STABILIZATION OF A NB3SN PERSISTENT CURRENT SWITCH

A 2000 A class Nb3Sn persistent current switch has been successfully fabricated in the Toshiba R&D Center. The Nb tube processed conductor with Cu-10wt.%Ni matrix has been developed for the switch in the Showa Electric Wire and Cable Co. Ltd. The magnetic instability which was observed in the previous 35 OMEGA Nb3Sn persistent current switch was improved in the present switch. The problem of quench current degradation and flux jump on magnetization, emerged in the previous switch, were confirmed to be solved. In the fast ramp, however, the switch degrades from the calculated results assuming the self field ac loss. In the Nb3Sn reaction process, Sn in the bronze diffuses into the Nb tube, which decreases the switch resistance. It was observed by a computer aided micro analysis (CMA) that Ni in the CuNi matrix precipitated on the Nb tube, which slightly reduced the switch resistance.