Compactly composed strong magnetic field generators with cryo-cooled high temperature bulk superconductors as quasi-permanent magnets

The authors have constructed various types of strong magnetic field generators using superconducting bulk magnets in conjunction with compact refrigerators. The magnetic field in the open space outside the vacuum chamber that contains a bulk magnet has been estimated as over 3 T when activated by the static fields of a 5 T superconducting solenoid magnet. The authors have tried to extend the variation of such strong field generators which are promised to develop in the future. In the study, a novel and compact bulk magnet system with use of a compact pulse tube cryocooler has recorded the maximum trapped field of 2.78 T on the magnetic pole surface. The characteristic feature of superconducting bulk magnet is defined as a compact and strong magnetic field generator. This implies that various kinds of equipments must be successively proposed even in the very early stage of industrialization of strong magnetic field generators.