X 線天文衛星「ASTRO-H」搭載軟X 線検出器用冷却システム

抄録

The space cryogenics cooling system for the X-ray spectrometer installed on the ASTRO-H is introduced in this report. ASTRO-H is an X-ray astronomy satellite that the Japan Aerospace Exploration Agency (JAXA) developed to support studying the evolution of the universe and other physical phenomena yet to be discovered. The primary scientific instrument installed on the ASTRO-H is a soft X-ray spectrometer (SXS). Its detectors are cooled to 50 mK using a complex cryogenic system with a multistage adiabatic demagnetization refrigerator (ADR) developed by the National Aeronautics and Space Administration (NASA), and a cryogenics system developed by Sumitomo Heavy Industries, Ltd. (SHI). SHI’s cryogenics system is needed to cool the heatsink of the ADR to 1.3 K or less while in orbit, and is capable of doing so for three years or longer. To meet these requirements, SHI developed a hybrid cryogenics system consisting of a liquid helium tank, a 4 K cooler, and two two-stage Stirling coolers. ASTROH was launched from Tanegashima Space Center on February 17, 2016. Initial operation of the SXS cryogenics system in orbit has been completed successfully. The cooling performance was as expected and may exceed the lifetime requirement of three years.