Performance evaluation of plastic scintillators for gamma-ray portal monitors

The paper describes the tests carried out with plastic scintillators developed by TIFR for applications in gamma-ray portal monitors. Two types of slabs with dimensions 24.5 x 24.5 x 2.1 cm and 50 x 50 x 5 cm were evaluated for gamma sensitivity using standard gamma-ray sources. The slabs were coupled to PM tubes of the type 9266KSB23, made by Electron Tubes Ltd. A system consisting of 1k channel MCA, spectroscopy amplifier and PC-based scintillation counting setup was used to acquire count data and spectra. A windows based utility was developed to enhance the speed and accuracy of computation of various performance parameters of the scintillators. The two slabs could be used to detect minimum quantity 0.187 μCi and 0.082μCi of 60Co, 0.388μCi and 0.228μCi of 137Cs and 0.137 mCi and 0.246 mCi of 241Am respectively. (author)