A Continuous adiabatic demagnetization refrigeration system for cryogenic cooling

This project concerns the design and optimization of a novel multi-stage continuous adiabatic demagnetization refrigerator (CADR) with cooling capability at cryogenic temperatures. The CADR is intended for use in space astronomy missions with large infrared and x-ray detector arrays that require refrigeration down to 50 mK and power dissipation of as much as 10 [mu]W. A desired feature is the ability for the CADR device to reject heat to a mechanical cryocooler, operating in the 6-10 K range. Theoretical concerns involved in CADR operation are discussed. Design and optimization of the thermal busses, salt growth, and the new liquid helium gap heat switch and the new magnetostrictive mechanical heat switch are presented. Computer programs for providing control of the individual components of the CADR were written, and a two-stage CADR prototype was assembled to test experimental performance against theoretical predictions. Results of these tests are reported