Electromagnetic properties of bronze processed Nb3Sn superconducting wiresand multi-strand cables for AC use with a Cu-Sn-X(X;Ge,Ni,Mn,Si) matrix and a Nb-Ta core

A bronze processed 0.275mm-dia. Nb3Sn strand composed of Nb-0.5at%Ta cores and a Cu-2.7at%Sn-1.0at%Ge matrix was fabricated into cables of 6 and 36 st rands. Each strand contained 75990 filaments 0.28 mu m in diameter. The AC quench current for the 36-strand cable reached 2500A(peak) at 50Hz and 0.5T DC field. The 6-strand cable showed a significantly improved irreversible bending strain limit of over 10% due to the fine filament size. This result enabled to build a magnet through the react and wind method. A 50 mm-bore 2T-class magnet wound by the 6 strand cable was successfully operated at 52 .7Hz and 4.2K. In order to reduce AC losses, another bronze processed 0.218 mm-dia. Nb3Sn strand with 147510 0.15 mu m-dia. filaments was fabricated fr om Nb0.5%Ta/Cu-4.9%Sn-2.0%Ge/Cu-2.7%Sn-2%Ni-1%Mn double matrix composite. T he strand showed a hysteresis loss of 447 J/m(3) at +/-0.5T/cycle and lambd a J(c) of 857A/mm(2) at 0.5T affer the heat treatment at 500 degrees C for 100h.