The ITER Central Solenoid

The central solenoid for the International Thermonuclear Experimental Reactor (ITER), a fusion tokamak experiment with the goal of generating 500 MW of fusion power with high gain (Q>10), must provide most of the volt-seconds needed to induce and sustain a 15 MA plasma for burn times of >400 s. The 6.4 GJ central solenoid design requires a 45 kA conductor and has a peak field of 13 T. The central solenoid consists of six pancake-wound modules, stacked vertically, and held in axial compression by an external structure. The five-stage cable has 1/3 copper and 2/3 advanced Nb3Sn strands in a thick superalloy conduit and is cooled by the forced-flow of supercritical helium through the cable space. Key design issues include the qualification of a conduit with adequate fatigue strength, avoiding filament damage from transverse Lorentz loads, eliminating axial tension in the winding insulation, and qualification of space-saving intramodule butt joints