EAGER: CRYO: Sub-Kelvin Refrigerator using a Superfluid Helium Vortex Cooling Principle

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This EArly-concept Grant for Exploratory Research (EAGER) supports the development of a new type of refrigerators that reaches 1K based on the design of new two-stage cooling approaches. This temperature range is needed for physicalists to demonstrate novel quantum phenomena, for materials scientists to discover new form of materials, and for astronomers to develop extremely sensitive detectors. The need for sub-1K temperatures has been increased with the advent of new quantum computers, currently operating in these temperature ranges. Current technology for such cooling relies on a rare isotope of helium (Helium-3) as a necessary component of the refrigeration fluid to reach this temperature. The stockpile of helium is depleting worldwide, and new technologies are needed to meet the new demand for cooling and refrigeration below 1K without the use of diminishing He-3 gases. This grant also trains students in this important area increasing the workforce.The combination of a superfluid vortex cooler (SVC) and a Joule-Thompson precooler is researched to achieve high-capacity sub-kelvin cooling without the use of He-3 in the system. The complete system is closed cycle with zero helium boiloff. Benefiting from the fountain-pump effect of superfluid helium-4, the superfluid vortex cooler does not require any moving parts or an external pump, is compact, and can be conveniently attached to various types of precooling stages that reach a temperature below 2K for heat rejection. The complete system would be compact and provide significant cooling capacity ( 1mW) at 0.9K, with a theoretical cooling limit of 0.65K. This research program will analyze and design the system based on a thermal analysis of the energy transfer. The program will build a prototype cooler and benchmark the performance against estimates.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.