Abstract: A precursor, which is a drawn wire product of a composite pipe, the composite pipe having: a composite wire group; a barrier layer; and a protective layer, wherein the composite wire group has: a plurality of tin wires each having at least one tin core being made of tin or a tin alloy, and a copper matrix which surrounds the at least one tin core; and a plurality of niobium wires each having a plurality of niobium cores being 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 wires, the composite wire group contains titanium in an amount of from 0.38% by mass to 0.55% by mass.

Abstract: Provided is a magnet structure (MS) which includes a plurality of permanent magnets (2) fixed onto a baseplate (1), and a cover structure (3) for covering the plurality of permanent magnets (2). The cover structure (3) includes a plurality of covers (3a) that is formed of a non-magnetic material and covers the plurality of permanent magnets (2). A relative position between the plurality of covers (3a) is fixed, and there is a gap (G) between the neighboring covers (3a).