Transport characteristics of a CuNb/Nb₃Sn superconducting coil fabricated using a react and wind method

Superconducting magnets wound with conventional Cu/Nb₃Sn are designed considering a stress design criterion of 150 MPa. If the highly strengthened CuNb/Nb₃Sn wire is used instead of the conventional CuNb/Nb₃Sn wire, the stress design criterion of 250 MPa is applicable. Furthermore, the high strength enables us to make the Nb ₃Sn superconducting coil using a react and wind method. In order to confirm the stress design criterion of 250 MPa in a CuNb/Nb₃Sn coil fabricated by a react and wind method, stress-strain and quench characteristics of the coil were investigated under high electromagnetic stress. The hoop stress of 279 MPa was applied and the measured strain was 0.34%. The quench currents were 50-60% of the critical current for the short sample, and their relevant deterioration of the quench current strongly influenced the large hoop stress. It was confirmed that the design criterion of 250 MPa is adequate for the CuNb/Nb₃Sn superconducting coil using the react and wind method.