EAGER: CRYO: Actively-Controlled Fast-Switching Thermal Switch for Sub-Kelvin Cooling with Low He3 Usage

University Of New Mexico, Albuquerque NM

Investigators

Abstract

This EArly-concept Grant for Exploratory Research (EAGER) will fund research supporting the development of ultra-low temperature refrigeration with low He3 usage. Helium and its even rarer isotope He3, which has a crustal abundance of only 0.00014 percent of helium on Earth, are currently in short supply and the situation is projected to get worse. There is an urgent need to drastically reduce the usage of helium in ultra-low refrigeration applications needed for the national capability for the advancement of quantum-enabled devices and their many applications in computing, sensing, and communications. The project will thus promote the progress of science, advance the national prosperity, and help secure the national defense utilizing these unique technologies. Currently, refrigeration at temperatures below 1° Kelvin is largely limited to He3-dilution refrigerators, none of which are manufactured in the United States. Magnetic refrigeration is a low- He3 sub-Kelvin approach that has been developed for spaceflight experiments by NASA. This award supports fundamental research to remove a key technical obstacle to the commercial development of magnetic refrigeration as a low- He3 replacement for dilution refrigeration. This project has the opportunity to recruit and train students from an exceptionally diverse pool at the University of New Mexico is a Hispanic Serving Institution into an area needing an increased workforce. Sub-Kelvin magnetic refrigeration has been developed for spaceflight experiments by NASA. However, commercial development has proven difficult because of the overall complexity of these systems and the lack of simple design rules to engineer the subsystems, particularly the thermal switches. A further challenge is the difficulty of incorporating the fixed-temperature stages needed to support heat-sinking and thermal radiation shields. This award will perform fundamental research to develop a new thermal switch for the 0.5K-4K temperature range. The new switch’s features include rapid active control, high switching ratio, and a clear and simple set of design rules. Research objectives are to design; develop manufacturing techniques for; demonstrate; and characterize the new thermal switch, and then to demonstrate a single stage of magnetic refrigeration using the new switch, operating between two constant-temperature stages. Detailed modeling and experiment will be closely coupled. The project will use an existing research cryostat for measurements and will build on an extensive base of magnetic refrigeration simulation and modeling tools in the PI’s laboratory. Comparison of modeling and experiment will increase knowledge of magnetic refrigeration parameters and performance, and of static and dynamic heat flow in complex heat switch geometries containing materials with widely varying thermal properties. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.