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

Nb3Sn conductors for large scale applications consisting of a high vol ume fraction of structural material which degrades I-c drastically bec ause of the compressive prestrain on the Nb3Sn filaments. This results from the higher thermal contraction of the structural components in c omparison to that of Nb3Sn during cooling from reaction to operation t emperature. For example, in Nb3Sn ''Cable in Conduit'' conductors usin g steel conduits I-c decreases by about 50 % relative to the peak valu e at 12 T. Several alternatives for the reduction of the prestrain are possible,leading to a remarkable improvement of I-c: - Prestraining o f the reacted conductor at room temperature. - Attaching the structura l components onto the Nb3Sn cable after reaction heat treatment of the cable. - Using reinforcing materials with lower thermal contraction c oefficient comparable with that of Nb3Sn.