The importance of the classical channel in the impurity transport of optimized stellarators
Journal article, 2019

In toroidal magnetic confinement devices, such as tokamaks and stellarators, neoclassical transport is usually an order of magnitude larger than its classical
counterpart. However, when a high-collisionality species is present in a stellarator optimized for low Pfirsch–Schlüter current, its classical transport can be comparable
to the neoclassical transport. In this letter, we compare neoclassical and classical fluxes and transport coefficients calculated for Wendelstein 7-X (W7-X) and Large Helical Device (LHD) cases. In W7-X, we find that the classical transport of a collisional impurity is comparable to the neoclassical transport for all radii, while it is negligible in the LHD cases, except in the vicinity of radii where the neoclassical transport changes sign. In the LHD case, electrostatic potential variations on the flux surface significantly enhance the neoclassical impurity transport, while the classical transport is largely insensitive to this effect in the cases studied.

fusion plasma

Author

Stefan Buller

Chalmers, Physics, Subatomic and Plasma Physics

Albert Mollén

Chalmers, Physics, Subatomic and Plasma Physics

Håkan Smith

Max Planck Society

Istvan Pusztai

Chalmers, Physics, Subatomic and Plasma Physics

Journal of Plasma Physics

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

Vol. 85 4 175850401

Implementation of activities described in the Roadmap to Fusion during Horizon 2020 through a Joint programme of the members of the EUROfusion consortium (EUROfusion)

European Commission (FP7), 2014-01-01 -- 2019-01-01.

Driving Forces

Sustainable development

Areas of Advance

Energy

Roots

Basic sciences

Subject Categories

Fusion, Plasma and Space Physics

DOI

10.1017/S002237781900045X

More information

Latest update

12/18/2019