Performance of the Three-Stage ADR that Provides Cooling of the Soft X-Ray Spectrometer Aboard Astro-H

The requirements levied upon the cooling system for the soft X-ray spectrometer (SXS) aboard the Astro-H satellite are demanding: Provide an operating temperature of 0.050 degrees Kelvin for a minimum of 24 hours, recycle in less than 2 hours (less than 1 hour in some cases), produce a dipole moment of less than 10 amperes per square meter at the detector location, and do all this with a mass less than 15 kilograms. This is further complicated by the availability of both a 1.3 degrees Kelvin helium bath and a 4.5 degrees Kelvin JT (Joule-Thomson) cooler to recycle the refrigerator. Here we detail the performance of the adiabatic demagnetization refrigerator (ADR) built specifically for SXS that is capable of meeting, and often significantly exceeding, the requirements placed upon it.