1. Tuomas Tala 1/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 NBI Modulation Experiments to Study Momentum Transport on JET + Status of TC-15 Tuomas Tala, Association Euratom-Tekes, VTT, Finland JET-EFDA Culham Science Centre Abingdon, UK Transport and Confinement ITPA Meeting, 31 March - 2 April 2009

2. Tuomas Tala 2/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Scientific Team T. Tala 1,J. Ferreira 2, P. Mantica 3, D. Strintzi 4, G. Tardini 5, K.-D. Zastrow 6, M. Brix 6, G. Corrigan 6, C. Giroud 6, L. Hackett 6 I. Jenkins 6, T. Johnson 7, J. Lönnroth 8, V. Naulin 9, V. Parail 6, A.G. Peeters 10, A. Salmi 8, M. Tsalas 4, T. Versloot 11, P.C. de Vries 6 and JET-EFDA contributors* And data from J. Rice and M. Yoshida for TC-15 JET-EFDA, Culham Science Centre, Abingdon, OX14 3DB, United Kingdom 1 Association EURATOM-Tekes, VTT, P.O. Box 1000, FIN-02044 VTT, Finland 2 Associação EURATOM/IST, Centro de Fusão Nuclear, 1049-001 Lisbon, Portugal 3 Istituto di Fisica del Plasma CNR-EURATOM, via Cozzi 53, 20125 Milano, Italy 4 National Technical University of Athens, Euratom Association, Athens, Greece 5 Max-Planck-Institut für Plasmaphysik, EURATOM-Assoziation, Garching, Germany 6 EURATOM/UKAEA Fusion Association, Culham Science Centre, United Kingdom 7 Association Euratom-VR, KTH, Stockholm, Sweden 8 Association EURATOM-Tekes, TKK, P.O. Box 2200, FIN-02150 TKK, Finland 9 Association Euratom-Risø DTU, Denmark 10 Center for Fusion, Space and Astrophysics, Department of Physics, Univ. of Warwick, United Kingdom 11 FOM Instituut for Plasmafysica Rijnhuizen, Association EURATOM-FOM, The Netherlands *See Appendix of F. Romanelli et al., paper OV/1-2, IAEA 2009, Geneva

3. Tuomas Tala 3/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Outline  Summary and status of the NBI modulation experiments on JET  Dependence of the momentum pinch on q-profile and density gradient length R/L n and comparison with linear Gyro-Kinetic simulations with GKW  NBI modulation experiments in plasmas with toroidal magnetic field ripple  Status of TC-15 Joint ITPA Experiment: Dependence of Momentum and Particle Pinch on Collisionality

4. Tuomas Tala 4/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Summary of NBI Modulation Sessions on JET  NBI modulation without ripple: –Non-compensated modulation: 10+4 good physics pulses –Compensated modulation: 2+2 good physics pulses  NBI modulation with using toroidal magnetic field ripple: –Non-compensated modulation: 4+2 good physics pulses –Compensated modulation: 1+2 good physics pulses P NBI Time P NBI Time Non-compensated Compensated Tangential NBI Normal NBI

5. Tuomas Tala 5/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Determination of the Momentum Diffusivity and Pinch 1 st harmonic 2 nd harmonic Exp. amplitude A ω Exp. phase  ω Sim. amplitude A ω  Sim. phase  ω   Step 1: Determination χ i and χ ,eff – Calculate χ i  Step 2: Determination of P r or χ  = P r χ i – Fix P r by fitting the modelled phase profile with the experimental one, as phase almost independent of v pinch – Choose P r profile reproducing best the experimental phase  Step 3: Determination of v pinch – Vary v pinch profile to fit both the amplitude of ω  and the steady-state profile of ω  -v pinch (m/s) T. Tala et al., PRL 102, 075001 (2009)

6. Tuomas Tala 6/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Outline  Summary and status of the NBI modulation experiments on JET  Dependence of the momentum pinch on q-profile and density gradient length R/L n and comparison with linear Gyro-Kinetic simulations with GKW  NBI modulation experiments in plasmas with toroidal magnetic field ripple  Status of TC-15 Joint ITPA Experiment: Dependence of Momentum and Particle Pinch on Collisionality

7. Tuomas Tala 7/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Dependence of the Pinch on q-profile and Density Gradient Length R/L n 1/2  4 discharges chosen for accurate comparison  Plasmas very similar, similar B t, heating power, temperatures, edge conditions  q-profile (plasma current) and R/L n (density) scans performed among the 4 shots, 66128, original reference 73701, reference 73702, low q pulse 73709, low R/L n q-scan R/L n -scan

8. Tuomas Tala 8/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Dependence of the Pinch on q-profile and Density Gradient Length R/L n 2/2 66128, original reference 73701, reference 73702, low q pulse 73709, low R/L n Preliminary

9. Tuomas Tala 9/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Comparison of the Pinch and P r with Linear Gyro-Kinetic GKW Simulations 1/4 Pulse number 66128, old reference Experiment x GKW simulation

10. Tuomas Tala 10/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Comparison of the Pinch and P r with Linear Gyro-Kinetic GKW Simulations 2/4 Pulse number 73701, reference pulse Experiment x GKW simulation

11. Tuomas Tala 11/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Comparison of the Pinch and P r with Linear Gyro-Kinetic GKW Simulations 3/4 Pulse number 73702, low q pulse Experiment x GKW simulation

12. Tuomas Tala 12/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Comparison of the Pinch and P r with Linear Gyro-Kinetic GKW Simulations 4/4 Pulse number 73709, low R/L n pulse Experiment x GKW simulation Preliminary

13. Tuomas Tala 13/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Outline  Summary and status of the NBI modulation experiments on JET  Dependence of the momentum pinch on q-profile and density gradient length R/L n and comparison with linear Gyro-Kinetic simulations with GKW  NBI modulation experiments in plasmas with toroidal magnetic field ripple  Status of TC-15 Joint ITPA Experiment: Dependence of Momentum and Particle Pinch on Collisionality

14. Tuomas Tala 14/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Use of Magnetic Field to Perturb/Modulate Rotation at the Edge  NBI torque source very different at large magnetic field ripple  The torque density profile peaks towards the edge at 1.5% ripple  Can be used to induce a rotation perturbation at the edge (this technique used in JT-60U)  On JET, due to beam geometry, its use is complicated due to non-edge localised source Comparison of ASCOT and PENCIL torque density profiles with 1.5% ripple

15. Tuomas Tala 15/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 The Amplitude and Phase of the Rotation Very Different in Plasmas with Magnetic Ripple 1/2 steady-state ω  non-ripple shot, normal PINIs modulated, P NBI =5MW 1.5% ripple, tangential PINIs modulated, P NBI =5MW 1.5% ripple, normal PINIs modulated, P NBI =5MW 1.5% ripple, normal PINIs modulated P NBI =5MW, + 2MW of ICRH Modulation in non-ripple plasma, normal PINIs #77089 1 st harmonic A 2 nd harmonic A 1 st harmonic  2 nd harmonic 

16. Tuomas Tala 16/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 The Amplitude and Phase of the Rotation Very Different in Plasmas with Magnetic Ripple 2/2 Modulation of tangential PINIs at 1.5% ripple, #77091 1 st harmonic A 2 nd harmonic A 1 st harmonic  2 nd harmonic  1 st harmonic  2 nd harmonic A 1 st harmonic A Modulation of normal PINIs at 1.5% ripple, 77090

17. Tuomas Tala 17/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Comparison of TRANSP and ASCOT Torque in non-ripple Plasma Phase (torque, degrees) Amplitude (torque, N/m 2 ) Agreement is good, the shift of the peak JxB torque amplitude due to equilibrium, ASCOT uses EFIT, TRANSP its own internal equilibrium

18. Tuomas Tala 18/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Outline  Summary and status of the NBI modulation experiments on JET  Dependence of the momentum pinch on q-profile and density gradient length R/L n and comparison with linear Gyro-Kinetic simulations with GKW  NBI modulation experiments in plasmas with toroidal magnetic field ripple  Status of TC-15 Joint ITPA Experiment: Dependence of Momentum and Particle Pinch on Collisionality

19. Tuomas Tala 19/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Status of TC-15 Joint Experiment: Dependence of Momentum and Particle Pinch on Collisionality Colour codes: XXX No progress (to my knowledge) XXX Some data exist, but not directly linked to this Joint Experiment XXX Experiment planned XXX Experiment done DeviceMomentumParticlePeriodLocal Key Person JETXXX 2009T. Tala DIII-DXXX 2009W. Solomon NSTXXXX 2009S. Kaye JT-60UXXX 2009M. Yoshida C-MODXXX 2009J. Rice / J. Hughes TCVXXX 2009H. Weisen

20. Tuomas Tala 20/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 He Gas Puff Modulation on JT-60U H. Takenaga, Nucl. Fusion 39, 1917 (1999) The difference between Deuterium and Helium D and v?

21. Tuomas Tala 21/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Momentum Pinch Versus Collisionality on JT-60U Database e * is the effective electron collision frequency normalized to the bounce frequency. I p ~1.5 MA, B T ~3.8 T,  ~0.3, q 95 ~4.2, n e ~1.6-2.5x10 19 m -3,  N ~0.26-1.07,  *~0.04-0.05, I p ~0.9 MA, B T ~3.8 T,  ~0.3, q 95 ~8.2, n e ~1.6x10 19 m -3,  N ~0.34,  *~0.04, Yoshida M. et al 2007 Nucl. Fusion 47 856 Plot of momentum pinch versus collisionality

22. Tuomas Tala 22/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Comparison of Toroidal Velocity and Electron Density Profiles in C-Mod J. Rice

23. Tuomas Tala 23/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Collisionality Dependence of Momentum and Particle Pinch in GK Simulations  ITG (Waltz standard case with R/L n = 2)  Particle flux changes sign with collisionality, but momentum pinch does not Weaker dependence on collisionality  For particle pinch, the perturbation in the trapped region is important while for the momentum pinch, it is the symmetry in the low field side. This is not affected by collisions.  Other parameters to be scanned in TC-15 (R/L n, q and s)? Effective particle diffusivity Momentum Pinch Number A.G. Peeters, Self consistent mode structure, submitted PoP

24. Tuomas Tala 24/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Conclusions  NBI modulation experiments shown to be a very good tool to study momentum transport and torque sources on JET  Significant inward momentum pinch v pinch  -20m/s found on JET, decrease of v pinch with R/L n observed. Experiments show a pinch number 2-3 larger than GKW simulations. –Reasons for the discrepancy between GKW and experiments could be: GKW includes only Coriolis pinch (ExB pinch term missing), non-linear simulations would be different from linear ones, some torque source is modulated in the experiments and not taken into account in the experimental analysis.  Values of P r =0.6–1.2 found in JET experiments, consistent with theory and gyro- kinetic calculations.  NBI modulation data with magnetic field ripple to be analysed  TC-15 Joint Experiment is now under planning stage on DIII-D, JET and NSTX.

25. Tuomas Tala 25/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Does v pinch Affect the Prediction of Toroidal Rotation Profile in ITER?  ITER scenario 2 (baseline scenario) –Plasma profiles from ITER Scenario 2 –Torque profiles from ASCOT orbit- following Monte-Carlo code, 1MeV NBI – χ i from GLF23 transport model  Predictive simulations with JETTO code for toroidal rotation ω   Assuming similar plasma parameters and pinch number Rv pinch / χ  in ITER as in JET v pinch,ITER  R JET /R ITER  χ ,ITER / χ ,JET  v pinch,JET  1/6  v pinch,JET Torque from ASCOT T i (and χ i ) from GLF23 P r =0.3, v pinch = 0  v pinch,JET  0 P r =0.9, v pinch = 1/8  v pinch,JET  -2m/s P r =0.9, v pinch = 1/4  v pinch,JET  -5m/s P r =0.9, v pinch = 1/3  v pinch,JET  -7m/s Note: Not the ‘final’ ITER simulation, considers only NBI driven rotation v pinch  -2m/s v pinch  -5m/s v pinch  0 v pinch  -7m/s

26. Tuomas Tala 26/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Similar v pinch and P r Profiles Confirmed in Plasma with Slightly Different Profiles T. Tala et al., submitted to PRL AωAω AωAω ωω ωω P r =0.25, v pinch =0 shown in blue in frames (c) and (d) Frame (a): P r ~1, v pinch ~ -20m/s shown in black in frames (c) and (d) Frame (b): Exp. amplitude A ω Exp. phase  ω Sim. amplitude A ω  Sim. phase  ω 

27. Tuomas Tala 27/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Gyro-Kinetic Simulations Also Show P r  1 and Inward Momentum Pinch  Linear gyro-kinetic simulations with GKW code (A. Peeters et al., PRL 2007) versus JET experiment  The slope of the curves indicates the Prandtl number and the intersection of y-axis the Pinch number –Prandtl number P r = χ  /χ i GKW: P r =0.6–1.2 Experiment: P r =0.5–1.2 –‘Pinch’ number - Rv pinch / χ  GKW: -Rv  / χ  =2–4 Experiment: -Rv  / χ   4–8  Excellent agreement between gyro- kinetic calculation and experiment in P r (including the radial variation)  Roughly a factor of 2 discrepancy in the Pinch number JET pulse no. 66128 using parameters from JET pulse no. 66128 GKW

28. Tuomas Tala 28/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 The Pinch Velocity Increases with Increasing Rotation (Mach Number) GKW code: Calculated using parameters from JET pulse no. 66128 JET Experiments: Data from the JET momentum database using the JETTO interpretive transport code Normalised toroidal velocity u=v  /v th

29. Tuomas Tala 29/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 A Sizeable Inward Momentum Pinch Results from the Analysis  P r  0.5–1 (radial variation) needed to reproduce the phase profile  Inward momentum pinch velocity up to v pinch ~ 25 m/s needed to reproduce the amplitude and steady-state at P r  0.5–1. Important aspects to be taken into account in the analysis:  Plasma movement due to modulation –Profiles mapped inside TRANSP onto a plasma movement independent co-ordinate  Modulation in T i and T e, the amplitude being about 1 % – Studied in simulations using time- dependent χ i – Owing to the small amplitude 1–2 % in χ i, the impact on v pinch and P r is insignificant

30. Tuomas Tala 30/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009  Energy and momentum confinement times similar in many tokamaks    E  E =W th /P in   = mnRω  /S NBI  In this work, we concentrate on core momentum transport studies … while the global confinement includes significant contribution from the edge pedestal  While core momentum transport smaller than that of ion heat, the opposite observed in pedestal resulting in roughly equal global momentum and energy confinement times on JET Global Energy and Momentum Confinement Times Example from JET momentum database

31. Tuomas Tala 31/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009  Coupling of momentum and ion heat transport (characterised by the Prandtl number P r = χ  /χ i ): –Early ITG fluid theory χ  /χ i =1 N. Mattor & P. Diamond, Phys. Fluids 1988 –Recent gyro-kinetic simulations χ  /χ i  0.8 A. Peeters, PoP 2005  Effective Prandtl number, P r,eff = χ ,eff /χ i,eff from JET rotation database significantly smaller  Small effective Prandtl number P r,eff could be due –Torque sources other than NBI in the momentum flux   (now consists only of NBI torque) –Inward momentum pinch resulting in χ ,eff < χ  and P r,eff < P r Discrepancy in the Ratio of Effective Momentum and Ion Heat Diffusivity between JET Database and Theory JET rotation database covering over 600 shots: P. de Vries et al., NF 2008   = momentum flux q i = ion heat flux

32. Tuomas Tala 32/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Intrinsic Rotation Much Smaller than Rotation in NBI Heated Plasmas  In NBI driven JET discharges (co- beams), ω  in the plasma centre is typically 50–150 krad/s, an order of magnitude larger than ω  from intrinsic rotation  Intrinsic rotation cannot explain the small P r,eff  0.2 or χ ,eff found on JET momentum database  Torque source from intrinsic rotation neglected as the NBI is by far the dominant torque source L.-G. Eriksson et al., RF Topical Conference 2007 M.F.F. Nave et al., EPS 2007 2 MW LHCD, no NBI torque JET pulses no. 66128, 66302 and 66399 6MW ICRH, no NBI torque 12 MW NBI (high torque input)

33. Tuomas Tala 33/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Ion Heat Diffusivity Similar among All the 4 Discharges

34. Tuomas Tala 34/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Momentum transport much less studied than heat and particle transport, no reliable predictions for ITER rotation exist. Momentum Transport: –The magnitude of diffusive and convective (pinch) terms not studied in detail Sources of rotation: –NBI torque source well established (without ripple) –Other torque sources less understood, such as the driving mechanism for intrinsic rotation, sources at the edge, for example torque originating from edge ion losses due to finite toroidal magnetic field ripple Edge rotation: –Similar problem as predicting the temperature profile – the pedestal value must be known in order to predict the core toroidal rotation profile Why to Do Such a Complicated NBI Modulation Experiments?

35. Tuomas Tala 35/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 NBI Modulation Experiments on JET, Non-ripple Plasmas  Steady-state analysis cannot separate diffusivity and pinch terms in the momentum flux, modulation of rotation needed  H-mode plasma at I p =1.5MA, B t =3.0T and low collisionality  Modulation measured with CX at 12 radial channels and time resolution of 10 ms  Typical modulation amplitudes: –ω  ~ 4–5% – T i and T e ~ 1% – n e ~ negligible

36. Tuomas Tala 36/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Calculation of the Torque Profiles  Two separate torque mechanisms: –instantaneous J  B torque (red) due to beam ions injected into trapped orbits –collisional torque (blue) due to slowing down of beam ions on passing orbits  Torque has been calculated with NUBEAM Monte-Carlo code in TRANSP using 160 000 particles to minimise the noise  J  B torque dominates in the core region  Accurate calculation of torque mandatory  As modulated torque is not radially localised, determination of diffusivity and pinch is difficult directly from data modelling needed 1 st harmonic 2 nd harmonic No Alfven Eigenmodes or any other MHD activity observed Amplitude of torque Phase of torque

37. Tuomas Tala 37/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Determination of the Momentum Diffusivity and Pinch  Simulate ω  (using the time-dependent torque profiles from TRANSP) with JETTO transport code to fit the amplitude and phase of the modulated ω  together with steady- state ω  by trying different P r profile and v pinch profile  Step 1: Determination of χ i and χ ,eff – Calculate χ i (assuming no ion heat pinch) – Calculate P r,eff = χ ,eff / χ i  0.25

38. Tuomas Tala 38/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Determination of the Momentum Diffusivity and Pinch  Step 1: Determination χ i and χ ,eff – Calculate χ i – Calculate P r,eff  χ ,eff / χ i,eff  0.25  Step 2: Determination of P r or χ  = P r χ i – Fix P r by fitting the modelled phase profile with the experimental one, as phase is almost independent of v pinch – Try first P r = 0.25 1 st harmonic 2 nd harmonic Exp. amplitude A ω Exp. phase  ω Sim. amplitude A ω  Sim. phase  ω 

39. Tuomas Tala 39/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 A Sizeable Inward Momentum Pinch Results from the Analysis  P r  0.5–1 (radial variation) needed to reproduce the phase profile  Inward momentum pinch velocity up to v pinch ~ 25 m/s needed to reproduce the amplitude and steady-state at P r  0.5–1.  Profiles of v pinch and χ  similar T. Tala et al., PRL 2009

40. Tuomas Tala 40/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Summary of Data Analysis and Modelling Performed so Far Performed: –OFMC and SELFO/ASCOT analyses for safety assessment of fast particle ripple losses (only pulses with large ripple amplitude needed this) –Data validation of CXRS and MSE data, part of the shots has also HRTS data –FFT of the modulated rotation data –TRANSP performed for most of the shots without ripple for VERY accurate torque calculation –JETTO analysis to determine the pinch and diffusivity carried out for part of the discharges –Linear Gyro-kinetic calculation with GKW performed to compare the Coriolis pinch theory with experiments for part of the discharges –Comparison of Prandtl number between experiments, GKW and GS2 for some shots To be performed: –TRANSP torque for the rest of non-ripple pulses Jorge Ferreira’s talk –Comparison of TRANSP and ASCOT (JINTRAC) torque Antti Salmi’s talk –JINTRAC torque calculations for the ripple session –Linear GKW simulations taking into account the collisions Arthur Peeters’ talk –Non-linear GKW simulations for the pinch and diffusivity

41. Tuomas Tala 41/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 Determination of the Momentum Diffusivity and Pinch 1 st harmonic 2 nd harmonic Exp. amplitude A ω Exp. phase  ω Sim. amplitude A ω  Sim. phase  ω   Step 1: Determination χ i and χ ,eff – Calculate χ i  Step 2: Determination of P r or χ  = P r χ i – Fix P r by fitting the modelled phase profile with the experimental one, as phase almost independent of v pinch – Choose P r profile reproducing best the experimental phase PrPr

42. Tuomas Tala 42/24 ITPA TC Meeting, Naka, Japan 31 March – 2 April 2009 The Diffusivity Is the Dominant Contributor to the Phase Profile Exp. amplitude A ω Exp. phase  ω Sim. amplitude A ω  Sim. phase  ω  Two simulations compared with same P r,no pinch (dashed), large pinch (solid)