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Nicolas Fedorczak

Poloidal mapping of turbulent transport in SOL plasmas. Nicolas Fedorczak. nicolas.fedorczak@cea.fr. J.P. Gunn. G. Bonhomme, F. Brochard, H. Bufferand, G. Ciraolo, M. Farge, Ph. Ghendrih, J.P. Gunn, P. Hennequin , L. Isoardi, R. Nguyen,

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Nicolas Fedorczak

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  1. Poloidal mapping of turbulent transport in SOL plasmas. Nicolas Fedorczak nicolas.fedorczak@cea.fr J.P. Gunn G. Bonhomme, F. Brochard, H. Bufferand, G. Ciraolo, M. Farge, Ph. Ghendrih, J.P. Gunn, P. Hennequin , L. Isoardi, R. Nguyen, C. Reux, F. Schwander, P. Tamain, L. Vermare

  2. Poloidal mapping of turbulent transport in SOL plasmas Multi-diagnostics investigation of transport at the edge I. Fast visible imaging :  Evidences of transport phenomena & asymmetries Fast visible imaging turbulence II. Local turbulence with probe :  blobby ExB convection III. Steady-state flows (probe)  Poloidal mapping of the radial flux Rake probe turbulence Tunnel Probe // flow

  3. 2. Fast visible imaging : evidences of transport phenomena Fast imaging in the visible range --> fluctuations of SOL plasma density Similar gas injections on High Field Side / Low Field Side Clear evidence of transport asymmetry --> filaments on the Low Field Side • Aligned with magnetic field & propagation (r,) • filaments with k// >0

  4. 2. Plasma filaments : not a SOL phenomenon • Other experiment : stationary fully detached plasmas (3-4 sec.) --> emissive ring in the confined region (r/a ~0.5 ) + local conditions ( * , P ) similar to SOL 20ms picture 20µs snapshot Again,field alignedstructures only on theLow Field Side filaments  k// > 0 + open / closed field lines

  5. 3. Local fluctuations : blobby ExB radial transport Turbulent radial flux : Transport coefficient : • Good coupling between E & ne for radial transport (all time scales) • Intermittent flux with a residual time averaged amplitude

  6.  few cm. 3. Local fluctuations : blobby ExB radial transport Whole radial profiles are treated in term of transport coefficient: Value coherent with density profile ? Radial increase of the velocity measured at the midplane TCV Garcia, Pitts PPCF 2007 Alcator-C mod Moyer JNM 1997  Need of a poloidal mapping of the radial flux in the SOL

  7. 4. Steady-state flows and flux asymmetries : evidences • Near sonic // flows usually measured at the plasma top Flow transition when rolling the plasma up-down on outboard limiters. M// (@ Top) & plasma position J.P. Gunn JNM 2007  Main contribution from particle source asymmetry

  8. 4. Steady-state flows and radial flux : Amplitude & asymmetry L. Isoardi & al. P2. 58 G. Ciraolo et al. P2. 60 E. Serre P2. 61 Line integrated radial flux Sr Initial data

  9. 4. Radial flux tailoring : poloidal mapping Fine mapping around the outboard midplane by varying the SOL magnetic topology Multi-limiter SOL shaping: G. Ciraolo P2. 60 Radial particle flux centered on the outboard midplane (  ~  50 ° )

  10. 5. Mutli-diagnostics coherency • Fast visible imaging • Convection of density filaments • Evidence of asymmetries Radial flux poloidal mapping @ LCFS Probes Local blobby ExB transport consistent with Global particle balance (steady-state flux mapping) SOL transport : LFS blobby ExB convection + k// >0

  11. 6. Multi-Tokamak coherency : Top to midplane measurements Local ExB flux @ Top + Poloidal flux mapping (function of radius) Top  midplane extrapolation Radial decrease @ Top Usual behavior - Tore Supra - JET Radial increase @ midplane Usual behavior - TCV - Alcator C-mod - DIII-D Extrapolated transport behavior coherent with midplane measurements

  12. 7. Conclusion & perspectives • Radial particle transport in the SOL : • High fraction due to ExB density convections ( ~ 100%) • highly asymmetrical : centered on outboard midplane + k//>0 modes. • Do not depend on magnetic topology - open / closed field lines - X-point / limiter • Involved in apparent incoherencies : • Local / Global particle flux balance • Multi machine comparison • Realistic transport parameters for simulations of edge plasmas • SOLEDGE 2D / SOLEDGE 3D Kelvin-Helmotz instability F. Schwander P1. 35 Multi-limiters SOL profiles G. Ciraolo, L. Isoardi, H. Bufferand • Driver of SOL // flow  Boundary conditions for core rotation. TORE SUPRA : P. Hennequin EPS 2010 ALCATOR C-mod : LaBombard NF 2004

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