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Efficiencies of Some Spherical Ion Chambers in Continuous and Pulsed Radiation: A Numerical Evaluation.

Maghraby AM - Pol J Radiol (2015)

Bottom Line: Evaluation of the collection efficiencies of ion chambers is a necessity for the proper evaluation of radiation quantities in different applications.Through current work there is an attempt of focusing on how the selection of ion chamber dimensions may affect the overall collection efficiency in addition to the proper selection of other influencing parameters.Also, collection efficiencies considering diffusion current values (fd) were evaluated for the five chambers, and plotted versus the applied polarizing potential.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Faculty of Science - Alzulfi - Almajmaah University, Almajmaah, Saudi Arabia ; Department of Radiation Dosimetry, National Institute of Standards (NIS), Ionizing Radiation Metrology Laboratory, Giza, Egypt.

ABSTRACT

Background: Evaluation of the collection efficiencies of ion chambers is a necessity for the proper evaluation of radiation quantities in different applications. Overall collection efficiency is the product of three different values: collection efficiencies considering contributions of, volume recombination, back-diffusion loss and initial recombination, the later may be neglected at low charge rates.

Material/methods: Five common spherical ion chambers of different volumes and specifications were included in this study for the evaluation of volume recombination collection efficiency and back diffusion collection efficiency for continuous and pulsed radiation and at different values of the applied polarizing potential. Through current work there is an attempt of focusing on how the selection of ion chamber dimensions may affect the overall collection efficiency in addition to the proper selection of other influencing parameters.

Results: Collection efficiencies considering volume recombination (fv) for five spherical ion chambers of common types were evaluated for continuous and pulsed radiation over a wide range of polarizing potential. The relation between the ion chamber volume and its evaluated collection efficiencies were studied for both continuous and pulsed radiation; transit time values for the ion chambers included in this study were evaluated at different values of applied potential. Also, collection efficiencies considering diffusion current values (fd) were evaluated for the five chambers, and plotted versus the applied polarizing potential.

Conclusions: Through this study it was feasible to evaluate numerically the collection efficiencies of some spherical ion chambers considering volume recombination and back diffusion effects; the affecting parameters were studied and highlighted.

No MeSH data available.


Volume collection efficiency for pulsed radiation (fV) values corresponding to different values of chamber volume (cm3) evaluated at different charge density per pulse values (q).
© Copyright Policy - open-access
Related In: Results  -  Collection


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f4-poljradiol-80-515: Volume collection efficiency for pulsed radiation (fV) values corresponding to different values of chamber volume (cm3) evaluated at different charge density per pulse values (q).

Mentions: Figure 4 represents the relation between the chamber volume (cm−3) and the evaluated collection efficiencies (fv) over a wide range of charge density per pulse (q) values at polarizing potential of V=700 V. From Figure 4, and despite the absence of a certain behavior regarding the change in fv as a function in the chamber volume, it is noticeable that fv decreases as the chamber volume increases; for example at the same charge density per pulse, q=7.8×10−4 cm−3/pulse which is corresponding to a high ionization intensity, fv for the A4 ion chamber is found to be 1.27%, i.e. less than that for the A3 ion chamber and 1.89% higher than that for the A5 ion chamber, while the A6 ion chamber had fv of about 12.27%. i.e. less than A5 and a very poor value for the A8 ion chamber because of the high q value. At a much lower q value, q=1.3×10−5 cm−3/pulse, fv values became better and closer to each other; fv for the A4 ion chamber was only 0.02% lower than that for A3, and 0.03% higher than fv of the A5 ion chamber, while A6 showed fv value of 0.21% lower than that of A5 and even the A8 ion chamber volume efficiency, fv was 0.9971 which was 2.88% lower than that of A3.


Efficiencies of Some Spherical Ion Chambers in Continuous and Pulsed Radiation: A Numerical Evaluation.

Maghraby AM - Pol J Radiol (2015)

Volume collection efficiency for pulsed radiation (fV) values corresponding to different values of chamber volume (cm3) evaluated at different charge density per pulse values (q).
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4664224&req=5

f4-poljradiol-80-515: Volume collection efficiency for pulsed radiation (fV) values corresponding to different values of chamber volume (cm3) evaluated at different charge density per pulse values (q).
Mentions: Figure 4 represents the relation between the chamber volume (cm−3) and the evaluated collection efficiencies (fv) over a wide range of charge density per pulse (q) values at polarizing potential of V=700 V. From Figure 4, and despite the absence of a certain behavior regarding the change in fv as a function in the chamber volume, it is noticeable that fv decreases as the chamber volume increases; for example at the same charge density per pulse, q=7.8×10−4 cm−3/pulse which is corresponding to a high ionization intensity, fv for the A4 ion chamber is found to be 1.27%, i.e. less than that for the A3 ion chamber and 1.89% higher than that for the A5 ion chamber, while the A6 ion chamber had fv of about 12.27%. i.e. less than A5 and a very poor value for the A8 ion chamber because of the high q value. At a much lower q value, q=1.3×10−5 cm−3/pulse, fv values became better and closer to each other; fv for the A4 ion chamber was only 0.02% lower than that for A3, and 0.03% higher than fv of the A5 ion chamber, while A6 showed fv value of 0.21% lower than that of A5 and even the A8 ion chamber volume efficiency, fv was 0.9971 which was 2.88% lower than that of A3.

Bottom Line: Evaluation of the collection efficiencies of ion chambers is a necessity for the proper evaluation of radiation quantities in different applications.Through current work there is an attempt of focusing on how the selection of ion chamber dimensions may affect the overall collection efficiency in addition to the proper selection of other influencing parameters.Also, collection efficiencies considering diffusion current values (fd) were evaluated for the five chambers, and plotted versus the applied polarizing potential.

View Article: PubMed Central - PubMed

Affiliation: Department of Physics, Faculty of Science - Alzulfi - Almajmaah University, Almajmaah, Saudi Arabia ; Department of Radiation Dosimetry, National Institute of Standards (NIS), Ionizing Radiation Metrology Laboratory, Giza, Egypt.

ABSTRACT

Background: Evaluation of the collection efficiencies of ion chambers is a necessity for the proper evaluation of radiation quantities in different applications. Overall collection efficiency is the product of three different values: collection efficiencies considering contributions of, volume recombination, back-diffusion loss and initial recombination, the later may be neglected at low charge rates.

Material/methods: Five common spherical ion chambers of different volumes and specifications were included in this study for the evaluation of volume recombination collection efficiency and back diffusion collection efficiency for continuous and pulsed radiation and at different values of the applied polarizing potential. Through current work there is an attempt of focusing on how the selection of ion chamber dimensions may affect the overall collection efficiency in addition to the proper selection of other influencing parameters.

Results: Collection efficiencies considering volume recombination (fv) for five spherical ion chambers of common types were evaluated for continuous and pulsed radiation over a wide range of polarizing potential. The relation between the ion chamber volume and its evaluated collection efficiencies were studied for both continuous and pulsed radiation; transit time values for the ion chambers included in this study were evaluated at different values of applied potential. Also, collection efficiencies considering diffusion current values (fd) were evaluated for the five chambers, and plotted versus the applied polarizing potential.

Conclusions: Through this study it was feasible to evaluate numerically the collection efficiencies of some spherical ion chambers considering volume recombination and back diffusion effects; the affecting parameters were studied and highlighted.

No MeSH data available.