Design and performance of the soft gamma-ray detector for the NeXT mission

H. Tajima*, T. Kamae, G. Madejski, T. Mitani, K. Nakazawa, T. Tanaka, T. Takahashi, S. Watanabe, Y. Fukazawa, T. Ikagawa, J. Kataoka, M. Kokubun, K. Makishima, Y. Terada, M. Nomachi, M. Tashiro

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)


The soft gamma-ray detector (SGD) onboard the Japanese future high energy astrophysics mission (NeXT) is a Compton telescope with narrow field of view, which utilizes Compton kinematics to enhance its background rejection capabilities. It is realized as a hybrid semiconductor gamma-ray detector which consists of silicon and cadmium telluride (CdTe) detectors. It can detect photons in a wide energy band (0.05-1 MeV) at a background level of 5 × 10-7 counts/s/cm2/keV; the silicon layers are required to improve the performance at a lower energy band (<0.3 MeV). Excellent energy resolution is the key feature of the SGD, allowing it to achieve both high angular resolution and good background rejection capability. An additional capability of the SGD, its ability to measure gamma-ray polarization, opens up a new window to study properties of astronomical objects. We will present the development of key technologies to realize the SGD: high quality CdTe, low noise front-end application-specific integrated circuit, and bump bonding technology. Energy resolutions of 1.7 keV (full-width at half-maximum) for CdTe pixel detectors and 1.1 keV for Si strip detectors have been measured. We also present the validation of Monte Carlo simulation used to evaluate the performance of the SGD.

Original languageEnglish
Pages (from-to)2749-2757
Number of pages9
JournalIEEE Transactions on Nuclear Science
Issue number6
Publication statusPublished - 2005 Dec
Externally publishedYes


  • Cadmium telluride (CdTe)
  • Compton camera
  • Gamma-ray astronomy detectors
  • Polarimetry
  • Silicon radiation detectors

ASJC Scopus subject areas

  • Nuclear and High Energy Physics
  • Nuclear Energy and Engineering
  • Electrical and Electronic Engineering


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