Exploring a no-ELM regime in ASDEX Upgrade: EDA H-mode parameter scans

The EDA H-mode, first discovered in Alcator C-Mod, is a regime without edge-localized modes (ELMs) that holds the world record for average plasma pressure in magnetic fusion devices [1]. The EDA H-mode has also been achieved in ASDEX Upgrade (AUG) [2], featuring qualities such as high energy confinement and density, compatibility with no/low input torque/power, electron heating, tungsten (W) walls, and impurity seeding. However, the physics of the regime is not fully understood, so its extrapolation to a reactor remains an active research topic.

This presentation reports on scans of heating power, fueling, and plasma current performed in strongly shaped EDA H-mode discharges on AUG. The plasma dynamics as it traverses different confinement regimes is described, and scaling laws for access conditions, plasma parameters, and global confinement properties are derived. These show, for example, that the no-ELM power window is extended with higher fueling and that the pedestal density is proportional to plasma current but mostly insensitive to power and gas. Conversely, temperature and pressure increase with power and decrease with fueling.

This work impacts upcoming experiments in AUG and other EDA-capable devices, like DIII-D and EAST. Furthermore, the presented datasets are a valuable resource for understanding the EDA H-mode, which could become the main scenario in future reactors such as SPARC and the full-W ITER.

[1] J.W. Hughes et al 2018 Nucl. Fusion 58 112003

[2] L. Gil et al 2020 Nucl. Fusion 60 054003