Effect of layout on magnetization of NbTi strands

Magnetization measurements at background fields up to 3 T were performed for 4 NbTi strands of various layouts both at a superposition of a sinusoidal varying field with a frequency of 0.5-3 Hz and at fast exponential sweep of external field. Strand layouts are distinguished by filament diameter, Cu/non-Cu ratio and filament zone location in the cross section of the wires. One of the strands contains resistive barriers of CuNi alloy, which surround a filament zone on the both sides. Using magnetization loops, the total and coupling losses for each strand have been calculated along with time constant values. The results showed that no matter how the field variation was performed, minimum losses as well as minimum time constant values were obtained for the sample with smallest filament diameter, having rather small copper core area (4.5%) and resistive CuNi barriers. For the sample with the same filament size but copper core area of 25% both losses and time constant were maximum.