Internally Cu-Stabilized RHQT Superconductors With Ta Matrix

An attempt was made to incorporate the Cu stabilizer internally to the Ta-matrix jelly-roll RHQT Nb₃Al round-wire, based on less-reactivity of Cu with Ta at elevated temperatures during the RHQ operation of wire. Compared to the conventional internal stabilization technique using Ag filaments jacketed with Nb, the present round wire has several advantages; (1) less induced-radioactivity when irradiated with fast neutrons, (2) higher mechanical strength at both elevated and cryogenic temperatures, and (3) less reactivity with Ga-coolant. The overall residual resistance ratio RRR_ov of the internally Cu stabilized Ta matrix RHQT Nb₃Al round-wire is as much as 75 in spite of a smaller stabilizer-ratio, and magnetoresistance is comparable to that of the conventional Cu clad stabilized Nb matrix RHQT Nb₃Al flat-wire. Core J_c is also comparable to that of the Nb matrix wire