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