Electron temperature fluctuation measurements of the weakly coherent mode in I-mode at ASDEX Upgrade and Alcator C-Mod

I-mode is a naturally ELM-free improved confinement regime, which exhibits high energy confinement without high particle confinement, and holds promise for future reactors. The weakly coherent mode (WCM) appears in the pedestal region of I-mode plasmas in both ASDEX Upgrade (AUG) and Alcator C-Mod. The precise nature of the mode and its role in particle and heat transport is an open question. In this work, the WCM is studied in I-mode plasmas in AUG and C-Mod through electron temperature fluctuation measurements (CECE) and nT phase angle measurements. In C-Mod the electron temperature fluctuations associated with the WCM are found to be much smaller in magnitude than density fluctuations [1]. In AUG the WCM is observed in I-mode, and a mode at the same radius is also observed in L-mode [2]. Comparison between the two devices and nT phase observations in AUG may provide insight into the effect of the WCM on density and temperature transport. [1] White, Nuclear Fusion 51, 1130005 (2011) [2] Happel 23^rd PSI Conference, June 2018