SuperCIC: Enhanced Winding Current Density for Hybrid Windings of Tokamaks

The design is presented for a new approach to cable-in-conduit (SuperCIC) for use in the high-field windings of tokamaks. Two layers of high-field superconductor wires are cabled onto a thin-wall perforated center tube. An overwrap is applied and the cable is inserted as a loose fit into a sheath tube. The sheath tube is drawn down onto the cable to compress the wires onto the center tube and immobilize them. The SuperCIC is then co-wound with a high-strength armor extrusion, which is kerf-cut so that the co-winding onto a coil mandrel can be made without deformation within the armor or the CIC. SuperCIC facilitates hybrid windings, in which sub-windings of NbTi are used where B <; 7 T, Nb
₃
Sn where B <; 14 T, and Bi-2212 where B > 14 T to minimize superconductor cost. Demountable splices are used to interconnect layers. A conceptual design has been prepared for a tokamak with aspect ratio A ~2.0, magnetic field of 17.4 T at the inner windings and 6.7 T at the plasma, and winding current density ~140 A/mm
²
- sufficient for optimizing the fusion power density in a compact spherical tokamak.