Validation of gyrokinetic simulations with measurements of electron temperature fluctuations and density-temperature phase angles on ASDEX Upgrade
Résumé
Measurements of turbulent electron temperature fluctuation amplitudes, dTe?=T e, frequency
spectra, and radial correlation lengths, LrðT e? Þ, have been performed at ASDEX Upgrade using
a newly upgraded Correlation ECE diagnostic in the range of scales k? < 1:4 cm1; k r < 3:5 cm1
(k?qs < 0:28 and k rqs < 0:7). The phase angle between turbulent temperature and density
fluctuations, anT, has also been measured by using an ECE radiometer coupled to a reflectometer
along the same line of sight. These quantities are used simultaneously to constrain a set of ion-
scale non-linear gyrokinetic turbulence simulations of the outer core (qtor ¼ 0.75) of a low density,
electron heated L-mode plasma, performed using the gyrokinetic simulation code, GENE. The ion
and electron temperature gradients were scanned within uncertainties. It is found that gyrokinetic
simulations are able to match simultaneously the electron and ion heat flux at this radius within the
experimental uncertainties. The simulations were performed based on a reference discharge for
which dT e?=T e measurements were available, and L rðTe? Þ and anT were then predicted using syn-
thetic diagnostics prior to measurements in a repeat discharge. While temperature fluctuation
amplitudes are overestimated by >50% for all simulations within the sensitivity scans performed,
good quantitative agreement is found for L rðT e? Þ and anT. A validation metric is used to quantify
the level of agreement of individual simulations with experimental measurements, and the best
agreement is found close to the experimental gradient values. Published by AIP Publishing.
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