Edge turbulence studies across confinement regime transitions at ASDEX Upgrade

Rachel Bielajew


Tuesday, September 20, 2022



PSFC Student Seminars

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.