Improved predictive capabilities in full-f gyrokinetic simulations of DIII-D negative triangularity discharges

We present gyrokinetic simulations of DIII-D inner-wall-limited (IWL) discharges using the Gkeyll code to study how triangularity and neutral interactions influence profile formation and edge turbulence. Building on prior triangularity studies [1], this work incorporates an adaptive source model and neutral collisions to better match experimental conditions. Results demonstrate reduced fluctuation levels and increased kinetic profile (n, Te, Ti) values in negative triangularity (NT) simulations compared to positive triangularity (PT). Neutral interactions provide a heat loss channel yielding more realistic temperature values in the scrape-off layer. A spectral analysis in the edge shows turbulence driven at ion scales in the electron diamagnetic direction, indicative of trapped electron mode (TEM), consistent with experimental measurements [2]. Near the last closed flux surface, the turbulence drive is in the ion diamagnetic direction. These validation efforts build confidence in the predictive capabilities of the Gkeyll code as the tool progresses towards modeling reactor-relevant scenarios.



[1] Bernard et al., PPCF 66 (2024)

[2] Stewart et al., PPCF 67 (2025)