Assessment of equilibrium field coil misalignments on the divertor footprints in NSTX-U*

A study of the heat load distribution at the divertor plates of NSTX-U due to misalignment of the equilibrium magnetic field coils indicates that a rigid shift in the installation of the toroidal field coils will produce the largest impact. Non-axisymmetric magnetic field perturbations due to error fields produce complex 3D edge magnetic topologies that alter the properties of the heat and particle flux distributions on the target plates. The perturbed equilibria due to shift and tilt of several coils are simulated using the MHD code M3D-C¹. The produced footprints are estimated using the field line tracing code TRIP3D through the OMFIT framework. The effect the misalignment of several poloidal field coils separately has on the footprint is negligible for shifts up to 5mm and tilts up to 5mrad with the maximum current flowing in the coils.A rigid 5mm shift of the toroidal field coils relative to the centerline of NSTX-U will lead to a 10cm spread footprint on each of the outer divertor plates. Combination of shift and tilt of the toroidal field coils and estimation of the heat flux are also presented. These results will be used to determine the precision needed to install the equilibrium field coils in NSTX-U.