Installation of a superconducting magnet in a cryogen-free dilution refrigerator

A cryogen-free dilution refrigerator equipped with an 8 T superconducting magnet is developed. The dilution unit and the magnet are cooled together by a common Gifford-McMahon refrigerator in the same vacuum chamber. A heat flow from room temperature terminals through a pair of copper current leads is well absorbed by thermal anchors connected to a 1st stage of the GM refrigerator. Between the 1st stage and the 2nd stage, a pair of flexible high-T_C DyBCO coated conductors is used as a material for the current leads to reduce the heat leakage to the magnet. The dilution cycle is not affected by coexistence of the magnet, because the heat load imposed by the magnet is much less than that by the dilution unit. When a quench event happens, the temperatures of the magnet and a 4 K plate of the dilution unit rise rapidly up to 20 K, but safely recover in 18 min without causing serious trouble in the dilution process.