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Collisionless microinstabilities in stellarators. Part 4. The ion-driven trapped-electron mode

Part of: Focus on Fusion Frontiers in Plasma Physics Conference

Published online by Cambridge University Press:  22 August 2017

G. G. Plunk ,
J. W. Connor  and
P. Helander
G. G. Plunk*
Affiliation:
Max-Planck-Institut für Plasmaphysik, EURATOM Association, 17491 Greifswald, Germany
J. W. Connor
Affiliation:
Culham Centre for Fusion Energy, Abingdon OX14 3DB, UK
P. Helander
Affiliation:
Max-Planck-Institut für Plasmaphysik, EURATOM Association, 17491 Greifswald, Germany
*
†Email address for correspondence: [email protected]
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Abstract

Optimised stellarators and other magnetic-confinement devices having the property that the average magnetic curvature is favourable for all particle orbits are called maximum-$J$ devices. They have recently been shown to be immune to trapped-particle instabilities driven by the density gradient. Gyrokinetic simulations reveal, however, that another instability can arise, which is also associated with particle trapping but causes less transport than typical trapped-electron modes. The nature of this instability is clarified here. It is shown to be similar to the ‘ubiquitous mode’ in tokamaks and is driven by ion free energy, but requires trapped electrons to exist.

Keywords

fusion plasmaplasma confinementplasma instabilities
Type
Research Article
Information
Journal of Plasma Physics , Volume 83 , Issue 4 , August 2017 , 715830404
Copyright
© Cambridge University Press 2017 

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