The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD)

Shin Watanabe, Hiroyasu Tajima, Yasushi Fukazawa, Yuto Ichinohe, Shinichiro Takeda, Teruaki Enoto, Taro Fukuyama, Shunya Furui, Kei Genba, Kouichi Hagino, Atsushi Harayama, Yoshikatsu Kuroda, Daisuke Matsuura, Ryo Nakamura, Kazuhiro Nakazawa, Hirofumi Noda, Hirokazu Odaka, Masayuki Ohta, Mitsunobu Onishi, Shinya SaitoGoro Sato, Tamotsu Sato, Tadayuki Takahashi, Takaaki Tanaka, Atsushi Togo, Shinji Tomizuka

Research output: Contribution to journalArticle

36 Citations (Scopus)

Abstract

The Soft Gamma-ray Detector (SGD) is one of the instrument payloads onboard ASTRO-H, and will cover a wide energy band (60-600 keV) at a background level 10 times better than instruments currently in orbit. The SGD achieves low background by combining a Compton camera scheme with a narrow field-of-view active shield. The Compton camera in the SGD is realized as a hybrid semiconductor detector system which consists of silicon and cadmium telluride (CdTe) sensors. The design of the SGD Compton camera has been finalized and the final prototype, which has the same configuration as the flight model, has been fabricated for performance evaluation. The Compton camera has overall dimensions of 12 cm×12 cm×12 cm, consisting of 32 layers of Si pixel sensors and 8 layers of CdTe pixel sensors surrounded by 2 layers of CdTe pixel sensors. The detection efficiency of the Compton camera reaches about 15% and 3% for 100 keV and 511 keV gamma rays, respectively. The pixel pitch of the Si and CdTe sensors is 3.2 mm, and the signals from all 13,312 pixels are processed by 208 ASICs developed for the SGD. Good energy resolution is afforded by semiconductor sensors and low noise ASICs, and the obtained energy resolutions with the prototype Si and CdTe pixel sensors are 1.0-2.0 keV (FWHM) at 60 keV and 1.6-2.5 keV (FWHM) at 122 keV, respectively. This results in good background rejection capability due to better constraints on Compton kinematics. Compton camera energy resolutions achieved with the final prototype are 6.3 keV (FWHM) at 356 keV and 10.5 keV (FWHM) at 662 keV, which satisfy the instrument requirements for the SGD Compton camera (better than 2%). Moreover, a low intrinsic background has been confirmed by the background measurement with the final prototype.

Original languageEnglish
Pages (from-to)192-201
Number of pages10
JournalNuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment
Volume765
DOIs
Publication statusPublished - 2014 Nov 21

Keywords

  • ASTRO-H SGD
  • CdTe detector
  • Compton camera
  • Gamma-ray detector
  • Semiconductor detector
  • Silicon detector

ASJC Scopus subject areas

  • Instrumentation
  • Nuclear and High Energy Physics

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  • Cite this

    Watanabe, S., Tajima, H., Fukazawa, Y., Ichinohe, Y., Takeda, S., Enoto, T., Fukuyama, T., Furui, S., Genba, K., Hagino, K., Harayama, A., Kuroda, Y., Matsuura, D., Nakamura, R., Nakazawa, K., Noda, H., Odaka, H., Ohta, M., Onishi, M., ... Tomizuka, S. (2014). The Si/CdTe semiconductor Compton camera of the ASTRO-H Soft Gamma-ray Detector (SGD). Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 765, 192-201. https://doi.org/10.1016/j.nima.2014.05.127