Advances in ITER-relevant Nb-Ti and Nb$_{3}$Sn strands and low-loss Nb-Ti strands in RF

The review of the main results of R&D directed on the enhancement of ITER relevant NbTi and Nb3Sn strands performance recently carried out in Russia (the Bochvar Institute) are presented. For ITER PF type (NbTi) strands with Cu/non Cu ratio of 1.6 the attainment of ITER specified critical current density (Jc) ≥ 2900 A/mm (5 T, 4.2 K) has been shown. For Toroidal Field (TF) strands (Nb3Sn) the influence of doping and layout peculiarities of the wires produced by bronze method on their current-carrying ability has been investigated. It was shown that with non-doped matrix and doped filaments Jc exceeds 800 A/mm (12 T, 4.2 K) while with the application of the doped bronze and nondoped filaments it exceeds 900 A/mm. Internal-tin Nb3Sn strand meeting the ITER TF specification requirements was also developed and fabricated. The results of testing of CICC samples in a SULTAN facility have shown that performance parameters are higher than ITER qualification requirements Low loss model fine filament NbTi strands, intended for operating in fields with a ramp rate from 1 up to 4 T/s, has been developed and manufactured. The use of commercial MN-5 alloy (Cu-5wt.%Ni) and the Cu0.5wt.%Mn alloy for matrix of strands are discussed. The critical current density higher than 2700 A/mm (5 T, 4.2 K was shown to be attainable.