Design and performance of soft Gamma-ray detector for NeXT mission

The soft gamma-ray detector (SGD) on board NeXT (Japanese future high energy astrophysics mission) is a Compton telescope with narrow field of view (FOV), which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor gamma-ray detector which consists of silicon and CdTe (cadmium telluride) detectors. It can detect photons in a wide energy band (0.05-1 MeV) at a background level of 5 /spl times/ 10/sup -7/ counts/s/cm/sup 2//keV; the silicon layers are required to improve the performance at a lower energy band (