金属系超電導線材 [3]

—Nb₃Sn線材及びV₃Ga線材 (その1)—

抄録

Nowadays Nb₃Sn wires are being widely used as one of the key materials in advanced science and technology, with various applications such as NMR, fusion and cryogen-free superconducting magnets. In this article, at first microstructures and fundamental aspects as well as the effect of additional elements in Nb₃Sn are outlined. Intrinsic superconducting performances, e.g. T_c and B_c2, are quite sensitive to the stoichiometry of the Sn concentration. A small amount of Ti and Ta doping is much effective for the increase of B_c2 in Nb₃Sn. The effect of Cu on the enhancement of Nb₃Sn synthesis has yielded a significant breakthrough for the industrial production of the wires. At present the bronze process and internal Sn process are the twin major fabrication techniques of Nb₃Sn wires. The recent status of both processes is reviewed in this article. Pronounced progress has been achieved in the performance of Nb₃Sn wires fabricated through both techniques. Although just half a century has passed since the first fabrication of Nb₃Sn wire, further progress in Nb₃Sn technology may be expected like the proverb saying “Fresh water still comes out from an old spring”.