Comparisons between Edge Turbulence in EDA and QCE Plasmas Using the CECE Diagnostic at ASDEX Upgrade*

Large Type I ELM-free plasmas are imperative for sustainable operation of fusion power plants. Many Type I ELM-free regimes have been developed over the past years [Viezzer et al Nucl. Mater. Energy 2023], with promising regimes, such as enhanced D_α (EDA) and quasi-continuous exhaust (QCE), having been observed at ASDEX Upgrade. Both regimes display a ubiquitous edge fluctuation dubbed the quasi-coherent mode (QCM), and have similar access conditions. It is not clear if these regimes are fully distinct or some operational limit of the same regime. The correlation ECE (CECE) diagnostic [Creely et al RSI 2018] is used to compare properties of the QCM between each regime by investigating differences in the QCM’s coherence spectrum, electron temperature fluctuations, and correlation length. Additionally, transitions between EDA and QCE and vice versa and discharges performed in non-deuterium plasmas are investigated to understand the underlying physics of the QCM in these different scenarios.