Development of ultra-fine superconducting wires

The use of superconducting wire for applications utilizing their fluctuating magnetic field, pulse, and AC characteristics is drawing interest and is now under study. The typical of such applications of the wire are dipole magnet for giant particle accelerator, poloidal coil of Tokamak type nuclear fusion system, and AC generator operated at commercial frequencies. They require a superconducting wire capable of withstanding an average magnetic field fluctuating rate of at least 300 T/sec. We earlier embarked upon researches in very fine multi-core superconducting wires and have since been working on the development of technology to manufacture NbTi alloy wires and compound wires such as of Nb3Sn and V3Ga. Particularly our superconducting wire having a submicron filament diameter excels others in properties and is earning a favorrable comment. This report describes the features of very fine superconducting wires, the meaning of their development, the technology of AC superconducting wires elements, the present state of their development, and the possibility of their application to the commercial frequency band. (author)