Hybrid Cooler System for Superconducting Electronics

"We propose to develop an innovative 10 K cooling system that will be 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 proposeto combine a multi-stage, linear-drive pulse tube with a low-temperature reverse-Brayton stage. In this way we will take advantage of the strengths of each system, while minimizing their respective weaknesses. The system avoids the inherent lossesassociated 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. The use of a low-vibration, linear,compressor for the pulse-tube stage provides a large pressure ratio allowing the size and expense of the recuperative heat exchanger to be minimized. These features result in a low-mass reverse-Brayton stage that can be fabricated reliably, at a reasonablecost, without sacrificing performance. The proposed hybrid cryocooler will achieve unprecedented efficiency below 10 K without resorting to high-unit-cost technologies such as super-critical shafts or extremely precise bearing clearances. The system willexhibit the high reliability and low vibration associated with pulse-tube and turbomachine-based reverse-Brayton systems. Many advances in missile defense applications, such as ground or space-based systems for surveillance and missile tracking, willrequire advances in electronic devices. For example, to improve the ultimate signal to noise ratio obtainable from cryogenic IR focal plane arrays (FPA), it is desirable to have on-focal plane, high-resolution, analog-to-digital data (A/D) converters. SuchA/D converters, based on the Josephson effect in low-temperature superconductors, and supporting technology are currently in various stages of developmentCryocoolers can also be employed in a wide variety of commercial applications. The following lists present and potential future applications: cryopumps for