IMAGER PROTOTYPE FOR GAMMA-RAY ASTRONOMY - FUNCTIONAL PERFORMANCE

A prototype module for the imager on INTEGRAL (INTErnational Gamma Ray Astrophysics Laboratory) [1], has been constructed for laboratory and space tests by means of a balloon launch. The main detector is design ed to operate in the energy range from 0.25 to 10 MeV and consists of 96 CsI(Tl) bars 15 cm in length. At 662 keV, the typical performance i s 1.5 cm FWHM spatial resolution (1 sigma) along the bar, and 15% ener gy resolution. In this paper, the work carried out during instrument c onstruction and calibration is described with emphasis on the simple m ethod which has been implemented to normalise the non uniformity of th e performance of the bars. The measurements of energy threshold and en ergy and position resolution are presented and discussed.