Magnetization and critical current density of ultra-fine multifilamentary superconducting wires

Multifilamentary superconducting wires with a greatly reduced level of losses have been produced with lengths of several tens of kilometers. In spite of the reduction of the filament diameter, proximity effects are avoided, and the best possible use of the reversible motion of the flux lines is made, so that the hysteretic losses are reduced. The concepts lead to a realization of conductors comprising filaments of Nb-Ti (0.1-0.2- mu m diameter) embedded in a highly resistive CuNi matrix. In order to characterize the possible application to industrial power systems, it is necessary to investigate the losses in submicrometric filaments. It is possible to determine the correct value of the critical current density with critical current measurements and magnetization curves on such wires.