Fabrication and characterization of <i>i</i> <i>n</i> <i>s</i> <i>i</i> <i>t</i> <i>u</i> superconducting multifilamentary copper-niobium wires

I n situ superconducting multifilamentary Cu–17 wt% Nb wires have been produced. The cross-section reduction ratio varied from 1 to 62 500. The critical current density in zero field at liquid-helium temperature dramatically increases from a few hundred amperes per square centimeter in the as-cast condition to a value of 6×105 A/cm2 for the highly reduced wires. A model based on the nonhomogeneous deformation of the niobium network accounts for the observed results. The evolution of the I-V curves from a broad transition to a sharp transition with increasing deformation is explained in terms of the geometry of the niobium chains.

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