CRITICAL CURRENT-DENSITY IN AG-SHEATHED WIRES OF YBACUO

Transport critical currents in Ag-sheathed wires of YBCO have been studied. At zero field the characteristic weak-link properties were masked by the self-field of the transport current. From a scaling law with respect to temperature and diameter the self-field effects could be separated, allowing the weak-link parameters to be determined. The observed improvement of the weak-link properties with decreasing wire diameter is due to the reduction of the junction length and the enhancement of the number of junctions. For a wire of 0.25 mm diameter a maximum Josephson current density of 2.7 x 10(4) A cm-2 at 4.2 K has been obtained.