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Turbulent impurity transport simulations in Wendelstein 7-X plasmas

Published online by Cambridge University Press:  02 February 2021

J. M. García-Regaña*
Laboratorio Nacional de Fusión, CIEMAT, Av. Complutense, 28040, Spain
M. Barnes
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, OxfordOX1 3PU, UK
I. Calvo
Laboratorio Nacional de Fusión, CIEMAT, Av. Complutense, 28040, Spain
F. I. Parra
Rudolf Peierls Centre for Theoretical Physics, University of Oxford, OxfordOX1 3PU, UK
J. A. Alcusón
Max-Planck Institut für Plasmaphysik, Wendelsteinstrasse 1, 17491, Germany
R. Davies
York Plasma Institute, Department of Physics, University of York, Heslington, YorkYO10 5DD, UK
A. González-Jerez
Laboratorio Nacional de Fusión, CIEMAT, Av. Complutense, 28040, Spain
A. Mollén
Princeton Plasma Physics Laboratory, Princeton, NJ08543-0451, USA
E. Sánchez
Laboratorio Nacional de Fusión, CIEMAT, Av. Complutense, 28040, Spain
J. L. Velasco
Laboratorio Nacional de Fusión, CIEMAT, Av. Complutense, 28040, Spain
A. Zocco
Max-Planck Institut für Plasmaphysik, Wendelsteinstrasse 1, 17491, Germany
Email address for correspondence:


A study of turbulent impurity transport by means of quasilinear and nonlinear gyrokinetic simulations is presented for Wendelstein 7-X (W7-X). The calculations have been carried out with the recently developed gyrokinetic code stella. Different impurity species are considered in the presence of various types of background instabilities: ion temperature gradient (ITG), trapped electron mode (TEM) and electron temperature gradient (ETG) modes for the quasilinear part of the work; ITG and TEM for the nonlinear results. While the quasilinear approach allows one to draw qualitative conclusions about the sign or relative importance of the various contributions to the flux, the nonlinear simulations quantitatively determine the size of the turbulent flux and check the extent to which the quasilinear conclusions hold. Although the bulk of the nonlinear simulations are performed at trace impurity concentration, nonlinear simulations are also carried out at realistic effective charge values, in order to know to what degree the conclusions based on the simulations performed for trace impurities can be extrapolated to realistic impurity concentrations. The presented results conclude that the turbulent radial impurity transport in W7-X is mainly dominated by ordinary diffusion, which is close to that measured during the recent W7-X experimental campaigns. It is also confirmed that thermodiffusion adds a weak inward flux contribution and that, in the absence of impurity temperature and density gradients, ITG- and TEM-driven turbulence push the impurities inwards and outwards, respectively.

Research Article
Copyright © The Author(s), 2021. Published by Cambridge University Press

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