Neutrals in the tokamak edge: neoclassical ions and momentum transport

Edge Physics Forum

  • Datum: 04.04.2017
  • Uhrzeit: 15:30 - 17:00
  • Vortragende(r): John Omotani
  • Department of Physics, Chalmers University of Technology
  • Ort: Garching
  • Raum: Seminarraum D3
Due to their high cross-field mobility, neutral particles interacting with the plasma through charge-exchange can contribute to the radial transport of toroidal angular momentum even at low relative densities. The contribution of non-Maxwellian parts of the ion distribution function is particularly interesting, as it can generate a momentum flux through the neutrals even in the absence of rotation. The neutrals can therefore contribute to intrinsic rotation. We model neutrals using a short mean-free-path approximation, in a background of neoclassical ions having arbitrary collisionality, on closed flux surfaces near the edge. As an application, we will show the effect of flux surface geometry on plasma rotation in 'predictive' mode where the neutrals are assumed to dominate the angular momentum transport. We will also show the momentum flux through neutrals in 'interpretive' mode, where plasma profiles from an L-mode AUG discharge are used to estimate the magnitude of the angular momentum flux through neutrals, finding that it may be a significant fraction of the angular momentum input from NBI.
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