Multiscale Investigations of Drift-Wave Turbulence and Plasma Flows: Measurements and Total-Distribution-Function Gyrokinetic Simulations

Abstract

Direct measurements of micro-, meso-, and macroscale transport phenomena in the FT-2 tokamak are shown to be quantitatively reproduced by global full f nonlinear gyrokinetic simulation predictions. A detailed agreement with mean equilibrium E×B flows, oscillating fine-scale zonal flows, and turbulence spectra observed by a set of sophisticated microwave backscattering techniques as well as a good fit of the thermal diffusivity data are demonstrated. A clear influence of the impurity ions on the fluctuating radial electric field is observed.

Core turbulence behavior moving from ion-temperature-gradient regime towards trapped-electron-mode regime in the ASDEX Upgrade tokamak and comparison with gyrokinetic simulation

“…While good agreement has been found between electric field fluctuations in both frequency and amplitude in global simulations [32] and density turbulence level in both directions perpendicular to the magnetic field [29], mixed results have been obtained when comparing the radial dependence of density and temperature fluctuation levels [6,15,28]. The scarcity of results, in particular of scale-resolved comparisons [6,15], indicates that these studies are demanding on both experimental and simulation sides, all the more reason to dedicate more effort into validation of gyrokinetic models and their predictions through comparison with microturbulence measurements.…”

“…They have been successfully applied to describe core transport properties like profile stiffness [15][16][17][18][19][20] and (internal) transport barriers [21]. However, while substantial effort has been dedicated to the verification of the codes [22][23][24][25][26][27], a careful validation including measurements of microturbulence and non-linear simulations, which has to be applied to many different plasma regimes, has only started in the last years [15,[28][29][30][31][32][33][34]. The definition of the terms verification and validation are used as in Refs.…”

Drift and geodesic effects on the ion sound eigenmode in tokamak plasmas

“…Typically, BAE oscillations are much easier detected by magnetic probes due to large magnetic field component, contrary to geodesic acoustic modes (BAAEs) with [9], which involves acoustic sidebands where , that was detected due to strong NB drive despite of their Landau dissipation for . Fluctuations in the GAM frequency range have been observed in tokamaks with strong NB and/or ICR heating [2,9,[12][13][14]17], as well in tokamaks with ohmic and ECR heating [18][19][20][21][22]. Strong evidence exist that experimentally observed frequencies follow the electron temperature [19] even in presence of plasma turbulence [23] suggesting the important role of geodesic and ion sound effects.…”

“…Many of these observations are generically referred as geodesic oscillations. The experimental values of geodesic oscillations in the inner plasma regions bulk have the frequency [18][19][20][21][22][23] below the theoretically predicted GAMs continuum.…”

Special issue on comparing gyrokinetic simulations to experiments

“…White et al (2010)) and comparison with Doppler reflectometry (e.g. Leerink et al (2012)). A complication along these lines is that all experimental diagnostics are limited to viewing the plasma turbulence through particular glasses, i.e.…”