EFFECTS OF THE GERMANIUM ADDITION TO THE MATRIX OF BRONZE-PROCESSED NB3SN WIRES

The simultaneous addition of 0.5 at%Ge to the matrix and 1 at%Ta to th e core enhances the Jc of Nb3Sn at 12T by more than one order of magni tude. The increase in the Jc seems to be attributed to the grain refin ement of Nb3Sn by the Ge addition. The formation of thin layer richer in Ge is observed at the interface between the Nb3Sn and matrix, which may be effective for reducing the proximity effect among Nb3Sn filame nts in the AC use. Ultrafine filamentary Nb3Sn wires with Ge addition to the matrix have been successfully fabricated. The addition of 0.25 at%Ge to the matrix and 1 at%Ta to the core improves the Qh/Jc ratio a t 0.5 T by a factor of nearly four.