Optimized finite-build stellarator coils using automatic differentiation

A new stellarator coil design code is introduced that optimizes the position and winding pack orientation of finite-build coils. The code, called FOCUSADD, performs gradient-based optimization in a high-dimensional, non-convex space. derivatives with respect to parameters coils are easily efficiently computed using automatic differentiation. FOCUSADD parametrizes positions free space Fourier series uses multi-filament approximation pack. parametrized can be optimized as well. Optimized for W7-X-like found, compared filamentary results. final shifted, on average, by approximately 2.5mm relative These results suggest effects should accounted stellarators low tolerances.