Detector to study low-flux hard X-ray/gamma-ray sources

Abstract We have developed a new kind of phoswich counters that will be capable of detecting low flux hard X-rays/gamma-rays from astronomical objects. The new phoswich counter consists of a small inorganic scintillator with a fast decay time (the detection part) glued to the interior bottom surface of a rectangular well-shaped block of another inorganic scintillator with a slow decay time (the shielding part). Here, the well-shaped shielding part acts as an active collimator as well as an active shield. We have built a detector system consisting of 64 such phoswich counters: newly developed scintillator (GSO) is used for the detection part and CsI( Tl ) is used for the shielding part. The total geometrical area of the 64 detection parts is about 740cm 2 and its 3σ sensitivity is expected to reach below 10 −5 cm −2 s −1 keV −1 up to 700keV. With several improvements such detectors will be able to detect hard X-rays/gamma-rays at a flux level around 10 −6 cm −2 s −1 keV −1 upto 2 MeV.