Turbulent impurity transport simulations in Wendelstein 7-X plasmas
- 2 February 2021
- journal article
- research article
- Published by Cambridge University Press (CUP) in Journal of Plasma Physics
- Vol. 87 (1)
- https://doi.org/10.1017/s0022377820001543
Abstract
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.Keywords
This publication has 36 references indexed in Scilit:
- Global calculation of neoclassical impurity transport including the variation of electrostatic potentialJournal of Plasma Physics, 2020
- Charge-state independent anomalous transport for a wide range of different impurity species observed at Wendelstein 7-XPhysics of Plasmas, 2020
- stella: An operator-split, implicit–explicit δf-gyrokinetic code for general magnetic field configurationsJournal of Computational Physics, 2019
- Observation of anomalous impurity transport during low-density experiments in W7-X with laser blow-off injections of ironNuclear Fusion, 2019
- Stellarator impurity flux driven by electric fields tangent to magnetic surfacesNuclear Fusion, 2018
- Large tangential electric fields in plasmas close to temperature screeningPlasma Physics and Controlled Fusion, 2018
- Impurity Transport in a Mixed-Collisionality Stellarator PlasmaPhysical Review Letters, 2017
- Quasilinear carbon transport in an impurity hole plasma in LHDPhysics of Plasmas, 2014
- On neoclassical impurity transport in stellarator geometryPlasma Physics and Controlled Fusion, 2013
- Turbulent Transport and Heating of Trace Heavy Ions in Hot Magnetized PlasmasPhysical Review Letters, 2012