data Exchange (ETDEWEB)

Filho, Octavio L.T.; Conceição, Dayana A. da; Silva, Carlos J. da; Delgado, José U.; Oliveira, Antônio E. de; Iwahara, Akira; Tauhata, Luiz, E-mail: octavio@ird.gov.br [Instituto de Radioproteção e Dosimetria (IRD/CNEN-RJ), Rio de Janeiro, RJ (Brazil)

2017-07-01

Ionization chambers are used as secondary standard in order to maintain the calibration factors of radionuclides in the activity measurements in metrology laboratories. Used as radionuclide calibrator in nuclear medicine clinics to control dose in patients, its long-term performance is not evaluated systematically. A methodology for long-term evaluation for its stability is monitored and checked. Historical data were analyzed via control chart, produced between 2012-2017 by an ionization chamber, electrometer and {sup 226}Ra, aiming to follow the long-term performance. The results for monitoring systematic errors were consistent within the limits of control, demonstrating the quality of measurements in compliance with ISO17025. (author)

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

International Nuclear Information System (INIS)

Tong Boting; Wang Jianqing; Dong Mingli; Tang Peijia; Wang Xiaorong; Lin Cansheng

2000-01-01

Parallel plate grid ionization chamber with cathode area of 300 cm 2 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 244 Cm 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/cm 2

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

Science.gov (United States)

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

2006-04-01

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

A two-dimensional liquid-filled ionization chamber array prototype for small-field verification: characterization and first clinical tests

International Nuclear Information System (INIS)

Brualla-González, Luis; Vicedo, Aurora; Roselló, Joan V; Gómez, Faustino; González-Castaño, Diego M; Gago-Arias, Araceli; Pazos, Antonio; Zapata, Martín; Pardo-Montero, Juan

2012-01-01

In this work we present the design, characterization and first clinical tests of an in-house developed two-dimensional liquid-filled ionization chamber prototype for the verification of small radiotherapy fields and treatments containing such small fields as in radiosurgery, which consists of 2 mm × 2 mm pixels arranged on a 16×8 rectangular grid. The ionization medium is isooctane. The characterization of the device included the study of depth, field-size and dose-rate dependences, which are sufficiently moderate for a good operation at therapy radiation levels. However, the detector presents an important anisotropic response, up to ≃ 12% for front versus near-lateral incidence, which can impact the verification of full treatments with different incidences. In such a case, an anisotropy correction factor can be applied. Output factors of small square fields measured with the device show a small systematic over-response, less than 1%, when compared to unshielded diode measurements. An IMRT radiosurgery treatment has been acquired with the liquid-filled ionization chamber device and compared with film dosimetry by using the gamma method, showing good agreement: over 99% passing rates for 1.2% and 1.2 mm for an incidence-per-incidence analysis; 100% passing rates for tolerances 1.8% and 1.8 mm when the whole treatment is analysed and the anisotropy correction factor is applied. The point dose verification for each incidence of the treatment performed with the liquid-filled ionization chamber agrees within 1% with a CC01 ionization chamber. This prototype has shown the utility of this kind of technology for the verification of small fields/treatments. Currently, a larger device covering a 5 cm × 5 cm area is under development. (paper)

General collection efficiency in liquid iso-octane and tetramethylsilane used as sensitive media in a thimble ionization chamber

International Nuclear Information System (INIS)

Johansson, B.E.; Bahar-Gogani, J.; Wickman, G.

1999-01-01

The general collection efficiency in the dielectric liquids iso-octane (C 8 H 18 ; 2-2-4 trimethylpentane) and tetramethylsilane (Si(CH 3 ) 4 ), used as sensitive media in a thimble liquid ionization chamber (LIC) with a liquid layer thickness of 1 mm, has been studied. Measurements were made for continuous radiation at varying dose rates using 140 keV photons from the decay of 99m Tc for chamber polarizing voltages of 50, 100 and 500 V. The maximum dose rate in each measurement session was about 150 mGy min -1 . The experimental results were compared with theoretical general collection efficiencies calculated by the equation for the general collection efficiency in gases. The results show that the general collection efficiency in a thimble LIC for continuous radiation can be calculated with the equation for the general collection efficiency in gas ionization chambers, using the same chamber geometry correction factors and analogous characteristic ion recombination parameters for the dielectric liquids. (author)

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

International Nuclear Information System (INIS)

Souza, Roberto Salomon de

2004-01-01

With the purpose to guarantee an uncertainty in the dosimetry in radiation therapy, the International Atomic Energy Agency (IAEA) published in 1987 the Technical Reports Series (TRS) number 277 - Absorbed Dose Determination in Photon and Electron Beams - An International Code of Practice -, updated in 1997, when was published its second edition. In 2000 was published the TRS number 398 - Absorbed Dose Determination in External Beam Radiotherapy - An International Code of Practice for Dosimetry Based on Standards of Absorbed Dose to Water. The TRS number 398 brings a great conceptual change in relation to the basis of the formalism, before based on calibration factor in terms of air kerma, and now based on calibration factor in terms of absorbed dose in water. Since the TRS number 398 was published, the Secondary Standard Dosimetry Laboratories are calibrating the user's ionization chambers in terms of absorbed dose to water. However, nor all the clinics in Rio de Janeiro and Brazil have its ionization chambers calibrated in terms of absorbed dose to water. The National Cancer Institute, where the measurements were taken, was the first institution in the Rio de Janeiro to have its ionization chambers calibrated in terms of a new formalism. This work describes a comparison between dosimetry done with a cylindrical ionization chamber under electron beams utilizing the TRS number 277 formalism, based on air kerma, and the TRS number 398 formalism, based on absorbed dose to water, reporting the uncertainties variation of the dosimetry associated to each protocol. (author)

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

International Nuclear Information System (INIS)

Nasr, Amgad

2012-01-01

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 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

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

International Nuclear Information System (INIS)

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

1986-01-01

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 [fr

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

International Nuclear Information System (INIS)

Dias, Daniel Menezes

2010-01-01

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)

Multi-probe ionization chamber system for nuclear-generated plasma diagnostics

International Nuclear Information System (INIS)

Choi, W.Y.; Ellis, W.H.

1990-01-01

This paper reports on the pulsed ionization chamber (PIC) plasma diagnostic system used in studies of nuclear seeded plasma kinetics upgraded to increase the capabilities and extend the range of plasma parameter measurements to higher densities and temperatures. The PIC plasma diagnostic chamber has been provided with additional measurement features in the form of conductivity and Langmuir probes, while the overall experimental system has been fully automated, with computerized control, measurement, data acquisition and analysis by means of IEEE-488 (GPIB) bus control and data transfer protocols using a Macintosh series microcomputer. The design and use of a simple TTL switching system enables remote switching among the various GPIB instruments comprising the multi-probe plasma diagnostic system using software, without the need for a microprocessor. The new system will be used to extend the present study of nuclear generated plasma in He, Ar, Xe, fissionable UF 6 and other fluorine containing gases

Evaluation of an ionization chamber response at small distances during dosimetry of gamma radiation beams

Energy Technology Data Exchange (ETDEWEB)

Afonso, Luciana C.; Potiens, Maria da Penha A.; Caldas, Linda V.E. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)]. E-mail: lafonso@ipen.br; mppalbu@ipen.br; lcaldas@ipen.br

2007-07-01

The beam dosimetry measurements of a gamma irradiator, utilized for calibration of mainly portable radiation monitors, at the Calibration Laboratory of IPEN, have been taken between the source-instrument distance of 1 m and 4 m. Due to the source decay and instruments with higher dose rate ranges, calibrations at distances smaller than 1 m are necessary. For this purpose, a 30 cm{sup 3} ionization chamber calibrated against a secondary standard system was utilized. The use of this chamber is appropriate, because it can be totally irradiated. The behavior of this ionization chamber was studied in terms of: repeatability, stability and current leakage, using a {sup 90}Sr+{sup 90}Y source. The repeatability test presented uncertainties lower than {+-}0.5%. Analyzing the stability results, the variation did not exceed {+-}1.0%. The current leakage did not exceed 0.5% of the reference value. The measurements at the irradiator beams were taken at smaller distances than 1 m (in steps of 10 cm). The distance square inverse law was verified for both {sup 137}Cs and {sup 60}Co sources; the variations did not exceed {+-}5%, according to the ISO 4037-1 standard. (author)

Evaluation of an ionization chamber response at small distances during dosimetry of gamma radiation beams

International Nuclear Information System (INIS)

Afonso, Luciana C.; Potiens, Maria da Penha A.; Caldas, Linda V.E.

2007-01-01

The beam dosimetry measurements of a gamma irradiator, utilized for calibration of mainly portable radiation monitors, at the Calibration Laboratory of IPEN, have been taken between the source-instrument distance of 1 m and 4 m. Due to the source decay and instruments with higher dose rate ranges, calibrations at distances smaller than 1 m are necessary. For this purpose, a 30 cm 3 ionization chamber calibrated against a secondary standard system was utilized. The use of this chamber is appropriate, because it can be totally irradiated. The behavior of this ionization chamber was studied in terms of: repeatability, stability and current leakage, using a 90 Sr+ 90 Y source. The repeatability test presented uncertainties lower than ±0.5%. Analyzing the stability results, the variation did not exceed ±1.0%. The current leakage did not exceed 0.5% of the reference value. The measurements at the irradiator beams were taken at smaller distances than 1 m (in steps of 10 cm). The distance square inverse law was verified for both 137 Cs and 60 Co sources; the variations did not exceed ±5%, according to the ISO 4037-1 standard. (author)

Comparison and uncertainty evaluation of different calibration protocols and ionization chambers for low-energy surface brachytherapy dosimetry

Energy Technology Data Exchange (ETDEWEB)

Candela-Juan, C., E-mail: ccanjuan@gmail.com [Radiation Oncology Department, La Fe University and Polytechnic Hospital, Valencia 46026 (Spain); Vijande, J. [Department of Atomic, Molecular, and Nuclear Physics, University of Valencia, Burjassot 46100, Spain and Instituto de Física Corpuscular (UV-CSIC), Paterna 46980 (Spain); García-Martínez, T. [Radiation Oncology Department, Hospital La Ribera, Alzira 46600 (Spain); Niatsetski, Y.; Nauta, G.; Schuurman, J. [Elekta Brachytherapy, Veenendaal 3905 TH (Netherlands); Ouhib, Z. [Radiation Oncology Department, Lynn Regional Cancer Center, Boca Raton Community Hospital, Boca Raton, Florida 33486 (United States); Ballester, F. [Department of Atomic, Molecular, and Nuclear Physics, University of Valencia, Burjassot 46100 (Spain); Perez-Calatayud, J. [Radiation Oncology Department, La Fe University and Polytechnic Hospital, Valencia 46026, Spain and Department of Radiotherapy, Clínica Benidorm, Benidorm 03501 (Spain)

2015-08-15

Purpose: A surface electronic brachytherapy (EBT) device is in fact an x-ray source collimated with specific applicators. Low-energy (<100 kVp) x-ray beam dosimetry faces several challenges that need to be addressed. A number of calibration protocols have been published for x-ray beam dosimetry. The media in which measurements are performed are the fundamental difference between them. The aim of this study was to evaluate the surface dose rate of a low-energy x-ray source with small field applicators using different calibration standards and different small-volume ionization chambers, comparing the values and uncertainties of each methodology. Methods: The surface dose rate of the EBT unit Esteya (Elekta Brachytherapy, The Netherlands), a 69.5 kVp x-ray source with applicators of 10, 15, 20, 25, and 30 mm diameter, was evaluated using the AAPM TG-61 (based on air kerma) and International Atomic Energy Agency (IAEA) TRS-398 (based on absorbed dose to water) dosimetry protocols for low-energy photon beams. A plane parallel T34013 ionization chamber (PTW Freiburg, Germany) calibrated in terms of both absorbed dose to water and air kerma was used to compare the two dosimetry protocols. Another PTW chamber of the same model was used to evaluate the reproducibility between these chambers. Measurements were also performed with two different Exradin A20 (Standard Imaging, Inc., Middleton, WI) chambers calibrated in terms of air kerma. Results: Differences between surface dose rates measured in air and in water using the T34013 chamber range from 1.6% to 3.3%. No field size dependence has been observed. Differences are below 3.7% when measurements with the A20 and the T34013 chambers calibrated in air are compared. Estimated uncertainty (with coverage factor k = 1) for the T34013 chamber calibrated in water is 2.2%–2.4%, whereas it increases to 2.5% and 2.7% for the A20 and T34013 chambers calibrated in air, respectively. The output factors, measured with the PTW chambers

Application of patent BR102013018500-0 in well type ionization chambers

International Nuclear Information System (INIS)

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

2015-01-01

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

The effect of build-up cap materials on the response of an ionization chamber to 60Co gamma rays

International Nuclear Information System (INIS)

Rocha, M.P.O.; Almeida, C.E. de

1993-01-01

Knowledge of the effect of wall and build-up cap materials on ionization chamber response is necessary to determine absorbed dose in a medium using a calibration factor based on exposure or kerma in air. Attenuation and scattering effects of 60 Co gamma rays in the ionization chamber wall and build-up cap, as well as their non-equivalence to air, were studied with an OFS ionization chamber (Delrin wall) and a set of build-up caps specially built for this purpose. Results for a specific material were plotted as functions of wall and cap total thickness, extrapolated to zero wall thickness, then corrected for mean centre of electron production in the wall (= 0.136 g cm -2 ). Correction factors for a specific thickness were analysed in relation to cap material, and to relative responses compared with values calculated by using AAPM, SEFM and IAEA formalisms for cap effects. A Monte Carlo calculation was performed to compare the experimental and theoretical values. Calculations showed an agreement within 0.1% with experimental values and a wall effect of approximately 1.6%. (Author)

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

NARCIS (Netherlands)

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

2015-01-01

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

Development of an optical digital ionization chamber

International Nuclear Information System (INIS)

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

Investigations of the signal production in liquid-ionization-chambers by the passage of strongly ionizing particles and a now theoretical description of recombination

International Nuclear Information System (INIS)

Supper, R.

1991-12-01

Starting from the original Onsager-theory an extended theory is presented describing the recombination of charge carriers and of signal production in TMS (tetramethylsilane) liquid ionization chambers. The shielding by the impurities of the liquid is explicitly taken into account. By dedicated measurements various parameter dependencies of the theory are checked and the parameter values are experimentally determined. The studies comprise test procedures of the TMS chamber operation and are in context of a hadron calorimeter set up of the cosmic ray experiment KASCADE. (orig.) [de

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

Construction, calibration and test of an ionization chamber for exposure measurement of x and gamma radiation in region from 40 keV to 1250 keV

International Nuclear Information System (INIS)

Campos, C.A.A.L.

1982-01-01

An unsealed thimble ionization chamber with connecting cable was designed, manufactured and tested at the IRD=CNEN, for exposure or exposure rate measurement of X or gamma rays in the energy range from 40 KeV up to Cobalt-60. Recommendations given by IEC, TC-62 (1974) were used as acceptance tests of the ionization chamber for use as a tertiary standard (field class instruments) in radiation therapy. In addition, intercomparison with commercially available chambers of reference class type were carried out in respect to field size dependence, energy dependence, short and long term stability. The results of those tests indicated the usefulness of the developed ionization chamber as a tertiary standard. (author)

IAEA/SSDL intercomparison of calibration factors for therapy level ionization chambers

International Nuclear Information System (INIS)

Lu Jilong; Cheng Jinsheng; Guo Zhaohui; Li Kaibao

2005-01-01

Objective: By participating in IAEA-SSDL intercomparison, a dose to water calibration factor was introduced in order to check the measuring accuracy of 60 Co radiotherapy dose level standard and ensure the reliability and consistency of our calibration. Methods: The authors carried out both air kerma and absorbed dose to water calibrations against 60 Co γ-rays for one of our field class ionization chambers, and sent the results together with the chamber to IAEA dosimetry laboratory for calibration, then IAEA calibrated it and gave the deviation of the intercomparison. Results: The deviation of our air kerma calibration factors is -0.5%, and the deviation of our absorbed dose to water calibration factors is 0.4%. Conclusion: The deviation of calibration factors between IAEA and SSDL should be no more than ±1.5%. Therefore, the result of this intercomparison is considered satisfactory. (authors)

Investigation of parameters of the working substance - low temperature plasma in the ionization resonator chamber of the RF reactive engine

International Nuclear Information System (INIS)

Vdovin, V.S.; Zajtzev, B.V.; Kobetz, A.F.; Bomko, V.A.; Rashkovan, V.M.; Bazyma, L.A.; Belokon, V.I.

2003-01-01

This paper is the extension of investigations of the RF engine designed for orientation and stabilization of the spacecrafts orbit, and it is undertaken for measuring of plasma parameters of RF discharge in the ionization resonator chamber. The experiments were performed at the frequency of 80 MHz on the model engine, in which a length of coaxial line with shortening capacities at the ends was used as the ionization resonator chamber. As the result of the experiments, conditions of the RF discharge ignition in the resonator chamber are studied; dependencies of plasma density and temperature versus applied power and working body pressure are obtained for various gases. The measurements of the thrust were performed at the special-purpose test bench

Application of the correction factor for radiation qualityK{sub q} in dosimetry with pencil-type ionization chambers using a Tandem system

Energy Technology Data Exchange (ETDEWEB)

Fontes, Ladyjane Pereira; Potiens, Maria da Penha Albuquerque, E-mail: lpfontes@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2017-11-01

The pencil-type ionization chamber widely used in computed tomography (CT) dosimetry, is a measuring instrument that has a cylindrical shape and provides uniform response independent of the angle of incidence of ionizing radiation. Calibration and measurements performed with the pencil-type ionization chamber are done in terms of Kerma product in air-length (P{sub k,l}) and values are given in Gy.cm. To obtain the values of (P{sub k,l}) during clinical measurements, the readings performed with the ionization chamber are multiplied by the calibration coefficient (N{sub k,l}) and the correction factor C for quality (K{sub q}) which are given in Calibration certificates of the chambers. The application of the correction factor for radiation quality K{sub q} is done as a function of the effective energy of the beam that is determined by the Half Value layer (HVL) calculation. In order to estimate the HVL values in this work, a Tandem system made up of cylindrical aluminum and PMMA absorber layers was used as a low cost and easy to apply method. From the Tandem curve, it was possible to construct the calibration curve and obtain the appropriate K{sub q} to the beam of the computed tomography equipment studied. (author)

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

International Nuclear Information System (INIS)

Aleksakov, A.N.; Emel'yanov, I.Ya.; Nikolaev, E.V.; Panin, V.M.; Podlazov, L.N.; Rogova, V.D.

1987-01-01

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

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)

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

International Nuclear Information System (INIS)

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.

2015-01-01

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 10,13,15 C+ 12 C fusion reactions at energies around the Coulomb barrier

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.

TH-AB-201-08: Ion Chamber Dose Measurements - Problems with the Temperature-Pressure Correction Factor

Energy Technology Data Exchange (ETDEWEB)

Bourgouin, A [Carleton University, Ottawa, Ontario (Canada); McEwen, M [National Research Council, Ottawa, ON (Canada)

2016-06-15

Purpose: To investigate the behavior of ionization chambers over a wide pressure range. Methods: Three cylindrical and two parallel-plate designs of ion chamber were investigated. The ion chambers were placed in vessel where the pressure was varied from atmospheric (101 kPa) down to 5 kPa. Measurements were made using 60Co and high-energy electron beams. The pressure was measured to better than 0.1% and multiple data sets were obtained for each chamber at both polarities to investigate pressure cycling and dependency on the sign of the charge collected. Results: For all types of chamber, the ionization current, corrected using the standard PTP, showed a similar behaviour. Deviations from the standard theory were generally small for Co-60 but very significant for electron beams, up to 20 % below P = 10 kPa. The effect was found to be always larger when collecting negative charge, suggesting a dependence on free-electron collection. The most likely source of such electrons is low-energy electrons emitted from the electrodes. This signal would be independent of air pressure within the chamber cavity. The data was analyzed to extract this signal and it was found to be a non-negligible component of the ionization current at atmospheric pressure. In the case of the parallel plate chambers, the effect was approximately 0.25 %. For the cylindrical chambers the effect was larger - up to 1.2 % - and dependent on the chamber type, which would be consistent with electron emission from different wall materials. For the electron beams, the correction factor was dependent on the electron energy and approximately double that observed in 60Co. Conclusion: Measurements have indicated significant deviations of the standard pressure correction that are consistent with electron emission from chamber electrodes. This has implications for both primary standard and reference ion chamber-based dosimetry.

Determination of absorbed dose calibration factors for therapy level electron beam ionization chambers.

Science.gov (United States)

McEwen, M R; Williams, A J; DuSautoy, A R

2001-03-01

Over several years the National Physical Laboratory (NPL) has been developing an absorbed dose calibration service for electron beam radiotherapy. To test this service, a number of trial calibrations of therapy level electron beam ionization chambers have been carried out during the last 3 years. These trials involved 17 UK radiotherapy centres supplying a total of 46 chambers of the NACP, Markus, Roos and Farmer types. Calibration factors were derived from the primary standard calorimeter at seven energies in the range 4 to 19 MeV with an estimated uncertainty of +/-1.5% at the 95% confidence level. Investigations were also carried out into chamber perturbation, polarity effects, ion recombination and repeatability of the calibration process. The instruments were returned to the radiotherapy centres for measurements to be carried out comparing the NPL direct calibration with the 1996 IPEMB air kerma based Code of Practice. It was found that, in general, all chambers of a particular type showed the same energy response. However, it was found that polarity and recombination corrections were quite variable for Markus chambers-differences in the polarity correction of up to 1% were seen. Perturbation corrections were obtained and were found to agree well with the standard data used in the IPEMB Code. The results of the comparison between the NPL calibration and IPEMB Code show agreement between the two methods at the +/-1% level for the NACP and Farmer chambers, but there is a significant difference for the Markus chambers of around 2%. This difference between chamber types is most likely to be due to the design of the Markus chamber.

Determination of high level absorbed dose in a 60Co gamma ray field with ionization chambers

International Nuclear Information System (INIS)

Zhongying Li; Benjiang Mao; Lu Zhang

1995-01-01

This paper relates to the principles and methods for determining the absorbed dose of high energy photons radiation with ionization chambers, and its shows the doserate results of high level 60 Co γ-rays in water measured with Farmer chambers. The results with two kinds of chambers at a same point are consistent within 0.3%, and the total uncertainty is less than ± 4%. In the domestic intercomparison on determining high level absorbed dose in which 12 laboratories participated, the deviation of our result from the mean result of the intercomparison is -0.04% [Chen Yundong (1992). Summing up report on a high level absorbed dose intercomparison (in Chinese)]. (author)

A low-pressure cloud chamber to study the spatial distribution of ionizations

International Nuclear Information System (INIS)

Hodges, D.C.; Marshall, M.

1977-01-01

To further the understanding of the biological effects of radiation a knowledge of the spatial distribution of ionizations in small volumes is required. A cloud chamber capable of resolving the droplets formed on individual ions in the tracks of low-energy electrons has been constructed. It is made to high-vacuum specifications and contains a mixture of permanent gases and vapours, unsaturated before expansion, at a total pressure of 10 kPa. Condensation efficiencies close to 100% are obtained without significant background from condensation on uncharged particles and molecular aggregates. This paper describes the chamber, associated equipment and method of operation and discusses the performance of the system. Photographs of the droplets produced from the interaction of low-energy X-rays in the chamber gas for various modes of operation are presented. The mean energy loss per ion pair for electrons produced by the interaction of Al X-rays in the chamber gas (8130 Pa H 2 , 700 Pa C 2 H 5 OH, 690 Pa H 2 O, 400 Pa He, 70 Pa air) has been measured as 29.8 +- 0.7 eV per ion pair compared with a calculated value of 29.6 +- 0.4 eV per ion pair. (author)

Apparatus and process for passivating an SRF cavity

Science.gov (United States)

Myneni, Ganapati Rao; Wallace, John P

2014-12-02

An apparatus and process for the production of a niobium cavity exhibiting high quality factors at high gradients is provided. The apparatus comprises a first chamber positioned within a second chamber, an RF generator and vacuum pumping systems. The process comprises placing the niobium cavity in a first chamber of the apparatus; thermally treating the cavity by high temperature in the first chamber while maintaining high vacuum in the first and second chambers; and applying a passivating thin film layer to a surface of the cavity in the presence of a gaseous mixture and an RF field. Further a niobium cavity exhibiting high quality factors at high gradients produced by the method of the invention is provided.

National pattern for the realization of the unit of the dose speed absorbed in air for beta radiation. (Method: Ionometer, cavity of Bragg-Gray implemented in an extrapolation chamber with electrodes of variable separation, exposed to a field of beta radiation of 90Sr/90Y)

International Nuclear Information System (INIS)

Alvarez R, M. T.; Morales P, J. R.

2001-01-01

From the year of 1987 the Department of Metrology of the ININ, in their Secondary Laboratory of Calibration Dosimetric, has a patron group of sources of radiation beta and an extrapolation chamber of electrodes of variable separation.Their objective is to carry out of the unit of the dose speed absorbed in air for radiation beta. It uses the ionometric method, cavity Bragg-Gray in the extrapolation chamber with which it counts. The services that offers are: i) it Calibration : Radioactive Fuentes of radiation beta, isotopes: 90 Sr/ 90 Y; Ophthalmic applicators 9 0 S r/ 90 Y; Instruments for detection of beta radiation with to the radiological protection: Ionization chambers, Geiger-Muller, etc.; Personal Dosemeters. ii) Irradiation with beta radiation of materials to the investigation. (Author)

Relative dosimetry of photon beam of 6 MV with a liquid ionization chamber

International Nuclear Information System (INIS)

Benitez Villegas, E. M.; Casado Villalon, F. J.; Martin-Cueto, J. A.; Caudepon Moreno, F.; Garcia Pareja, S.; Galan Montenegro, P.

2011-01-01

The increasing use of reduced size fields in the special techniques of treatment generates regions with high dose gradients. It therefore requires the use of detectors that present high spatial resolution. The aim of this study is to compare the dosimetric measurements obtained with a liquid ionization chamber PTW MicroLion recently acquired with other commonly used detectors for a photon beam of 6 MV linear electron accelerator Varian 600DBX.

OPAL Jet Chamber Prototype

CERN Multimedia

OPAL was one of the four experiments installed at the LEP particle accelerator from 1989 - 2000. OPAL's central tracking system consists of (in order of increasing radius) a silicon microvertex detector, a vertex detector, a jet chamber, and z-chambers. All the tracking detectors work by observing the ionization of atoms by charged particles passing by: when the atoms are ionized, electrons are knocked out of their atomic orbitals, and are then able to move freely in the detector. These ionization electrons are detected in the dirfferent parts of the tracking system. This piece is a prototype of the jet chambers

Ionization detection system for aerosols

International Nuclear Information System (INIS)

Jacobs, M.E.

1977-01-01

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 utilizes a measuring ionization chamber which is modified to minimize false alarms and reductions in sensitivity resulting from changes in ambient temperature. In the preferred form of the modification, an annular radiation shield is mounted about the usual radiation source provided to effect ionization in the measuring chamber. The shield is supported by a bimetallic strip which flexes in response to changes in ambient temperature, moving the shield relative to the source so as to vary the radiative area of the source in a manner offsetting temperature-induced variations in the sensitivity of the chamber. 8 claims, 7 figures

Air density dependence of the response of the PTW SourceCheck 4pi ionization chamber for 125I brachytherapy seeds.

Science.gov (United States)

Torres Del Río, J; Tornero-López, A M; Guirado, D; Pérez-Calatayud, J; Lallena, A M

2017-06-01

To analyze the air density dependence of the response of the new SourceCheck 4pi ionization chamber, manufactured by PTW. The air density dependence of three different SourceCheck 4pi chambers was studied by measuring 125 I sources. Measurements were taken by varying the pressure from 746.6 to 986.6hPa in a pressure chamber. Three different HDR 1000 Plus ionization chambers were also analyzed under similar conditions. A linear and a potential-like function of the air density were fitted to experimental data and their achievement in describing them was analyzed. SourceCheck 4pi chamber response showed a residual dependence on the air density once the standard pressure and temperature factor was applied. The chamber response was overestimated when the air density was below that under normal atmospheric conditions. A similar dependence was found for the HDR 1000 Plus chambers analyzed. A linear function of the air density permitted a very good description of this residual dependence, better than with a potential function. No significant variability between the different specimens of the same chamber model studied was found. The effect of overestimation observed in the chamber responses once they are corrected for the standard pressure and temperature may represent a non-negligible ∼4% overestimation in high altitude cities as ours (700m AMSL). This overestimation behaves linearly with the air density in all cases analyzed. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

Experimental study of the counting loss in an ionization chamber in pulsed radiation fields

International Nuclear Information System (INIS)

Goncalez, O.L.; Yanagihara, L.S.; Veissid, V.L.C.P.; Herdade, S.B.; Teixeira, A.N.

1983-01-01

The behavior of an ionization chamber gamma ray monitor in a pulsed radiation field at a linear electron accelerator facility was studied experiementally. A loss of sensitivity was observed as expected due to the pulsed nature of the radiation. By fitting the experiemental data to semi-empirical expressions, parameters for the correction of the counting efficiency were obtained. (Author) [pt

Proton beam dosimetry: a comparison between a plastic scintillator, ionization chamber and faraday cup

International Nuclear Information System (INIS)

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

2010-01-01

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

Determination of self-absorption coefficient in measurement of solid sample activity using 4π ionization chamber

International Nuclear Information System (INIS)

Dryak, P.

1982-01-01

Computation based on the Monte Carlo method was tested for a 4π cylindrical ionization chamber with a detection volume of 7 litres, filled with argon. The sources are placed in the geometrical centre. The correction coefficient for self-absorption was determined as being the ratio of ionization currents induced by a source of finite size and by a massless point source. A flowchart of the program is given. The computations were experimentally tested for cylindrical sources of aqueous 137 Cs and 57 Co solutions. (M.D.)

Evaluating the variation of response of ionizing chamber type pencil for different collimators

International Nuclear Information System (INIS)

Andrade, Lucio das Chagas de; Peixoto, Jose Guilherme Pereira

2014-01-01

The pencil ionization chamber is used in dosimetric procedures for X-ray beams in the energy range of a scanner. Calibration of such camera is still being extensively studied because the procedure is different from the others. To study the variation of response of the camera for different collimators was analyzed three different collimators. It was found that among the other showed the best response was the opening of 30 mm. (author)

Construction, calibration and testing of a ionization chamber for exposure measurement of X and gamma rays in the energy range from 40 keV up to 1250KEV

International Nuclear Information System (INIS)

Campos, Carlos A.A. Lima

1982-01-01

An unsealed thimble ionization chamber with connecting cable was designed, manufactured and tested at the IRD/CNEN, for exposure or exposure rate measurement of X or gamma rays in the energy range from 40 keV up to Cobalt-60. Recommendations given by IEC,TC-62(1974) were used as acceptance tests of the ionization chamber for use as a tertiary standard (field class instruments) in radiation therapy. In addition, intercomparison with commercially available chambers of reference class type were carried out in respect to field size dependence, energy dependence, short and long term stability.The results of those tests indicated the usefulness of the developed ionization chamber as a tertiary standard. (author)

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

International Nuclear Information System (INIS)

Majumdar, Bishnu; Patel, Narayan Prasad; Vijayan, V.

2006-01-01

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. (author)

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

CERN Document Server

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

2006-01-01

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

Advisory Committee for the calibration standards of ionizing radiation measurement

International Nuclear Information System (INIS)

1979-01-01

The meeting consisted exceptionally of two sessions (in May and December 1977). The members discussed the comparisons of absorbed dose standards and exposure standards which had taken place since 1975 and suggested improvements for future comparisons. A recommendation was made concerning the humidity correction factor to be applied when using cavity chambers and free-air chambers. Further studies were requested concerning the effective point of measurement of ionization chambers. No method was recommended for the statement of uncertainty in calibration certificates. The exposure standards and calibrations in terms of exposure were maintained but it was agreed that other possibilities should be explored. Finally, progress reports of the national laboratories and a description of the recent work carried out at BIPM were presented and appear as appendices to the report [fr

A longitudinal field multiple sampling ionization chamber for RIBLL2

International Nuclear Information System (INIS)

Tang Shuwen; Ma Peng; Lu Chengui; Duan Limin; Sun Zhiyu; Yang Herun; Zhang Jinxia; Hu Zhengguo; Xu Shanhu

2012-01-01

A longitudinal field MUltiple Sampling Ionization Chamber (MUSIC), which makes multiple measurements of energy loss for very high energy heavy ions at RIBLL2, has been constructed and tested with 3 constituent α source ( 239 Pu : 3.435 MeV, 241 Am : 3.913 MeV, 244 Cm : 4.356 MeV). The voltage plateau curve has been plotted and-500 V is determined as a proper work voltage. The energy resolution is 271.4 keV FWHM for the sampling unit when 3.435 MeV energy deposited. A Geant4 Monte Carlo simulation is made and it indicates the detector can provide unique particle identification for ions Z≥4. (authors)

Proton beam monitor chamber calibration

International Nuclear Information System (INIS)

Gomà, C; Meer, D; Safai, S; Lorentini, S

2014-01-01

The first goal of this paper is to clarify the reference conditions for the reference dosimetry of clinical proton beams. A clear distinction is made between proton beam delivery systems which should be calibrated with a spread-out Bragg peak field and those that should be calibrated with a (pseudo-)monoenergetic proton beam. For the latter, this paper also compares two independent dosimetry techniques to calibrate the beam monitor chambers: absolute dosimetry (of the number of protons exiting the nozzle) with a Faraday cup and reference dosimetry (i.e. determination of the absorbed dose to water under IAEA TRS-398 reference conditions) with an ionization chamber. To compare the two techniques, Monte Carlo simulations were performed to convert dose-to-water to proton fluence. A good agreement was found between the Faraday cup technique and the reference dosimetry with a plane-parallel ionization chamber. The differences—of the order of 3%—were found to be within the uncertainty of the comparison. For cylindrical ionization chambers, however, the agreement was only possible when positioning the effective point of measurement of the chamber at the reference measurement depth—i.e. not complying with IAEA TRS-398 recommendations. In conclusion, for cylindrical ionization chambers, IAEA TRS-398 reference conditions for monoenergetic proton beams led to a systematic error in the determination of the absorbed dose to water, especially relevant for low-energy proton beams. To overcome this problem, the effective point of measurement of cylindrical ionization chambers should be taken into account when positioning the reference point of the chamber. Within the current IAEA TRS-398 recommendations, it seems advisable to use plane-parallel ionization chambers—rather than cylindrical chambers—for the reference dosimetry of pseudo-monoenergetic proton beams. (paper)

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

International Nuclear Information System (INIS)

Viana, R.N.; Cassiano, D.H.; Peixoto, J.G.P.

2005-01-01

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 - 1 st and 2 nd CSR, from measurements carried out with appropriate ionisation chambers. The acceptance criteria of ISO 4037-1 states that the values of 1 st and 2 nd 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 1 st and 2 nd CSR with the use of different ionization chambers of varying volumes. The initial results indicate that the values of 1 st and 2 nd 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 1 st and 2 nd CSR

Electret ionization chamber: a new method for detection and dosimetry of thermal neutrons; Camara de ionizacao de eletretos: um novo metodo para deteccao e dosimetria de neutrons termicos

Energy Technology Data Exchange (ETDEWEB)

Ghilardi, A J.P.

1988-12-31

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 {gamma}-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 BF{sub 3} ionization chamber and that new technologies for deposition of the boron layer will produce higher efficiency detectors. (author). 102 refs, 32 fig, 10 tabs.

A multiwire ionization chamber readout circuit using current mirrors

International Nuclear Information System (INIS)

Rawnsley, W.R.; Smith, D.; Moskven, T.

1997-01-01

A circuit which utilizes current mirrors has been used to apply high voltage bias to the wires of a multiwire ionization chamber (MWIC) profile monitor while still allowing measurement of the beam-induced ion-electron currents collected on the wires. Bias voltages of up to 250 V have been used while wire currents over a range of 0.5 nA to 50 nA have been measured. The circuit is unipolar but can be designed for positive or negative bias. The mirrors also provide a current gain of 10, reducing the effects of transistor leakage and extending the useful range of the circuit to lower signal levels. A module containing 32 Wilson current mirrors has been constructed and is used with a MWIC monitor in TRIUMF close-quote s Parity experiment beamline. copyright 1997 American Institute of Physics

Recombination in liquid-filled ionization chambers beyond the Boag limit

International Nuclear Information System (INIS)

Brualla-González, L.; Roselló, J.; Aguiar, P.; González-Castaño, D. M.; Gómez, F.; Pombar, M.; Pardo-Montero, J.

2016-01-01

Purpose: The high mass density and low mobilities of charge carriers can cause important recombination in liquid-filled ionization chambers (LICs). Saturation correction methods have been proposed for LICs. Correction methods for pulsed irradiation are based on Boag equation. However, Boag equation assumes that the charge ionized by one pulse is fully collected before the arrival of the next pulse. This condition does not hold in many clinical beams where the pulse repetition period may be shorter than the charge collection time, causing overlapping between charge carriers ionized by different pulses, and Boag equation is not applicable there. In this work, the authors present an experimental and numerical characterization of collection efficiencies in LICs beyond the Boag limit, with overlapping between charge carriers ionized by different pulses. Methods: The authors have studied recombination in a LIC array for different dose-per-pulse, pulse repetition frequency, and polarization voltage values. Measurements were performed in a Truebeam Linac using FF and FFF modalities. Dose-per-pulse and pulse repetition frequency have been obtained by monitoring the target current with an oscilloscope. Experimental collection efficiencies have been obtained by using a combination of the two-dose-rate method and ratios to the readout of a reference chamber (CC13, IBA). The authors have also used numerical simulation to complement the experimental data. Results: The authors have found that overlap significantly increases recombination in LICs, as expected. However, the functional dependence of collection efficiencies on the dose-per-pulse does not change (a linear dependence has been observed in the near-saturation region for different degrees of overlapping, the same dependence observed in the nonoverlapping scenario). On the other hand, the dependence of collection efficiencies on the polarization voltage changes in the overlapping scenario and does not follow that of Boag

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

Energy Technology Data Exchange (ETDEWEB)

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

1998-12-31

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

SU-F-T-293: Experimental Comparisons of Ionization Chambers with Different Volumes for CyberKnife Delivery Quality Assurance

Energy Technology Data Exchange (ETDEWEB)

Nakayama, M [Kobe Minimally invasive Cancer Center, Kobe, Hyogo (Japan); Kobe University Graduate School of Medicine, Kobe, Hyogo (Japan); Munetomo, Y; Ogata, T; Uehara, K; Tsudou, S; Nishimura, H; Mayahara, H [Kobe Minimally invasive Cancer Center, Kobe, Hyogo (Japan); Sasaki, R [Kobe University Graduate School of Medicine, Kobe, Hyogo (Japan)

2016-06-15

Purpose: To evaluate the practicality use of ionization chambers with different volumes for delivery quality assurance of CyberKnife plans, Methods: Dosimetric measurements with a spherical solid water phantom and three ionization chambers with volumes of 0.13, 0.04, and 0.01 cm3 (IBA CC13, CC04, and CC01, respectively) were performed for various CyberKnife clinical treatment plans including both isocentric and nonisocentric delivery. For each chamber, the ion recombination correction factors Ks were calculated using the Jaffe plot method and twovoltage method at a 10-cm depth for a 60-mm collimator field in a water phantom. The polarity correction factors Kpol were determined for 5–60-mm collimator fields in same experimental setup. The measured doses were compared to the doses for the detectors calculated using a treatment planning system. Results: The differences in the Ks between the Jaffe plot method and two-voltage method were −0.12, −0.02, and 0.89% for CC13, CC04, and CC01, respectively. The changes in Kpol for the different field sizes were 0.2, 0.3, and 0.8% for CC13, CC04, and CC01, respectively. The measured doses for CC04 and CC01 were within 3% of the calculated doses for the clinical treatment plans with isocentric delivery with collimator fields greater than 12.5 mm. Those for CC13 had differences of over 3% for the plans with isocentric delivery with collimator fields less than 15 mm. The differences for the isocentric plans were similar to those for the single beam plans. The measured doses for each chamber were within 3% of the calculated doses for the non-isocentric plans except for that with a PTV volume less than 1.0 cm{sup 3}. Conclusion: Although there are some limitations, the ionization chamber with a smaller volume is a better detector for verification of the CyberKnife plans owing to the high spatial resolution.

Preliminary study of silica aerogel as a gas-equivalent material in ionization chambers

Science.gov (United States)

Caresana, M.; Zorloni, G.

2017-12-01

Since about two decades, a renewed interest on aerogels has risen. These peculiar materials show fairly unique properties. Thus, they are under investigation for both scientific and commercial purposes and new optimized production processes are studied. In this work, the possibility of using aerogel in the field of radiation detection is explored. The idea is to substitute the gas filling in a ionization chamber with the aerogel. The material possesses a density about 100 times greater than ambient pressure air. Where as the open-pore structure should allow the charge carriers to move freely. Small hydrophobic silica aerogel samples were studied. A custom ionization chamber, capable of working both with aerogel or in the classic gas set up, was built. The response of the chamber in current mode was investigated using an X-ray tube. The results obtained showed, under proper conditions, an enhancement of about 60 times of the current signal in the aerogel configuration with respect to the classic gas one. Moreover, some unusual behaviours were observed, i.e. time inertia of the signal and super-/sub-linear current response with respect to the dose rate. While testing high electric fields, aerogel configuration seemed to enhance the Townsend's effects. In order to represent the observed trends, a trapping-detrapping model is proposed, which is capable to predict semi-empirically the steady state currents measured. The time evolution of the signal is semi-quantitatively represented by the same model. The coefficients estimated by the fits are in agreement with similar trapping problems in the literature. In particular, a direct comparison between the benchmark of the FET silica gates and aerogel case endorses the idea that the same type of phenomenon occurs in the studied case.

Calibration of a scintillation dosemeter for beta rays using an extrapolation ionization chamber

International Nuclear Information System (INIS)

Hakanen, A.T.; Sipilae, P.M.; Kosunen, A.

2004-01-01

A scintillation dosemeter is calibrated for 90 Sr/ 90 Y beta rays from an ophthalmic applicator, using an extrapolation ionization chamber as a reference instrument. The calibration factor for the scintillation dosemeter agrees with that given by the manufacturer of the dosemeter within ca. 2%. The estimated overall uncertainty of the present calibration is ca. 6% (2 sd). A calibrated beta-ray ophthalmic applicator can be used as a reference source for further calibrations performed in the laboratory or in the hospital

Some studies on the pulse-height loss due to capacitive decay in the detector-circuit of parallel plate ionization chambers

International Nuclear Information System (INIS)

Sharma, S.L.; Anil Kumar, G.; Choudhury, R.K.

2006-01-01

Pulse-type ionization chambers are invariably operated in the electron-sensitive mode where the capacitive decay in the detector-circuit during the electron collection produces loss in the pulse-height. In order to understand and appreciate the effect of this capacitive decay on the detector response, we have carried out Monte Carlo simulations of the response of two-electrode parallel plate ionization chambers with and without the capacitive decay keeping shaping time so large that the ballistic deficit is negligibly small. These simulations have been carried out incorporating the physical processes, namely, emission of charged particles from a point radioactive source, the generation of charge carriers in the active volume, separation and acceleration of the charge carriers, transport of the charge carriers, induction of charges on the electrodes, pulse processing by preamplifier-amplifier network, etc. These simulations have shown that the concerned capacitive decay produces appreciable loss in the pulse-height, if the detector-circuit time constant is of the order of maximum electron collection time. We have also carried out measurements on the pulse-height loss due to the capacitive decay in the detector-circuit during the electron collection for a two-electrode parallel plate ionization chamber. The experimental data on the pulse-height loss match reasonably well with the theoretical predictions

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

International Nuclear Information System (INIS)

1981-01-01

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.)

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

International Nuclear Information System (INIS)

Dias, M.S.

1978-01-01

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: 241 Am, 139 Ce, 198 Au, 22 Na, 134 Cs, 54 Mn, 60 Co, 42 K, 24 Na. 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 [pt

Development of multi-layer ionization chamber for heavy-ion therapy

International Nuclear Information System (INIS)

Yajima, Kaori; Kusano, Yohsuke; Shimojyu, Takuya; Kanai, Tatsuaki

2007-01-01

In heavy-ion radiotherapy, depth dose distributions measured in water phantom are applied to estimate the dose distributions in a patient body. In order to obtain depth dose distributions in water phantom easily and rapidly, Multi-Layer Ionization Chamber (MLIC) was developed and had been adapted as a field dosimeter at NIRS since 2002. Production cross section of fragments in high Z material of the MLIC, however, is very different from those in water material. Then, empirical correction should be required. In order to obtain depth dose distributions with high accuracy, we have to use low Z material as a phantom, which are thought to produce similar fragments with water phantom. From this point of view, we have developed a new MLIC made up of low Z materials, PMMA and graphite film. (author)

Standardization Of 166mHo Using Merlin Gerin Ionization Chamber System

International Nuclear Information System (INIS)

Nazaroh; Chandra; Hermawan; Juita Erni

2000-01-01

Standardization of 166m Ho using Merlin Gerin ionization chamber system has been carried out. Solution of 166m Ho was obtained from ETL-Japan. Activity measurement of 166m Ho was done before and after preparation. The result of activity measurement by P3KRBiN before preparation was (134.47±0.4) kBq/g, and after preparation was (131.98±1.85) kBq/g, at reference time, 1 March 1999. The ETL's result was (130.4±0.4) kBq/g, at the same reference time. The difference between P3KRBiN's (without uncertainty) and ETL's measurement result was 1.2% and if the uncertainty was included, both measurements was agreed

Activity measurements of radioactive solutions by liquid scintillation counting and pressurized ionization chambers and Monte Carlo simulations of source-detector systems for metrology

International Nuclear Information System (INIS)

Amiot, Marie-Noelle

2013-01-01

The research works 'Activity measurements of radioactive solutions by liquid scintillation and pressurized ionization chambers and Monte Carlo simulations of source-detector systems' was presented for the graduation: 'Habilitation a diriger des recherches'. The common thread of both themes liquid scintillation counting and pressurized ionization chambers lies in the improvement of the techniques of radionuclide activity measurement. Metrology of ionization radiation intervenes in numerous domains, in the research, in the industry including the environment and the health, which are subjects of constant concern for the world population these last years. In this big variety of applications answers a large number of radionuclides of diverse disintegration scheme and under varied physical forms. The presented works realized within the National Laboratory Henri Becquerel have for objective to assure detector calibration traceability and to improve the methods of activity measurements within the framework of research projects and development. The improvement of the primary and secondary activity measurement methods consists in perfecting the accuracy of the measurements in particular by a better knowledge of the parameters influencing the detector yield. The works of development dealing with liquid scintillation counting concern mainly the study of the response of liquid scintillators to low energy electrons as well as their linear absorption coefficients using synchrotron radiation. The research works on pressurized ionization chambers consist of the study of their response to photons and electrons by experimental measurements compared to the simulation of the source-detector system using Monte Carlo codes. Besides, the design of a new type of ionization chamber with variable pressure is presented. This new project was developed to guarantee the precision of the amount of activity injected into the patient within the framework of diagnosis examination

Intercomparison of ionization chambers in standard X-ray beams, at radiotherapy, diagnostic radiology and radioprotection levels; Intercomparacao de camaras de ionizacao em feixes padroes de raios X, niveis radioterapia, radiodiagnostico e radioprotecao

Energy Technology Data Exchange (ETDEWEB)

Bessa, Ana Carolina Moreira de

2006-07-01

Since the calibration of radiation measurement instruments and the knowledge of their major characteristics are very important subjects, several different types of ionization chambers were intercompared in terms of their calibration coefficients and their energy dependence, in radiotherapy, diagnostic radiology and radioprotection standard beams. An intercomparison of radionuclide calibrators for nuclear medicine was performed, using three radionuclides: {sup 67}Ga, {sup 201}Tl and {sup 99m}Tc; the results obtained were all within the requirements of the national standard CNEN-NE-3.05. In order to complete the range of radiation qualities of the Calibration Laboratory of IPEN, standard radiation beam qualities, radiation protection and low energy radiation therapy levels, were established, according international recommendations. Three methodologies for the calibration of unsealed ionization chambers in X-ray beams were studied and compared. A set of Victoreen ionization chambers, specially designed for use in laboratorial intercomparisons, was submitted to characterization tests. The performance of these Victoreen ionization chambers showed that they are suitable for use in radioprotection beams, because the results obtained agree with international recommendations. However, these Victoreen ionization chambers can be used in radiotherapy and diagnostic radiology beams only with some considerations, since their performance in these beams, especially in relation to the energy dependence and stabilization time tests, did not agree with the international recommendations for dosimeters used in radiotherapy and diagnostic radiology beams. This work presents data on the performance of several types of ionization chambers in different X-ray beams, that may be useful for choosing the appropriate instrument for measurements in ionizing radiation beams. (author)

An ionization-chamber type of focal-plane detector for heavy ions

International Nuclear Information System (INIS)

Erskine, J.R.; Braid, T.H.; Stolfzfus, J.C.

1976-01-01

A focal-plane detector for heavy ions is described in which energy loss and total energy are measured with a gridded ionization chamber, and position along the focal plane and angle of incidence are measured with two resistive-wire proportional counters. The clean geometry of the detector makes it especially attractive for use with heavy ions of high specific ionization. Typical position resolutions of 1.0-1.5mm (fwhm) were observed over a 50 cm length of the detector in the focal plane of a split-pole magnetic spectrograph. Special tests were made which suggest that the limiting position resolution is 0.76 mm or better. The resolution of the energy-loss signal was typically 4.5% (fwhm). The resolution of the total energy signal was 1.0-1.5% (fwhm) for small entrance apertures of the spectrograph, although 0.7% resolution was observed under special circumstances. The angle of incidence was measured with an uncertainty of about 1.2% (fwhm). The availability of the many parameters needed for particle identification makes this detector especially useful for the study of weak reaction channels in heavy-ion-induced reactions. (Auth.)

Experimental determination of pcav factors for cylindrical ionisation chambers in electron beams

International Nuclear Information System (INIS)

Palm, Aa.; Mattsson, O.

2000-01-01

The electron beam method recommended for calibrating plane parallel ionisation chambers involves cavity correction factors for cylindrical chambers. The cavity correction factors in the IAEA TRS-381 Code of Practice are based on measurements at R 100 in a PMMA phantom using PMMA cylindrical chambers having different cavity radii. In the present work the recommended data were confirmed for electron beams delivered by modern medical accelerators by using the very same phantom and ionisation chambers that were used in the original work. From another series of measurements, using four specially designed wall-less chambers in a graphite phantom, the linear relation between p cav and the chamber radius that is the basis for the experimental method, was verified. The method was also used to determine the cavity correction factors for a set of Farmer-like graphite chambers placed in water. Compared to the TRS-381 Code of Practice a smaller correction was found for the cavity perturbation for the graphite chambers used in water. (author)

Determination of the air attenuation correction factor for a free air ionization chamber

International Nuclear Information System (INIS)

Silva, Natalia F.; Cintra, Felipe B.; Castro, Maysa C. de; Caldas, Linda V.E.

2016-01-01

The objective of this work is to present the experimental and simulation results for the air attenuation correction factor for a free air ionization chamber with concentric cylinders of Victoreen, model 481-5. This correction factor was obtained for the standard mammography qualities established in the Instrument Calibration Laboratory (LCI) of IPEN. The values were compared with the results from the German primary standard laboratory Physikalisch- Technische Bundesanstalt (PTB), and maximum differences of 0.40% in relation to the experimental value and 0.31% in relation to the simulated value were obtained. (author)

Technical note: A new wedge-shaped ionization chamber component module for BEAMnrc to model the integral quality monitoring system®

Science.gov (United States)

Oderinde, Oluwaseyi Michael; du Plessis, FCP

2017-12-01

The purpose of this study was to develop a new component module (CM) namely IQM to accurately model the integral quality monitoring (IQM) system® to be used in the BEAMnrc Monte Carlo (MC) code. The IQM is essentially a double wedge ionization chamber with the central electrode plate bisecting the wedge. The IQM CM allows the user to characterize the double wedge of this ionization chamber and BEAMnrc can then accurately calculate the dose in this CM including its enclosed air regions. This has been verified against measured data. The newly created CM was added into the standard BEAMnrc CMs, and it will be made available through the NRCC website. The BEAMnrc graphical user interface (GUI) and particle ray-tracing techniques were used to validate the IQM geometry. In subsequent MC simulations, the dose scored in the IQM was verified against measured data over a range of square fields ranging from 1 × 1-30 × 30 cm2. The IQM system is designed for the present day need for a device that could verify beam output in real-time during treatment. This CM is authentic, and it can serve as a basis for researchers that have an interest in real-time beam delivery checking using wedge-shaped ionization chamber based instruments like the IQM.

Sensitivity of gaseous xenon ionisation chambers (1961)

International Nuclear Information System (INIS)

Schuhl, C.

1960-01-01

It seems advantageous to fill an ionization chamber with xenon gas when this chamber is used for measuring a low intensity and high energy electron or positron beam, or monitoring a gamma beam. In the study of 5 to 50 MeV electrons, xenon allows for the ionization chamber yield, an improvement of a factor 4,5. (author) [fr

Design of monolithic preamplifiers employing diffused n-JFETs for ionization chamber colorimeters

International Nuclear Information System (INIS)

Demicheli, M.; Manfredi, P.F.; Speziali, V.; Radeka, V.; Rescia, S.

1990-01-01

Silicon n-channel JFETs obtained by diffusing the gate into the epitaxial layer which contains the channel still feature unsurpassed noise performances in charge measurements with radiation detectors. Compared to implanted-gate junction field-effect devices, they have a better behaviour in the low-frequency noise, while the thermal noise in the channel more closely conforms to the expected g m -dependence. With respect to MOSFETs they feature, besides lower noise, superior radiation hardness and resistance to electrostatic discharges into the gate. The actual paper discusses the basic design considerations of a preamplifier for ionization chamber calorimeters, which is intended for monolithic integration based on a dielectrically isolated process. (orig.)

Search for impurities of counting gases in ionization chambers

International Nuclear Information System (INIS)

Hofmann, T.

1992-03-01

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.) [de

Comparison of depth-dose distributions of proton therapeutic beams calculated by means of logical detectors and ionization chamber modeled in Monte Carlo codes

Energy Technology Data Exchange (ETDEWEB)

Pietrzak, Robert [Department of Nuclear Physics and Its Applications, Institute of Physics, University of Silesia, Katowice (Poland); Konefał, Adam, E-mail: adam.konefal@us.edu.pl [Department of Nuclear Physics and Its Applications, Institute of Physics, University of Silesia, Katowice (Poland); Sokół, Maria; Orlef, Andrzej [Department of Medical Physics, Maria Sklodowska-Curie Memorial Cancer Center, Institute of Oncology, Gliwice (Poland)

2016-08-01

The success of proton therapy depends strongly on the precision of treatment planning. Dose distribution in biological tissue may be obtained from Monte Carlo simulations using various scientific codes making it possible to perform very accurate calculations. However, there are many factors affecting the accuracy of modeling. One of them is a structure of objects called bins registering a dose. In this work the influence of bin structure on the dose distributions was examined. The MCNPX code calculations of Bragg curve for the 60 MeV proton beam were done in two ways: using simple logical detectors being the volumes determined in water, and using a precise model of ionization chamber used in clinical dosimetry. The results of the simulations were verified experimentally in the water phantom with Marcus ionization chamber. The average local dose difference between the measured relative doses in the water phantom and those calculated by means of the logical detectors was 1.4% at first 25 mm, whereas in the full depth range this difference was 1.6% for the maximum uncertainty in the calculations less than 2.4% and for the maximum measuring error of 1%. In case of the relative doses calculated with the use of the ionization chamber model this average difference was somewhat greater, being 2.3% at depths up to 25 mm and 2.4% in the full range of depths for the maximum uncertainty in the calculations of 3%. In the dose calculations the ionization chamber model does not offer any additional advantages over the logical detectors. The results provided by both models are similar and in good agreement with the measurements, however, the logical detector approach is a more time-effective method. - Highlights: • Influence of the bin structure on the proton dose distributions was examined for the MC simulations. • The considered relative proton dose distributions in water correspond to the clinical application. • MC simulations performed with the logical detectors and the

Determination of absorbed dose to water in a clinical carbon ion beam by means of fluorescent nuclear track detectors, ionization chambers, and water calorimetry

Energy Technology Data Exchange (ETDEWEB)

Osinga-Blaettermann, Julia-Maria

2016-12-20

Until now, dosimetry of carbon ions with ionization chambers has not reached the same level of accuracy as of high-energy photons. This is mainly caused by the threefold higher uncertainty of the k{sub Q,Q{sub 0}}-factor of ionization chambers, which is derived by calculations due to a lack of experimental data. The current thesis comprises two major aims with respect to the dosimetry of carbon ion beams: first, the investigation of the potential of fluorescent nuclear track detectors for fluence-based dosimetry and second, the experimental determination of the k{sub Q,Q{sub 0}}-factor. The direct comparison of fluence- and ionization-based measurements has shown a significant discrepancy of 4.5 %, which re-opened the discussion on the accuracy of calculated k{sub Q,Q{sub 0}}-factors. Therefore, absorbed dose to water measurements by means of water calorimetry have been performed allowing for the direct calibration of ionization chambers and thus for the experimental determination of k{sub Q,Q{sub 0}}. For the first time it could be shown that the experimental determination of k{sub Q,Q{sub 0}} for carbon ion beams is achievable with a standard measurement uncertainty of 0.8 %. This corresponds to a threefold reduction of the uncertainty compared to calculated values and therefore enables to significantly decrease the overall uncertainty related to ionization-based dosimetry of clinical carbon ion beams.

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

Directory of Open Access Journals (Sweden)

Koroush Arbabi

2007-12-01

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

Mobilities of positive ions in gas ionization chambers

International Nuclear Information System (INIS)

Kusumegi, Asao

1990-01-01

Observed ion mobilities of organic molecules in Ar are compared with a complete polarization model to examine the performance of the model, and its applicability is discussed. In spite of its simplicity, the polarization model (small sphere limit) is found to agree satisfactorily with observed mobilities in the case of alkali ions in Ar. However, the model fails to account for the mobility of Ar + in Ar due to a resonant charge transfer interaction between the ion and the parent gas. On the other hand, the values of k, a parameter which depends on the kinetic and the potential energy of the relevant ion, derived from observed ion mobilities of organic molecules in Ar and in the parent gas are found to be close to each other. Except for few cases, it appears that the complete polarization model gives a reasonable approximation for the positive ion mobilities of organic molecules in Ar, though the importance of the ion mass identification is significant in considering the applicability of the model to the positive ion mobility of those organic molecules in Ar used in a gas ionization chamber. (N.K.)

Charge collection efficiency in ionization chambers operating in the recombination and saturation regimes

International Nuclear Information System (INIS)

Chabod, Sebastien P.

2009-01-01

We solve the electric charge transport equations in the recombination and saturation regimes using an iterative perturbation method. We then calculate the charge collection efficiencies of ionization chambers. The formulae obtained are presented in the form of series for which we calculate the first coefficients. Our approach allows to account for the spatial as well as the temporal variations of the primary charge density N(r,t) in the calculations. Finally, we apply our method to study different density patterns, N, including the textbook case N=N 0 δ(t) and the charge clusters and columns.

Dosimetry in VMAT for prostate using ionization chambers of different volumes; Verificacao dosimetrica em VMAT para prostata com camaras de ionizacao de volumes diferentes

Energy Technology Data Exchange (ETDEWEB)

Groppo, Daniela P.; Anderson, Ernani; Pavan, Guilherme A., E-mail: danielagroppo@grupocoi.com, E-mail: ernanianderson@grupocoi.com [Clinicas Oncologicas Integradas (Grupo COI), Rio de Janeiro, RJ (Brazil); Caldas, Linda V.E., E-mail: lcaldas@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

2016-07-01

The volumetric modulated arc therapy is one of the most modern radiotherapy techniques. The advents of this modality in the dose delivery can also contribute to errors during the execution of the treatment, therefore various types of quality control are carried out. The individual assessment of dose delivered to the patient is also an important quality control test and required by the current regulations. The objective of this study was to evaluate the use of different volume ionization chambers for dosimetry of VMAT treatments for prostate cancer. Three ionization chambers were evaluated and all of them showed satisfactory results. (author)

Comparison between calibration methods of ionization chamber type pencil in greatness P_K_L

International Nuclear Information System (INIS)

Macedo, E.M.; Pereira, L.C.S.; Ferreira, M.J.; Navarro, V.C.C.; Garcia, I.F.M.; Pires, E.J.; Navarro, M.V.T.

2016-01-01

Calibration of radiation meters is indispensable on Quality Assurance Program in Radiodiagnostic procedures, mainly Computed Tomography. Thus, this study aims evaluate two calibration methods of pencil ionization chambers in terms of Kerma-length Product (P_K_L) (a direct substitution method and an indirect one, through Kerma and length measurements). The results showed a good equivalence, with minimal concordance of 98,5% between calibration factors. About uncertainties, both showed similar results (substitution 2.2% and indirect 2.3%), indicating that the last one is better, due the costs reduction to implant this calibration procedure. (author)

Pressurized rf cavities in ionizing beams

Directory of Open Access Journals (Sweden)

B. Freemire

2016-06-01

Full Text Available A muon collider or Higgs factory requires significant reduction of the six dimensional emittance of the beam prior to acceleration. One method to accomplish this involves building a cooling channel using high pressure gas filled radio frequency cavities. The performance of such a cavity when subjected to an intense particle beam must be investigated before this technology can be validated. To this end, a high pressure gas filled radio frequency (rf test cell was built and placed in a 400 MeV beam line from the Fermilab linac to study the plasma evolution and its effect on the cavity. Hydrogen, deuterium, helium and nitrogen gases were studied. Additionally, sulfur hexafluoride and dry air were used as dopants to aid in the removal of plasma electrons. Measurements were made using a variety of beam intensities, gas pressures, dopant concentrations, and cavity rf electric fields, both with and without a 3 T external solenoidal magnetic field. Energy dissipation per electron-ion pair, electron-ion recombination rates, ion-ion recombination rates, and electron attachment times to SF_{6} and O_{2} were measured.

The method of activity determination of Tc-99m in ionization chamber

International Nuclear Information System (INIS)

Broda, R.

1980-01-01

The paper presents a method of finding the efficiency of sup(99m)Tc activity measurements in the ionization chamber, basing on 99 Mo activity measurements and the activity ratio of sup(99m)Tc to 99 Mo in 99 Mo + sup(99m)Tc solution. The activity of 99 Mo has been determined in 4πβ-γ coincidence system with liquid scintillator in β channel by means of the absolute method of two-stage coincidence. The activity ratio of sup(99m)Tc to 99 Mo has been determined by means of spectrometric method. The 99 Mo and sup(99m)Tc activities have been measured in 99 Mo + sup(99m)Tc generators, and the activity of sup(99m)Tc solution after elution has been measured. It has been shown that sup(99m)Tc activity, determined by means of the chamber method on the basis of the efficiency found, corresponds to the activity determined by means of spectrometric method, and that sup(99m)Tc activity, measured in generator before elution, is equal to the sum of sup(99m)Tc activity eluted and the one remained in generator. (author)

Ionization particle detector

International Nuclear Information System (INIS)

Ried, L.

1982-01-01

A new device is claimed for detecting particles in a gas. The invention comprises a low cost, easy to assemble, and highly accurate particle detector using a single ionization chamber to contain a reference region and a sensing region. The chamber is designed with the radioactive source near one electrode and the second electrode located at a distance less than the distance of maximum ionization from the radioactive source

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.

Ionization dual-zone static detector having single radioactive source

International Nuclear Information System (INIS)

Ried, L. Jr.; Wade, A.L.

1977-01-01

This ionization detector or combustion product detector includes a single radioactive source located in an ionization chamber, and the ionization chamber includes portions comprising a reference zone and a signal zone. Electrical circuitry connected to the reference and signal zones provides an output signal directly related to changes in voltages across the signal zone in relation to the amount of particulates of combustion present in the ionization chamber

Activity measurements using recessed ionization chambers (activity meters) as performed in the Department for Nuclear Medicine at the Hanover Medical School

International Nuclear Information System (INIS)

Meyer, G.J.; Matzke, K.H.; Kuehn, J.

1992-01-01

Recessed ionization chambers have an application in the production and dose determination of radiopharmaceuticals. The measuring instrumentation installed in the radiochemical department, service instructions, quality assurance measures and relevant practical experiences are described in brief. (DG) [de

Simulation of the energy response of the I.S.O.C.A.L. IV pressurised re-entrant well type ionization chamber using the Penelope Monte-Carlo code

International Nuclear Information System (INIS)

Kryeziu, D.; Tschurlovits, M.; Kreuziger, M.; Maringer, F.J.

2006-01-01

In radiation metrology, pressurized ionization chambers are essential tools in secondary standard laboratories as relative calibration instruments.Calculations of the calibration figures for different radionuclides are very important parameters for radioactivity measurements. The calibration figures for the I.S.O.C.A.L. IV pressurized re-entrant ionization chamber (also called well-type ionisation chamber) are calculated here using the P.E.N.E.L.O.P.E.-2003 Monte-Carlo Code. In order to test and validate the Monte Carlo simulation, calculated and experimental calibration figures are compared. The task of this work was to calculate the activity of a radioactive solution when no experimental calibration figures are available as well as to improve the accuracy of activity measurements. The chamber is filled with nitrogen gas at 1 MPa pressure. The simulated models of the chamber are designed by means of reduced quadric equation applying the appropriate transformations including: a rotation defined through the Euler angles, an expansion along the directions of the axes and a translation defined by the components of the displacement vector t. The simulated geometries are defined for the cases:without shielding; lead shielding and lead and copper shielding. The effect of density variations of the nitrogen gas on the sensitivity of such ionization chambers has been investigated. The Penelope Monte-Carlo code is also used to examine the effects of using lead and copper shields. The sensitivity to electrons is evaluated as well. (authors)

Ionization efficiency calculations for cavity thermoionization ion source

International Nuclear Information System (INIS)

Turek, M.; Pyszniak, K.; Drozdziel, A.; Sielanko, J.; Maczka, D.; Yuskevich, Yu.V.; Vaganov, Yu.A.

2009-01-01

The numerical model of ionization in a thermoionization ion source is presented. The review of ion source ionization efficiency calculation results for various kinds of extraction field is given. The dependence of ionization efficiency on working parameters like ionizer length and extraction voltage is discussed. Numerical simulations results are compared to theoretical predictions obtained from a simplified ionization model

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

NARCIS (Netherlands)

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

2016-01-01

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

Ionization chamber smoke detectors

International Nuclear Information System (INIS)

1988-03-01

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

Signal enhancement due to high-Z nanofilm electrodes in parallel plate ionization chambers with variable microgaps.

Science.gov (United States)

Brivio, Davide; Sajo, Erno; Zygmanski, Piotr

2017-12-01

We developed a method for measuring signal enhancement produced by high-Z nanofilm electrodes in parallel plate ionization chambers with variable thickness microgaps. We used a laboratory-made variable gap parallel plate ionization chamber with nanofilm electrodes made of aluminum-aluminum (Al-Al) and aluminum-tantalum (Al-Ta). The electrodes were evaporated on 1 mm thick glass substrates. The interelectrode air gap was varied from 3 μm to 1 cm. The gap size was measured using a digital micrometer and it was confirmed by capacitance measurements. The electric field in the chamber was kept between 0.1 kV/cm and 1 kV/cm for all the gap sizes by applying appropriate compensating voltages. The chamber was exposed to 120 kVp X-rays. The current was measured using a commercial data acquisition system with temporal resolution of 600 Hz. In addition, radiation transport simulations were carried out to characterize the dose, D(x), high-energy electron current, J(x), and deposited charge, Q(x), as a function of distance, x, from the electrodes. A deterministic method was selected over Monte Carlo due to its ability to produce results with 10 nm spatial resolution without stochastic uncertainties. Experimental signal enhancement ratio, SER(G) which we defined as the ratio of signal for Al-air-Ta to signal for Al-air-Al for each gap size, was compared to computations. The individual contributions of dose, electron current, and charge deposition to the signal enhancement were determined. Experimental signals matched computed data for all gap sizes after accounting for several contributions to the signal: (a) charge carrier generated via ionization due to the energy deposited in the air gap, D(x); (b) high-energy electron current, J(x), leaking from high-Z electrode (Ta) toward low-Z electrode (Al); (c) deposited charge in the air gap, Q(x); and (d) the decreased collection efficiency for large gaps (>~500 μm). Q(x) accounts for the electrons below 100 eV, which are

Enhancement of precision and accuracy by Monte-Carlo simulation of a well-type pressurized ionization chamber used in radionuclide metrology

International Nuclear Information System (INIS)

Kryeziu, D.

2006-09-01

The aim of this work was to test and validate the Monte-Carlo (MC) ionization chamber simulation method in calculating the activity of radioactive solutions. This is required when no or not sufficient experimental calibration figures are available as well as to improve the accuracy of activity measurements for other radionuclides. Well-type or 4π γ ISOCAL IV ionization chambers (IC) are widely used in many national standard laboratories around the world. As secondary standard measuring systems these radionuclide calibrators serve to maintain measurement consistency checks and to ensure the quality of standards disseminated to users for a wide range of radionuclide where many of them are with special interest in nuclear medicine as well as in different applications on radionuclide metrology. For the studied radionuclides the calibration figures (efficiencies) and their respective volume correction factors are determined by using the PENELOPE MC computer code system. The ISOCAL IV IC filled with nitrogen gas at approximately 1 MPa is simulated. The simulated models of the chamber are designed by means of reduced quadric equation and applying the appropriate mathematical transformations. The simulations are done for various container geometries of the standard solution which take forms of: i) sealed Jena glass 5 ml PTB standard ampoule, ii) 10 ml (P6) vial and iii) 10 R Schott Type 1+ vial. Simulation of the ISOCAL IV IC is explained. The effect of density variation of the nitrogen filling gas on the sensitivity of the chamber is investigated. The code is also used to examine the effects of using lead and copper shields as well as to evaluate the sensitivity of the chamber to electrons and positrons. Validation of the Monte-Carlo simulation method has been proved by comparing the Monte-Carlo simulation calculated and experimental calibration figures available from the National Physical Laboratory (NPL) England which are deduced from the absolute activity

MICAP, Ionization Chamber Detector Response by Monte-Carlo

International Nuclear Information System (INIS)

2002-01-01

1 - Description of program or function: MICAP has been developed to determine the response of a gas-filled cavity ionization chamber or other detector type (plastic scintillator, calorimeter) in a mixed neutron and photon radiation environment. In particular, MICAP determines the neutron, photon, and total response of the detector system. The applicability of MICAP encompasses all aspects of mixed field dosimetry analysis including detector design, pre-experimental planning and post-experimental analysis. MICAP is a modular code system developed to be general with respect to problem applicability The transport modules utilize combinatorial geometry to accurately model the source/detector geometry and also use continuous energy and angle cross section and material data to represent the materials for a particular problem. 2 - Method of solution: The calculational scheme used in MICAP follows individual radiation particles incident on the detector wall material. The incident neutrons produce photons and heavy charged particles, and both primary and secondary photons produce electrons and positrons. As these charged particles enter or are produced in the detector material, they lose energy and produce ion pairs until their energy is completely dissipated or until they escape the detector. Ion recombination effects are included along the path of each charged particle rather than applied as an integral correction to the final result. The neutron response is determined from the energy deposition resulting from the transport of the charged particles and recoil heavy ions produced via the neutron interactions with the detector materials. The photon response is determined from the transport of both the primary photon radiation incident on the detector and also the secondary photons produced via the neutron interactions. MICAP not only yields the energy deposition by particle type and total energy deposited, but also the particular type of reaction, i.e. elastic scattering

Metrological reliability of the calibration procedure in terms of air kerma using the ionization chamber NE2575

International Nuclear Information System (INIS)

Guimaraes, Margarete Cristina; Silva, Teogenes Augusto da; Rosado, Paulo H.G.

2016-01-01

Metrology laboratories are expected to provide X radiation beams that were established by international standardization organizations to perform calibration and testing of dosimeters. Reliable and traceable standard dosimeters should be used in the calibration procedure. The aim of this work was to study the reliability of the NE 2575 ionization chamber used as standard dosimeter for the air kerma calibration procedure adopted in the CDTN Calibration Laboratory. (author)

Very high intensity reaction chamber design

International Nuclear Information System (INIS)

Devaney, J.J.

1975-09-01

The problem of achieving very high intensity irradiation by light in minimal regions was studied. Three types of irradiation chamber are suggested: the common laser-reaction chamber, the folded concentric or near-concentric resonator, and the asymmetric confocal resonator. In all designs the ratio of high-intensity illuminated volume to other volume is highly dependent (to the 3 / 2 power) on the power and fluence tolerances of optical elements, primarily mirrors. Optimization of energy coupling is discussed for the common cavity. For the concentric cavities, optimization for both coherent and incoherent beams is treated. Formulae and numerical examples give the size of chambers, aspect ratios, maximum pass number, image sizes, fluences, and the like. Similarly for the asymmetric confocal chamber, formulae and numerical examples for fluences, dimensions, losses, and totally contained pass numbers are given

Comparison of the half-value layer: ionization chambers vs solid-state meters; Comparacao entre medidas de camada semirredutora: camara de ionizacao vs medidores de estado solido

Energy Technology Data Exchange (ETDEWEB)

Pereira, L.C.S.; Navarro, V.C.C.; Navarro, M.V.T.; Macedo, E.M., E-mail: larapereira@ifba.edu.br [Instituto Federal da Bahia (LABPROSAUD/IFBA), Salvador, BA (Brazil). Laboratorio de Produtos para a Saude

2015-07-01

Generally, the half value layer (HVL) is determined by using ionization chambers and aluminum filters. However, some solid-state dosimeters allow simultaneous measurements of X-ray's parameters, among which the HVL. The main objective of this study was to compare the HVL's values indicated by four different solid-state dosimeters, whose values were measured by ionization chambers. The maximum difference found between the two methods was 11.42%, one the solid-state dosimeters, showing that the use these instruments to determine CSR in industrial X-ray should be subject to a more thorough evaluation. (author)

(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)

Normal Conducting RF Cavity for MICE

International Nuclear Information System (INIS)

Li, D.; DeMello, A.; Virostek, S.; Zisman, M.; Summers, D.

2010-01-01

Normal conducting RF cavities must be used for the cooling section of the international Muon Ionization Cooling Experiment (MICE), currently under construction at Rutherford Appleton Laboratory (RAL) in the UK. Eight 201-MHz cavities are needed for the MICE cooling section; fabrication of the first five cavities is complete. We report the cavity fabrication status including cavity design, fabrication techniques and preliminary low power RF measurements.

Ionization efficiency of a COMIC ion source equipped with a quartz plasma chamber

International Nuclear Information System (INIS)

Suominen, P.; Stora, T.; Sortais, P.; Medard, J.

2012-01-01

Increased ionization efficiencies of light noble gases and molecules are required for new physics experiments in present and future radioactive ion beam facilities. In order to improve these beams, a new COMIC-type ion source with fully quartz made plasma chamber was tested. The beam current stability is typically better than 1 % and beams are easily reproducible. The highest efficiency for xenon is about 15 %. However, the main goal is to produce molecular beam including radioactive carbon (in CO or CO 2 ), in which case the efficiency was measured to be only about 0.2%. This paper describes the experimental prototype and its performance and provides ideas for future development. This paper is followed by the associated poster. (authors)

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

International Nuclear Information System (INIS)

Petrascu, H.; Kumagai, H.; Tanihata, I.; Petrascu, M.

1999-01-01

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 mm 2 were perpendicular to the beam direction. Each pad and each of the position wire groups were connected to a preamplifier. The energy resolution

Establishment of a primary standard system for low energy X-rays using a free air ionization chamber

International Nuclear Information System (INIS)

Silva, Natalia Fiorini da

2016-01-01

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

Display of charged ionizing particles

International Nuclear Information System (INIS)

Cano S, D.; Ortiz A, M. D.; Amarillas S, L. E.; Vega C, H. R.

2017-10-01

The human being is exposed to sources of ionizing and non-ionizing radiation, both of natural or anthropogenic origin. None of these, except non-ionizing such as visible light and infrared radiation, can be detected by the sense of sight and touch respectively. The sun emits charged particles with speeds close to the light that interact with the atoms of the gases present in the atmosphere, producing nuclear reactions that in turn produce other particles that reach the surface of the Earth and reach the living beings. On Earth there are natural radioisotopes that, when they disintegrate, emit ionizing radiation that contributes to the dose we receive. A very old system that allows the visualization of the trajectories of the charged ionizing particles is the Fog Chamber that uses a saturated steam that when crossed by particles with mass and charge, as alpha and beta particles produce condensation centers along its path leaves a trace that can be seen. The objective of this work was to build a fog chamber using easily accessible materials. To measure the functioning of the fog chamber, cosmic rays were measured, as well as a source of natural metal uranium. The fog chamber allowed seeing the presence of traces in alcohol vapor that are produced in a random way. Introducing the uranium foil inside the fog chamber, traces of alpha particles whose energy varies from 4 to 5 MeV were observed. (Author)

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

International Nuclear Information System (INIS)

Lima, Mateus Hilario de

2014-01-01

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)

Usage of shape of signal from liquid ionization chamber for rejection delta electrons and multiple measurement of dE/d x

International Nuclear Information System (INIS)

Kulinich, P.A.

1994-01-01

The results of numerical simulation of separation of different kinds of charged particles with β 2 cm) ionization liquid medium chamber is proposed to be used for rejection of energetic delta electrons and for few measurements of dE/d x inside one gap. Possibility of separating π- and k-mesons at the level of 2 σ in a 4 cm L Kr medium chamber in the momentum range (0.5 N - 0.8) GeV/c is shown. 15 refs.; 13 figs.; 3 tabs. (author)

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

International Nuclear Information System (INIS)

Snowden-Ifft, Daniel P.

2014-01-01

This paper focuses on the surprising discovery of multiple species of ionization-created CS 2 anions in gas mixtures containing electronegative CS 2 and O 2 , 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

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

International Nuclear Information System (INIS)

Christie, W.B.; Romero, J.L.; Brady, F.P.; Tull, C.E.; Castaneda, C.M.; Barasch, E.F.; Webb, M.L.; Drummond, J.R.; Sann, H.; Young, J.C.

1987-01-01

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

Micro ionization chamber dosimetry in IMRT verification: Clinical implications of dosimetric errors in the PTV

International Nuclear Information System (INIS)

Sanchez-Doblado, Francisco; Capote, Roberto; Rosello, Joan V.; Leal, Antonio; Lagares, Juan I.; Arrans, Rafael; Hartmann, Guenther H.

2005-01-01

Background and purpose: Absolute dose measurements for Intensity Modulated Radiotherapy (IMRT) beamlets is difficult due to the lack of lateral electron equilibrium. Recently we found that the absolute dosimetry in the penumbra region of the IMRT beamlet, can suffer from significant errors (Capote et al., Med Phys 31 (2004) 2416-2422). This work has the goal to estimate the error made when measuring the Planning Target Volume's (PTV) absolute dose by a micro ion chamber (μIC) in typical IMRT treatment. The dose error comes from the assumption that the dosimetric parameters determining the absolute dose are the same as for the reference conditions. Materials and Methods: Two IMRT treatment plans for common prostate carcinoma case, derived by forward and inverse optimisation, were considered. Detailed geometrical simulation of the μIC and the dose verification set-up was performed. The Monte Carlo (MC) simulation allows us to calculate the delivered dose to water and the dose delivered to the active volume of the ion chamber. However, the measured dose in water is usually derived from chamber readings assuming reference conditions. The MC simulation provides needed correction factors for ion chamber dosimetry in non reference conditions. Results: Dose calculations were carried out for some representative beamlets, a combination of segments and for the delivered IMRT treatments. We observe that the largest dose errors (i.e. the largest correction factors) correspond to the smaller contribution of the corresponding IMRT beamlets to the total dose delivered in the ionization chamber within PTV. Conclusion: The clinical impact of the calculated dose error in PTV measured dose was found to be negligible for studied IMRT treatments

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)

Dusautoy, A.; Roos, M.; Svensson, H.; Andreo, P.

2000-01-01

An IAEA Co-ordinated Research Project was designed to validate the data and procedures included in the International Code of Practice Technical Reports Series (TRS) No. 381, ''The Use of Plane Parallel Ionization Chambers in High Energy Electron and Photon Beams''. This work reviews and analyses the procedures used and the data obtained by the participants of the project. The analysis shows that applying TRS-381 generally produces reliable results. The determination of absorbed dose to water using the electron method in reference conditions is within the stated uncertainties (2.9%). Comparisons have shown TRS-381 is consistent with the AAPM TG-39 protocol within 1% for measurements made in water. Based on the analysis, recommendations are given with respect to: (i) the use of plane parallel ionization chambers of the Markus type, (ii) the values for the fluence correction factor for cylindrical chambers, (iii) the value of the wall correction factor for the Roos chamber in 60 Co beams, and (iv) the use of plastic phantoms and the values of the fluence correction factors. (author)

Neutron accelerator tube having improved ionization section

International Nuclear Information System (INIS)

Givens, W.W.

1982-01-01

A neutron accelerator tube is described having a target section, an ionization section, and a replenisher section for supplying accelerator gas to the ionization section. The ionization section is located between the target and the replenisher section and includes an ionization chamber adapted to receive accelerator gas from the replenisher section. The ionization section further includes spaced cathodes having opposed active surfaces exposed to the interior of the ionization chamber. An anode is located intermediate the cathodes whereby in response to an applied positive voltage, electrons created by field emission are transmitted between the opposed active surfaces of the cathodes and produce the emission of secondary electrons. The active surface of at least one of the cathodes is formulated of a material having a secondary electron emission factor of at least one cathode member located in the tube adjacent to th replenisher section may have a protuberant portion extending axially into the ionization chamber. The other cathode spaced from the first cathode member in the direction of the target has an aperture therein along the axis of the protuberant portion. An annular magnet extends around the exterior of the ionization chamber and envelops the anode member. Means are provided to establish a high permeability magnetic flux path extending outwardly from the opposed poles from the magnet to the active surfaces of the cathode members

Double chamber ion source

International Nuclear Information System (INIS)

Uman, M.F.; Winnard, J.R.; Winters, H.F.

1978-01-01

The ion source is comprised of two discharge chambers one of which is provided with a filament and an aperture leading into the other chamber which in turn has an extraction orifice. A low voltage arc discharge is operated in an inert gas atmosphere in the filament chamber while an arc of higher voltage is operated in the second ionization chamber which contains a vapor which will give the desired dopant ion species. The entire source is immersed in an axial magnetic field parallel to a line connecting the filament, the aperture between the two chambers and the extraction orifice. (author)

Method for detecting and distinguishing between specific types of environmental radiation using a high pressure ionization chamber with pulse-mode readout

Science.gov (United States)

Degtiarenko, Pavel V.

2017-12-19

An environmental radiation detector for detecting and distinguishing between all types of environmental radiation, including photons, charged particles, and neutrons. A large volume high pressure ionization chamber (HPIC) includes BF.sub.3 gas at a specific concentration to render the radiation detector sensitive to the reactions of neutron capture in Boron-10 isotope. A pulse-mode readout is connected to the ionization chamber capable of measuring both the height and the width of the pulse. The heavy charged products of the neutron capture reaction deposit significant characteristic energy of the reaction in the immediate vicinity of the reaction in the gas, producing a signal with a pulse height proportional to the reaction energy, and a narrow pulse width corresponding to the essentially pointlike energy deposition in the gas. Readout of the pulse height and the pulse width parameters of the signals enables distinguishing between the different types of environmental radiation, such as gamma (x-rays), cosmic muons, and neutrons.

Ionizing radiations, detection, dosimetry, spectrometry

International Nuclear Information System (INIS)

Blanc, D.

1997-10-01

A few works in French language are devoted to the detection of radiations. The purpose of this book is to fill a gap.The five first chapters are devoted to the properties of ionizing radiations (x rays, gamma rays, leptons, hadrons, nuclei) and to their interactions with matter. The way of classification of detectors is delicate and is studied in the chapter six. In the chapter seven are studied the statistics laws for counting and the spectrometry of particles is treated. The chapters eight to thirteen study the problems of ionization: charges transport in a gas, ionization chambers (theory of Boag), counters and proportional chambers, counters with 'streamers', chambers with derive, spark detectors, ionization chambers in liquid medium, Geiger-Mueller counters. The use of a luminous signal is the object of the chapters 14 to 16: conversion of a luminous signal in an electric signal, scintillators, use of the Cerenkov radiation. Then, we find the neutron detection with the chapter seventeen and the dosimetry of particles in the chapter eighteen. This book does not pretend to answer to specialists questions but can be useful to physicians, engineers or physics teachers. (N.C.)

Implementation of a laboratory for manufacture, repair and electric calibration of dosemeters based in ionization chambers utilized in radiotherapy

International Nuclear Information System (INIS)

Becker, P.H.B.; Peres, M.A.L.; Moreira, A.J.C.; Nette, H.P.

1998-01-01

Manufacturers of ionization chamber dosimeters for radiotherapy maintain only sales representatives in Brazil with no servicing capability causing difficulties to customers/users to get broken equipment back into operation. Aiming to partially solve this problem, a laboratory for maintenance, repair and electrical calibration was started in 1995 with the support of a two year IAEA Technical Assistance Project (BRA/1/031). (Author)

Automatic control system for measuring currents produced by ionization chambers; Automatizacao de um sistema de medidas de correntes produzidas por camaras de ionizacao e aplicacao na calibracao do {sup 18}F e {sup 153}Sm

Energy Technology Data Exchange (ETDEWEB)

Brancaccio, Franco

2002-07-01

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 {sup 18}F and {sup 153}Sm were obtained, making possible to determine activities of these radionuclides. (author)

A combined segmented anode gas ionization chamber and time-of-flight detector for heavy ion elastic recoil detection analysis

Science.gov (United States)

Ström, Petter; Petersson, Per; Rubel, Marek; Possnert, Göran

2016-10-01

A dedicated detector system for heavy ion elastic recoil detection analysis at the Tandem Laboratory of Uppsala University is presented. Benefits of combining a time-of-flight measurement with a segmented anode gas ionization chamber are demonstrated. The capability of ion species identification is improved with the present system, compared to that obtained when using a single solid state silicon detector for the full ion energy signal. The system enables separation of light elements, up to Neon, based on atomic number while signals from heavy elements such as molybdenum and tungsten are separated based on mass, to a sample depth on the order of 1 μm. The performance of the system is discussed and a selection of material analysis applications is given. Plasma-facing materials from fusion experiments, in particular metal mirrors, are used as a main example for the discussion. Marker experiments using nitrogen-15 or oxygen-18 are specific cases for which the described improved species separation and sensitivity are required. Resilience to radiation damage and significantly improved energy resolution for heavy elements at low energies are additional benefits of the gas ionization chamber over a solid state detector based system.

Ion recombination characteristics of the MDH 10X5-6 ionisation chamber under continuous exposure

International Nuclear Information System (INIS)

Cerra, F.

1982-01-01

Volume recombination of the induced ionization in an X-ray ionization chamber is an important factor affecting the collection efficiency of the charge when such chambers are operated at atmospheric pressure. The volume recombination process is also dependent on the X-ray exposure rate. The theory for recombination in a cylindrical ionization chamber is shown to be in agreement with experimental measurements. For the MDH 10X5-6 cylindrical ionization chamber, the recombination loss is unimportant at exposure rates consistent with its intended usage. (U.K.)

Neutron accelerator tube having improved ionization section

International Nuclear Information System (INIS)

Givens, W.W.

1981-01-01

A neutron accelerator tube having a target section, an ionization section, and a replenisher section for supplying accelerator gas to the ionization section. The ionization section is located between the target and the replenisher section and includes an ionization chamber adapted to receive accelerator gas from the replenisher section. The ionization section further includes spaced cathodes having opposed active surfaces exposed to the interior of the ionization chamber. An anode is located intermediate the cathodes whereby in response to an applied positive voltage, electrons created by field emmission are transmitted between the opposed active surfaces of the cathodes and produce the emission of secondary electrons. The active surface of at least one of the cathodes is formulated of a material having a secondary electron emission factor of at least 2. One cathode member located in the tube adjacent to the replenisher section may have a protuberant portion extending axially into the ioization chamber. The other cathode spaced from the first cathode member in the direction of the target has an aperture therein along the axis of the protuberant portion. An annular magnet extends around the exterior of the ionization chamber and envelops the anode member. Means are provided to establish a high permeability magnetic flux path extending outwardly from the opposed poles from the magnet to the active surfaces of the cathode members

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

International Nuclear Information System (INIS)

Carvalho Conti, L.F. de.

1983-01-01

A high-resolution, parallel Frisch ionization chamber with an efficient area of 320 cm 2 was developed and applied as an alpha spectrometer. The resolution of the spectrum is approximatelly 40 KeV fwhm (full width half maximum) for 233 U 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 233 U 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 HNO 3 - aqueous solution with polymeric membranes containing tri-n-octyl-phosphine oxide adhered on the surface of the 314 cm 2 planchet. The integral back-ground is typically 7 counts/min between 4 and 6 MeV. The sensitivity of the procedure used ofr 238 U is about 30 Bq/1 based on 3S of back-ground, 1 liter sample volume and 30 min counting time. (Author) [pt

Uncertainty in measurements in practice ionization chamber; Incerteza nas medidas realizadas pela pratica da camara de ionizacao

Energy Technology Data Exchange (ETDEWEB)

Sales, Emer; Pinto, Fernando Sandi; Sousa Junior, Samuel Facanha; Freitas, Dayslon Luiz Gaudaret; Andrade, Lucio das Chagas de, E-mail: fernandopintofis@gmail.com [Universidade do Estado do Rio de Janeiro (UERJ), RJ (Brazil)

2016-07-01

The calculation of uncertainty is a mathematical tool widely used in the analysis of experimental data, ensuring that the values obtained by measuring equipment are the most accurate and close to the possible real. This paper presents a theoretical review of uncertainty, and with application of objective determination of uncertainty for repeatability and reproducibility of processes measuring for determining dose of a radioactive source, in practice ionization chamber, held at the Professional Master of Medical Physics State University of Rio de Janeiro. (author)

Uncertainty evaluation of the kerma in the air, related to the active volume in the ionization chamber of concentric cylinders, by Monte Carlo simulation

International Nuclear Information System (INIS)

Lo Bianco, A.S.; Oliveira, H.P.S.; Peixoto, J.G.P.

2009-01-01

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

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)

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)

Fugal, M; McDonald, D; Jacqmin, D; Koch, N; Ellis, A; Peng, J; Ashenafi, M; Vanek, K

2015-01-01

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

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

SU-F-T-362: Quantification and Modelling of the Ionization Chamber Simulation Effective Points On Monaco Treatment Planning System

Energy Technology Data Exchange (ETDEWEB)

Zhang, R; Bai, W [The Fourth Hospital of Hebei Medical University, Shijiazhuang, Hebei (China)

2016-06-15

Purpose: Because of statistical noise in Monte Carlo dose calculations, effective point doses may not be accurate. Volume spheres are useful for evaluating dose in Monte Carlo plans, which have an inherent statistical uncertainty.We use a user-defined sphere volume instead of a point, take sphere sampling around effective point make the dose statistics to decrease the stochastic errors. Methods: Direct dose measurements were made using a 0.125cc Semiflex ion chamber (IC) 31010 isocentrically placed in the center of a homogeneous Cylindric sliced RW3 phantom (PTW, Germany).In the scanned CT phantom series the sensitive volume length of the IC (6.5mm) were delineated and defined the isocenter as the simulation effective points. All beams were simulated in Monaco in accordance to the measured model. In our simulation using 2mm voxels calculation grid spacing and choose calculate dose to medium and request the relative standard deviation ≤0.5%. Taking three different assigned IC over densities (air electron density(ED) as 0.01g/cm3 default CT scanned ED and Esophageal lumen ED 0.21g/cm3) were tested at different sampling sphere radius (2.5, 2, 1.5 and 1 mm) statistics dose were compared with the measured does. Results: The results show that in the Monaco TPS for the IC using Esophageal lumen ED 0.21g/cm3 and sampling sphere radius 1.5mm the statistical value is the best accordance with the measured value, the absolute average percentage deviation is 0.49%. And when the IC using air electron density(ED) as 0.01g/cm3 and default CT scanned EDthe recommented statistical sampling sphere radius is 2.5mm, the percentage deviation are 0.61% and 0.70%, respectivly. Conclusion: In Monaco treatment planning system for the ionization chamber 31010 recommend air cavity using ED 0.21g/cm3 and sampling 1.5mm sphere volume instead of a point dose to decrease the stochastic errors. Funding Support No.C201505006.

OPAL Central Detector (Including vertex, jet and Z chambers)

CERN Multimedia

OPAL was one of the four experiments installed at the LEP particle accelerator from 1989 - 2000. OPAL's central tracking system consists of (in order of increasing radius) a silicon microvertex detector, a vertex detector, a jet chamber, and z-chambers. All the tracking detectors work by observing the ionization of atoms by charged particles passing by: when the atoms are ionized, electrons are knocked out of their atomic orbitals, and are then able to move freely in the detector. These ionization electrons are detected in the different parts of the tracking system. (This piece includes the vertex, jet and Z chambers) In the picture above, the central detector is the piece being removed to the right.

A novel DC microplasma sensor constructed in a cavity PDMS chamber with needle electrodes for fast detection of methanol-containing spirit.

Science.gov (United States)

Luo, Dai-bing; Duan, Yi-xiang; He, Yi; Gao, Bo

2014-12-12

A novel microplasma device, for the first time, was constructed in a cavity Poly (dimethylsiloxane) (PDMS) chamber with two normal syringe needles serve as both the gas channels and the electrodes. This device employs argon plasma with direct current for molecular fragmentation and excitation. The microplasma is generated at atmospheric pressure in the PDMS chamber of 0.5 mL (5 × 10 × 10 mm(3)) volume with a sealable plug. Since the microplasma is maintained in a chamber by separation of the discharge zone and the substrate, stability for a long time of the microplasma is realized which could be observed by argon background emission fluctuation and SEM characterization. This property is beneficial for spectrometric detection of many volatile organics in this chamber. Besides, this kind of microplasma sensor has advantages such as flexibility in replacement of electrodes, convenience in clearance of the discharge chamber, small instrument volume, simple structure, and ease of operation. In addition, methanol-containing spirit samples were chosen to estimate the detecting performance of this microplasma for volatile organic compounds (VOCs) analysis by molecular emission spectrometry. Significant differences are observed upon the introduction of the spirit and the methanol-containing spirit samples. A detection limit of 0.3% is obtained on this microplasma device.

Study of the collecting electrode material of an extrapolation chamber by Monte Carlo simulation

International Nuclear Information System (INIS)

Vedovato, Uly Pita; Santos, William S.; Perini, Ana Paula; Belinato, Walmir

2017-01-01

In this work, the influence of different materials of the collecting electrode on the response of an extrapolation ionization chamber, was evaluated. This ionization chamber was simulated with the MCNP-4C Monte Carlo code and the spectrum of a standard diagnostic radiology beam (RQR5) was utilized. The different results are due to interactions of photons with different materials of the collecting electrode contributing with different values of energy deposited in the sensitive volume of the ionization chamber, which depends on the atomic number of the evaluated materials. The material that presented the least influence was graphite, the original constituent of the ionization chamber. (author)

(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)

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

International Nuclear Information System (INIS)

Cruz E, P.; Villaverde L, A.

2002-01-01

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)

Comparison of measurements of absorbed dose to water using a water calorimeter and ionization chambers for clinical radiotherapy photon and electron beams

International Nuclear Information System (INIS)

Marles, A.E.M.

1981-01-01

With the development of the water calorimeter direct measurement of absorbed dose in water becomes possible. This could lead to the establishment of an absorbed dose rather than an exposure related standard for ionization chambers for high energy electrons and photons. In changing to an absorbed dose standard it is necessary to investigate the effect of different parameters, among which are the energy dependence, the air volume, wall thickness and material of the chamber. The effect of these parameters is experimentally studied and presented for several commercially available chambers and one experimental chamber, for photons up to 25 MV and electrons up to 20 MeV, using a water calorimeter as the absorbed dose standard and the most recent formalism to calculate the absorbed dose with ion chambers. For electron beams, the dose measured with the calorimeter was 1% lower than the dose calculated with the chambers, independent of beam energy and chamber. For photon beams, the absorbed dose measured with the calorimeter was 3.8% higher than the absorbed dose calculated from the chamber readings. Such differences were found to be chamber and energy independent. The results for the photons were found to be statistically different from the results with the electron beams. Such difference could not be attributed to a difference in the calorimeter response

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

International Nuclear Information System (INIS)

Teixeira, G.J.; Peixoto, J.G.P.

2013-01-01

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)

Free-air ionization intensity in the lower atmosphere due to cosmic-ray

International Nuclear Information System (INIS)

Urabe, Itsumasa; Katsurayama, Kousuke

1979-01-01

Being able to be determined by subtracting the gamma-ray ionization intensity from that obtained with ionization chamber, cosmic-ray ionization intensity in free air was estimated by using with 15l air-filled ionization chamber and 3''diameter spherical NaI(Tl) scintillation spectrometer. Optimum applied voltage to 15l air-filled ionization chamber was determined in accordance with Scott and Greening's formula to obtain the ionization intensity caused by gamma-rays and cosmic-rays. Pulse-height distribution of cosmic-rays created in 3''diameter spherical NaI(Tl) scintillation spectrometer was investigated for the precise determination of gamma-ray ionization intensity. Field measurements were carried out by using with these two instruments at about 1.5 meter above the ground in the several locations around Research Reactor Institute of Kyoto University. Cosmic-ray ionization intensity in free air was estimated from the results obtained with air-filled ionization chamber and was 3.33 +- 0.15 μR/hr equivalent in natural environment near Research Reactor Institute of Kyoto University. (author)

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

International Nuclear Information System (INIS)

Guzman Calcina, Carmen S; Oliveira, Lucas N de; Almeida, Carlos E de; Almeida, Adelaide de

2007-01-01

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 cm 2 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

Comparing of the yield curve of the pediatric X-ray equipment using thermoluminescent dosimeters and cylindrical ionization chamber

International Nuclear Information System (INIS)

Filipov, Danielle; Schelin, Hugo R.; Tilly Junior, Joao G.

2014-01-01

The determination of the yield curve of a radiographic equipment should be realized once a year, or when the unit be serviced. Besides being a requirement of ANVISA, through this test is possible to determine the incident air kerma (at a given point in the center of the beam) - INAK. Based on these concepts, the main objective of this work is the comparison of yield curves of the pediatric X-ray apparatus using two different detectors: one cylindrical ionization chamber and thermoluminescent dosimeters type LiF: Mg, Cu, P, as per protocol RLA / 9/057 IAEA. Then the equation of the yield curve (generated by each detector) was used to determine the INAK of 10 pediatric examinations, performed on this equipment. After the process of calibration of both detectors, they were placed side by side at a focus of the tube equipment for determining the performance of the same curve. Finally, using the curves generated by two detectors, INAK values of the 10 tests were calculated (from the kVp values, and mAs focus-patient of each exams), generating difference values at most 5%. As a conclusion, it can be said that the TLD lithium fluoride doped with Mg, Cu and P and the cylindrical ionization chambers may be used satisfactorily to determine the yield curve, whether as quality control or dosimetry

Algorithm for evaluation of parameters of ionization chamber signals from the flash-ADC date

International Nuclear Information System (INIS)

Baturin, V.N.; Balin, D.V.; Maev, E.M.; Petrov, G.E.; Semenchuk, G.G.

1991-01-01

An algorithm for evaluation of parameters of pulses obtained from the ionization chamber (IC) and digitized by Flash-ADC is described. It was designed for determination of the energies and times of arrival of charged particles in DTμ catalyzed fusion that occurs in the IC sensitive volume, in order to measure directly the probability of muon sticking. The algorithm provides the extraction of weak pulses of sloped muon with 50% efficiency, the measurement of fusion energy, especially for long and low amplitude pulses, the recognition of pulse pileups, using special shape analysis procedure. The algorithm was tuned with a special electronic hardware that supplied sequences of pulses with specified amplitudes, durations and shapes and simulation of simulated tritium-noise background. 6 refs.; 7 figs.; 1 tab

Technical Note : A direct ray-tracing method to compute integral depth dose in pencil beam proton radiography with a multilayer ionization chamber

NARCIS (Netherlands)

Farace, Paolo; Righetto, Roberto; Deffet, Sylvain; Meijers, Arturs; Vander Stappen, Francois

2016-01-01

Purpose: To introduce a fast ray-tracing algorithm in pencil proton radiography (PR) with a multilayer ionization chamber (MLIC) for in vivo range error mapping. Methods: Pencil beam PR was obtained by delivering spots uniformly positioned in a square (45x45 mm(2) field-of-view) of 9x9 spots capable

Monte Carlo correction factors for a Farmer 0.6 cm3 ion chamber dose measurement in the build-up region of the 6 MV clinical beam

International Nuclear Information System (INIS)

Pena, J; Sanchez-Doblado, F; Capote, R; Terron, J A; Gomez, F

2006-01-01

Reference dosimetry of photon fields is a well-established subject and currently available protocols (such as the IAEA TRS-398 and AAPM TG-51) provide methods for converting the ionization chamber (IC) reading into dose to water, provided reference conditions of charged particle equilibrium (CPE) are fulfilled. But these protocols cannot deal with the build-up region, where the lack of CPE limits the applicability of the cavity theorems and so the chamber correction factors become depth dependent. By explicitly including the IC geometry in the Monte Carlo simulations, depth-dependent dose correction factors are calculated for a PTW 30001 0.6 cm 3 ion chamber in the build-up region of the 6 MV photon beam. The corrected percentage depth dose (PDD) agrees within 2% with that measured using the NACP 02 plane-parallel ion chamber in the build-up region at depths greater than 0.4 cm, where the Farmer chamber wall reaches the phantom surface

Correction of measured Gamma-Knife output factors for angular dependence of diode detectors and PinPoint ionization chamber.

Science.gov (United States)

Hršak, Hrvoje; Majer, Marija; Grego, Timor; Bibić, Juraj; Heinrich, Zdravko

2014-12-01

Dosimetry for Gamma-Knife requires detectors with high spatial resolution and minimal angular dependence of response. Angular dependence and end effect time for p-type silicon detectors (PTW Diode P and Diode E) and PTW PinPoint ionization chamber were measured with Gamma-Knife beams. Weighted angular dependence correction factors were calculated for each detector. The Gamma-Knife output factors were corrected for angular dependence and end effect time. For Gamma-Knife beams angle range of 84°-54°. Diode P shows considerable angular dependence of 9% and 8% for the 18 mm and 14, 8, 4 mm collimator, respectively. For Diode E this dependence is about 4% for all collimators. PinPoint ionization chamber shows angular dependence of less than 3% for 18, 14 and 8 mm helmet and 10% for 4 mm collimator due to volumetric averaging effect in a small photon beam. Corrected output factors for 14 mm helmet are in very good agreement (within ±0.3%) with published data and values recommended by vendor (Elekta AB, Stockholm, Sweden). For the 8 mm collimator diodes are still in good agreement with recommended values (within ±0.6%), while PinPoint gives 3% less value. For the 4 mm helmet Diodes P and E show over-response of 2.8% and 1.8%, respectively. For PinPoint chamber output factor of 4 mm collimator is 25% lower than Elekta value which is generally not consequence of angular dependence, but of volumetric averaging effect and lack of lateral electronic equilibrium. Diodes P and E represent good choice for Gamma-Knife dosimetry. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

X-ray and γ-radiation personnel monitoring by means of ionization chambers

International Nuclear Information System (INIS)

Gavrilovskij, L.P.; Nikitin, V.I.

1981-01-01

Several sets of condensator ionization chambers for measuring a dose of short-wave X-ray and gamma radiations within the limits of 0.005-50 R is described in short. In particular the following sets for personnel monitoring are described: the KID-2 set intended for determining an exposure dose of roentgen and gamma radiations of 150 keV - 2 MeV energy within the limits of 0.005-1R; the DK-02 set providing the measurement of personnel exposure doses of X-ray and gamma radiations within the limits of 0.02-200 mR in the energy range of 100 keV-2 MeV; the DP-22 V, DP-24 sets providing the measurement of an exposure dose of X-ray and gamma radiations within the limits of 1-50 R at a power of 0.5-200 R/h in the energy range of 0.1-2 MeV. An order of work with the sets is described [ru

Large-Area Neutron Detector based on Li-6 Pulse Mode Ionization Chamber

International Nuclear Information System (INIS)

Chung, K.; Ianakiev, K.D.; Swinhoe, M.T.; Makela, M.F.

2005-01-01

Prototypes of a Li-6 Pulse Mode Ionization Chamber (LiPMIC) have been in development for the past two years for the purpose of providing large-area neutron detector. this system would be suitable for remote deployment for homeland security and counterterrorism needs at borders, ports, and nuclear facilities. A prototype of LiPMIC is expected to provide a similar level of performance to the current industry-standard, He-3 proportional counters, while keeping the initial cost of procurement down by an order of magnitude, especially where large numbers of detectors are required. The overall design aspect and the efficiency optimization process is discussed. Specifically, the MCNP simulations of a single-cell prototype were performed and benchmarked with the experimental results. MCNP simulations of a three dimensional array design show intrinsic efficiency comparable to that of an array of He-3 proportional counters. LiPMIC has shown steady progress toward fulfilling the design expectations and future design modification and optimization are discussed.

201 MHz Cavity R and D for MUCOOL and MICE

International Nuclear Information System (INIS)

Li, Derun; Virostek, Steve; Zisman, Michael; Norem, Jim; Bross, Alan; Moretti, Alfred; Norris, Barry; Torun, Yagmur; Phillips, Larry; Rimmer, Robert; Stirbet, Mircea; Reep, Michael; Summers, Don

2006-01-01

We describe the design, fabrication, analysis and preliminary testing of the prototype 201 MHz copper cavity for a muon ionization cooling channel. Cavity applications include the Muon Ionization Cooling Experiment (MICE) as well as cooling channels for a neutrino factory or a muon collider. This cavity was developed by the US muon cooling (MUCOOL) collaboration and is being tested in the MUCOOL Test Area (MTA) at Fermilab. To achieve a high accelerating gradient, the cavity beam irises are terminated by a pair of curved, thin beryllium windows. Several fabrication methods developed for the cavity and windows are novel and offer significant cost savings as compared to conventional construction methods. The cavity's thermal and structural performances are simulated with an FEA model. Preliminary high power RF commissioning results will be presented

Absorbed dose to water determination with ionization chamber dosimetry and calorimetry in restricted neutron, photon, proton and heavy-ion radiation fields.

Science.gov (United States)

Brede, H J; Greif, K-D; Hecker, O; Heeg, P; Heese, J; Jones, D T L; Kluge, H; Schardt, D

2006-08-07

Absolute dose measurements with a transportable water calorimeter and ionization chambers were performed at a water depth of 20 mm in four different types of radiation fields, for a collimated (60)Co photon beam, for a collimated neutron beam with a fluence-averaged mean energy of 5.25 MeV, for collimated proton beams with mean energies of 36 MeV and 182 MeV at the measuring position, and for a (12)C ion beam in a scanned mode with an energy per atomic mass of 430 MeV u(-1). The ionization chambers actually used were calibrated in units of air kerma in the photon reference field of the PTB and in units of absorbed dose to water for a Farmer-type chamber at GSI. The absorbed dose to water inferred from calorimetry was compared with the dose derived from ionometry by applying the radiation-field-dependent parameters. For neutrons, the quantities of the ICRU Report 45, for protons the quantities of the ICRU Report 59 and for the (12)C ion beam, the recommended values of the International Atomic Energy Agency (IAEA) protocol (TRS 398) were applied. The mean values of the absolute absorbed dose to water obtained with these two independent methods agreed within the standard uncertainty (k = 1) of 1.8% for calorimetry and of 3.0% for ionometry for all types and energies of the radiation beams used in this comparison.

Dosimetry with tissue-equivalent ionisation chambers in fast neutron fields for biomedical applications

International Nuclear Information System (INIS)

Zoetelief, J.; Broerse, J.J.

1983-01-01

The use of calibrated tissue-equivalent (TE) ionisation chambers is commonly considered to be the most practical method for total absorbed dose determinations in mixed neutron-photon fields for biomedical applications. The total absorbed dose can be derived from the charge produced within the cavity of an ionisation chamber employing a number of physical parameters. To arrive at the charge produced in the cavity several correction factors have to be introduced which are related to the operational characteristics of the chambers. Information on the operational characteristics of four TE ionisation chambers is presented in relation to ion collection, density and composition of gas in the cavity, wall thickness and effective point of measurement. In addition, some recent results from an ionisation chamber operated at high gas pressures are presented. The total absorbed doses derived from TE ionisation chambers show agreement within the uncertainty limits with results from other independent dosimetry methods, i.e., differential fluence measurements and a TE calorimeter. Conscientious experimentation and a common data base can provide dosimetry results with TE ionisation chambers with variations of less than +-2%. (author)

The magic cube and the pixel ionization chamber: detectors for monitor and dosimetry of radiotherapy beams

International Nuclear Information System (INIS)

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

2003-01-01

Tumor therapy takes advantage of the energy deposition of radiation to concentrate high doses in the target while sparing healthy tissue. Elective pathologies for highly conformal radiotherapies such as photon Intensity Modulated Radiotherapy (IMRT) and radiotherapy with hadrons are head and neck, eye, prostate and in general all tumors that are either deep or located close to critical organs. In the world there are several centers that are using such techniques and a common problem that is being experienced is the verification of treatment plans and monitoring of the beam. We have designed and built two detectors that allow 2D and 3D measurements of dose and fluence of such beams. The detectors allow measurements on big surfaces, up to 25*25 cm 2 . The active media are parallel plate, strip and pixel segmented ionization chambers with front-end Very Large Scale Integration (VLSI) readout and PC based data acquistion. The description of dosimeter, chamber and electronics will be given with results from beam tests and therapy plan verification

Calibration of well-type ionization chambers

International Nuclear Information System (INIS)

Alves, C.F.E.; Leite, S.P.; Pires, E.J.; Magalhaes, L.A.G.; David, M.G.; Almeida, C.E. de

2015-01-01

This paper presents the methodology developed by the Laboratorio de Ciencias Radiologicas and presently in use for determining of the calibration coefficient for well-type chambers used in the dosimetry of 192 Ir high dose rate sources. Uncertainty analysis involving the calibration procedure are discussed. (author)

Characterization of 2 MeV, 4 MeV, 6 MeV and 18 MeV buildup caps for use with a 0.6 cubic centimeter thimble ionization chamber

International Nuclear Information System (INIS)

Salyer, R.L.; VanDenburg, J.W.; Prinja, A.K.; Kirby, T.; Busch, R.; Hong-Nian Jow

1996-07-01

The purpose of this research is to characterize existing 2 MeV, 4 MeV and 6 MeV buildup caps, and to determine if a buildup cap can be made for the 0.6 cm 3 thimble ionization chamber that will accurately measure exposures in a high-energy photon radiation field. Two different radiation transport codes were used to computationally characterize existing 2 MeV, 4 MeV, and 6 MeV buildup caps for a 0.6 cm 3 active volume thimble ionization chamber: ITS, The Integrated TIGER Series of Coupled Electron-Photon Monte Carlo Transport Codes; and CEPXS/ONEDANT, A One-Dimensional Coupled Electron-Photon Discrete Ordinates Code Package. These codes were also used to determine the design characteristics of a buildup cap for use in the 18 MeV photon beam produced by the 14 TW pulsed power HERMES-III electron accelerator. The maximum range of the secondary electron, the depth at which maximum dose occurs, and the point where dose and collision kerma are equal have been determined to establish the validity of electronic equilibrium. The ionization chamber with the appropriate buildup cap was then subjected to a 4 MeV and a 6 MeV bremmstrahlung radiation spectrum to determine the detector response

Calibration methods of plane-parallel ionization chambers used in electron dosimetry; Metodos de calibracao de camaras de ionizacao de placas paralelas para dosimetria de feixes de eletrons

Energy Technology Data Exchange (ETDEWEB)

Bulla, Roseli Tadeu

1999-07-01

The use of linear accelerators in radiotherapy is of great importance in Medicine, and according to international recommendations the electron beam dosimetry has to be performed using plane-parallel ionization chambers, previously calibrated in standard gamma radiation fields at accredited laboratories. In this work, calibration methods of plane-parallel ionization chambers used in dosimetry procedures of high energy electron beams of clinical accelerators were presented, tested and intercompared. The experiments were carried out using gamma radiation beams of {sup 60} Co at the Calibration Laboratory of Clinical Dosemeters at IPEN and electron beams od 4 to 16 MeV at the Radiotherapy Department of Hospital Israelita Albert Einstein, Sao Paulo. A method was chosen to be established at IPEN. Proposals of the calibration procedure, calibration certificate and data sheets are presented. (author)

Space shuttle orbit maneuvering engine reusable thrust chamber program

Science.gov (United States)

Senneff, J. M.

1975-01-01

Reusable thrust chamber and injector concepts were evaluated for the space shuttle orbit maneuvering engine (OME). Parametric engine calculations were carried out by computer program for N2O4/amine, LOX/amine and LOX/hydrocarbon propellant combinations for engines incorporating regenerative cooled and insulated columbium thrust chambers. The calculation methods are described including the fuel vortex film cooling method of combustion gas temperature control, and performance prediction. A method of acceptance of a regeneratively cooled heat rejection reduction using a silicone oil additive was also demonstrated by heated tube heat transfer testing. Regeneratively cooled thrust chamber operation was also demonstrated where the injector was characterized for the OME application with a channel wall regenerative thrust chamber. Bomb stability testing of the demonstration chambers/injectors demonstrated recovery for the nominal design of acoustic cavities. Cavity geometry changes were also evaluated to assess their damping margin. Performance and combustion stability was demonstrated of the originally developed 10 inch diameter combustion pattern operating in an 8 inch diameter thrust chamber.

Resonance ionization in a gas cell: a feasibility study for a laser ion source

International Nuclear Information System (INIS)

Qamhieh, Z.N.; Vandeweert, E.; Silverans, R.E.; Duppen, P. van; Huyse, M.; Vermeeren, L.

1992-01-01

A laser ion source based on resonance photo-ionization in a gas cell is proposed. The gas cell, filled with helium, consists of a target chamber in which the recoil products are stopped and neutralized, and an ionization chamber where the atoms of interest are selectively ionized by the laser light. The extraction of the ions from the ionization chamber through the exit hole-skimmer setup is similar to the ion-guide system. The conditions to obtain an optimal system are given. The results of a two-step one-laser resonance photo-ionization of nickel and the first results of laser ionization in a helium buffer gas cell are presented. (orig.)

Reactor oscillator project - Theoretical study; operation problems; choice of the ionization chamber; Projekat reaktorskog oscilatora - Teorijska razmatranja; Problematika rada, Izbor jonizacione komore

Energy Technology Data Exchange (ETDEWEB)

Lolic, B; Markovic, V [Institute of Nuclear Sciences Boris Kidric, Laboratorija za fiziku reaktora, Vinca, Beograd (Serbia and Montenegro)

1961-12-15

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.

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

International Nuclear Information System (INIS)

Barreras Caballero, A. A.; Hernandez Garcia, J.J.; Alfonso Laguardia, R.

2009-01-01

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)

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

International Nuclear Information System (INIS)

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. (orig.)

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

International Nuclear Information System (INIS)

Gorlachev, G.E.

2002-01-01

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