Japanese Patent Laying-Open No. 2009-32758 (PTD 1) is a prior art document disclosing a configuration of a conduction-cooled superconducting magnet device with a superconducting coil less quenchable despite power failure.
The conduction-cooled superconducting magnet device described in PTD 1 includes a cryogenic refrigerator, a tank having a refrigerant therein, a superconducting coil immersed in the refrigerant, and a heat transfer means in thermal contact with both the tank and the cryogenic refrigerator for allowing thermal conduction therebetween.
When the conduction-cooled superconducting magnet device has the cryogenic refrigerator in operation, it is adapted to allow the thermal conduction between the tank and the cryogenic refrigerator via the heat transfer means to cool the tank. Once the cryogenic refrigerator has stopped from operating, an interruption means that is provided for the heat transfer means interrupts the thermal conduction between the tank and the cryogenic refrigerator to prevent the heat transfer means from letting external heat enter the tank and thus vaporize the refrigerant.