Performance of the XRS/ASTRO-E engineering model ADR

Abstract

NASA's Goddard Space Flight Center (GSFC) has developed an x-ray Spectrometer (XRS) to be flown aboard ASTRO-E, in cooperation with the Japanese Institute of Space and Astronomical Science (ISAS). XRS uses an array of 32 microcalorimeters capable of detecting X-rays in the energy range of 0.3–10 keV with a resolution of 12 eV. In order to accomplish this, the detectors must be operated at a temperature of 0.065 K. In space, an Adiabatic Demagnetization Refrigerator (ADR) must be used to cool the detectors to that temperature. A spaceworthy ADR has been developed at GSFC to be used in the XRS. Originally, the ADR was developed to be flown aboard the Advanced X-ray Astrophysics Facility (AXAF) [2]. Budgetary constraints necessitated the move of the XRS to the ASTRO-E program and this resulted in much tighter thermal specifications for the ADR. The allowable average thermal load of the ADR to the LHe dewar was changed from 2.6 mW to 270 μW. Time constraints did not allow a complete redesign of the ADR. The original shape and size were left unchanged and the new specifications were met by streamlining the heat switch and lengthening the salt pill magnetization cycle time. For a LHe bath temperature of 1.3 K the gas gap heat switch presently used has an on/off ratio of 22 000 and a parasitic heat leak of 2.9 μW/K.