Evaluating the Response of Polyvinyl Toluene Scintillators used in Portal Detectors; Master's thesis

摘要

Scintillator panels of the same type as those used in portal detector units, made of polyvinyl toluene and measuring 12 x 15 x 2 in were purchased from three vendors. Each vendor supplied two scintillators, one wrapped by the vendor with aluminum foil coated mylar, and two unwrapped. The scintillators where exposed to an approximately 8 microCurie source collimated 137Cs source which decays with a 662 keV gamma-ray 85% of the time. A Hamamatsu R329-02 photomultiplier tube was optically mated to the 12 x 2 in surface of the scintillator. The pulse-height spectrum was recorded with the source placed at different positions across the surface of the scintillator. Analysis of the pulse-height spectrum determined efficiency and resolution differences across the surface of the scintillation panels. The resolution ranged from 23% at the corner furthest from the PMT to 33% an inch away from the PMT. The absolute efficiency ranged from 0.02 to 0.027 . The location and height of the Compton edge had trends, with the greatest height at the center and dropping off on the sides, but the peak location having a maximum in the corner along the axis of the PMT.