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Impurity transport and bulk ion flow in a mixed collisionality stellarator plasma

Part of: Focus on Fusion

Published online by Cambridge University Press:  11 October 2017

S. L. Newton ,
P. Helander ,
A. Mollén  and
H. M. Smith
S. L. Newton*
Affiliation:
Department of Physics, Chalmers University of Technology, Göteborg SE-412 96, Sweden CCFE, Culham Science Centre, Abingdon, Oxon OX14 3DB, UK
P. Helander
Affiliation:
Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
A. Mollén
Affiliation:
Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
H. M. Smith
Affiliation:
Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
*
†Email address for correspondence: sarahn@chalmers.se
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Abstract

The accumulation of impurities in the core of magnetically confined plasmas, resulting from standard collisional transport mechanisms, is a known threat to their performance as fusion energy sources. Whilst the axisymmetric tokamak systems have been shown to benefit from the effect of temperature screening, that is an outward flux of impurities driven by the temperature gradient, impurity accumulation in stellarators was thought to be inevitable, driven robustly by the inward pointing electric field characteristic of hot fusion plasmas. We have shown in Helander et al. (Phys. Rev. Lett., vol. 118, 2017a, 155002) that such screening can in principle also appear in stellarators, in the experimentally relevant mixed collisionality regime, where a highly collisional impurity species is present in a low collisionality bulk plasma. Details of the analytic calculation are presented here, along with the effect of the impurity on the bulk ion flow, which will ultimately affect the bulk contribution to the bootstrap current.

Keywords

fusion plasmaplasma confinementplasma flows
Type
Research Article
Information
Journal of Plasma Physics , Volume 83 , Issue 5 , October 2017 , 905830505
Copyright
© Cambridge University Press 2017 

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