Prototype fine-imaging narrow field of view semiconductor Compton telescope with shielded coded-mask, mini-SGI

Semiconductor Compton telescope (SCT) is one of the promising technologies in cosmic MeV gamma-ray observation, because of good angular resolution measure thanks to its high energy and positional resolutions. However, it cannot be better than a few degrees because of quantum limitation. With improving sensitivity in MeV astronomy, realization of 10-arcmin-level of angular resolution is the essential. Since the mask made of heavy metal is a BGD source and the strong CXB limits the statistical significance of the mask decoding, we propose to adopt this concept on a narrow field of view Si/CdTe SCT, like the SGD onboard ASTRO-H mission. We developed a concept verification system, mini-SGI, adopting 0.5 mm thick DSSDs and 2 mm thick CdTe-DSD, covered with BGO active shield. We irradiated gamma-rays and verified the coded-mask and Compton reconstruction combined analysis.