Compact 20 T superconducting magnet for a 50 T-class hybrid magnet

The repeated prebending treatment for Nb3Sn wires with CuNb reinforcing stabilizer (CuNb/Nb3Sn) largely enhances the critical current. Since the employment of the highstrength CuNb/Nb3Sn wire is very effective for a react-and-wind process Nb3Sn superconducting magnet, we focus on the application of this prebending effect to the reactand-wind process of high-strength strand cables. The Rutherford flat cables composed of sixteen CuNb/Nb3Sn strands were fabricated to be applicable to the react-and-wind method. High-strength CuNb/Nb3Sn strand cables will exhibit the critical current of Ic = 1890 A at 13 T and 4.2 K. In order to construct a compact hybrid magnet, a 20 T-440 mm room temperature bore superconducting magnet consisting of YBCO, CuNb/Nb3Sn, and NbTi section coils is designed, using such Rutherford flat cables in pool-boiling liquid helium.