18 July 2016 Thermal analyses for initial operations of the Soft X-Ray Spectrometer (SXS) onboard ASTRO-H
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The Soft X-ray Spectrometer (SXS) onboard ASTRO-H (Hitomi) achieved a high energy resolution of ~ 4.9 eV at 6 keV with an X-ray microcalorimeter array kept at 50 mK in the orbit. The cooling system utilizes liquid helium, and a porous plug phase separator is utilized to confine it. Therefore, it is required to keep the helium temperature always lower than the λ point of 2.17 K in the orbit. To clarify the maximum allowable helium temperature at the launch also considering the uncertainties of the initial operation in the orbit, we constructed a thermal mathematical model of the SXS dewar which properly implements the helium mass flow rate through the porous plug, and carried out time-series thermal simulations. Based on the results, the maximum allowable helium temperature at the launch was set at 1.7 K. We also conducted a transient thermal calculation using the actual temperatures at the launch as initial conditions. As a result, the helium mass flow rate when the helium temperature was in equilibrium is estimated to be 34–42 μg/s, and the life time of the helium mode is predicted to be ~ 3.9–4.7 years. The present paper reports model structures, simulation results, and the comparisons with temperatures measured in the orbit.
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Hirofumi Noda, Hirofumi Noda, Kazuhisa Mitsuda, Kazuhisa Mitsuda, Atsushi Okamoto, Atsushi Okamoto, Yuichiro Ezoe, Yuichiro Ezoe, Kumi Ishikawa, Kumi Ishikawa, Ryuichi Fujimoto, Ryuichi Fujimoto, Noriko Yamasaki, Noriko Yamasaki, Yoh Takei, Yoh Takei, Takaya Ohashi, Takaya Ohashi, Yoshitaka Ishisaki, Yoshitaka Ishisaki, Ikuyuki Mitsuishi, Ikuyuki Mitsuishi, Seiji Yoshida, Seiji Yoshida, Michael DiPirro, Michael DiPirro, Peter Shirron, Peter Shirron, } "Thermal analyses for initial operations of the Soft X-Ray Spectrometer (SXS) onboard ASTRO-H", Proc. SPIE 9905, Space Telescopes and Instrumentation 2016: Ultraviolet to Gamma Ray, 99053R (18 July 2016); doi: 10.1117/12.2231356; https://doi.org/10.1117/12.2231356

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