In-orbit performance and calibration of the Hard X-ray Imager onboard Hitomi (ASTRO-H)

Abstract

The Hard X-ray Imager (HXI) onboard Hitomi (ASTRO-H) is an imaging spectrometer covering hard X-ray energies of 5-80 keV. Combined with the hard X-ray telescope, it enables imaging spectroscopy with an angular resolution of $1^{\prime }.7$ half-power diameter, in a field of view of $9^{\prime }\times 9^{\prime }$. The main imager is composed of 4 layers of Si detectors and 1 layer of CdTe detector, stacked to cover wide energy band up to 80 keV, surrounded by an active shield made of BGO scintillator to reduce the background. The HXI started observations 12 days before the Hitomi loss, and successfully obtained data from G21.5$-$0.9, Crab and blank sky. Utilizing these data, we calibrate the detector response and study properties of in-orbit background. The observed Crab spectra agree well with a powerlaw model convolved with the detector response, within 5% accuracy. We find that albedo electrons in specified orbit strongly affect the background of Si top layer, and establish a screening method to reduce it. The background level over the full field of view after all the processing and screening is as low as the pre-flight requirement of $1$-$3\times 10^{-4}$ counts s${}^{-1}$ cm${}^{-2}$ keV${}^{-1}$.

arXiv comment46 pages, 18 figures, published in Journal of Astronomical Telescopes, Instruments, and Systems

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Cited by in corpus (7)

• Detailed Design of the Science Operations for the XRISM mission
• Modeling of proton-induced radioactivation background in hard X-ray telescopes: Geant4-based simulation and its demonstration by Hitomi's measurement in a low Earth orbit
• New Measurement of the Vertical Atmospheric Density Profile from Occultations of the Crab Nebula with X-Ray Astronomy Satellites Suzaku and Hitomi
• Radiation Damage Effects on Double-SOI Pixel Sensors for X-ray Astronomy
• A broadband X-ray imaging spectroscopy in the 2030s: the FORCE mission
• Sub-pixel Response of Double-SOI Pixel Sensors for X-ray Astronomy
• Origin of the in-orbit instrumental background of the Hard X-ray Imager onboard Hitomi