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SUMMARY:Neutral atom dynamics and plasma turbulence in the tokamak periphe
 ry
DTSTART:20170606T103000
DTEND:20170606T113000
DTSTAMP:20260916T050053Z
UID:e02674dab034462850537f0e531bf641fbad3476454dbf0d65619ab4
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr. C. Wersal\, SPC-EPFL\nUnderstanding the physical mechanism
 s at play in the interaction between turbulent plasma and neutral particle
 s in the tokamak periphery is a crucial issue that we approach by using a 
 first-principles self-consistent model that is implemented in the GBS code
 . While the plasma is modeled by the drift-reduced two-fluid Braginskii eq
 uations\, a kinetic model for the neutrals is used\, valid in short and in
  long mean free path scenarios. The model includes ionization\, charge-exc
 hange\, recombination\, and elastic collisional processes. The neutral kin
 etic equation is solved by using the method of characteristics.\n\nBy stud
 ying the dynamics of the neutral-plasma interplay along the magnetic field
  lines in the SOL of a limited tokamak\, we derive a refined two-point mod
 el from the drift-reduced Braginskii equations that balances the parallel 
 and perpendicular transport of plasma and heat\, and takes into account th
 e plasma-neutral interaction. The model estimates the electron temperature
  drop along a field line\, from a region far from the limiter to the limit
 er plates. The refined two-point model is shown to be in very good agreeme
 nt with the simulation results.\n\nFurthermore\, we use the model to self-
 consistently simulate a diagnostic neutral gas puff\, which is often used 
 experimentally as a tool to learn about the turbulence properties in the t
 okamak periphery. In particular\, we investigate the impact of neutral den
 sity fluctuations on the D-alpha light emission\, finding that at a radial
  distance from the gas puff smaller than the neutral mean free path\, neut
 ral density fluctuations are anti-correlated with plasma density\, electro
 n temperature\, and D-alpha fluctuations\, while at distances from the gas
  puff larger than the neutral mean free path\, a non-local shadowing effec
 t influences the neutrals\, and the D-alpha fluctuations are correlated wi
 th the neutral density fluctuations.
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STATUS:CONFIRMED
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