1 / 28

L. Vermare, P. Hennequin, O. Gurcan, C. Honoré

TORE SUPRA. Turbulence measurements during dimensionless parameters scans on Tore Supra using Doppler reflectometry. L. Vermare, P. Hennequin, O. Gurcan, C. Honoré Laboratoire de Physique des Plasmas Ecole Polytechnique, 91 128 Palaiseau, France

duer
Download Presentation

L. Vermare, P. Hennequin, O. Gurcan, C. Honoré

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. TORE SUPRA Turbulence measurements during dimensionless parameters scans on Tore Supra using Doppler reflectometry L. Vermare, P. Hennequin, O. Gurcan, C. Honoré Laboratoire de Physique des PlasmasEcole Polytechnique, 91 128 Palaiseau, France C. Bourdelle, T. Aniel, F. Clairet, R. Dumont, C. Fenzi, R.Sabot and the Tore Supra team Association Euratom-CEA,DSM/DRFC, Centre de Cadarache, France Laure Vermare, IRW9, Lisbon 3-6th May

  2. Outline • Doppler System on Tore Supra & fluctuations measurements • Dimensionless scaling experiments • k-spectrum shape in the medium k range : effect of r* and n* / comparison with theoretical model • Perpendicular velocity profiles during such scans • High k spectrum in presence of electron heating Ultra-brief presentation of a new reflectometry project on Tore Supra Laure Vermare, IRW9, Lisbon 3-6th May

  3. incident wave Cut-off layer : N=0 kd k ki Doppler system on Tore Supra Measurement of the backscattered electric field Ed (t) : • Tiltable motorized antenna - Gaussian optics (beam waist 40mm) - Low diverging beam (2.2° HPBW) - Poloidal angle 0 to 20° (typically 3° to 9°) =>k : 3 to 25 cm-1 =>kri ~0.5 to 5 • O mode / V-band r/a = 0.3 to 0.9 • New channel : X mode / W-band r/a = 0.5 to 1.2 Selection in wavenumber : Bragg rule kd = ki + k backscatteredkd=-ki => k=-2ki Laure Vermare, IRW9, Lisbon 3-6th May

  4. Density fluctuations measurements Tore Supra => long pulse discharges : stationary phaseslong enough toscan the poloïdal angle =>k-spectrum Steps of the probing frequency (∼200ms) Laure Vermare, IRW9, Lisbon 3-6th May

  5. Scattering position and wave-number from ray tracing (F, q)  (r,k) from ray tracing ±0.05 S(k) Beam Tracing using density profiles from fast sweep reflectometry Laure Vermare, IRW9, Lisbon 3-6th May

  6. Doppler shift => ∆w ~ kv Best fitting function : Taylor function from the fit => Frequency spectra Laure Vermare, IRW9, Lisbon 3-6th May

  7. Tore Supra experiments : r* and n* scans in L mode plasmas Laure Vermare, IRW9, Lisbon 3-6th May

  8. Scan en * • Difficult to vary r*in a wide range in the same machine • The density changes during the scan ->reflectometry accessibility also changes x 4 Scan en * n constant • Motivations of this new scan ->reach lowest collisionnality regime • Significative variation in n* achievable (limitation from the heating power) • Thedensity remains constant during the scan-> reflectometry accessibility also x 1.2 Dimensionless profiles well matched Dimensionless scaling experiments in Tore Supra Similarity principle => Laure Vermare, IRW9, Lisbon 3-6th May

  9. k-spectrum Laure Vermare, IRW9, Lisbon 3-6th May

  10. Doppler [Hennequin et al, NF 2006] • Various theories / models -2D inverse cascade (Kolmogorov Kraichnan) • Finite Larmor effects • (Hasegawa-Mima, Horton) • More recently : • Interaction with disparate scales: drift waves – ZF • [O. Gürcan, s. PRL] Laser scattering [Hennequin et al. PPCF 2004] [A. Casati et al. PRL2009] => Compared against gyrokinetic simulations: good agreement [A. Casati PRL2009] Transition in the k-spectrum at high k :an universal feature? Usual power law : S(k) ~ k-3 0.5 for krs < 1 Faster decrease at higher k =>Observed withvarious diagnostics & conditions on Tore Supra + others machines [Gusakov EPS06, Basse PPCF05] Laure Vermare, IRW9, Lisbon 3-6th May

  11. High r*, high n* Shape of k-spectrum during r* scan Low r*, high n* -Similar shape between low and high r* -Fair agremment with the shell model except at low and high k Laure Vermare, IRW9, Lisbon 3-6th May

  12. Shape of k-spectrum during n* scan High r*, high n* high r*, low n* Fair agreement for all cases with model taking into account interactions between disparate scales (drift-waves-zonal flows) Laure Vermare, IRW9, Lisbon 3-6th May

  13. Perpendicular velocity profiles Laure Vermare, IRW9, Lisbon 3-6th May

  14. Perpendicular velocity profile • Perpendicular velocity in the laboratory frame: • with usually • =>direct access to the radial electric field (see work by E. Trier NF08 ) X-mode • In Tore Supra, V profiles measured using Doppler are alwayscounter-current direction (V<0), inside the separatrix • Hollow profiles => Vdecreases from the edge to the core O-mode Laure Vermare, IRW9, Lisbon 3-6th May

  15. Perpendicular velocity profile during r* scan Low r*, high n* High r*, high n* V <0 ! Counter-current ! Laure Vermare, IRW9, Lisbon 3-6th May

  16. Comparison @ k=8cm-1 low * high * The velocity does not change significantly during the r* scan Laure Vermare, IRW9, Lisbon 3-6th May

  17. Perpendicular velocity profile during n* scan High r*, high n* High r*, low n* Laure Vermare, IRW9, Lisbon 3-6th May

  18. Comparision @ k=10cm-1 low * high * The velocity increases with deacreasing n* Laure Vermare, IRW9, Lisbon 3-6th May

  19. High k-spectrum during electron heating Laure Vermare, IRW9, Lisbon 3-6th May

  20. main component 2nd component High k-spectrum with electron heating • 2nd harmonic ICRH, B=2T electron heating • Observation 2nd Doppler componant at high k, v<0 (electronic diamagnetic) => only for r/a > 0.7 • Similar to the observation in FT-2 [Gusakov et al, IAEA 2008] Laure Vermare, IRW9, Lisbon 3-6th May

  21. Which modes are instable ? • 2nd harmonic ICRH, B=2T,electron heating changes parameters governing TEM/ETG instabilities • R/LT compared to ETG theshold(Jenko PRL01) using kinezero :unstable in the outer region => observed by Doppler reflectometry for r/a > 0.7 fETG ~ 500 kHz (fmes800kHz) gmax at kre~0.7 => krs~50 still to be confirmed with specific experiments and transport analysis … Laure Vermare, IRW9, Lisbon 3-6th May

  22. Summary • Robust features observed in k-spectrum: departure from a classical k-spectrum power law with fast decrease for ki>1 • Fair agreement with model taking into account interactions between disparate scales (drift-waves-zonal flows) • Perpendicular velocity increases with decreasing * • Additional component at higher frequency observed in some cases: related to ETG ? Laure Vermare, IRW9, Lisbon 3-6th May

  23. New reflectometry project on Tore Supra Laure Vermare, IRW9, Lisbon 3-6th May

  24. One channel identical to the equatorial Doppler system (0-mode, V-band) The project has started and is planned to be ready for the end of this year … Main motivations Vertical Doppler reflectometer • Role of turbulence driven flows and long-range correlations Characterisation of long-range correlations of density fluctuation and of their velocity in L mode plasmas using correlation between equatorial and vertical reflectometers (toroidal + poloidal) Access to GAMs =>Accessibility in vertical line of sight(poloidal structure m=1) Has been observed on density fluctuations and velocity at the plasma edge (L-mode) on AUG [Doppler measurements. conway] Supported by EFDA Laure Vermare, IRW9, Lisbon 3-6th May

  25. DREVE O-mode F=60GHz =-88° DIFDOP r/a = 0.87 2k= 8.55 cm-1 z(cm) vertical z(cm) vertical O-mode F=60GHz =6.5° r/a = 0.87 2k= 8.78 cm-1 X(cm) radial X(cm) radial The projet has started … • One channel identical to the equatorial • Doppler system • O-mode polarisation, V-band • Tiltable antenna with Gaussian optics Same cut-off (O-mode) but poloidal angle will depend on the Shafranov shift : Laure Vermare, IRW9, Lisbon 3-6th May

  26. * with Te Laure Vermare, IRW9, Lisbon 3-6th May

  27. ETG thershold Laure Vermare, IRW9, Lisbon 3-6th May

  28. 2D Fluid turbulence: • Inverse energy cascade leads to the • formation of large scale structures. k-spectrum characterizes non-linear interaction between modes • 3D Fluid Turbulence: • Kolmogorov direct energy cascade • Kinetic Energy E(k)=<vk2> ~k-5/3 • Magnetized plasma turbulence: • strong anisotropy induced by large B 2D. • 1 field isotropic 2D simplified picture • inertial range Laure Vermare, IRW9, Lisbon 3-6th May

More Related