118 research outputs found
Gyrokinetic studies of core turbulence features in ASDEX Upgrade H-mode plasmas
Gyrokinetic validation studies are crucial in developing confidence in the
model incorporated in numerical simulations and thus improving their predictive
capabilities. As one step in this direction, we simulate an ASDEX Upgrade
discharge with the GENE code, and analyze various fluctuating quantities and
compare them to experimental measurements. The approach taken is the following.
First, linear simulations are performed in order to determine the turbulence
regime. Second, the heat fluxes in nonlinear simulations are matched to
experimental fluxes by varying the logarithmic ion temperature gradient within
the expected experimental error bars. Finally, the dependence of various
quantities with respect to the ion temperature gradient is analyzed in detail.
It is found that density and temperature fluctuations can vary significantly
with small changes in this parameter, thus making comparisons with experiments
very sensitive to uncertainties in the experimental profiles. However,
cross-phases are more robust, indicating that they are better observables for
comparisons between gyrokinetic simulations and experimental measurements
Corrigendum: Electromagnetic turbulence suppression by energetic particle driven modes (2019 Nucl. Fusion 59 124001), Nuclear Fusion 60, 089501 (2020)
In recent years, a strong reduction of plasma turbulence in the presence of
energetic particles has been reported in a number of magnetic confinement
experiments and corresponding gyrokinetic simulations. While highly relevant to
performance predictions for burning plasmas, an explanation for this primarily
nonlinear effect has remained elusive so far. A thorough analysis finds that
linearly marginally stable energetic particle driven modes are excited
nonlinearly, depleting the energy content of the turbulence and acting as an
additional catalyst for energy transfer to zonal modes (the dominant turbulence
saturation channel). Respective signatures are found in a number of simulations
for different JET and ASDEX Upgrade discharges with reduced transport levels
attributed to energetic ion effects
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