Superconducting coil with pure copper wires for thermal protection outside cable-in-conduit conductors

In order to realize a low cost toroidal field (TF) superconducting coil system for tokamak fusion reactors, the design of TF superconducting coil with a copper coil in place of pure copper wires which are needed for the thermal protection within cable-in-conduit (CIC) conductors is considered. This consideration is carried out under the condition that hot spot temperature of conductor is less than 250 K and a plasma-confinement vacuum vessel has no damage during the TF coil fast discharge. As the result, it is found that the conductor area is reduced by 35% and the copper coil is installed into the original coil case together with a TF coil winding. An external resistor system is reduced to around 30% of the original system because 70% of magnetic energy (40 GJ) stored in the ITER TF coil is dissipated into the copper coil during the fast discharge.