A 12-T forced flow type superconducting magnet

As part of the development work for the high field superconducting toroidal field coil for a tokamak fusion reactor, a 12-T 4-kA forced-flow type superconducting coil was designed, fabricated, and tested. The objective of this coil is to verify that a coil wound by the Nb3Sn cable-in-conduit type conductor can generate a magnetic field of 12 T. The test was carried out with a background field of around 8 T, and a total magnetic field of 12.0 T was achieved with the transport current of 4.0 kA. The average current density in the winding area was 60.5 A/mm²at that time. These results demonstrate that high-field, large-current and high-current-density coils can be fabricated with a cable-in-conduit type conductor.