Patent ID: 8778841

Claim:
A method for manufacturing a precursor for a Nb 3 Sn superconductor wire, said method comprising: coating a Nb-based core with a Cu-based matrix to provide a plurality of Nb-based single core wires; coating a Sn-based core with a Cu-based matrix to provide a plurality of Sn-based single core wires; inserting the plurality of Nb-based single core wires and the plurality of Sn-based single core wires that are bundled regularly into a cylindrical diffusion barrier comprising Ta or Nb; and inserting a bulk comprising the plurality of Nb-based single core wires, the plurality of Sn-based single core wires and the diffusion barrier into a Cu-tube, wherein the plurality of Nb-based single core wires comprises Nb-based single core wires having a Cu/Nb ratio of 0.4 or more and Nb-based single core wires having a Cu/Nb ratio of less than 0.4, wherein the Cu/Nb ratio is a cross sectional area ratio of the Cu-based coating to the Nb-based core, and wherein a diameter of a region, in which the Nb-based single core wires having the Cu/Nb ratio of less than 0.4 are adjacent to each other, is 300 μm or less.