Current connectivity in Bi-2223 silver-sheathed tapes for power cables

The mechanism limiting the transport critical currents of long-length (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub x/ tapes is still debatable. Such knowledge is important for improving the current performance of tapes for their use in superconducting applications. Transport and magnetic measurements have been used to study the current connectivity in tapes fabricated for power cable prototypes. The field dependence does not clearly distinguish between the different mechanisms of connectivity but is a useful parameter for characterising these tapes, even if they may be operated only in very low fields. Future improvements will come from better processing control and for operation at 77 K the intragranular pinning may need to be increased.