Comparative study of NbTi strands developed for ITER PF coils

Last year Bochvar Institute (VNIINM) has developed and produced several NbTi strands of various layouts intended for the cables of ITER PF coils. Strand layouts distinguish by filament diameter, Cu/non-Cu ratio and Cu matrix distribution between the center and periphery of cross-section. Among them two strands contain an internal CuNi resistive barrier. The studies on critical current properties at 4.5-8 T are performed and also on electrodynamics behavior of the strands, including AC losses at varying magnetic fields up to 3 T and frequency up to 10 Hz. The experimental results are presented on hysteresis losses and time constant.