Development of an Nb3Sn AC coil with react and 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. The authors 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. They made a 400kVA class superconducting coil using the developed Nb3Sn cable with the React and Wind method. The loss density of this coil was 25.7MW/m3 at the point just before the quench. In this case, the temperature of the cable increases about 3.39K. This means that the coil using Nb3Sn cables has a very high stability in AC use