Conduction-Cooling System for Superconducting Magnets at 20-30 K

A cryogenic system is designed and experimentally tested for superconducting magnets conductively cooled at 20-30 K by a cryocooler. Metallic parts are fabricated for the thermal connection between coldhead of a single-stage GM cooler and six magnet bobbins in hexagonal array, and assembled with bolt- joints. The material of all parts is oxygen-free copper with a high RRR value ( ~ 525), and the GM cooler is a newly released model from Sumitomo Heavy Industries. All six bobbins are uniformly cooled down to 13.0 K under no load and can be maintained at 20-30 K under additional thermal load of 26-60 W. It is verified by analytical simulation that this excellent performance is due to the extremely high thermal conductivity of copper conductors and the good thermal contacts by bolt-joints. The conduction-cooling system is a thermally feasible option for 20-30 K magnets, including the wind turbine generators.