Development of the hard X-ray detector for the ASTRO-E mission

The Hard X-ray Detector (HXD) is one of three instruments on the fifth Japanese X-ray astronomy satellite, ASTRO-E, scheduled for launch in 2000. The HXD consists of a 4x4 = 16 modular assembly of identical counters, each consisting of a combination of YAP(or GSO)/BGO well-type phoswich counters and silicon PIN diodes. The field of view of the detector for high energy photons is restricted to 4 degrees x 4 degrees by active collimators made of BGO and the fov for low energy photons is restricted to 0.5 degrees x 0.5 degrees by the fine passive collimators made of phosphor bronze. The detector is characterized by a low background reaching severalx10(-6) c/s/cm(2)/keV. Combined with the other two instruments for soft X-ray observations (0.5-12 keV), the ASTRO-E mission will cover the entire range of soft and hard X-rays with the highest sensitivity ever achieved. Furthermore, thick EGO counters which surround the 4x4 matrix of well-type phoswich counters act as a gamma-ray burst detector in the energy band of 100-2000 keV.