The Soft X-ray Spectrometer (SXS) instrument that flew on the Astro-H observatory was designed to perform imaging and spectroscopy of x-rays in the energy range of 0.2 to 13 keV with a resolution requirement of 7 eV or better. This was accomplished using a 6x6 array of x-ray microcalorimeters cooled to an operating temperature of 50 mK by an adiabatic demagnetization refrigerator (ADR). The ADR consisted of three stages in order to operate using either a 1.2 K superfluid helium bath or a 4.5 K Joule-Thomson (JT) cryocooler as its heat sink. The design was based on the following operating strategy. After launch, while liquid helium was present (cryogen mode), two of the ADR's stages would be used to single-shot cool the detectors, using the helium as a heat sink. When the helium was eventually depleted (cryogen-free mode), all three ADR stages would be used to continuously cool the helium tank to about 1.5 K, and to single-shot cool the detectors (to 50 mK), using the JT cryocooler as a heat sink. The Astro-H observatory, renamed Hitomi after its successful launch in February 2016, carried approximately 36 liters of helium into orbit. Based on measurements during ground testing, the average heat load on the helium was projected to be 0.66 mW, giving a lifetime of more than 4 years. On day 5, the helium had cooled to <1.4 K and ADR operation began, successfully cooling the detector array to 50 mK. The ADR's hold time steadily increased to 48 hours as the helium cooled to a temperature of 1.12 K. As the commissioning phase progressed, the ADR was recycled (requiring approximately 45 minutes) periodically, either in preparation for science observations or whenever the 50 mK stage approached the end of its hold time. In total, 18 cycles were completed by the time an attitude control anomaly led to an unrecoverable failure of the satellite on day 38. This paper presents the design, operation and on-orbit performance of the ADR in cryogen mode as the foreshortened mission did not provide an opportunity to test cryogen-free mode.

中文翻译：

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Hitomi天文台的软X射线光谱仪ADR的设计和在轨操作。

飞越Astro-H天文台的软X射线光谱仪（SXS）仪器旨在对能量范围为0.2到13 keV的X射线进行成像和光谱分析，分辨率要求为7 eV或更高。这是通过将6x6的X射线微热量计阵列通过绝热退磁制冷机（ADR）冷却到50 mK的工作温度来完成的。为了使用1.2 K超流氦浴或4.5 K Joule-Thomson（JT）低温冷却器作为散热器，ADR分为三个阶段。该设计基于以下操作策略。发射后，当存在液态氦气（低温模式）时，将使用ADR的两个阶段，以氦气为散热器，单次冷却探测器。当氦最终被耗尽（无制冷剂模式）时，使用JT低温冷却器作为散热器，所有三个ADR级都将用于将氦气罐连续冷却至约1.5 K，并单次冷却检测器（至50 mK）。Astro-H天文台在2016年2月成功发射升空后更名为Hitomi，将约36升氦气送入轨道。根据地面测试的测量结果，氦气的平均热负荷预计为0.66 mW，使用寿命超过4年。第5天，氦气冷却至<1.4 K，开始进行ADR操作，成功将检测器阵列冷却至50 mK。随着氦气冷却到1.12 K的温度，ADR的保持时间稳定地增加到48小时。随着调试阶段的进行，ADR定期进行了再循环（大约需要45分钟），无论是准备进行科学观测还是在50 mK阶段接近其保留时间结束时。到了第38天，姿态控制异常导致卫星无法恢复故障时，总共完成了18个周期。本文介绍了低温模式下ADR的设计，运行和在轨性能，因为缩短的任务没有完成提供了测试无制冷剂模式的机会。