1. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 1 Spontaneous stationary toroidal rotation in the TCV tokamak A. Scarabosio, A. Bortolon, B. P. Duval, A. Karpushov and A. Pochelon 10 th ITPA TP Group Meeting

2. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 2 Layout of the talk Stationary toroidal rotation in H-mode - Ohmic regime with small and frequent ELM’s - ECH heated H-mode with large ELM 1 A. Scarabosio et al., Plasma Phys. Control. Fusion 48 (2006) 663–683 2 A. Bortolon et al., to be submitted to PRL The DNBI and CXRS diagnostic on TCV - The effect of the DNBI on toroidal rotation Stationary toroidal rotation in limited ohmic L-mode: 1 - Plasma current scan and effect of sawteeth - Density dependence, basic scaling and T i -v  similarity - Comparison with neoclassical predictions - Inverted rotation regime at high I p and n e 2

3. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 3 The TCV DNBI-CXRS system

4. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 4 CXRS: the TCV rotation diagnostic Doppler shift of CVI 529 nm charge exchange recombination line is measured Diagnostic Neutral Beam Injector (H 0 ) Extracted current 3A, acceleration voltage 50 kV Injected power < 80 kW (20-70% absorbed) Small injection angle: 11.25 º Monochromator Czerny-Turner (f/7.5, 5.5Å/mm) 2400 l/mm holographic grating CCD front illuminated detector Magnetic axis is moved vertically to change radial coverage

5. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 5 TCV parameters and conventions Plasma height max. 1.44m Plasma width max. 0.48m Plasma major radius0.875m Plasma current1.2MA Plasma elongation max. 3 Aspect ratio3.6 Toroidal magnetic field max.1.43T

6. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 6 CXRS signals analysis Charge exchange background subtraction by means of DNBI modulation Typical uncertainty: ±2 km/s in the core ±5 km/s in the edge Standard set up:  t NBI pulse =   t int = 30 ms  sample rate 90 ms (It may reduced to 45 ms) Wavelength calibration from reference Ne spectrum (Ne lamp) after each shot.

7. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 7 The effect of the DNBI on rotation 1-2 km/s beam induced velocity for 30 ms beam pulse length Simple 3 three forces one-dimensional model: Exponential solution with characteristic time  on ~  off ~60-80 ms Experiments with 180 ms NBI pulse length Sawtooth precursors frequency is modulated by the neutral beam! Max. excursion of ~1 kHz  6 km/s

8. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 8 Spontaneous rotation in limited L-mode ohmic plasmas

9. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 9 Plasma current scan: typical exp. q E = 2.4 - 8 I p =-350 - +320 kA =1.4 - 7  10 19 m -3  = 1.15 - 1.5  = -0.4 - 0.4 T e = 500 -1600 eV T i = 150 - 700 eV  p = 0.2 - 1 l i = 0.8 - 2 Database of ohmic limited L-mode Very basic experiments in steady state condition and ohmic limited L- mode regime Average over several profiles (~10) to minimize errors No simultaneous high n e and low q E ! # 27098

10. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 10 Plasma current scan: rotation profiles Counter-current carbon rotation also confirmed by MHD spectroscopy. (electron diamagnetic drift) of several tens of km/s Central rotation increases with q E. Peak profile in the outer region and flat or hollow central profile. Knee in profiles correlates with position of the sawtooth inversion radius from SXR. Expected (from neoclassical theory) deuterium rotation (dashed lines) differs significantly in the low current case

11. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 11 Negative plasma current scan Negative current scan Comparison positive-negative I p co-current rotation (ion diamagnetic drift) with similar velocities and profile shape with respect to I p >0 q E ~6 Same profile within the errors: - same absolute rotation velocity in the core plasma. - some difference in outer part profile (not due to the beam! - radial shift of ~1cm (ex. error in equilibrium reconstruction) can explain difference in outer region (  >0.4 ) # 27098 # 27484

12. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 12 Edge profiles with Z axis scan By varying (from shot to shot) the axis vertical position we get the edge rotation profile too! Data consistent with   being a flux function Inverted (co-current) edge rotation   =+3 km/s as suggested by current scan experiments (but large error bar!!) q E =4.4 n e =2.5

13. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 13 Sawteeth flatten core rotation Rotation profiles response to a flattened current profile by off-axis ECH # 27677 Rotation profile peaks when  inv is reduced 500 kW of off-axis ECH power. The temperature and current profiles flattened  inv from 0.35 to 0.15. 

14. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 14 v  -T i similarity # 27098 Strong similarity (same gradient) between the rotation and temperature profile from CXRS outside  inv.

15. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 15 Scaling law of toroidal rotation v ,Max (~v  (  inv )) scales linearly with the plasma current and ion temperature Averaged values on steady state discharges For q E  3.2 deviate from this scaling v ,Max [km/s]= -12.5 T i,0 /I p [eV/kA]

16. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 16 Neoclassical prediction: effect of E r E r and diamagnetic contribution Neglecting E  1: In this configuration TCV rotation dominated by E  B flow 1 Kim Y B et al 1991 Phys. Fluid B 3 2050–60

17. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 17 Neoclassical prediction In neoclassical theory the radial angular momentum flux has a diffusive part (velocity gradient) and a non-diffusive part related with gradients in plasma parameters. 1,2 1 Catto P J and Simakov A N 2005 Phys. Plasmas 12 012501 2 Wong S K and Chan V S 2005 Phys. Plasmas 12 092513 The steady state condition in absence of external momentum input:

18. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 18 Spontaneous rotation in limited L-mode ohmic plasmas (2) High density- high current plasma A new rotation regime

19. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 19 Inverted core rotation at high I p and n e t = 1.1s (n e0 = 6x10 19 m -3 ) carbon toroidal velocity flips from -12 to +12 km/s change in toroidal rotation also observed on MHD mode rotation frequency I p ~ 340 kA, q e ~ 3.5 see next presentation of A. Bortolon for details! Low n e or low I p  counter-current rotation High n e and high I p  core co-current rotation

20. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 20 Spontaneous rotation in H-mode ohmic and ECH plasmas

21. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 21 Toroidal rotation in ohmic H-mode Ohmic, diverted H-mode with frequent ELM’s. (T i (0.6)=600 eV, q 95 =2.5) Standard H-mode at Z axis =20 cm  limited radial coverage Co-current rotation in the observed region Only outer region available  no core rotation measurements 

22. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 22 Toroidal rotation in ECH H-mode Central X3 ECH increases stored energy. T i (0.6)~1000 eV!! New ELM regime, less frequent but more energy released. Co-current rotation increases with stored energy and T i MHD mode rotation frequency confirms co-current rotation

23. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 23 Conclusions Carbon toroidal rotation, with negligible external input (spontaneous), is routinely measured in TCV L-mode and recently in H-mode discharges. Toroidal rotation shows a rich phenomenology: 1.Counter-current rotation in limited L-mode at low n e or I p 2.Core co-current rotation in limited L-mode at high n e and high I p 3.Co-current rotation in ohmic and ECH heated H- mode (core and edge) Similarity between v  and T i (in L-mode v  [km/s]=- 12.5T i /I p [eV/kA] Neoclassical predictions of radial flux of angular momentum does not agree with L-mode TCV data (H- mode??)

24. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 24 Directions of future researches Effect of divertor on edge and core plasma rotation Central rotation in H-mode plasmas Establish a scaling law for H-mode plasmas Study toroidal rotation in plasmas with ITB’s Up-grades of the DNBI - New arc source (full energy fraction 60 → 85%) - Reduced beam divergence (0.8 → 0.5 degrees ) - A/P ratio increased by a -factor of 2.5-3 without increasing deposited power Up-grades of CXRS: - New back illuminated CCD detector (QE X4) - New bundle of optic fibers (8 to 20 measurement points) New vertical CXRS view to measure poloidal rotation is under commissioning Hardware improvements Physics issues

25. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 25 Extra slides

26. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 26 Density scan at low I p

27. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 27 Empirical momentum flux k~1

28. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 28 MHD Spectroscopy

29. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 29 Sawteeth flatten core rotation  inv vs.  s = width of the flat region in the rotation profile Good correlation between  inv and the outer position of the flat rotation region. For large  inv profile is hollow even outside  inv. Existence of a co-current torque? Negative I p Positive I p

30. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 30 MHD spectroscopy #29500

31. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 31 Neoclassical prediction: effect of E  E  contribution to C rotation The neoclassical drive 1 from E  to V // is negligible for TCV ohmic plasmas 1 Kim Y B et al 1991 Phys. Fluid B 3 2050–60

32. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 32 Overview on #29475

33. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 33 Temporal evolution #29475

34. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 34 Vertical CXRS 40 vertical chords for poloidal velocity measurement Czerny-Turner monochromator Back illuminated CCD

35. 10th ITPA TP Meeting - 24 April 2006 - A. Scarabosio 35 Energy confinement time as a function of *e (n e,I p )  *e  No power degradation or or I p effect!  Rotation inversion depends on collisionality and plasma current! 370 kA 340 kA 320 kA 290 kA Collisionality at rotation inversion  Time