Cryogen free cooling of ASTRO-H SXS Helium Dewar from 300 K to 4 K

• Published in: Cryogenics (Guildford) 2017-12, Vol.88, p.143-146
• Main Authors: Kanao, Ken'ichi, Yoshida, Seiji, Miyaoka, Mikio, Tsunematsu, Shoji, Otsuka, Kiyomi, Hoshika, Shunji, Narasaki, Katsuhiro, Mitsuda, Kazuhisa, Yamasaki, Noriko, Takei, Yoh, Fujimoto, Ryuji, Sato, Yoichi, Okamoto, Atsushi, Noda, Hirofumi, DiPirro, Michel J., Shirron, Peter J.
• Format: Article
• Language: English
• Subjects: Adiabatic demagnetization cooling; Coolers; Cooling system; Cryogen free; Demagnetization; Electric power; Helium; Laboratory equipment; Liquid helium; Low temperature physics; Sensors; Soft x rays; Space cryogenics; Studies; X ray spectrometers
• ISSN: 0011-2275; 1879-2235
• DOI: 10.1016/j.cryogenics.2017.10.018

•SXS Dewar has hybrid cooling system combining liquid helium and cryocoolers.•SXS Dewar has cryogen free operation mode without liquid helium.•Cold mass in 4 K area is 35 kg.•He tank temperature reached to 4.5 K in 37 days.•Maximum power was 264 W in total. Soft X-ray Spectrometer instrument (SXS) is one of the primary scientific instruments of ASTRO-H. SXS has a cold detector that is cooled to 50 mK by using a multi-stage Adiabatic Demagnetization Refrigerator (ADR). SXS Dewar containing ADR provides 1.3 K heat sink by using liquid helium in nominal operation. After liquid helium is dried up, 4 K heat sink is provided by using mechanical coolers. Both nominal operation and cryogen free operation were successfully demonstrated. This paper describes the test result of cryogen free operation and cool-down performance from room temperature by using only mechanical coolers without liquid helium. The coolers on the Dewar cooled down cold mass from around 300 K to 4 K with 260 W electric power in 40 days. Cold mass is 35 kg in 4 K area including the helium tank, ADR and detector assembly.