Discretization error estimation for EU-DEMO plasma-edge simulations using SOLPS-ITER with fluid neutrals

A grid refinement study is performed for mean-field plasma boundary simulations with fluid neutrals in an EU-DEMO geometry. In general, grid convergence of the simulations is achieved, with differences between the finest and second-finest grid of <5% for the majority of the quantities of interest. The estimated discretization errors for the original 96 x 36 grid are mostly in the 4%-25% range. However, it is also shown that exceptions are possible due to the non-linear nature of plasma boundary codes. Hence, it is advised to regularly perform grid refinement studies on subsets of cases.