Turbulence mixing and transport in magnetized plasmas
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Turbulence mixing and transport in magnetized plasmas

Turbulence, mixing and transport in magnetized plasmas

Turbulence is found to dominate the transport of plasma across the confining magnetic field.In the edge region turbulent transport is order of magnitude stronger than classical – collision dominated – transport.All lost plasma must go through the edge region!

Numerical and theoretical studies of turbulence and transport!Purpose:Understanding turbulence and the associated anomalous transport in magnetized plasmas

Predictive model

Ultimate goal:

Odd-Erik Garcia, Volker Naulin, Anders H.Nielsen, Jens Juul Rasmussen

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Content

Content:

  • A general description of turbulence

  • Turbulence in fluids

  • Turbulence and mixing/transport

  • Turbulence in plasmas, quasi 2-dimensional

  • Vortex structures

  • Vortex structures and transport

  • Plasma edge turbulence: modelling comparison with experiments

  • Transport of impurities.

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Turbulence

Turbulence?

Every day phenomena: nature --- administration

Leonardo da Vinci : 1452 –1519

van Gogh

Turbolenza

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Turbulence1

Turbulence?

A.N. Kolmogorov 1903 - 1987

Irregularity and randomness

Fluctuations on all scales

”Unpredictability”

Diffusivity, rapid mixing

E(k) ~ k-5/3

Nonlinearity dominates

Energy cascade, input at large scales – dissipation at small scales

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Turbulence effective mixer

Turbulence: effective mixer

Turbulence

Laminar

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Turbulence in a magnetized plasma

Turbulence in a magnetized plasma

ITER

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Plasma turbulence

Plasma turbulence

The turbulence degrades the confinement:

Turbulent transport is the main cause for loosing plasma across the magnetic field lines

Our turbulence studies are concentrated on edge turbulence

Lost plasma has to go through the edge!

Numerical Tokamak, Dorland et al.

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Plasma turbulence is 2 dim

Plasma Turbulence is ”2-Dim”

Vortex

Inverse cascade: energy concentrate at large scales.

Vortical structures dominate the dynamics

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Self organisation coherent structures

Self-organisation Coherent structures

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Dipole vortices

Dipole vortices

Red : positive vorticity

Blue : negative vorticity

Vortices of opposite vorticity do not cancel

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Vortex merger

Vortex merger

Like signed vortices merge

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Vortices trap particles

Vortices trap particles

Dipole vortices

Passive tracer field

Red : positive vorticity Blue : negative vorticity

Vortices : transport barriers

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


3 dimentional vortices

3-Dimentional vortices

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Vortex ring

Vortex ring

Vortex ring bubble

Silver ring

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Particle dispersion

Particle dispersion

Potential

Density

Drift-wave turbulence

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Turbulent flux

Turbulent flux:

Flux PDF

Particle flux: Γ = n v = n vExB

The probability distribution function for the plasma flux across the magnetic field is strongly non-Gaussian, i.e., strong bursts are dominating!

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Modelling turbulence at the edge

Modelling turbulence at the edge

Two-dimensional dynamics: outboard midplane

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Modelling turbulence at the edge1

Modelling turbulence at the edge

Global model 2D: self consistent evolution of pressure profile

The source region is separated from the loss region, SOL

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Particle flux at the edge

Particle flux at the edge

Pdf of edge particle flux

Strong possitive flux events!

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Edge turbulence transport in jet

Edge turbulence transport in JET

Pdf of flux

Large intermittent burst

B. Gonçalves: 11th EuropeanFusion Physics Workshop, Heraklion, Crete 8-11 Dec. 2003

.

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Edge transport events

Edge transport events

Bursts of density and heat are released and propagate far out in the SOL

Strong lasting effect on plasma facing components

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Blobs in experiment alcator c mod o grulke et al 2004

Blobs in ExperimentAlcator C-Mod (O. Grulke et al 2004)

H-alpha light: proportional to density. CCD: Looking along B-field

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Blobs aligned with b field mast culham uk kirk et al 2005

Blobs aligned with B-fieldMast, Culham UK (Kirk et al 2005)

H-alpha light,

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Impurity transport

Impurity transport.

Impurities are also transported by the turbulence.

Modelled by passive tracer transport: e.g., trace tritium experiments

3-Dim simulations, full geometry, flux-tube coordinated

Global variations self-consistent profiles

Poloidal projection of 3-D turbulent field

Turbulent transport statistics; transport barriers

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Dynamics of impurity density

Dynamics of impurity density

Projected from a 3D fluxtube simulation onto a poloidal cut

Timespan: 120 μs

Poloidal Asymmetry in transport, pinch

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


Film blobs summary

Film blobs:Summary:

  • We are approaching models with results that can be compared directly with experiments!

  • In hot plasmas: Dynamics of fast ions, alphas etc. Confinement!

  • --------------------------------------------------

  • Spændende Eksamensprojekter og PhD Projekter.

  • Med ITER mange nye udfordringer.

Kursus i Plasmafysik, OPL, Risø Juni 6 - 24, 2005

Turbulence, mixing and transport, June 21, 2005


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