The present status and future of high-field superconductors

The present status of the development of superconductors is described. A technique of hydrostatic extrusion for making superconducting wires has been developed. The technique is suitable for manufacturing Nb3sn and Nb-Ti multifilamentary superconducting wires. The diameter of manufactured Nb-Ti filaments is uniform. Oxygen-free copper is used as the covering material which has stabilization effect. Nb3Sn filaments were made by the bronze method. The relation of magnetic field and critical current density for Nb-Ti and Nb3Sn alloys is shown. It can be said from the relation that Nb-Ti is suitable for the field less than 8T and Nb3Sn for the field above 8T. The Nb-Ti-Zr alloy is also used for the coils of superconducting magnets. The superconductor wires for pulse magnets have multilayer structure. The Cu-Ni is used as separators to reduce the AC loss. The future problems of superconductors are the improvement of characteristics for strong field, large current capacity, distortion endurance, low AC loss and manufacturing techniques. (Kato, T.)