Validation of Hermes-3 turbulence simulations against the TCV-X21 diverted L-mode reference case

TL;DR

This study validates Hermes-3 turbulence simulations against TCV-L-mode experimental data, demonstrating good agreement in plasma profiles and target behavior, while highlighting the importance of neutral gas effects.

Contribution

First validation of Hermes-3 turbulence code against TCV-L-mode data, showing accurate reproduction of plasma profiles and divertor target features.

Findings

Simulations match experimental plasma profiles and target shifts.

Reproduction of outer strike point splitting in reversed field.

Neutral gas effects are crucial for accurate edge plasma modeling.

Abstract

Electrostatic flux-driven turbulence simulations with the Hermes-3 code are performed in TCV L-mode conditions in forward and reversed toroidal field configurations, and compared to the TCV-X21 reference dataset [D.S. Oliveira and T. Body et al. 2022] qualitatively and with a quantitative methodology. Using only the magnetic equilibrium, total power across the separatrix (120kW) and total particle flux to the targets (3e21/s) as inputs, the simulations produce time-averaged plasma profiles in good agreement with experiment. Shifts in the target peak location when the toroidal field direction is reversed are reproduced in simulation, including the experimentally observed splitting of the outer strike point into two density peaks. Differences between simulation and experiment include density profiles inside the separatrix and at the inner target in forward (favorable Grad-B) field configuration. These differences in target temperature in forward field configuration lead to differences in the balance of current to the inner and outer divertor in the private flux region. The cause of these differences is most likely the lack of neutral gas in these simulations, indicating that even in low recycling regimes neutral gas plays an important role in determining edge plasma profiles. These conclusions are consistent with findings in [D.S. Oliveira and T. Body et al. 2022].