Hard X-ray/soft γ-ray detector with high directionality development of well-type phoswich counters

A new hard X-ray/soft γ-ray detector with sensitivity much higher than existing ones has been developed for astronomical observation. This detector, the well-type phoswich counter, is inherently highly directional and suppresses internal and external background effectively. Two prototype detectors, Welcome-1(Mk1) and Welcome-1(Mk2), have been built and flown on balloons in Brazil and Japan to observe several astronomical hard X-ray/soft γ-ray sources successfully. Based on these experiences, an improved version, Welcome-2, is under development for the Astro-E satellite project. In this improved version, a new inorganic scintillator YAP is combined with BGO to give sensitivity around 10-7/cm2/s/keV. This report describes our R/D works on the well-type phoswich counters and improvements we have made on new inorganic scintillators GSO and YAP. (author)