Development of an Nb3Sn AC coil with react & wind method

The Nb₃Sn superconductor possesses a higher critical temperature than the NbTi strand. Therefore, it is now possible to make highly stable superconducting strands. We examined the manufacturing process of AC Nb₃Sn strands. The internal Sn diffusion process showed a higher critical current density than the conventional process. Nb₃Sn strands for AC use have a high Jc with low temperature reaction heat treatment, because they have fine filaments to decrease AC loss. We made a 400 kVA class superconducting coil using the developed Nb₃Sn cable with the React and Wind method. The loss density of this coil was 25.7 MW/m³ at the point just before the quench. In this case, the temperature of the cable increases about 3.39 K. This means that the coil using Nb₃Sn cables has a very high stability in AC use