Tuesday, September 20, 2022
Edge turbulence is thought to play an important role in tokamaks in the transition between the low confinement operating regime, L-mode, and high confinement operating regimes such as H-mode. High confinement regimes that are free of damaging Edge-Localized Modes, such as the “improved confinement regime” I-mode, are promising for future reactor operation. However, open questions remain about the role of turbulence in regulating transport in I-mode, and changes in edge turbulence leading up to the I-mode and H-mode transitions. The Correlation Electron Cyclotron Emission (CECE) diagnostic measures long-wavelength electron temperature fluctuations at ASDEX Upgrade with high temporal and spatial resolution. This work presents outer core and pedestal electron temperature fluctuation measurements in a variety of experiments with L-modes, I-modes, and H-modes in different magnetic configurations. These measurements provide important information on scaling and transitions between confinement regimes and the changes in turbulence which may affect access to I-mode and its relationship with magnetic configuration in terms of favorable and unfavorable ion grad B drift.