Journal
PHYSICS OF PLASMAS
Volume 23, Issue 6, Pages -Publisher
AMER INST PHYSICS
DOI: 10.1063/1.4954905
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Funding
- U.S. Department of Energy, Office of Science, Office of Fusion Energy Sciences, Theory Program [DE-FG02-95ER54309, DE-FC02-08ER54963]
- DOE [DE-FC02-99ER54512-CMOD]
- Office of Science of the U.S. Department of Energy [DE-AC02-05CH11231]
- U.S. Department of Energy (DOE) [DE-FC02-08ER54963] Funding Source: U.S. Department of Energy (DOE)
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The 2D spectrum of the saturated electric potential from gyrokinetic turbulence simulations that include both ion and electron scales (multi-scale) in axisymmetric tokamak geometry is analyzed. The paradigm that the turbulence is saturated when the zonal (axisymmetic) ExB flow shearing rate competes with linear growth is shown to not apply to the electron scale turbulence. Instead, it is the mixing rate by the zonal ExB velocity spectrum with the turbulent distribution function that competes with linear growth. A model of this mechanism is shown to be able to capture the suppression of electron-scale turbulence by ion-scale turbulence and the threshold for the increase in electron scale turbulence when the ion-scale turbulence is reduced. The model computes the strength of the zonal flow velocity and the saturated potential spectrum from the linear growth rate spectrum. The model for the saturated electric potential spectrum is applied to a quasilinear transport model and shown to accurately reproduce the electron and ion energy fluxes of the non-linear gyrokinetic multi-scale simulations. The zonal flow mixing saturation model is also shown to reproduce the non-linear upshift in the critical temperature gradient caused by zonal flows in ionscale gyrokinetic simulations. Published by AIP Publishing.
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