A New Position-Sensitive Detector For Gamma-Ray Astronomy In The Energy-Range Of 15 Kev To 1 Mev

ABSTRACT A new position-sensitive gamma-ray detector to cover the energy band from 15 keY to 1 MeV has been investigated. The detector concept is based on the use of an array of discrete 1 x 1 x 5 cm phoswich scintillation bars viewed by position-sensitive photomultiplier tube(PSPMT). The test results show that the energy resolution, about 40%FWHM at 60 keY and 12% FWHM at 511 keY, can be easily obtained when using CsI(Na) crystals. The point-spread function for the location of each event is smaller than the cross section of a single bar over the entire energy range. This means that there is virtually no ambiguity in locating signals from different bars. The outputs from the CsI(Na) and GSO veto crystals can be distinguished by a pulse-shape discriminator designed especially for thissystem. Those multi-site events which deposit energy only in the CsI(Na) array can be recognised using the positionsensing capability of the tube. 1. INTRODUCTION In order to image hard X-rays, some telescopes have incorporated multi-wire proportional counters as the position-sensitive detector1 . Whilst their energy and position-resolutions are superior to that of scintillation detectors, their