Higher order Larmor radius corrections to guiding-centre equations and application to fast ion equilibrium distributions. (15th March 2017)

• Record Type: Journal Article
• Authors: Lanthaler, S; Pfefferlé, D; Graves, J P; Cooper, W A
• Is Part Of: Plasma physics and controlled fusion. Volume 59:Number 4(2017:Apr.)
• Publication Date: 2017-03-15
• Subjects: Banos drift -- NBI model -- Lie perturbation theory -- guiding-centre following -- anisotropy; Plasma (Ionized gases) -- Periodicals; Controlled fusion -- Periodicals; 530.44
• DOI: 10.1088/1361-6587/aa5e70
• Languages: English
• ISSNs: 0741-3335

Abstract

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.