A hexagonal multi-element CsI(Tl)-photodiode module for gamma-ray imaging

The technique of producing images of gamma-ray sources by means of coded masks, wherein the shadow of an aperture is cast onto a position-sensitive detector plane is already well-known and has been employed for some time in the fields of nuclear physics, medical diagnostics and high energy astronomy. In order to evaluate several design and scientific aspects of a proposed astronomical gamma-ray images, a prototype module has been constructed consisting of 37 hexagonal CsI(Tl) elements, each of 1 cm² cross-section and 3 cm length. Each bar is viewed by a photodiode for read-out thus constituting a two dimensional position-sensitive array which can operate from 0.1 to 6 MeV. In this paper we describe the experimental arrangement, the readout electronics and some of the experimental results