Speaker
Javier Rodrigo Pinzon
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/P1.1097.pdf
Experimental investigation of the mean turbulence structure tilt angle and
its comparison with gyrokinetic simulations
J.R. Pinzón1,2 , T. Happel1 , C. Angioni1 , P. Hennequin3 , E. Blanco4 , T. Estrada4 , U. Stroth1,2
and the ASDEX Upgrade Team1
1 Max-Planck Institut für Plasmaphysik,Garching, Germany
2 Physics-Department E28, TUM, Garching Germany
3 Laboratoire de Physique de Plasmas, Ecole Polytechnique, Palaiseau, France
4 Laboratorio Nacional de Fusión, CIEMAT, Madrid, Spain
The experimental characterization of the turbulence and its comparison with theory and sim-
ulations is fundamental for the understanding of the turbulence dynamics in fusion plasmas.
Detailed fluctuation measurements are required in order to investigate specific phenomena. In
particular, the tilt angle of the turbulence structures in the radial-perpendicular plane, is a quan-
tity predicted by theories and gyrokinetic simulations, which can provide information on the tur-
bulence interaction with sheared flows and the type of the dominant micro-instabilities [1], e.g.
ion-temperature gradient (ITG) and trapped-electron mode (TEM) instabilities. Nevertheless,
tilt angle measurements are challenging, especially in the confined region of fusion plasmas.
Radial correlation Doppler reflectometry is an experimental technique that provides infor-
mation on the radial structure of the density turbulence. It is based on the correlation analysis
of two Doppler reflectometry channels measuring at different radial positions. A new analysis
technique of the time delays of the correlation has been developed. It provides a measurement
of the tilt angle and can be applied in the confined region of fusion plasmas where Doppler
reflectometry measurements are usually performed.
The tilt angle measurement method is applied at the ASDEX Upgrade tokamak. A low density
L-mode discharge is investigated. Two phases with either dominant ion or dominant electron
heating are considered. The tilt angle is measured in the confined region ρpol = 0.70 − 0.84
for the first time in the ASDEX Upgrade tokamak. Moreover, a tilt angle difference of 26◦ is
observed between both phases. The linear gyrokinetic stability analysis confirms a transition
from an ITG to a more TEM dominated turbulence regime between the phases with dominant
ion and dominant electron heating, respectively. The tilt angle is compared with results from
gyrokinetic simulations, and the use of this new measurement as a signature of the turbulence
regime is discussed.
References
[1] Y. Camenen et. al., Nucl. Fusion 51, 073039 (2011)
