Kein Folientitel

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Numerical Simulations of Plasma
Guram N. Kervalishvili
5 May, 2008, Physikalisch-Technische
Bundesanstalt (PTB), Berlin
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My scientific activities

• Analytical theory of non-neutral plasmasstudy
  of electron density evolution taking into account
  Diocotroninstability
• Simulation of turbulence in linear
  devicessimulation of linear/nonlinear
  instabilities in linear device VINETA
• Simulation of high/low pressure gas
  dischargesmodeling of breakdown process in argon
  at atmospheric pressure

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Motivation

• Study and understanding of turbulence under
  simplified conditions pre-requisite for
  understanding turbulence in tokamaks or
  stellarators

VINETA
ITER
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Motivation

• In fusion devices significant part of
  cross-field transport in the SOL is carried by
  blobs
• S. I. Krasheninnikov, Phys. Lett. A. (2001)
• Blobs exist in devices with linear magnetic
  geometry
• Radial movement of blobs in PISCES
  experiments was explained by the concept of
  neutral wind net force
  to wall replaces effect of
  curvature
• T.Windish et. al., POP (2006) G. Y. Antar
  et. al., POP (2003) S.I. Krasheninnikov at al.,
  POP (2003)

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Motivation

• Linear device VINETA
• Research topics
• study of blob dynamics
• the dynamics of Helikon- and Whistlerwaves
• kinetic  Alfvénwaves 

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Motivation

• Linear device VINETA
• One research topic study of blob dynamics

• Aim
• Turbulence modeling of linear VINETA device,
  using the gyrofluid 3D code GEM3
• B. D. Scott, PPCF (2003)
• B. D. Scott, POP (2005)

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Gyrofluid Code GEM3

• Electromagnetic gyrofluid model
• Two-moment (in general six-moment) equations
  for each species density, parallel velocity
• Species electrons and ions
• Two spaces are connected by polarization and
  induction equations

Density equations for electrons and ions
(normalized) Parallel velocity equations for
electrons and ions (normalized) Polarization
and induction equations (normalized)
and
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Gyrofluid Code GEM3

• Necessary changes to model linear devices
  (VINETA)
• Generalizing of metric
• Changing of main equations Electrostatic,
  no curvature effects, Radial dependence of
  collisionality
• Taking into account the concept of neutral
  wind
• New boundary conditions
• New diagnostic and post-processing modules

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Simulation parameters
Number of grid points Time step Duration of the
run Run time takes from 3 days up to 1
week Magnetic field Electron temperature Ion
temperature Drift scale Sound speed Peak density
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Results
Time evolution of potential, electron and ion
densities
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Results
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Results
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Results
Time-averaged density profiles and density
fluctuation level

• Initial background profile modified by
  turbulence

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Max-Planck-Institut für Plasmaphysik, EURATOM
Association Results
Temporal evolution of wavenumber spectrum
(density fluctuations)
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Results
Experiment
Simulation
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Summary

• Adapted GEM3 is able to capture experimental
  features of VINETA
• Qualitative agreement
• character of fluctuations across the radial
  background profile, temporal evolution of
  wavenumber spectrum, radial motion of blobs
• Influence of neutral wind seems to be
  negligible for VINETA
• Radial motion due to drift
• For better agreement with experimental results
• Background profile should be calculated
  selfconsistently

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Thank you for your attention
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Gyrofluid Code GEM3



















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Gyrofluid Code GEM3
Ions and electrons are connected by the
polarization equation









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Max-Planck-Institut für Plasmaphysik, EURATOM
Association Gyrofluid Code GEM3
Boundary conditions

• Perpendicular ( direction)

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http//www.pppl.gov/szweben
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Max-Planck-Institut für Plasmaphysik, EURATOM
Association Code GEM3