Superconducting induction coil for a doublet tokamak experimental fusion power reactor

A superconducting induction coil system was designed for a noncircular tokamak experimental fusion power reactor based on the Doublet concept. This coil system is used for inducing and sustaining the plasma current during the thermonuclear burn. The coil must be cycled in about 2 seconds; thus, it is important to design it for low AC loss during pulsing operation. A braided superconducting cable capable of carrying 450 kA at a central field of 5.65 Tesla was chosen as the conductor. The coil system consists of a central solenoid and 12 outer coils, with a total of 157 series connected turns. The central solenoid has a single layer winding of 134 turns on a fiberglass epoxy spool. The outer coils are located so that the error field generated at the plasma location is limited to a few gauss. The winding is reinforced by prestressed stainless steel bands on the outer surface, so that there is no relative motion between the cable and the coil spool or insulation during pulsing.