AC losses in composite superconducting wires

Measurements have been made at 4·2 K of the losses in filamentary composites of niobium in copper carrying transport currents of up to 70 A at frequencies in the range 50 to 800 Hz. Critical currents and B-H loops were also measured. The experimental results can be accounted for on the basis of a physical model in which the composite wire behaves as a solid superconductor. The effect on the losses due to twisting the composite wires has also been investigated.