Abstract
Abstract
Understanding poloidal asymmetries in main chamber neutral fueling is essential for characterizing the balance between particle sources and transport in the formation of the H-mode density pedestal. The primary goal of this work is to study changes in these fueling asymmetries and their relationship to divertor recycling across different magnetic configurations in DIII-D lower single-null type-I ELMy H-mode plasmas, using direct measurements of the pedestal ionization source obtained with the LLAMA (Lyman-alpha Measurement Apparatus) diagnostic. By combining these direct measurements of the neutral population and studying how it influences the pedestal density structure and overall pedestal performance, this work aims to provide new insights into the role of neutrals in H-mode pedestal physics. We find that the main chamber ionization on the high-field-side (HFS) strongly dominates when the ion ∇B drift is in the favorable direction. In contrast, reversing the drift direction to the unfavorable direction significantly reduces HFS fueling, that is only partially compensated by a moderate increase in low-field-side (LFS) fueling. The resulting changes in the edge particle source are accompanied by a decrease in pedestal electron density and an increase in pedestal temperature, such that the pedestal pressure remains approximately unchanged. Measurements of divertor recycling and divertor radiation indicate that these fueling asymmetries are also linked to the divertor regime. In particular, inner divertor detachment in the favorable drift configuration decouples main chamber fueling on the HFS from target recycling, while attached divertor conditions in unfavorable drift cases lead to a strong correlation between divertor recycling and main chamber fueling asymmetries. These results suggest that the ion
∇B drift direction, by modifying main chamber fueling, can influence the pedestal density structure and overall pedestal performance.