Self-field ac losses in dc external fields and non-uniform transverse J_c distribution in Ag sheathed multifilamentary PbBi-2223 tapes

摘要

Measurements of self-field ac losses in dc external fields were carried out on Ag sheathed multifilamentary PbBi-2223 tapes at different stages of thermal processing. Using a novel method as described in [1,2], the transverse distributions of the local critical current density J_c were deduced from the measured losses as a function of the ac transport current., Compared with data obtained from mechanical sectioning [3] of a sample, our results showed in greater detail the J_c distribution in the outer region of the core, which carries most of the critical current. The non-destructive nature of the method allows the monitoring of the evolution of local: J_c at different processing times. For example, the J_c in the outer region exhibits a faster deterioration when the tape is processed beyond the optimal time. It is also observed that the local critical current density in the outer area of the core has a stronger dependence on the applied magnetic field in both parallel and perpendicular directions, compared with the overall: I_c-B dependence obtained from the dc measurement.