Coil performance of multifilamentary Nb3Sn conductors

The solid-state diffusion process was used to manufacture copperstabilized Nb3Sn multifilament conductors. For higher currents also fully transposed and calibrated flattened cables were fabricated. The effects of diffusion temperature, filament diameter and conductor geometry on the critical current density were studied and values up to 8.6 × 10⁴A/cm²at 10 T were obtained. Solenoids with graduated windings were manufactured from long lengths (km) of these conductors by means of the wind-and-react technique and also by using prereacted conductors. The solenoids attained the short sample current usually without training and reached in a free bore of 51 mm diameter flux densities up to 14 T with NbTi background fields around 8 T. Excitation speeds up to 1.3 T/s were obtained without degradation of the quench current.