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

Gary A. Sneiderman, Peter J. Shirron, Ryuichi Fujimoto, Thomas G. Bialas, Kevin R. Boyce, Meng P. Chiao, Michael J. DiPirro, Megan E. Eckart, Leslie Hartz, Yoshitaka Ishisaki, Caroline A. Kilbourne, Candace Masters, Dan McCammon, Kazuhisa Mitsuda, Hirofumi Noda, Frederick S. Porter, Andrew E. Szymkowiak, Yoh Takei, Mashiro Tsujimoto, Seiji Yoshida

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)


The Soft X-ray Spectrometer (SXS) is the first space-based instrument to implement operational redundancy of a sub-Kelvin cooling system. Its cooling system includes a superfluid helium cryostat and five cryocoolers, provided by Japan Aerospace Exploration Agency, and three adiabatic demagnetization refrigerators (ADRs) with four active heat switches, provided by NASA. These elements are configured in one of two ways to control the heat sink of the x-ray microcalorimeter detectors at 50 mK. The "helium mode," the simpler of the two modes, is used while liquid helium is present and uses all five cryocoolers and two ADRs. The first two ADR stages operate together and reject their heat directly to the liquid at ∼1.1 K. In the "cryogen-free mode," for operation after the helium is depleted, the first stage ADR operation is unchanged, the second stage is repurposed to control the empty helium tank at ∼1.5 K, and the third stage transfers heat from the 1.5-K stage to the 4.5-K interface of the Joule-Thomson cooler. The development and verification details of this capability are presented within this paper and offer valuable insights into the challenges, successes, and lessons that can benefit other missions, particularly those employing cryogen-free or hybrid cooling systems.

Original languageEnglish
Article number021408
JournalJournal of Astronomical Telescopes, Instruments, and Systems
Issue number2
Publication statusPublished - 2018 Apr 1


  • Astro-H
  • Soft X-ray Spectrometer
  • adiabatic demagnetization refrigerator
  • cooling system
  • cryocooler
  • cryogen free
  • cryogenic
  • magnetic refrigeration

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Control and Systems Engineering
  • Instrumentation
  • Astronomy and Astrophysics
  • Mechanical Engineering
  • Space and Planetary Science


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