Performances of compact magnetic field generators using cryo-cooled high temperature bulk superconductors as quasi-permanent magnets

Two types of strong magnetic field generator have been newly constructed by using superconducting bulk magnets that mainly consist of rare earth 123 single domain compounds (REBa₂Cu₃O_y) in conjunction with different kinds of compact cryocoolers. The magnetic flux densities in the open space outside the vacuum chambers that contain bulk magnets have reached 3.37T and 2.78T when a Gifford-McMahon (GM) cryocooler and a Stirling-cycle (ST) pulse tube cryocooler cooled them to 30.8K and 62.0K, respectively. In this study, the activation of a bulk magnet was accomplished by field cooling magnetization using the static field of a 5T superconducting solenoid magnet. It was clarified that the trapped field distributions strongly reflect the temperature dependence of superconducting properties of the bulk magnet. The conditions for supplying intense fields in the open space are discussed to utilize them in practical applications. The most characteristic feature of superconducting bulk magnets is defined as a compact and strong magnetic field generator, which is discussed on the map from the industrial point of view.