Experimental study of the effect of filament orientation on transport and magnetic ac loss in Bi-2223/Ag multifilamentary tapes

Losses of electromagnetic energy in cyclic regimes were investigated for two tapes with hat Bi-2223 grains in different directions with respect to the tape wide face. This was achieved through having different angles between the wide faces of strip-like filaments and that of the tape: in the first tape this angle was zero while in the second it was a right angle. In transport (self-field) conditions, comparison with theoretical predictions for a homogeneous and isotropic material revealed opposite deviations at low currents. The tape with parallel filament orientation exhibited higher loss than that extrapolated from the critical current density measured in the fully saturated state, and for the tape with transversal filaments it was lower than expected. We explain this through the different orientation of filaments with respect to the self-held in the boundary shell carrying the ac current at low amplitude. We also performed measurements in the external magnetic field, which was always perpendicular to the tape wide face. Magnetization results can be interpreted in terms of flux penetration in individual filaments. Spread in filament quality caused the absorption peak to be broader than expected for an ideal, homogeneous material.