Comparison of AC losses of superconducting wires for ramped-field applications

A local maximum at a slow field variation was measured in the AC-loss profile vs. field ramping rate in a double-stacked wire, which is not predicted by the existing AC-loss models. The AC losses of three important superconducting wires, manufactured mainly for superconducting magnets running at large amplitudes and slowly ramping fields, have been measured. These three single-strand samples, including a NbTi, an internal-tin, and a modified jelly-roll internal-tin wire, have different cross sectional constructions. A model taking into account the saturation of the filament bundle walls caused by strong local interbundle coupling currents in the inner multifilament region is proposed to provide a possible explanation to this special loss dependency.<>