Fluctuation Measurements in EDA and QCE H-modes at AUG and Alcator C-Mod

ELM-free plasmas are imperative for sustainable operation of fusion power plants. Many ELM-free regimes have been developed over the past years [Viezzer NF 2018], with two promising ELM-free modes, enhanced D_α (EDA) and quasi-continuous exhaust (QCE), having been observed at ASDEX Upgrade (AUG). The underlying physics of these two regimes is not fully understood, so it is not known if these represent two distinct regimes or the limiting bounds of the same ELM-free regime, making it challenging to accurately predict the performance in future devices. Without ELMs to drive transport in the edge, a different, unknown process must be driving it. Here, we study the ion scale turbulent modes by measuring electron temperature fluctuations in the plasma edge using the Correlation ECE (CECE) diagnostic on AUG [Creely et al RSI 2018] and tracking changes in these fluctuations with other plasma parameters. Correlations between turbulent mode parameters and local plasma properties are made to determine the drivers of this transport process. Further comparisons are made between Deuterium-fueled and Hydrogen-fueled plasmas, and early EDA/small-ELM discharges from Alcator C-Mod which exhibit similar behavior to the regimes observed in AUG [Mossessian et al PoP 2003] are studied as a part of a multi-device, dimensionless parameter comparison.