Development of Active Gas-Gap Heat Switch for Double-Stage Adiabatic Demagnetization Refrigerators

Abstract

We designed and fabricated an active gas-gap heat switch (AGGHS), which ON/OFF the heat conduction between the 1st stage (0.05-2 K) and the 2nd stage (1-4 K) of a double-stage adiabatic demagnetization refrigerator (DADR). Our design geometrically separates two components which dominates the ON or OFF performance, and achieved heat conductivity of 6 mW/K (ON) or 4 µW/K (OFF) at 2 K. The ON/OFF is controlled by a heater attached to the charcoal box to adsorb/deadsorb 4 He gas inside. We introduced the AGGHS to the DADR and successfully cooled the detector stage down to 60 mK, working properly more than a year.

Energy Applications of Magnetocaloric Materials

“…A typical adiabatic demagnetization refrigerator ( Figure 18 ) consists of the full body of a magnetocaloric material placed in the bore of a superconducting magnet. A connection between the magnetocaloric material and the heat sink is established using a thermal switch, which has been extensively researched in several investigations in the past decade . A typical adiabatic demagnetization cycle performs four processes.…”

Exploring the Potential of Metal–Organic Frameworks for Cryogenic Helium-Based Gas Gap Heat Switches via High-Throughput Computational Screening

“…The heat switches have a high thermal conductance in the ON state and a high thermal resistance in the OFF state. Typical applications of the heat switches include thermally connecting/disconnecting the heat source to the redundant refrigerator in a spacecraft, , precooling/separating the cooling stages in a cooler chain, , coupling/decoupling the evaporator to the heat sink in a helium sorption refrigerator, , and controlling the heat flow between the heat sink and the sorption cell in a sorption compressor. , In these situations, the heat switches’ performance dramatically affects the whole systems’ performance and sometimes even determines their feasibility.…”