Studies on commercially available thin wall G-M detectors

Thin-wall G.M. detectors are widely used for detection and estimation of beta contamination. These detectors can be classified into two categories i) glass-wall detectors ii) metal-wall detectors. Wall thickness of glass wall detectors is about 35-40 mg/cm2 and that of metal wall detectors about 40-50 mg/cm2. Commercially available glass-wall g.m. detectors made by ECIL, Hyderabad and metal-wall detector manufactured by LND, USA were studied for their response to beta particles of 137Cs. Efficiency was determined for a small disc source, line source and a plane source. Also response to a point gamma source of 60Co and 137Cs was studied. It was observed that efficiency of glass-wall detectors was at least two times the efficiency of metal-wall detectors for beta radiation of 137Cs and hence it should be the detector of choice for detecting mixed fission product contamination. The report presents the details of the measurements. (author)