Comparison of calculated and measured hysteresis loss in multifilamentary superconducting wire

A previously developed theory for a single round filament of type II superconductor is applied to hysteresis losses in multifilamentary composite conductors. The single filament theory was extended for a wider range of time varying field amplitudes. Two contrasting wires were used to test the theory which predicts a universal curve for the loss in all conductors. A very close agreement was obtained in all details between theory and experiment for the wire with widely spaced (∼2.5 μm) large-diameter (15 μm) filaments. The other wire had closely spaced (<1 μm) small-diameter (2 μm) filaments and the shapes of the loss versus field plots for theory and experiment were in excellent agreement for this case. However, the effective filament diameter and superconductor volume fraction λ extracted from fitting the theory and measurements are much larger than the physical diameter and slightly larger than the physical λ, respectively. This is expected due to the proximity effect and possible interfilament contact. This effective diameter is approximately the size of clearly defined filament bundles.