Laure Vermare, IRW9, Lisbon 3-6th May 1 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, 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 TORE SUPRA

Laure Vermare, IRW9, Lisbon 3-6th May 2 Outline 1.Doppler System on Tore Supra & fluctuations measurements 2.Dimensionless scaling experiments  k-spectrum shape in the medium k range : effect of * and * / comparison with theoretical model  Perpendicular velocity profiles during such scans 3.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 Doppler system on Tore Supra  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 =>k i ~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  Cut-off layer : N=0 incident wave kd = ki + k backscattered kd=-ki => k=-2ki kiki kdkd k Selection in wavenumber : Bragg rule Measurement of the backscattered electric field Ed (t) :

Laure Vermare, IRW9, Lisbon 3-6th May 4 Density fluctuations measurements Tore Supra => long pulse discharges : stationary phases long enough to scan 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 Beam Tracing using density profiles from fast sweep reflectometry (F, )  (r,k) from ray tracing S(k) ±0.05

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

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

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

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

Laure Vermare, IRW9, Lisbon 3-6th May 10 Transition in the k-spectrum at high k : an universal feature? Usual power law : S(k) ~ k -3 0.5 for k s < 1 Faster decrease at higher k =>Observed with various diagnostics & conditions on Tore Supra + others machines [Gusakov EPS06, Basse PPCF05] Laser scattering [Hennequin et al. PPCF 2004] Doppler [ Hennequin et al, NF 2006] => Compared against gyrokinetic simulations : good agreement [A. Casati PRL2009] [A. Casati et al. PRL2009]  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]

Laure Vermare, IRW9, Lisbon 3-6th May 11 Shape of k-spectrum during * scan Low *, high *High *, high * -Similar shape between low and high * -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 * scan High *, high *high *, low * 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  In Tore Supra, V  profiles measured using Doppler are always counter- current direction (V <0), inside the separatrix  Hollow profiles => V decreases from the edge to the core Perpendicular velocity in the laboratory frame: with usually => direct access to the radial electric field (see work by E. Trier NF08 ) O-mode X-mode

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

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

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

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

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

Laure Vermare, IRW9, Lisbon 3-6th May 20 High k-spectrum with electron heating  2 nd 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] main component 2nd component

Laure Vermare, IRW9, Lisbon 3-6th May 21 Which modes are instable ? still to be confirmed with specific experiments and transport analysis …  2 nd 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 f ETG ~ 500 kHz (f mes 800kHz)  max at k   e ~0.7 => k   s ~50

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 Vertical Doppler reflectometer Main motivations 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 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 …

Laure Vermare, IRW9, Lisbon 3-6th May 25 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 : r/a = k  = 8.78 cm-1 z(cm) vertical X(cm) radial O-mode F=60GHz =-88° DREVEX(cm) radial r/a = k  = 8.55 cm-1 z(cm) vertical O-mode F=60GHz =6.5° DIFDOP

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 k-spectrum characterizes non-linear interaction between modes 3D Fluid Turbulence: –Kolmogorov direct energy cascade Kinetic Energy E(k)= ~k -5/3 Magnetized plasma turbulence: –strong anisotropy induced by large B  2D. –1 field isotropic 2D simplified picture –inertial range 2D Fluid turbulence: –Inverse energy cascade leads to the formation of large scale structures.