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

Research results are given for stabilized (NbTi)(3)Sn strand with titanium artificial doped filaments. This work has been performed with the aim to im prove 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 do ping element have been investigated. Critical current densities for some st rands were investigated in the range of magnetic fields 8 - 22 T. It was sh own that the strand containing 12684 filaments with 4 cores of Nb-Ti alloy in each filament had the best superconducting properties. J(c) (non Cu) of this type of the strand with diameter of 0.81 mm was equal to 750 A/mm(2) a t 12 T and had hysteresis losses - 100 mJ/cm(3) (+/- 3 T). This value was 1 .3 times larger than the J(c) value of the strand, which contained 1 core o f Nb-Ti alloy. The maximum J(c) (non Cu) attained for the strand 0.5 mm in dia with 12684 filaments was equal to 900 A/mm(2) at 12 T. Hysteresis losse s for this strand were also less than 100 mJ/cm(3) (+/-3T). It was shown that the developed strand with four cores of Nb-Ti alloy met b oth ITER Specifications HP-I and HP-II simultaneously. Also it is a perspec tive material for high field applications.