Precursor for use in manufacturing superconducting wire, production method of precursor, and superconducting wire

A method for producing a precursor, the method comprising:

• preparing a composite pipe comprising:
• a composite wire group;
• a cylindrical barrier layer being disposed such that the cylindrical barrier layer surrounds the composite wire group to prevent permeation of tin;
• and
• a cylindrical protective layer covering an outer circumferential surface of the cylindrical barrier layer, and
• drawing the composite pipe,
• wherein the composite wire group comprises:
• a plurality of tin wires each comprising a tin core made of tin or a tin alloy, and a copper matrix which surrounds the tin core;
• a plurality of niobium wires each comprising a plurality of niobium cores made of niobium or a niobium alloy, and a copper matrix which surrounds the plurality of niobium cores, the plurality of niobium wires being disposed such that each of the tin wires is surrounded by the niobium;
• and
• titanium in a range of from 0.38 to 0.55% by mass and the titanium is comprised evenly in each of the tin wires and the niobium wires,
• wherein, in a cross-sectional view of the composite pipe following the drawing, centers of gravity of cross-sectional regions of respective tin linear bodies each resulting from the plurality of tin wires are positioned to form a substantially planar lattice, and
• wherein, in the drawing, the composite pipe is drawn such that an average distance from a center of gravity of a unit cell forming the substantially planar lattice to each center of gravity of the cross-sectional region of each of the tin linear bodies on lattice points of the unit cell is in a range of from 35 to 50 μm.

A superconducting wire, comprising:

• composite linear bodies each comprising a plurality of pores along a longitudinal direction, and comprising at least Nb3Sn and copper;
• a cylindrical barrier layer being disposed such that the cylindrical barrier layer surrounds the composite linear bodies to prevent permeation of tin;
• and
• a cylindrical protective layer covering an outer circumferential surface of the cylindrical barrier layer,
• wherein, in a cross-sectional view,
• centers of gravity of cross-sectional regions of respective pores are positioned to form a substantially planar lattice, and
• an average distance from a center of gravity of a unit cell forming the substantially planar lattice to each center of gravity of the cross-sectional region of each of the pores on lattice points of the unit cell is in a range of from 35 to 50 μm, and
• wherein the composite linear bodies comprise titanium in a range of from 0.38 to 0.55% by mass and the titanium is comprised evenly in each of the tin wires and the niobium wires.