Impact of Yacora evaluated molecular rates on detached SOLPS-ITER simulations
The Yacora solver has been used to generate two novel molecular rate databases for use in SOLPS-ITER. The reduced Yacora database utilises updated cross-sectional data, whilst the full Yacora database includes the same updated cross-sectional data in addition to the inclusion of vibrational reactions such as off-diagonal vibrational electron-impact-excitation. When applied to a SOLPS-ITER isolated divertor setup, both models produce greater levels of molecular charge exchange that result in elevated molecular ion densities (D2+) than the default rate setup. The higher levels of D2+ contribute to detachment via molecular activated recombination and molecular activated dissociation. During deep detachment this triples the levels of molecular activated recombination and molecular activated dissociation in the reduced Yacora case, whilst quadrupling these plasma-molecular interactions in the full Yacora case. This elevates the neutral population which subsequently increases the hydrogenic power losses. The power and momentum losses caused by the increased plasma-molecular interactions leads to a reduction in the ion target flux. Detachment onset occurs at lower upstream densities in the Yacora models than in the AMJUEL reference case. 9% and 16% lower in the reduced Yacora and full Yacora setups respectively. Overall, we see an improvement in the agreement with experimental findings from TCV (Verhaegh et al 2023 Nucl. Fusion 63 076015) when using the novel molecular databases.