Improvements of (NbTi)/sub 3/Sn bronze processed superconductor performance

Research results are given for stabilized (NbTi)/sub 3/Sn strand with titanium artificial doped filaments. This work has been performed with the aim to improve the critical current density of the bronze processed strands designed for ITER. Strands with diameters in range 0.4 mm to 1.7 mm with composite filaments containing one or four cores made of Nb-Ti alloy as sources of doping element have been investigated. Critical current densities for some strands were investigated in the range of magnetic fields 8-22 T. It was shown that the strand containing 12684 filaments with 4 cores of Nb-Ti alloy in each filament had the best superconducting properties. J/sub c/ (non Cu) of this type of the strand with diameter of 0.81 mm was equal to 750 A/mm/sup 2/ at 12 T and had hysteresis losses /spl sim/100 mJ/cm/sup 3/ (/spl plusmn/3 T). This value was 1.3 times larger than the J/sub c/ value of the strand, which contained 1 core of Nb-Ti alloy. The maximum J/sub c/ (non Cu) attained for the strand 0.5 mm in dia with 12684 filaments was equal to 900 A/mm/sup 2/ at 12 T. Hysteresis losses for this strand were also less than 100 mJ/cm/sup 3/ (/spl plusmn/3T). It was shown that the developed strand with four cores of Nb-Ti alloy met both ITER Specifications HP-I and HP-II simultaneously. Also it is a perspective material for high field applications.