AC Losses and Critical Current Densities of NbTi/Cu Multifilamentary Tapes

Several kinds of NbTi/Cu multifilamentary tapes with high aspect-ratio cross-sections were fabricated in order to develop new conductors used for windings of conduction-cooled LTS pulse- coils with both low ac losses and high stability. These tapes were obtained by the cold rolling process from normal multifilamentary wires. For the edge-on transverse magnetic field at 4.2 K, about 20% increases in critical current densities at 6 T were observed for the tape with the highest aspect ratio of 7.4, and its hysteresis losses estimated from the observed magnetization were reduced to approximately one-half of those in the original wire. In this edge-on filed condition, the observed coupling losses in the tape were also decreased to about 1/17 times as large as those in the original wire. These experimental results showed that the NbTi/Cu multifilamentary tape had strong anisotropy of electromagnetic properties such as critical currents, hysteresis losses, and coupling losses and that good performances were obtained for edge-on transverse magnetic fields.