Anomalous Low Hysteresis Losses in NbTi Superconductors with Very Fine Filaments
Hysteresis losses of multifilamentary NbTi/Cu/CuNi mixed matrix conductors with very fine filaments were measured in the frame of the VAMAS intercomparison. A calorimetric technique was developed for the purpose allowing short sample measurements in the microwatt range. This method allows an independent variation of the magnetic background field and the alternating field amplitude. For low amplitudes, the losses were found to be well below the values expected from the Bean model. A similar behaviour, found recently in magnetization measurements, was explained by reversible flux line motion. The present data are reasonably well described by an existing theory. The paper includes also the results of two samples having thicker filaments.
KeywordsVortex Helium CuNi
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