BARC/PUB/2024/0031

 
 

Development and establishment of a parallel plate ionization chamber as a transfer standard for measurement of dose to tissue in beta radiation fields

 
     
 
Author(s)

Rakshit, S.; Kulkarni, M. S.
(RSSD;HPD)

Source

Applied Radiation and Isotopes, 2024. Vol. 206: pp. 1-6: Article no. 111213

ABSTRACT

A parallel-plate ionization chamber (PPC) with a nominal volume of 8.16 cm3 was developed based on theo-retically simulated design parameters. Its purpose is to serve as a transfer standard for dosimetry in a beta ra-diation field. The entrance window of the PPC consists of an aluminized Mylar sheet with a thickness of 1.4 mg/ cm2. The collecting and guard electrodes are created by applying a graphite coating on a Poly Methyl Meth-acrylate (PMMA) substrate with a thickness of 5 mm. The nominal sheet resistance of the graphite-coated PMMA substrate was measured using a four-probe technique and found to be approximately 800 Ω per square (Ω/□). Dosimetric characterization of the PPC was performed in the ISO 6980 reference beta radiation field, utilizing 90Sr-90Y and 85Kr beta radiation sources. The assessment included studies on short-term stability, linearity, current-to-voltage characteristics, stabilization time, and leakage current. The PPC was calibrated and estab-lished as a transfer standard using the ‘Extrapolation Ionization Chamber,’ recognized as an absolute standard for dose to tissue in 90Sr-90Y and 85Kr beta sources within the laboratory. The calibration coefficient of the PPC indicates an energy dependence of 0.6 % for 90Sr-90Y and 85Kr beta sources.

 
 
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