Fabrication of 90-m length Bi₂Sr₂CaCu₂O_{8 + x} Ag-sheathed superconducting tapes

Initial results of a 90-m length Ag-sheathed Bi₂Sr₂Ca₁Cu₂O_8+x (Bi-2212) tape prepared by the oxide-powder-in-tube method are described. The transport J_c of one 90-m length tape measured in 10-m length sections was ~20,000 A/cm² at 4.2 K. The J_c of this tape was reduced to ~40% of expected values because the tape was processed in close contact with a ceramic cloth, rather than freestanding. Transport J_cs of 10-m sections of the 90-m length tape were uniform within ~10% variation. Unique problems that must be addressed to obtain uniform property, 90-m length tapes include: (i) bubble defect formations, (ii) ~2 cm interval "kinks", and (iii) effusion of melted oxides out of the Agsheathed tape. Possible solutions to these problems are suggested.