Electromagnetic properties of bronze processed Nb3Snsuperconducting wires and multi-strand cables for AC use with aCu-Sn-X(X; Ge,Ni,Mn,Si) matrix and a Nb-Ta core

摘要

A bronze processed 0.275 mm-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 strands. Each strand contained 75990 filaments 0.28 μm in diameter. The AC quench current for the 36-strand cable reached 2500 Apeak at 50 Hz and 0.5 T 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 building of 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 52.7 Hz and 4.2 K. In order to reduce AC losses another bronze processed 0.218 mm-dia. Nb3Sn strand with 147510 0.15 μm-dia. filaments was fabricated from Nb05%Ta/Cu-4.9%Sn-2.0%Ge/Cu-2.7%Sn-2%Ni-1%Mn double matrix composite. The strand showed a hysteresis loss of 447J/m3 at ±0.5 T/cycle and λJc of 857A/mm2 at 0.5 T after the heat treatment at 500°C for 100 h