MAGNETIC-FLUX DISTRIBUTION DYNAMICS IN BI-2223 AG TAPES/

We have studied magnetic flux distribution dynamics in silver sheathed Bi-2223 superconducting tapes at 77 K using a novel Hall sensor techn ique. The flux distribution exhibits a strongly time dependent behavio ur due to thermally activated flux creep in the intergranular current system. In applied constant fields the decrease of measured magnetic f ield profiles was due to a logarithmic relaxation in time of induced i ntergranular screening currents. In slowly swept AC magnetic fields th e flux distribution dynamics was governed by a continuous relaxation o f intergranular screening currents. The screening current density was logarithmically dependent on the sweep rate of the applied field.