Application of High Temperature Ceramic Superconductors (CSC) to Commercial Tokamak Reactors

Ceramic superconductors operating near liquid nitrogen temperature may experience higher heating rates without losing stability, compared to conventional superconductors. This will permit cable design with less stabilizer, reducing fabrication costs for large fusion magnets. Magnet performance is studied for different operating current densities in the superconductor, and cost benefits to commercial tokamak reactors are estimated. It appears that 10 kA ⋅ cm⁻² (at 77 K and ∼ 10 T) is a target current density which must be achieved in order for the ceramic superconductors to compete with conventional materials. At current densities around 50 kA ⋅ cm⁻² most potential benefits have already been gained, as magnet structural steel begins to dominate the cost at this point. For a steady state reactor reductions of ∼ 7% are forecast for the overall capital cost of the power plant in the best case. An additional ∼ 3% cost saving is possible for pulsed tokamaks.