X-ray Lithography Fabricated Microchannel Regenerators for Cryocoolers

Abstract

NASA, Air Force, Missile Defense Agency (MDA), and DoD repeatedly express the need for long-life, low maintenance space cryocoolers. Two types of cryocoolers that meet these requirements are the pulse tube and the Stirling coolers. One of the major factors limiting the efficiency of these coolers is the regenerator. Improving the regenerator performance would substantially increase the efficiency and thus reduce the power required to operate these coolers.

Recent advances in the field of microfabrication have resulted in the ability to create advanced geometries in lead and erbium alloys for use as regenerators in cryocoolers. The performance of cryocoolers, both in terms of power efficiency and the attainable cold end temperature, is strongly influenced by the geometry and cryogenic thermal properties of the regenerator material. These new fabrication techniques allow for the ability to reduce the pressure drop across the regenerator and improve the thermal capacity by optimizing the porosity, channel shape, channel size, and material of construction. Previous work indicates that the resulting regenerators support lower NPH/NTU values over current screens and powders used in cryocoolers.

While these advanced geometries have already been formed in both lead and erbium, the technology can be expanded to include a wide variety of materials such as other rare-earth alloys, stainless steel, copper, and nickel alloys. A complete regenerator has been formed out of lead and is currently being evaluated. Improvements in the thermal performance of the regenerator will result in an overall improvement in regenerative cryocoolers, especially at the lower temperature ranges (<30K).