Collisional transport of impurities with flux-surface varying density in stellarators
Journal article, 2018

High-Z impurities in magnetic-confinement devices are prone to develop density variations on the flux surface, which can significantly affect their transport. In this paper, we generalize earlier analytic stellarator calculations of the neoclassical radial impurity flux in the mixed-collisionality regime (collisional impurities and low-collisionality bulk ions) to include the effect of such flux-surface variations. We find that only in the homogeneous density case is the transport of highly collisional impurities (in the Pfirsch-Schlhter regime) independent of the radial electric field. We study these effects for a Wendelstein 7-X (W7-X) vacuum field, with simple analytic models for the potential perturbation, under the assumption that the impurity density is given by a Boltzmann response to a perturbed potential. In the W7-X case studied, we find that larger amplitude potential perturbations cause the radial electric field to dominate the transport of the impurities. In addition, we find that classical impurity transport can be larger than the neoclassical transport in W7-X.

plasma confinement

fusion plasma

Author

Stefan Buller

Chalmers, Physics, Subatomic and Plasma Physics

H. M. Smith

Max Planck Institute

P. Helander

Max Planck Institute

A. Mollen

Max Planck Institute

S. L. Newton

Culham Science Centre

Istvan Pusztai

Chalmers, Physics, Subatomic and Plasma Physics

Journal of Plasma Physics

0022-3778 (ISSN) 1469-7807 (eISSN)

Vol. 84 4 905840409

Subject Categories

Meteorology and Atmospheric Sciences

Fusion, Plasma and Space Physics

Condensed Matter Physics

DOI

10.1017/S0022377818000867

More information

Latest update

9/2/2019 2