TRANSPORT CRITICAL-CURRENT AND ITS DISSIPATION IN Y1BA2CU3O7-DELTA GRANULAR SUPERCONDUCTORS

The transport and magnetic properties of the intergrain Josephson junc tion network were measured in Y1Ba2Cu3O7-delta and Y1Ba2Cu3O7-delta/Ag (2 wt.%) granular superconductors using a novel technique which emplo ys a self-sustaining (persistent) current flowing in a superconducting ring and a contact-less detection of the critical current with a Hall probe. The measurements were performed as a function of temperature o ver a temperature range 64-90 K in a magnetic field up to 60 G. This t echnique allowed, for the first time, the direct measurement of the Jo sephson critical current dissipation (and the associated activation en ergy for the Josephson flux motion) as a function of temperature and m agnetic field.