Performance Enhancement for 4 K Pulse-Tube Cryocoolers

Future military communication systems will rely on advanced superconductor digital electronics. These electronics will require efficient cooling at low temperatures near 4 K. Pulse-tube cryocoolers are a candidate cooling technology for this application. We propose to improve the efficiency of the pulse-tube cryocooler by addressing one of its primary performance limitations, namely the performance of the regenerator at low temperatures. Our proposed regenerator uses an innovative non-rare-earth material to achieve a very high volumetric specific heat; it also has a novel configuration for high thermal and fluid performance. The regenerator"s large heat capacity, small void volume, and low flow restriction will substantially improve the thermal efficiency of low-temperature pulse-tube cryocoolers. In Phase I, we proved the feasibility of our approach by (1) optimizing the regenerator matrix material and flow configuration, (2) developing microfabrication procedures for the regenerator, (3) calculating thermal and fluid flow performance in the regenerator by CFD simulation, and (4) assessing the performance of a pulse-tube cryocooler using our regenerator. In Phase II, we will optimize the regenerator fabrication method, and then fabricate and test a full-size regenerator in prototypical environments.