Critical temperature， upper critical field and critical current relationships in as-reacted and mechanically treated （pre-bent） Nb3Sn wires with different architecture
Critical temperature， upper critical field and critical current relationships in as-reacted and mechanically treated （pre-bent） Nb3Sn wires with different architecture

BADICA Petre , 淡路 智 , 西島 元 , 小黒 英俊 （東北大）；SANDIM Maria （Sao Paulo Univ.）；渡辺 和雄 （東北大）；片桐 一宗 （岩手大）
h-oguro*imr.tohoku.ac.jp

Abstract: Six practical composite wires of Nb3Sn （Furukawa） with different architecture （design and reinforcement） were compared from the critical temperature， upper critical field and critical current points of view. Wires were as follows: three of near-the-edge design with Nb reinforcement of 0， 20， 50 vol% in the CuNb region， and of central reinforcement design with Nb of 20 and 50vol%. As-reacted wires are showing very different patterns of Tconset， Tcoffset and delta Tc determined from the ac. susceptibility measurements vs. Bc2 （4.2K）. This is due to 3D residual stress. Data suggest that architecture of the wire can control residual stress. Introduction of the reinforcement improves relaxation of the residual stress and especially of the radial component during multiple bending of the wires at room temperature （named pre-bending）. As a consequence Bc2 and Ic vs. pre-bending strain （epsilonpb＝0-1.5%） are enhanced to values closer to those of the Nb3Sn in the stress-free state. After pre-bending， maximum attained values of Bc2 and Ic and curve profiles of Bc2（epsilonpb） and Ic（epsilonpb） are much depending on the initial （as-reacted） state that can be monitored through the mentioned Tconset， Tcoffset and delta Tc vs Bc2 patterns. For Ic（epsilonpb） details are complicated due to formation of cracks. It is concluded that reinforcement vs. design can be useful to maximize critical parameters of the Nb3Sn wires toward theoretical strain-free values when pre-bending is applied.