Hybrid Cooler System for Superconducting Electronics

Atlas Scientific, in conjunction with the University of Wisconsin Cryogenic Engineering Group, is developing an innovative 10 K cooling system that is ideally suited to the cryogenic packaging requirements of a space-based superconducting electronics system. To achieve the most efficient and reliable hybrid cooler possible, we are combining a single-stage, linear-drive pulse tube with a low-temperature reverse-Brayton stage. The system avoids the inherent losses associated with a regenerator at low temperature, as well as, the inefficiencies associated with the Joule-Thompson process, by incorporating a novel turbo-expander in the low temperature reverse-Brayton stage. We are currently developing hydrostatic bearings for use in the turbine. Hydrostatic bearings provide support even in the absence of shaft rotation and therefore eliminate rubbing contact and increase the life and reliability of the bearing. Also, because hydrostatic bearings do not directly depend on viscous action for operation, relatively larger clearances can be used without significantly sacrificing rotordynamic performance at low temperatures, thus making them cost effective. In Phase II we will design and fabricate the complete miniature cryogenic turbine, using hydrostatic bearings, for inclusion in the hybrid cooler.