Design and Implementation of a Persistent Switch for Superconducting Magnet

Abstract

QCD axions are a promising candidate for dark matter. One essential component of an axion search is a high-strength large-volume magnet. This thesis addresses the design and implementation of a scaled-down version of a persistent switch for a superconducting magnet to be used as part of an axion experiment. As part of the switch, phosphor bronze leads conduct current from room temperature to the 40K stage. We designed and installed a set of these leads in a cryostat such that the power delivered to the next 40K temperature stage was maximized and Joule heating was minimized. We computed the expected thermal and Joule heating loads that resulted from connecting these phosphor bronze leads and using the leads to run current into the cryostat. By measurement, we verified the estimated added load resulting from the installation of the phosphor bronze to be about 1 W with estimation resulting from slight variations in physical properties and geometries of the leads. By running 12.5 A of current through the phosphor bronze leads, which results in 1.25 W of joule heating, the 40K stage of the cryostat received an additional 0.51 W of heating for a total of 1.5 W introduced into the system.