INVESTIGATION OF PULSE SHAPE ANALYZERS FOR PHOSWICH DETECTORS IN SPACE-BORNE HARD X-RAY EXPERIMENTS

A low-background telescope for hard X-ray astronomy (15-250 keV), comprising arrays of NaI(Tl)/CsI(Na) phoswiches as photon collectors, was recently developed by our group in collaboration with the Center for Space Research at MIT. The background rejection efficiency of such a telescope, and hence the minimum source detectability in a given time, critically depends on the performance of the phoswich pulse shape analyzer (PSA) in a space radiation environment. Results from theoretical and experimental work on analyzer configurations based on zero-crossing detection are presented. This led to the selection of an optimum configuration for space application. The in-situ performance of this analyzer was evaluated in a balloon-borne hard X-ray experiment, showing excellent discrimination efficiency throughout the entire energy regime. © 1979.