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Linear electrostatic gyrokinetics for electron–positron plasmas

Published online by Cambridge University Press:  16 November 2018

D. Kennedy Open the ORCID record for D. Kennedy [Opens in a new window] ,
A. Mishchenko Open the ORCID record for A. Mishchenko [Opens in a new window] ,
P. Xanthopoulos  and
P. Helander
D. Kennedy*
Affiliation:
Max Planck Institute for Plasma Physics, D-17491 Greifswald, Germany
A. Mishchenko
Affiliation:
Max Planck Institute for Plasma Physics, D-17491 Greifswald, Germany
P. Xanthopoulos
Affiliation:
Max Planck Institute for Plasma Physics, D-17491 Greifswald, Germany
P. Helander
Affiliation:
Max Planck Institute for Plasma Physics, D-17491 Greifswald, Germany
*
†Email address for correspondence: daniel.kennedy@ipp.mpg.de
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Abstract

Gyrokinetic stability of plasmas in different magnetic geometries is studied numerically using the GENE code. We examine the stability of plasmas, varying the mass ratio between the positive and negative charge carriers, from conventional hydrogen plasmas through to electron–positron plasmas. Stability is studied for prescribed temperature and density gradients in different magnetic geometries: (i) An axisymmetric, circular flux surface, low $\unicode[STIX]{x1D6FD}$ (tokamak) configuration. (ii) A non-axisymmetric quasi-isodynamic (optimised stellarator) configuration using the geometry of the stellarator Wendelstein 7-X. We also present the analytic theory of trapped particle modes in electron–positron plasmas. We found similar behaviour of the growth rate and real frequency compared to previous studies on the tokamak case. We are able to identify two distinct regimes dominated by modes propagating in the electron diamagnetic direction and modes propagating in the ion/positron diamagnetic direction, depending on the mass ratio. In both the tokamak and the stellarator case we observe that the real frequency tends to zero as the mass ratio approaches unity and are able to explain this using gyrokinetic theory.

Keywords

plasma confinementplasma instabilities
Type
Research Article
Information
Journal of Plasma Physics , Volume 84 , Issue 6 , December 2018 , 905840606
Copyright
© Cambridge University Press 2018 

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