Speaker
Zhouji Huang
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/I1.103.pdf
The effect of triangularity on plasma turbulence and transport in
tokamaks
Z. Huang, M. Fontana, S. Coda, L. Porte, and the TCV team∗
1 École Polytechnique Fédérale de Lausanne (EPFL), Swiss Plasma Center (SPC), CH-1015
Lausanne, Switzerland
The effects of plasma shaping, in particular of the triangularity δ , on plasma turbulence in
terms of relative density and temperature fluctuations, have been studied in the Tokamak à
Configuration Variable (TCV) using the Tangential Phase Contrast Imaging (TPCI) [1] and
the Correlation Electron Cyclotron Emission (CECE) [2] diagnostics, respectively. It has been
found that for inner wall limited L-mode plasmas, negative triangularity leads to a substantial
reduction of turbulence amplitude, as well as of the decorrelation time and radial correlation
length, consistent with the beneficial effect on energy confinement. Crucially, this reduction
extends deepin the core, where the local triangularity becomes vanishingly small. Additionally,
the electron temperature profile of negative triangularity plasmas features a narrower and less
stiff core region [3], as well as a higher value of critical electron temperature gradient for the
onset of turbulence. A stabilizing effect of effective collisionality νeff = 0.1ne Zeff /Te2 on TEM-
type turbulence was also observed. The increase of turbulence amplitude with decreasing νeff
is slower with negative triangularity, while the triangularity effect vanishes at high νeff . These
observations are consistent with previous experimental results on the triangularity effect on
electron heat transport [4], as well as with global gyrokinetic GENE simulation results [5]. It
is also observed that the GAM frequency and wavenumber increases with the triangularity.
Experiments are ongoing on the effects of varying electron to ion temperature ratio in plasmas
with positive and negative triangularity to investigate the transition between TEM and ITG
dominated turbulence regimes.
References
[1] A. Marinoni, et al., Review of Scientific Instruments 77, 10E929 (2006)
[2] M. Fontana, et al., 44th EPS conference on plasma physics (2016)
[3] O. Sauter, et al., Physics of Plasmas 21, 055906 (2014)
[4] Y. Camenen, et al., Nuclear Fusion 47, 510 (2007)
[5] G. Merlo, PhD thesis (2016)
∗
See author list of S. Coda et al 2017 Nucl. Fusion 57 102011
