Effect of stress on the critical current of Nb3Sn multifilamentary composite wire

A critical-current study of flexible Nb3Sn multifilamentary composite wires has been conducted at 4 K in magnetic fields to 90 kOe (7.2×106 A/m) while the wire is subjected to high mechanical stresses. The results show that at stresses above 1–2×108 Pa (strains of 0.1–0.2%) the critical current is significantly degraded, with the magnitude of the reduction dependent on reinforcement techniques used in the wire’s construction. The effect increases with magnetic field and results in the introduction of significant resistance at current levels well below the zero-stress critical current. Design considerations for the use of Nb3Sn wires in the high-stress environments of large-scale superconducting magnets are discussed.