25 July 2016 The hard x-ray imager (HXI) onboard ASTRO-H
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Hitomi X-ray observatory launched in 17 February 2016 had a hard X-ray imaging spectroscopy system made of two hard X-ray imagers (HXIs) coupled with two hard X-ray telescopes (HXTs). With 12 m focal length, they provide fine (2' half-power diameter; HPD) imaging spectroscopy at 5 to 80 keV. The HXI main imagers are made of 4 layers of Si and a CdTe semiconductor double-sided strip detectors, stacked to enhance detection efficiency as well as to enable photon interaction-depth sensing. Active shield made of 9 BGO scintillators surrounds the imager to provide with low background. Following the deployment of the Extensible Optical Bench (EOB) on 28 February, the HXI was gradually turned on. Two imagers successfully started observation on 14 March, and was operational till the incident lead to Hitomo loss, on 26 March. All detector channels, 1280 ch of imager and 11 channel of active shields and others each, worked well and showed performance consistent with those seen on ground. From the first light observation of G21.5-0.9 and the following Crab observations, 5-80 keV energy coverage and good detection efficiency were confirmed. With blank sky observations, we checked our background level. In some geomagnetic region, strong background continuum, presumably caused by trapped electron with energy ~100 keV, is seen. But by cutting the high-background time-intervals, the background became significantly lower, typically with 1-3 x 10-4 counts s-1 keV-1 cm-2 (here cm2 is shown with detector geometrical area). Above 30 keV, line and continuum emission originating from activation of CdTe was significantly seen, though the level of 1-4 x 10-4 counts s-1 keV-1 cm-2 is still comparable to those seen in NuSTAR. By comparing the effective area and background rate, preliminary analysis shows that the HXI had a statistical sensitivity similar to NuSTAR for point sources, and more than twice better for largely extended sources.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Kazuhiro Nakazawa, Kazuhiro Nakazawa, Goro Sato, Goro Sato, Motohide Kokubun, Motohide Kokubun, Teruaki Enoto, Teruaki Enoto, Yasushi Fukazawa, Yasushi Fukazawa, Kouichi Hagino, Kouichi Hagino, Atsushi Harayama, Atsushi Harayama, Katsuhiro Hayashi, Katsuhiro Hayashi, Jun Kataoka, Jun Kataoka, Junichiro Katsuta, Junichiro Katsuta, Philippe Laurent, Philippe Laurent, François Lebrun, François Lebrun, Olivier Limousin, Olivier Limousin, Kazuo Makishima, Kazuo Makishima, Tsunefumi Mizuno, Tsunefumi Mizuno, Kunishiro Mori, Kunishiro Mori, Takeshi Nakamori, Takeshi Nakamori, Toshio Nakano, Toshio Nakano, Hirofumi Noda, Hirofumi Noda, Hirokazu Odaka, Hirokazu Odaka, Masanori Ohno, Masanori Ohno, Masayuki Ohta, Masayuki Ohta, Shinya Saito, Shinya Saito, Rie Sato, Rie Sato, Hiroyasu Tajima, Hiroyasu Tajima, Hiromitsu Takahashi, Hiromitsu Takahashi, Tadayuki Takahashi, Tadayuki Takahashi, Shin'ichiro Takeda, Shin'ichiro Takeda, Yukikatsu Terada, Yukikatsu Terada, Hideki Uchiyama, Hideki Uchiyama, Yasunobu Uchiyama, Yasunobu Uchiyama, Shin Watanabe, Shin Watanabe, Kazutaka Yamaoka, Kazutaka Yamaoka, Yoichi Yatsu, Yoichi Yatsu, Takayuki Yuasa, Takayuki Yuasa, } "The hard x-ray imager (HXI) onboard ASTRO-H", Proc. SPIE 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray, 990511 (25 July 2016); doi: 10.1117/12.2231176; https://doi.org/10.1117/12.2231176


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