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 technique. The flux distribution exhibits a strongly time dependent behaviour due to thermally activated flux creep in the intergranular current system. In applied constant fields the decrease of measured magnetic field profiles was due to a logarithmic relaxation in time of induced intergranular screening currents. In slowly swept AC magnetic fields the flux distribution dynamics was governed by a continuous relaxation of intergranular screening currents. The screening current density was logarithmically dependent on the sweep rate of the applied field.<>