IMPROVEMENT OF I-C IN NB3SN CONDUCTORS BY REDUCTION OF AXIAL PRESTRAIN

Nb3Sn conductors for large scale applications consisting of a high volume fraction of structural material which degrades I-c drastically because of the compressive prestrain on the Nb3Sn filaments. This results from the higher thermal contraction of the structural components in comparison to that of Nb3Sn during cooling from reaction to operation temperature. For example, in Nb3Sn ''Cable in Conduit'' conductors using steel conduits I-c decreases by about 50 % relative to the peak value at 12 T. Several alternatives for the reduction of the prestrain are possible,leading to a remarkable improvement of I-c: - Prestraining of the reacted conductor at room temperature. - Attaching the structural components onto the Nb3Sn cable after reaction heat treatment of the cable. - Using reinforcing materials with lower thermal contraction coefficient comparable with that of Nb3Sn.