Performance of the helium dewar and cryocoolers of ASTRO-H SXS

Fujimoto, R.; Takei, Yoh; Mitsuda, Kazuhisa; Yamasaki, Noriko Y.; Tsujimoto, Masahiro; Koyama, Shu; Ishikawa, Kumi; Sugita, Hiroyuki; Sato, Yoichi; Shinozaki, Kazuo; Okamoto, Atsushi; Kitamoto, Shunji; Hoshino, Akio; Sato, Kosuke; Ezoe, Yuichiro; Ishisaki, Yoshitaka; Yamada, S.; Seta, Hiromi; Ohashi, T.; Tamagawa, Toru; Noda, Hirofumi; Sawada, Makoto; Tashiro, M.; Yatsu, Yoichi; Mitsuishi, Ikuyuki; Kanao, Kenichi; Yoshida, Seiji; Miyaoka, Mikio; Tsunematsu, Shoji; Otsuka, Kiyomi; Narasaki, Katsuhiro; DiPirro, Michael; Shirron, Peter; Sneiderman, Gary A.; Kilbourne, Caroline A.; Porter, F. S.; Chiao, Meng P.; Eckart, Megan E.; Kelley, R. L.

doi:10.1117/12.2232933

Cited by 14 publications

(17 citation statements)

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“…In this case, the liquid peaked at 1.87 K when the initial temperature was lower, ∼1.64 K. Therefore, we adopted 1.7 K as the upper limit of the LHe temperature at launch and required SC operation to start at half the nominal power or higher within 12 h of launch. That shows that the launch would have to be aborted and the helium reconditioned if T LHe exceeded 1.7 K. As shown by Fujimoto et al, 4 the LHe temperature was ∼1.5 K at the final prelaunch decision point, due to careful operations of the SXS team in the procedures 1 and 2 as shown in Sec. 1.…”

Section: Transient Simulations With Various Initial Lhe Temperaturesmentioning

confidence: 89%

“…By radiating in the anti-Sun direction, the DMS cooled to ∼260 K, 4 which was ∼30 K lower than that on the ground, and hence, we fixed the temperature of the DMS node at 260 K as a boundary. In the analysis, the SC 25-W, SC 50-W, and JT operations started ∼3 h, ∼4 h, and ∼1 day after the launch, following the actual sequence.…”

Section: Temperature Simulations In Orbitmentioning

confidence: 99%

“…In the cooling system of the SXS, 4 the two-stage Stirling Shield Coolers (SCs) cool from ∼300 K to a base temperature of ∼20 K, and subsequently, the 4 He Joule-Thomson (JT) cooler produces ∼4 K. In the case when LHe is present, the venting helium (He) vapor assists in cooling the radiation shields inside the dewar. As a result, the LHe can be kept at ∼1.1 K. Finally, two ADR stages operate to stabilize the temperature of the x-ray microcalorimeter array at 50 mK, requiring periodic recycles about once per two days.…”

Section: Introductionmentioning

confidence: 99%

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Thermal analyses for initial operations of the soft x-ray spectrometer onboard the Hitomi satellite

Noda

Mitsuda

Okamoto

et al. 2017

J. Astron. Telesc. Instrum. Syst

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Abstract. The soft x-ray spectrometer (SXS) onboard the Hitomi satellite achieved a high-energy resolution of ∼4.9 eV at 6 keV with an x-ray microcalorimeter array cooled to 50 mK. The cooling system utilizes liquid helium, confined in zero gravity by means of a porous plug (PP) phase separator. For the PP to function, the helium temperature must be kept lower than the λ point of 2.17 K in orbit. To determine the maximum allowable helium temperature at launch, taking into account the uncertainties in both the final ground operations and initial operation in orbit, we constructed a thermal mathematical model of the SXS dewar and PP vent and carried out time-series thermal simulations. Based on the results, the maximum allowable helium temperature at launch was set at 1.7 K. We also conducted a transient thermal calculation using the actual temperatures at launch as initial conditions to determine flow and cooling rates in orbit. From this, the equilibrium helium mass flow rate was estimated to be ∼34 to 42 μg∕s, and the lifetime of the helium mode was predicted to be ∼3.9 to 4.7 years. This paper describes the thermal model and presents simulation results and comparisons with temperatures measured in the orbit. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Section: Transient Simulations With Various Initial Lhe Temperaturesmentioning

confidence: 89%

Section: Temperature Simulations In Orbitmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Thermal analyses for initial operations of the soft x-ray spectrometer onboard the Hitomi satellite

Noda

Mitsuda

Okamoto

et al. 2017

J. Astron. Telesc. Instrum. Syst

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“…The microcalorimeter is cooled down from room temperature to 50 mK using a dewar, four 2-stage Stirling cryocoolers, a Joule-Thomson cryocooler, superfluid helium-4, and a 3-stage adiabatic demagnetization refrigerator (ADR). 3,4 Although the SXS was still in the commissioning phase, it had successfully shown the superb energy resolution on-orbit and provided valuable data sets from aspects of both science and engineering. 2 At nominal operation, an average heat load on the helium tank is ∼0.7 mW.…”

mentioning

confidence: 99%

“…2 At nominal operation, an average heat load on the helium tank is ∼0.7 mW. [3][4][5] Assuming this heat load and an initial fill level of 30 L, the lifetime of the helium will be ∼4 years. As shown in Table 1, this heat load is lower than any previous space missions using superfluid helium, even compared to values of the two previous x-ray microcalorimeter instruments, the ASTRO-E XRS and the Suzaku XRS2.…”

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confidence: 99%

Porous plug phase separator and superfluid film flow suppression system for the soft x-ray spectrometer onboard Hitomi

Ezoe

DiPirro

Fujimoto

et al. 2017

J. Astron. Telesc. Instrum. Syst

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, "Porous plug phase separator and superfluid film flow suppression system for the soft x-ray spectrometer onboard Hitomi," J. Astron. Telesc. Instrum. Syst. 4(1), 011203 (2017), doi: 10.1117/1.JATIS.4.1.011203. Abstract. When using superfluid helium in low-gravity environments, porous plug phase separators are commonly used to vent boil-off gas while confining the bulk liquid to the tank. Invariably, there is a flow of superfluid film from the perimeter of the porous plug down the vent line. For the soft x-ray spectrometer onboard ASTRO-H (Hitomi), its approximately 30-liter helium supply has a lifetime requirement of more than 3 years. A nominal vent rate is estimated as ∼30 μg∕s, equivalent to ∼0.7 mW heat load. It is, therefore, critical to suppress any film flow whose evaporation would not provide direct cooling of the remaining liquid helium. That is, the porous plug vent system must be designed to both minimize film flow and to ensure maximum extraction of latent heat from the film. The design goal for Hitomi is to reduce the film flow losses to <2 μg∕s, corresponding to a loss of cooling capacity of <40 μW. The design adopts the same general design as implemented for Astro-E and E2, using a vent system composed of a porous plug, combined with an orifice, a heat exchanger, and knife-edge devices. Design, on-ground testing results, and in-orbit performance are described.

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