Persistent Mode Superconducting Magnet with Demountable Leads

Abstract

An experimental apparatus is set up to examine the persistence of current and helium boil off rate of a self contained magnet in a cryostat. Two 100 A rated persistent current switches are soldered in parallel with a superconducting solenoid. A diode is also wired in parallel with the switches to clamp the voltage in case the switches quench. The magnet power supply is connected to the magnet via multiple contact band demountable leads. The magnet cryostat is connected to a model 1410 Koch helium liquefier. The magnet is found to operate at 200 A with the two 100 A switches, and the diode is found to provide adequate protection during quench of up to 200 A. The current decay due to the resistive joints is measured. The transition to persistent mode and removal of the demountable leads indicate a significant reduction in heat leak. A 200 A persistent switch is designed and fabricated.