AC losses in a multifilamentary Nb3Al/Cu composite superconductor made by a jelly roll process

Hysteresis losses in a multifilamentary Nb3Al/Cu composite superconductor have been examined by means of measuring magnetization. The Nb3Al conductor consists of 397 Nb3Al filaments, whose diameter is 21 μm, embedded in the copper matrix. The non-copper critical current density is 510 A/mm2 at 12 T which is the same level as that of commercial Nb3Sn conductors. Magnetization measurements of the Nb3Al conductor have been performed in the parallel and perpendicular fields. For the field perpendicular to the conductor length. It was shown that the effective filament diameter is almost equal to the actual filament diameter. On the other hand, the hysteresis loss for the field parallel was around one-fourth as large as that for the perpendicular, corresponding to the effective filament diameter of approximately 8 μm. The reason for this result is considered to be that the Nb3Al layer produced between Al and Nb sheets after reaction is in a whirlpool state, and it shows that the Nb3Al conductor is fully available for application to magnets in fusion machines such as ITER, which are operated in a pulsed field