Higher order Larmor radius corrections to guiding-centre equations and application to fast ion equilibrium distributions

S. Lanthaler, D. Pfefferlé, J. P. Graves, W. A. Cooper

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

An improved set of guiding-centre equations, expanded to one order higher in Larmor radius than usually written for guiding-centre codes, are derived for curvilinear flux coordinates and implemented into the orbit following code VENUS-LEVIS. Aside from greatly improving the correspondence between guiding-centre and full particle trajectories, the most important effect of the additional Larmor radius corrections is to modify the definition of the guiding-centre's parallel velocity via the so-called Baños drift. The correct treatment of the guiding-centre push-forward with the Baños term leads to an anisotropic shift in the phase-space distribution of guiding-centres, consistent with the well-known magnetization term. The consequence of these higher order terms are quantified in three cases where energetic ions are usually followed with standard guiding-centre equations: (1) neutral beam injection in a MAST-like low aspect-ratio spherical equilibrium where the fast ion driven current is significantly larger with respect to previous calculations, (2) fast ion losses due to resonant magnetic perturbations where a lower lost fraction and a better confinement is confirmed, (3) alpha particles in the ripple field of the European DEMO where the effect is found to be marginal.

Original languageEnglish
Article number044014
JournalPlasma Physics and Controlled Fusion
Volume59
Issue number4
DOIs
Publication statusPublished - 15 Mar 2017
Externally publishedYes

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