Electrostatic potential variations on stellarator magnetic surfaces in low collisionality regimes

Iván Calvo, José Luis Velasco, Félix I. Parra, J. Arturo Alonso, José Manuel García-Regaña

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

The component of the neoclassical electrostatic potential that is non-constant on the magnetic surface, that we denote by π, can affect radial transport of highly charged impurities, and this has motivated its inclusion in some modern neoclassical codes. The number of neoclassical simulations in which π is calculated is still scarce, partly because they are usually demanding in terms of computational resources, especially at low collisionality. In this paper the size, the scaling with collisionality and with aspect ratio and the structure of π on the magnetic surface are analytically derived in the 1=/, p and superbanana-plateau regimes of stellarators close to omnigeneity; i.e. stellarators that have been optimized for neoclassical transport. It is found that the largest π that the neoclassical equations admit scales linearly with the inverse aspect ratio and with the size of the deviation from omnigeneity. Using a model for a perturbed omnigenous configuration, the analytical results are verified and illustrated with calculations by the code KNOSOS. The techniques, results and numerical tools employed in this paper can be applied to neoclassical transport problems in tokamaks with broken axisymmetry.

Original languageEnglish (US)
Article number905840407
JournalJournal of Plasma Physics
Volume84
Issue number4
DOIs
StatePublished - Aug 1 2018
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Condensed Matter Physics

Keywords

  • Fusion plasma
  • Plasma confinement

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