Limits...
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.


Transit time (τi) as a function in applied polarizing potential, inset: the linear relation between τi (s) and the chamber volume (cm3).
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4664224&req=5

f5-poljradiol-80-515: Transit time (τi) as a function in applied polarizing potential, inset: the linear relation between τi (s) and the chamber volume (cm3).

Mentions: Transit time (τi) was evaluated for the chambers included in this study and over a range of the applied potential of (200–1200) V and is represented in Figure 5. As shown in that figure, transit time decreased in a power trend as the applied potential (V) increased, and it is clear from the inset of the figure that at constant V, transit time increases as the chamber volume increases. For the chamber A3, τi was 0.078 s at 200 V of the applied voltage, and reached 0.0013 s at 1200 V. On the other hand, A8, the largest among the studied ion chambers, had a τi value of 1.097 s at 600 V while it decreased to become 0.548 s at V=1200 V. Close values were obtained by Geleijns et al., [23] where transit time (τi) was evaluated for the A5 Exradin ion chamber resulting in a value of 0.050 s at an ambient polarizing potential (300 V). The value obtained through this work for the same conditions was 0.045 s. However, dimensions mentioned for the A5 ion chamber are slightly different from those mentioned in this work.


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

Maghraby AM - Pol J Radiol (2015)

Transit time (τi) as a function in applied polarizing potential, inset: the linear relation between τi (s) and the chamber volume (cm3).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f5-poljradiol-80-515: Transit time (τi) as a function in applied polarizing potential, inset: the linear relation between τi (s) and the chamber volume (cm3).
Mentions: Transit time (τi) was evaluated for the chambers included in this study and over a range of the applied potential of (200–1200) V and is represented in Figure 5. As shown in that figure, transit time decreased in a power trend as the applied potential (V) increased, and it is clear from the inset of the figure that at constant V, transit time increases as the chamber volume increases. For the chamber A3, τi was 0.078 s at 200 V of the applied voltage, and reached 0.0013 s at 1200 V. On the other hand, A8, the largest among the studied ion chambers, had a τi value of 1.097 s at 600 V while it decreased to become 0.548 s at V=1200 V. Close values were obtained by Geleijns et al., [23] where transit time (τi) was evaluated for the A5 Exradin ion chamber resulting in a value of 0.050 s at an ambient polarizing potential (300 V). The value obtained through this work for the same conditions was 0.045 s. However, dimensions mentioned for the A5 ion chamber are slightly different from those mentioned in this work.

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.