Heat switches are key elements in the cyclic operation of Adiabatic Demagnetization Refrigerators (ADRs). Several of the types of heat switches that have been used for ADRs are described in this paper. Key elements in selection and design of these switches include not only ON/OFF switching ratio, but also method of actuation, size, weight, and structural soundness. Some of the trade-off are det...

We consider the adiabatic demagnetization in the rotating reference frame (ADRF) of a system of dipolar coupled nuclear spins s = 1/2 in an external magnetic field. The demagnetization starts with the offset of the external magnetic field (in frequency units) from the Larmor frequency being several times greater than the local dipolar field. For different subsystem sizes, we have found from num...

Low-temperature refrigeration is of crucial importance in fundamental research of condensed matter physics, because the investigations of fascinating quantum phenomena, such as superconductivity, superfluidity, and quantum criticality, often require refrigeration down to very low temperatures. Currently, cryogenic refrigerators with (3)He gas are widely used for cooling below 1 K. However, usag...

We present the design of a novel, miniature ADR with no moving parts, which could be used to cool detectors for astrophysics research, semiconductor analysis, and mass spectrometry. The miniature ADR relies on the development of a magnetoresistive heat switch. We present measurements of the thermal conductivity of a single-crystal tungsten heat switch at temperatures below 4 K and magnetic fiel...

This pathway describes the development of a Continuous Adiabatic Demagnetization Refrigerator (CADR) within NASA’s Goddard Space Flight Center’s (GSFC, or Goddard) cryogenics and fluids branch. After more than a decade of concerted development efforts, the team is still awaiting a mission opportunity on which to fly the full system. Like the traditional ADR, the CADR will maintain spacecraft in...

Abstract Generation of very low temperatures has been crucially important for applications and fundamental research, as low-temperature quantum coherence enables operation computers formation exotic states, such superfluidity superconductivity. One the major techniques to reach milli-Kelvin is adiabatic demagnetization refrigeration. This method uses almost non-interacting magnetic moments para...