Hitomi/XRISM micro-calorimeter

TL;DR

This paper reviews the design and performance of the Hitomi/XRISM micro-calorimeter spectrometers, highlighting their high energy resolution capabilities for X-ray astronomy and the lessons learned from the Hitomi mission.

Contribution

It provides an overview of the micro-calorimeter technology used in Hitomi and XRISM, including design specifications and expected performance improvements.

Findings

Hitomi's SXS achieved ~5 eV energy resolution in orbit.

XRISM's Resolve spectrometer is designed to replicate SXS performance.

The instruments are intended for long-term X-ray observations in space.

Abstract

We present an overview of the ASTRO-H (Hitomi) Soft X-Ray Spectrometer (SXS) and the X-Ray Imaging and Spectrometer Mission (XRISM) {\it Resolve} spectrometer. In each, a 36-pixel X-ray micro-calorimeter array operated at 50 mK covers a $3 \times 3$ arc-minute field of view. The instruments are designed to achieve an energy resolution of better than 7 eV over the 0.3 -- 12 keV energy range and operate for more than 3 years in orbit. Actually, the SXS achieved the energy resolution of $\sim$5 eV in orbit, but it was lost after only a month of operation due to the loss of spacecraft attitude control. For the recovery mission, XRISM will be equipped with the {\it Resolve} spectrometer which has mostly the same design as SXS and is expected to have the same in-flight performance.