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A. T. Serlemitsos, B. A. Warner, S. Castles,
Code 713 (now Code 552)
NASA/ Goddard Space Flight Center
Greenbelt, MD 20771
M. San Sebastian and Thomas Hait STX Corp.
An Adiabatic Demagnetization Refrigerator (ADR) for space use is under development at NASA's Goddard Space Flight Center (GSFC). In the early 1980's Dr. Stephen Castles designed and built a technology demonstration model of a spaceworthy ADR. Subsequently, an ADR was built at the GSFC to serve as a breadboard model for cooling the X-ray sensors of the X-Ray Spectrometer (XRS), an instrument on the Advanced X-Ray Astrophysics Facility (AXAF). The breadboard ADR operated at 100 mK for 400 minutes. We now report some significant changes to that ADR, designed to eliminate shortcomings revealed during tests. To increase thermal contact, the ferric ammonium sulfate crystals were grown directly on gold-plated copper wires which serve as the thermal bus. The thermal link to the X-ray sensors was also markedly improved. To speed up the testing required to determine the best design parameters for the gas gap heat switch, the new heat switch has a modular design and is easy to disassemble.