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Gyrokinetic stability theory of electron–positron plasmas

Published online by Cambridge University Press:  04 May 2016

P. Helander  and
J. W. Connor
P. Helander*
Affiliation:
Max-Planck-Institut für Plasmaphysik, 17491 Greifswald, Germany
J. W. Connor
Affiliation:
Culham Centre for Fusion Energy, Abingdon OX14 3DB, UK
*
†Email address for correspondence: per.helander@ipp.mpg.de
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Abstract

The linear gyrokinetic stability properties of magnetically confined electron–positron plasmas are investigated in the parameter regime most likely to be relevant for the first laboratory experiments involving such plasmas, where the density is small enough that collisions can be ignored and the Debye length substantially exceeds the gyroradius. Although the plasma beta is very small, electromagnetic effects are retained, but magnetic compressibility can be neglected. The work of a previous publication (Helander, Phys. Rev. Lett., vol. 113, 2014a, 135003) is thus extended to include electromagnetic instabilities, which are of importance in closed-field-line configurations, where such instabilities can occur at arbitrarily low pressure. It is found that gyrokinetic instabilities are completely absent if the magnetic field is homogeneous: any instability must involve magnetic curvature or shear. Furthermore, in dipole magnetic fields, the stability threshold for interchange modes with wavelengths exceeding the Debye radius coincides with that in ideal magnetohydrodynamics. Above this threshold, the quasilinear particle flux is directed inward if the temperature gradient is sufficiently large, leading to spontaneous peaking of the density profile.

Type
Research Article
Information
Journal of Plasma Physics , Volume 82 , Issue 3 , June 2016 , 905820301
Copyright
© Cambridge University Press 2016 

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