Impurity Transport in a Mixed-Collisionality Stellarator Plasma
Journal article, 2017

A potential threat to the performance of magnetically confined fusion plasmas is the problem of impurity accumulation, which causes the concentration of highly charged impurity ions to rise uncontrollably in the center of the plasma and spoil the energy confinement by excessive radiation. It has long been thought that the collisional transport of impurities in stellarators always leads to such an accumulation (if the electric field points inwards, which is usually the case), whereas tokamaks, being axisymmetric, can benefit from "temperature screening," i.e., an outward flux of impurities driven by the temperature gradient. Here it is shown, using analytical techniques supported by results from a new numerical code, that such screening can arise in stellarator plasmas, too, and indeed does so in one of the most relevant operating regimes, where the impurities are highly collisional while the bulk plasma is at low collisionality.

Diffusion

Neoclassical Transport

Author

P. Helander

Max Planck Institute

Sarah Newton

Chalmers, Physics, Subatomic and Plasma Physics

Albert Mollén

Max Planck Institute

Håkan Smith

Max Planck Institute

Physical Review Letters

0031-9007 (ISSN) 1079-7114 (eISSN)

Vol. 118 15 155002 - 155002

Subject Categories

Fusion, Plasma and Space Physics

DOI

10.1103/PhysRevLett.118.155002

More information

Latest update

2/21/2018