Effect of twisting on strain tolerance of Bi-2212 multifilamentary round wires

Silver sheath Bi2Sr2Ca1Cu2Ox superconducting multifilamentary round wires having various twist pitch lengths and an untwisted one were fabricated by the oxide powder-in-Ag-tube method. The twisting process to a pitch length of 4.5 mm at a diameter of 1.45 mm did not influence the superconducting critical current density Jc whose value was about 90 000 A/cm2 at 4.2 K, 0 T. The Jc of the twisted wires is less sensitive to bending strain as twist pitch length becomes shorter. This phenomenon is explained by the calculated results that the filament’s curvature, which is added by the bending, becomes less as pitch length becomes shorter.