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Magnetic well and Mercier stability of stellarators near the magnetic axis

Part of: Focus on Fusion

Published online by Cambridge University Press:  15 October 2020

Matt Landreman Open the ORCID record for Matt Landreman [Opens in a new window]  and
Rogerio Jorge Open the ORCID record for Rogerio Jorge [Opens in a new window]
Matt Landreman*
Affiliation:
Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD20742, USA
Rogerio Jorge
Affiliation:
Institute for Research in Electronics and Applied Physics, University of Maryland, College Park, MD20742, USA
*
†Email address for correspondence: mattland@umd.edu
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Abstract

We have recently demonstrated that by expanding in small distance from the magnetic axis compared with the major radius, stellarator shapes with low neoclassical transport can be generated efficiently. To extend the utility of this new design approach, here we evaluate measures of magnetohydrodynamic interchange stability within the same expansion. In particular, we evaluate the magnetic well, Mercier's criterion, and resistive interchange stability near a magnetic axis of arbitrary shape. In contrast to previous work on interchange stability near the magnetic axis, which used an expansion of the flux coordinates, here we use the ‘inverse expansion’ in which the flux coordinates are the independent variables. Reduced expressions are presented for the magnetic well and stability criterion in the case of quasisymmetry. The analytic results are shown to agree with calculations from the VMEC equilibrium code. Finally, we show that near the axis, Glasser, Greene and Johnson's stability criterion for resistive modes approximately coincides with Mercier's ideal condition.

Keywords

fusion plasmaplasma instabilitiesplasma confinement
Type
Research Article
Information
Journal of Plasma Physics , Volume 86 , Issue 5 , October 2020 , 905860510
Copyright
Copyright © The Author(s), 2020. Published by Cambridge University Press

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References

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