The hard X-ray imager (HXI) onboard ASTRO-H

The HXI team

Research output: Chapter in Book/Report/Conference proceedingConference contribution

13 Citations (Scopus)

Abstract

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 × 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 × 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.

Original languageEnglish
Title of host publicationSpace Telescopes and Instrumentation 2016
Subtitle of host publicationUltraviolet to Gamma Ray
EditorsJan-Willem A. den Herder, Tadayuki Takahashi, Marshall Bautz
PublisherSPIE
ISBN (Electronic)9781510601895
DOIs
Publication statusPublished - 2016
EventSpace Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray - Edinburgh, United Kingdom
Duration: 2016 Jun 262016 Jul 1

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
Volume9905
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X

Other

OtherSpace Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray
CountryUnited Kingdom
CityEdinburgh
Period16/6/2616/7/1

Keywords

  • APD
  • BGO
  • CdTe-DSD
  • DSSD
  • Hard X-ray Imager
  • Hitomi
  • active-shield
  • in-orbit performance

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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