An efficient liquid helium / gas-gap switch allowing rapidly servicing low-Temperature dynamic nuclear polarization systems

Abstract

The authors present a novel design for servicing inserts for Hyperpolarising or similar systems operating at temperatures below 4 K. Sample space sleeves that accommodate variable temperature inserts are usually deeply integrated in the cryostat structure and are impossible to remove or to warm up in case of service needs. We present experimental results that show the performance of a liquid helium / gas-gap switch that will be used together with a sample space insert which is in direct contact to a cold plate. This sample space sleeve can be serviced by thermally disconnecting the switch from the cold plate. Furthermore, the additively manufactured heat switch features a novel cold plate interposer for heat transfer that allows the physical separation of the sample sleeve tube from the cold plate enabling a room temperature warm up or complete sleeve removal, if required.