AC loss measurements of Nb3Sn wire carrying transport current

This paper reports on the AC losses of internal-tin Nb3Sn wires measured by an isothermal calorimetric method in triangular-wave fields at ramp rates up to 1.2 T/sec and in small-amplitude ripple fields biased with dc fields up to 9 T. Measurements were made both with and without transport currents, which were both AC and DC. Without transport currents, losses had near-parabolic profiles when plotted against bias field with constant ripple amplitude, against triangular-wave ramp rate, or against triangular-wave ramp amplitude. With transport currents up to 90% of critical, losses for triangular-wave fields were shown to increase up to 17% with increasing DC currents and up to 10% with increasing AC currents. With DC transport currents, the scaling of loss by (1 + i2), where i is the ratio of transport-to-critical current, may be a good approximation