Speaker
Description
We have been using the SOLPS-ITER code to design and optimise the divertor for STEP (Spherical Tokamak for Energy Production). While this modelling has yielded important physical insights — such as the impacts of fuelling locations and dome shape — it has also highlighted significant numerical challenges. These issues introduce additional uncertainties on top of existing variances driven by assumed input parameters and reduced physics models. This presentation focuses on the two most significant numerical challenges encountered: unexpected up-down asymmetries under nominally symmetric conditions, and particle balance errors. We will detail the possible causes of these numerical issues and discuss actionable strategies to achieve more robust, reliable SOL/Divertor modelling within the timescales demanded by STEP.