Modular nitrogen boiling thermosyphons for multi-kiloampere current lead cooling

A high cooling power, low-complexity and passive system for pre-cooling of multi-kiloampere current leads for cryogenic applications with boiling nitrogen is presented. The system consists of a modular heat interceptor part with passively induced flow based on the thermosyphon effect, where evaporated nitrogen is vented into the atmosphere. This heat interceptor module may be placed between a normal conducting and superconducting cable, to substantially reduce the thermal load on a cryogenic setup. Two prototype heat interceptors with similar cross-sectional areas and boiling surface but different coolant channel geometries were designed, manufactured, and characterized. Both prototypes displayed a cold-end temperature below 79.3 K up to heat loads of 0.90 ± 0.09 kW for the wide flow-channel design and 1.25 ± 0.05 kW for the thin flow-channel design. The designed heat interceptors offer cooling capacities sufficient for intercepting heat loads from multi-kiloampere current leads without active pumping or flow regulation while being economical and relatively compact. This system can be useful when combined with cryocoolers, substantially reducing the load on the cold mass.