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N. Kazuhiro, T. Tadayuki, W. Shin (ISAS/JAXA), K. Tune, M. Greg, T. Hiroyasu (SLAC), F. Yasushi (Dept. Phys., Hiroshima University), N. Masaharu (Dept. Phys., Osaka University), K. Motohide, M. Kazuo (Dept. Phys., U. Tokyo), T. Makoto (Dept. Phys., Saitama University), T. Yukikatsu (Cosmic-Ray lab., RIKEN), K. Jun (Dept. Phys., Tokyo Institute of Technology), NeXT SGD Collaboration
The Soft Gamma-ray Detector (SGD) is a new generation compton telescope aiming at an order of magnitude improvement of sensitivity at the energy band of 80-1000 keV. The SGD is proposed to be launched at 2010-11, onboard the Japanese new astronomy satellite ``NeXT." Novel idea of the SGD is to use a Si/CdTe semiconductor multi-layer compton telescope within the low background environment achieved by the deep active shield with a narrow opening angle. Because compton telescope hosts an imaging capability, any residual backgrounds, such as the activation of the main detector itself, can by rejected by requiring the compton scattering angle to be consistent with the opening angle of the shield, which is about 4 degree with current design.
The key technologies of the SGD are the deep active shield which is a direct heritage of the Hard X-ray Detector onboard Astro-E2 mission, and the newly developed Si/CdTe compton telescope. Current design of the Si/CdTe compton telescope consists of 24 layers of 0.5 mm thick double-sided-silicon-strip-detector (DSSD) as a scatterer, surrounded by thin and thick CdTe pixel detectors with a total thickness of 5 mm as an absorber. The design is optimized for detecting gamma-rays at about 100-700 keV when operated at compton mode. We present the results from the first prototype of Si/CdTe compton telescope, made of a 300 um thick DSSD and 0.5 mm thick CdTe pixel detectors. We also present the estimated performance of the SGD with current design, and possible improvements in the future.
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Bulletin of the American Astronomical Society, 36 #3
© 2004. The American Astronomical Soceity.