Ground calibration of the Astro-H (Hitomi) soft x-ray spectrometer

Abstract

Ground calibration of the Astro-H (Hitomi) soft x-ray spectrometer," J. Astron. Telesc.Abstract. The Astro-H (Hitomi) Soft X-ray Spectrometer (SXS) was a pioneering imaging x-ray spectrometer with 5 eV energy resolution at 6 keV. The instrument used a microcalorimeter array at the focus of a highthroughput soft x-ray telescope to enable high-resolution nondispersive spectroscopy in the soft x-ray waveband (0.3 to 12 keV). We present the suite of ground calibration measurements acquired from 2012 to 2015, including characterization of the detector system, anti-coincidence detector, optical blocking filters, and filter-wheel filters. The calibration of the 36-pixel silicon thermistor microcalorimeter array includes parameterizations of the energy gain scale and line-spread function for each event grade over a range of instrument operating conditions, as well as quantum efficiency measurements. The x-ray transmission of the set of five Al/polyimide thin-film optical blocking filters mounted inside the SXS dewar has been modeled based on measurements at synchrotron beamlines, including with high spectral resolution at the C, N, O, and Al K-edges. In addition, we present the x-ray transmission of the dewar gate valve and of the filters mounted on the SXS filter wheel (external to the dewar), including beryllium, polyimide, and neutral density filters.

Multiabsorber transition-edge sensors for x-ray astronomy

“…These x-rays were produced using a channelcut crystal monochromator set-up for Cr-K α1 x-rays (5.4 keV), which has an intrinsic line-width of <0.5 eV. 33,34 In order to determine event position, we used two rise-time metrics to characterize the pre-equilibration signal for every measured x-ray, as opposed to the single rise-time metric used for the standard geometries discussed previously. Figures 8(c) and 8(d) show the rise time determined from the time interval between reaching 5% and 50% of the peak, as a function of that determined from 50% to 90%.…”

Cryogen-free operation of the Soft X-ray Spectrometer instrument

“…The peak temperature of the detectors corresponds to the energy of the x-ray photons they absorb. 17 Since the deposited energy of individual photons is tiny, the detectors must be extremely cold to measure the temperature response, and the reference temperature from which the response is measured must be extremely stable to obtain a precise measurement of the peak value. The requirements summarized below are imposed on the cooling system to enable the SXS to achieve these exquisitely sensitive measurements.…”

In-orbit operation of the soft x-ray spectrometer onboard the Hitomi satellite

“…A large angle (60 deg or 120 deg) rotation to change the filters was not originally planned until it was required during the performance verification phase. However, in order to calibrate the absolute gain of individual pixels before opening the GV and using the MXS, 10,11 we changed the position to illuminate the detector array with x-rays using the 55 Fe sources on the wheel for 22.3 h on Y þ 30 and 31 [ Fig. 3(d)].…”

“…4) in order to aid in planning for future microcalorimeter missions. Details are found in other articles of the same special section for the spacecraft, 1 the overall mission instrument, 2 the sensor and its performance, [8][9][10][11] the mirror and the aperture assembly, 12,13 the cooling chain, 5,14-17 the vibration isolation system, 18 the filter wheel (FW), 4 and the signal processing. 19,20 All data presented here are available in Ref.…”