MAGNETIC AC LOSS IN MULTI-FILAMENTARY BI-2223 AG TAPES/

The ac loss in high-T-c, superconducting tapes with twisted and non-tw isted filaments has been studied by a magnetic method. A brief overvie w of the theoretical background and the experimental set-up is present ed. Measurements were made at 77 K in a magnetic field of 50 Hz freque ncy and 0.001-0.7 T amplitude. Application of de transport current mad e 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 exte rnal field with respect to the tape was varied. Knowledge of the ac lo ss in parallel and in perpendicular field is sufficient to predict the ac loss for any intermediate orientations of the field. (C) 1997 Else vier Science B.V.