A New Criterion for the Design of Gas-Cooled Cryogenic Current Leads

Abstract

The performance of some electrical equipment such as superconducting magnets requires cryogenic temperatures. The literature therefore contains many discussions on the design of cryogenic current leads [^1–6]. Earlier evaluations deal with leads that are cooled by conduction at several points, and the existence of an optimum ratio length to area which yields a lead with minimum heat leak is clearly demonstrated [⁵]. Leads cooled in this fashion are found to have an objectionally high heat leak, even if of the optimum design, when carrying high currents. An obvious solution to this problem is to allow some cold gas to pass over the surface of the leads, creating a device similar to a counterflow exchanger, with parallel current and gas flow. This form of lead has also received a great deal of consideration in the literature with the goal of finding an optimum ratio of length to area.