Non-Contaminating Compressor for Closed-Cycle Cryocoolers

Creare will develop a compressor that works atcryogenic temperatures: 80K or nearly 350 degress below zero fahrenheit. The compressor works at high pressures for Joule-Thompson (J-T cryocoolers. J-T cryocoolers contain heat exhangers and expansion elements that are orders of magnitude smaller than Reverse Brayton or Stirling cryocoolers. Further, J-T cryocoolers contain no active components in the cold end. Hence, in theory, they can reach a high efficiency. Exclusive of the compressor a one-stage J-T can attain 50% of Carnot, while a 3-stage J-T goes up to 75% of Carnot. Unfortunately, J-T cryocoolers have a weak link: the compressor. Today's high pressure compressors use lubricants and rubbing seals that contaminate the cooling system gas, which in turn causes the J-T restrictor to clog and fail. Hence, gas cleanup systems must be installed downstream, but they need frequent maintenance, and will not function properly in space. This project will develop a new compressor that has no rubbing seals and needs no lubricants. Thus, it won't clog the restrictor, and it removes the need for a gas cleanup system. It also increases the efficiency make it a candidate for cooling space sensor systems. The compressor can also serve in coolers for portable night vision systems that use only a fraction of a watt. Other applications are closed-cycle J-T recondenscers for MRI systems, and miniature refrigerators for superconducting devices.