Cryogenic refrigeration apparatus

Claim 1

A cryogenic refrigeration apparatus, comprising: a cryogenic vessel which accommodates a superconducting coil immersed in a cryogenic cooling medium and which is disposed in surrounding relationship to an electromagnetic cavity in which a magnetic field is produced by said superconducting coil; a vacuum vessel disposed outwardly of said cryogenic vessel with a vacuum area interposed therebetween and provided with means defining an opening; thermal shield means which includes at least one layer disposed between said vacuum vessel and said cryogenic vessel; a magnetic shield disposed outwardly of said vacuum vessel for preventing a magnetic flux produced by said superconducting coil from leaking to the exterior, said magnetic shield having a wall thickness greater than said vacuum vessel; cooling means securely supported on said magnetic shield for cooling said thermal shield means; heat conducting means connected between said cooling means and said thermal shield means through said opening of said vacuum vessel for conducting to said thermal shield means a cooling effect provided by said cooling means; vibration absorbing means connected between said magnetic shield and said vacuum vessel so as to define said vacuum area which accommodates said cryogenic vessel and said thermal shield means, said vibration absorbing means having elasticity which substantially prevents vibration produced by said cooling means from being transmitted from said magnetic shield to said vacuum vessel; and access means for providing external access to a magnetic field which is produced in said electromagnetic cavity by said superconducting coil.