PROCESSING ISSUES OF BI-2212 WIRES

Long length (> 100 meters) Ag-sheathed high temperature superconductin g (HTS) Bi2Sr2CaCu2O8 (Bi-2212) oxide conductors have been processed u sing conventional powder-in-tube (PIT) and partial-melt-growth (PMG) t echniques. Results show that the critical current density (J(c)) of lo ng length tapes is significantly lower when compared with J(c)s of sho rter length conductors (< 1 meter). This decrease in J(c) is attribute d to: (a) processing temperature non-uniformities along the conductor length, and (b) J(c) sensitivity to temperature variations. The non-un iformity and sensitivity issues are being addressed by new furnace des igns and annealing methods (such as the isothermal melt process method which has the potential to reduce the J(c) temperature sensitivity), respectively. Simultaneously, other defects that are incorporated into the conductor during processing, with detrimental effect to the J(c), need to be addressed. The issues relevant to processing of long lengt h HTS Bi-2212 conductors with uniformly high J(c) are discussed.