Assessment of Alternative Divertor Configurations in TCV via experiments and interpretative SOLPS-ITER modelling

Alternative divertor configurations (ADCs) experiments are carried out in the TCV tokamak and analysed with the support of interpretative SOLPS-ITER simulations. Four different geometrical features are isolated in the outer divertor, and their impact on detachment access and control is tested: • Poloidal connection length • Poloidal flux expansion • Total flux expansion • The presence of a secondary X-point Each of these is expected to facilitate detachment access and control, through different mechanisms, according to simplified analytical models. However, such predictions must be validated by experiments and understood through comprehensive modelling, to verify their potential as an exhaust solution for future reactors. The TCV tokamak, thanks to its unique shaping capabilities and extensive set of divertor diagnostics, proves to be a perfect testbed for ADCs. SOLPS-ITER modelling, complete with drifts and impurities, allows for a thorough analysis of the different physical processes at play. The extensive set of experiments and simulations allows for a holistic investigation of the role of the magnetic geometry in the divertor. Significant discrepancies with respect to the simplified analytical models are highlighted, due to invalid assumptions or neglected effects. These are discussed in detail, together with their implications for the extrapolation to future reactors.