Precursor for a Nb3Sn superconductor wire, method for manufacturing the same, Nb3Sn superconductor wire, and superconducting magnet system

A precursor for a Nb3Sn superconductor wire to be manufactured by an internal diffusion method, the precursor comprising:

• a plurality of Nb-based single core wires, each of which comprises a Nb-based core coated with a Cu-based coating comprising a Cu-based matrix,
• a plurality of Sn-based single core wires, each of which comprises a Sn-based core coated with a Cu-based coating comprising a Cu-based matrix;
• a cylindrical diffusion barrier comprising Ta or Nb, in which the plurality of Nb-based single core wires and the plurality of Sn-based single core wires are regularly disposed, wherein the plurality of Nb-based single core wires comprise Nb-based single core wires having a Cu/Nb ratio of 0.4 or more, in which the Cu/Nb ratio is a cross sectional area ratio of the Cu-based coating to the Nb-based core;
• and
• a plurality of segments, in each of which Nb-based single core wires having the Cu/Nb ratio of less than 0.4 are arranged to be adjacent to each other around one Sn-based single core wire,
• wherein the segments are sectioned by the Nb-based single core wires having the Cu/Nb ratio of 0.4 or more and the Sn-based single core wires.