Magnetic ac loss in multi-filamentary Bi-2223 / Ag tapes

The ac loss in high-T_c superconducting tapes with twisted and non-twisted filaments has been studied by a magnetic method. A brief overview of the theoretical background and the experimental set-up is presented. Measurements were made at 77 K in a magnetic field of 50 Hz frequency and 0.001–0.7 T amplitude. Application of dc transport current made it possible to distinguish between the loss components, arising from intra-grain and from filament currents. The magnitude of the filament loss component indicates that the filaments are fully coupled, which agrees with theory. In other measurements, the orientation of the external field with respect to the tape was varied. Knowledge of the ac loss in parallel and in perpendicular field is sufficient to predict the ac loss for any intermediate orientations of the field.