Gas gap heat switches for conduction cooling of SRF cavities

Particle accelerators are used in a variety of ways to the benefit of people at large. Part of the challenge in making the benefits of these machines accessible to the broader society is their cost and complexity. The cryogenic system that cools the superconducting radio frequency (SRF) cavity contributes to this problem. Recent advances from Fermilab have shown that the conventional liquid helium cryogenic systems can be replaced by cryocoolers to cool SRF cavities down to operational temperatures. Though successful cooling of SRF cavities have been demonstrated, there is much to be gained by reducing the time taken to cool down the SRF cavities from room temperature to operating temperature. Cryocoolers used in such applications typically have a higher temperature stage and a low temperature stage at which heat is removed. If the capacities of both these stages can be coupled, it can accelerate the cooldown of SRF cavities thus reducing operational costs for such machines and making them more efficient. Novum Industria LLC will collaborate with the Massachusetts Institute of Technology (MIT) to develop a heat switch, and explore a heat pipe heat switch that can couple two stages of a cryocooler during the cooldown phase of the SRF cavity to reduce the time required to reach operating temperature. In Phase 1, we will explore the thermosyphon, heat pipe and gas gap approaches to the heat switch. Based on performance metrics such as heat transfer rates, size, ease of design and construction, ease of assembly etc., one of these designs will be chosen to advance its design maturity such that its performance is predicted over the desiredoperational range. InPhase 2, the preferreddesign is fabricated and experiments will be performed to characterize its performance and will be compared with the theoretical performance predictions from Phase I.