Equilibrium reconstruction sensitivity studies on SPARC

Accurate reconstruction of the plasma equilibrium is imperative for the successful operation of the SPARC tokamak. In order to assess the expected reconstruction accuracy throughout the duration of design-point discharges, the EFIT equilibrium reconstruction code was deployed for SPARC. Reconstructions from SPARC baseline scenarios were compared with free-boundary equilibria generated by FreeGS, Toksys, and the Tokamak Simulation Code (TSC). The key geometric areas of interest to focus design tolerances include: the inner and outer gaps, the X-point locations, as well as the strike point locations. The deviation of these and other geometric quantities from their nominal positions in the synthetic equilibria were determined considering the addition of error to synthetic measurements of magnetic flux and magnetic field, contributions from eddy currents in conducting structures, applied resonant magnetic perturbations, and the omission of certain sensor sets. Optimization of the magnetic sensor locations is presented, highlighting a Monte Carlo workflow that balances the engineering constraints of sensor placement with achieving sufficient reconstruction fidelity for science and operations missions.