Impurity Transport in a Mixed-Collisionality Stellarator Plasma

P. Helander, S. L. Newton, A. Mollén, and H. M. Smith
Phys. Rev. Lett. 118, 155002 – Published 12 April 2017

Abstract

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.

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  • Received 25 January 2017

DOI:https://doi.org/10.1103/PhysRevLett.118.155002

© 2017 American Physical Society

Physics Subject Headings (PhySH)

Plasma Physics

Authors & Affiliations

P. Helander1, S. L. Newton2,3, A. Mollén1, and H. M. Smith1

  • 1Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
  • 2Department of Physics, Chalmers University of Technology, SE-412 96 Göteborg, Sweden
  • 3CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, United Kingdom

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Vol. 118, Iss. 15 — 14 April 2017

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