Cryogenics & Fluids Home
P.J. Shirron, M.J. DiPirro,
Code 552
NASA/ Goddard Space Flight Center
Greenbelt, MD 20771
M. Jirmanus, Z. Zhao, and B. Shields
Janus Research Company
2 Jewel Dr., Wilmington MA 01887
We have recently assembled a 4-stage continuous adiabatic demagnetization refrigerator (CADR) that provides continuous cooling at 50 mK and below, while rejecting heat to a 4.2 K helium bath. Temperature control and cycling of the ADR is fully automated, making it simple to operater and stable. Temperature fluctuations of the cold stage are typically less than 10 microK rms (at 100 mK). The cooling power of 20 microW at 100 mK is comparable to that of small dilution refrigerators, but because its efficiency is so much higher (50% of Carnot), the peak heat rejection rate is less than 10 mW. This is significant in allowing the ADR to be cooled by relatively low-power cryocoolers. In addition to commercial pulse-tube and Gifford McMahon (GM) coolers, this potentially includes small GM systems that run on 120 V power and do not need water cooling. The present focus is to design and fabricate a small dewar to house the CADR and a cryocooler, in anticipation of making a cryogen-free, low cost CADR commercially available. Performance of the prototype CADR and the complete system are discussed.
Advances in Cryogenic Engineering: Transactions of the Cryogenic Engineering Conference -CEC, Vol. 49, ed. J. Waynert et al. pp. 1746 - 1753 (2004, American Institute of Physics).