Building a Thinner Gap in a Gas-Gap Heat Switch

A gas-gap heat switch (GGHS) reaches its highest conductance state when the gap between two exchange surfaces is filled with a conducting gas in a viscous regime. The broader the surface and the thinner the gap, the higher the ON conductance achieved. In this paper we describe a very thin cold gas-gap heat switch reached upon the use of the differential thermal expansion of the construction materials. Such technique overcomes the intricacies of the manufacturing process of the switch.

We designed built and tested a prototype of a very thin gap heat switch using our new methodology. The high conductance was measured with both helium and nitrogen, at temperatures ranging from 20 K (He) or 75 K (N2) up to room temperature. The inferred gap opening at low temperature (approximate to 17 mu m) has shown to be slightly above the expected, which allowed us to reinterpret the design calculations. The switch was also characterized along its extreme conductance states while using a sorption pump, and its performance was compared with a previously developed model.
Lessons learned from the first prototype led us to build a second one with better performance.
Our experiments suggest that the proposed design allows for the development of a customized cryogenic switch with improved ON conductance while keeping the assembly very simple and sturdy, hence widening the scope of applicability of these devices.