Incorporating refractometry measurements of local slope into plasma boundary reconstruction

Obtaining an accurate representation of the plasma boundary is integral to maintaining control in a fusion device. Present methods of equilibrium reconstruction use magnetic diagnostics that are susceptible to integration drift–due to noise and radiation-induced voltage–overtaking the desired signal. Previous work produced a framework to fit the plasma boundary using points measured by a poloidal array of reflectometers. A promising extension would be using refractometers to also measure the slope of each boundary point. This work explores the expected improvement of incorporating these additional constraints into the plasma boundary fit. Optimization of this model involves utilizing existing boundary data combined with synthetic noise in order to characterize the relationship between fitting quality and system parameters. Such parameters include the number and locations of diagnostics and expected error. Future devices can use this model to estimate the minimum number of diagnostics needed to measure the plasma position and shape.