Narrow gas gap in cryogenic heat switch

Abstract

A gas gap heat switch reaches its high conductance state when the gap between two exchange surfaces is filled with a conducting gas. The broader the surface and the narrower the gap the higher the conductance achieved. In this paper we describe how to leverage the differential of the thermal expansion of construction materials to narrow the gas gap in a heat switch, while overcoming the intricacies of the manufacturing process of the switch.We designed and evaluated a prototype of a narrow gap heat switch built using our new methodology. The high conductance was measured with both helium and nitrogen, and at temperatures ranging from 20 K (He) or 75 K (N2) up to room temperature. The inferred gap opening at low temperature (≈17 μm) showed up to be slightly larger than expected, which allowed us to reinterpret the design calculations performed. Using a sorption pump the switch was also characterized along its extreme conductance states, and its performance was compared with a previously developed model.As a proof of concept, we built a prototype and the results obtained in the testing phase support our claim that the design we propose allow the development of high-performance customized cryogenic switches while keeping the assembly very simple and sturdy, hence widening the scope of the applicability of these devices.