NbTi wires with ultra-fine filaments for 50 - 60 Hz use: Influence of the filament diameter upon losses

For eighteen months, we have manufactured long lengths of multifilamentary superconducting wires, which comprise from several ten thousand to several hundred thousand 0.08 to 1 micron-diameter NbTi filaments. In these wires, the matrix between the filaments is made of pure CuNi and their structure provides a good magnetic stability and leads to strongly reduced 50 Hertz losses. Obtained results open very new prospects for applications of superconductivity in fast pulsed magnets and in A.C. current devices. In this paper we present results of 50 Hz loss measurements in these wires and we discuss the influence of the filament diameter upon these losses.