A Protection Method for Large HTS Coil by Copper Plate in Conduction Cooling System

High Temperature Superconducting (HTS) coil is widely used in high field magnets and normally operated at cryogenic temperature for higher magnetic field. In conduction cooling system, copper plate is connected with the coil and the second stage of cryocooler due to its excellent thermal conductivity. Also, copper plate can be connected electrically with the coil as a shunt where current can flow through. An electro-thermal interface is formed when quench occurs. However, the shunt may delay the charging process and generate joule loss. In this work, a D-shaped no insulation (NI) coil is fabricated with constant winding tension and tested based on 20 K conduction cooling system. Charging/discharging process is conducted at different temperature range by adjusting heater. The copper plate shows a significant current sharing path to protect the coil. And the heat can be taken away by cryocooler rather lead to a hot spot. This passive protection method for HTS coil is verified to be effective in large magnet system.