Magnet Structural Design for the Fusion Ignition Research Experiment (fire)

The toroidal field coil system of the FIRE tokamak utilizes LN2 cooled, copper alloy Bitter plate type magnets. The wedged configuration is baseline structural concept for the project. A beryllium copper alloy has been chosen for the conductor. Reported are some of the refinements in the design and analysis of FIRE based on a re-sizing of the machine to 2.14m The larger machine offers greater structural margin, allowing simpler structural concepts to be used. FIRE has retained the wedged configuration after consideration of alternatives. The project perceives this to be a conservative approach. FIRE's high elongation and double null plasma results in high overturning moments. This was an early reason why the wedged configuration was considered attractive. Disruption effects on the out-of-plane loading of the TF have been studied with a transient electromagnetic analysis. These are presented in this paper, and have been found small. Desired design margin of the magnet structural system has influenced the choice of structural concept. For routine operation at full performance levels, a larger structural factor of safety has been proposed. Initially, simple scaling by toroidal field and build changes have been used to assess design margin[1]. In this paper, lead and terminal design, fit-up and alignment tolerance, insulation loading, and analytic qualification methods are discussed.