Nb/Ag-Sn fcc相及びNb/Ag-Sn ζ相の相互拡散反応により作られたNb3Sn線材の超伝導特性
(Superconducting Properties of Nb3Sn Superconductors made by Diffusion Reaction at Nb/Ag-Sn fcc Phase and Nb/Ag-Sn ζ Phase Alloy)