Spatial distribution of transport current in low and self field in BSCCO tapes

The spatial current distribution in monofilamentary BSCCO - 2223 tapes is evaluated numerically using the critical state model with a held dependent critical current density. The overall transport current density is the sum of the local currents which perceive different magnetic fields depending on their location within the tape. In self field a current peak in the center of the specimen occurs. This is caused by the field dependence of j(c). If a monofilamentary tape is sliced longditudinally the self field effect leads to an enhancement of j(c) in the slices that formed the tape edges, even though the microstructure of the monofilament itself is assumed homogeneous. Thus the fact that this enhanced current flow at the tape edges is found experimentally does not necessarily mean that the microstructure in the tape edges is better, but could be - at least in part - due to the self-field effect. In twisted multifilamentary tapes the current distribution is expected to be homogeneous since the filaments cross over the tape. The self field effect also leads to a reduction of the overall current density for use of stacks of tapes as current leads.