Non-superconducting magnet structures for near-term, large fusion experimental devices

Abstract

Water cooled copper magnets provide a means of producing high magnetic fields for tokamaks using a well developed existing technology. The basic function of these magnets is to provide reliable, both time varying and steady state, magnetic fields. Copper electrical properties, insulation, and water cooling systems play major roles in design selection. Aside from being electro-magnetic devices, coils designed for tokamaks must be self-supporting structures, capable of resisting large I × B magnetic forces. These magnets require the integration of both electrical and structural design considerations. Magnet integrity is enhanced by the presence of structures which lend additional external support. These external structural systems are highly stressed and, often, deflection limited. This paper describes the magnet and structural design in the following American tokamak devices: the Princeton Large Torus (PLT), the Princeton Divertor Experiment (PDX), and the Tokamak Fusion Test Reactor (TFTR). The Joint European Torus (JET), also presented herein, has a magnet structure evolved from several European programs and, like TFTR, represents state of the art magnet and structure design. The PLT device was designed in 1971 as a high plasma current tokamak. At the time it incorporated the latest in copper magnet and structure technology. Design features on this machine have in some fashion subsequently been incorporated on every major device built within the tokamak fusion community.