A Novel Superconducting Switch and Joints for an Axion Dark Matter Detector

Abstract

This thesis describes the design, fabrication, and testing of a persistent current switch (PCS) and superconducting joints for the Princeton Axion Search. A novel planar switch geometry is proposed and validated, offering improved thermal contact and reduced inductance without epoxy impregnation. The final switch iteration demonstrated a normal-state resistance of 7.5 Ω, an upper limit on superconducting-state resistance at 8.2 nΩ, and a critical current of 370 A below 5.5 K. The switch was driven normal in under six seconds using only 10% of available heater power, validating its quench protection capabilities. A PID-controlled metal bath was designed and constructed for fabricating superconducting joints. A constructed joint sustained 520 A of current at 3.08 K, and a persistent current utilizing the switch, two joints, and a mini-coil showed no measurable decay across three days, setting an upper limit on the joint resistance of 1.90 × 10−13 Ω.