New type of Nb3Sn fiber‐reinforced superconductors for high‐field pulsed magnet and effect of thermal stress

A new type of superconductor with high elastic modulus fibers is being developed for the application of high-field pulsed superconducting magnets called Fiber-Reinforced Superconductors (FRS). FRSs have great potential for the construction of a 15-T class pulses magnet with its size kept equal to ITER because stainless steels of cable-in-conduit-conductors could be reduced considerably. This paper presents a technique of preparing FRS and measuring its superconducting characteristics including strain-Ic relation. FRS has a critical current density of 600 (A/mm2/initial niobium) at 15 T, which is almost equal to one of the commercial bronze-processed wires. The intrinsic strain vs. Ic characteristics are similar to that of bronze-processed wire. Thermal strain on FRS also is discussed because materials with high elastic modulus tend to have low thermal contraction which leads to degradation of the superconducting characteristics of the Nb3Sn layer. Possibilities of overcoming the degradation while maintaining very high elastic modulus of tungsten fiber for reinforcement are shown.