Contents

1. State of art of toroidal rotation studies at JETP.Mantica on behalf of TFT momentum transport working group and TFH spontaneous rotation group

2. Contents • Toroidal rotation data base results • Modelling • Perturbative studies using NBI modulation • Effect of BT ripple on plasma rotation • Spontaneous toroidal rotation

3. Rotation and Momentum Confinement Database at JET P.C. de Vries, M-D. Hua, C. Giroud, M.F. Johnson and JET EFDA Contributors • At JET a database dedicated to NBI driven plasma rotation and momentum confinement has been set-up. • Database entries • Overlap with subsets of other JET databases • *as for April 2007 • Database details • Automatic generation enables easy updates/expansion • ‘Transparency’ information: problems with specific entries, errors Rotation and Momentum Confinement Database at JET - Peter de Vries

4. Parameters in the Database * Toroidal Rotation measured by core CXRS diagnostic Rotation and Momentum Confinement Database at JET - Peter de Vries

5. Thermal Mach number: Alfvén Mach number: Rotation in JET plasmas • Mach numbers • Dimensionless parameters • Enables comparison between various JET scenarios or other devices Rotation and Momentum Confinement Database at JET - Peter de Vries

6. Rotation in JET plasmas • Regression analysis ongoing: Mth Torque/Ptotand MA bf • Mth and MAis lower for Type III ELMy H-mode compared to Type I • Large central Mach number for ITB discharges Rotation and Momentum Confinement Database at JET - Peter de Vries

7. Energy and momentum confinement • General trend: tEkin tf • Kinetic energy is obtained by integrating over pe and pi profiles. • However, detailed cases show that often tEkin /tf is not unity • tEkin /tf ranges from 0.6 to 1.6 (for discharges with predominant NBI) Rotation and Momentum Confinement Database at JET - Peter de Vries

8. Prandtl number • Similar global confinement of energy and momentum • Transport processes for energy and momentum related? • But Local diffusivities in the gradient region have been determined • Prandtl number in the ‘core’ (i.e. averaged 0.3<r<0.7) is lower than unity 1.0 0.4 0.1 See also P.C. de Vries, et al. Plasma Phys. Control. Fusion 48 (2006) 1693 Rotation and Momentum Confinement Database at JET - Peter de Vries

9. Modelling using Weiland model and GLF23 Expt 57865 GLF23 Weiland Good reproduction of profiles cj/ci~0.2-0.5 Weiland model does not yield significant pinch term in most cases T.Tala IAEA 2006

10. However gyro-kinetic theory predicts cj/ci~0.8-1 Could the low effective Pr in JET be due to significant inward pinch whilst cj/ci~0.8-1? Existence of pinch also predicted by gyrokinetic theory

11. NBI modulation J.Ferreira, P.Mantica, T.Tala, G.Tardini, K.-D.Zastrow and JET EFDA contributors Steady-state only does not allow to distinguish between low Pr and no pinch or high Pr and inward momentum pinch Experimental technique Torque is modulated by modulating at 6.25 Hz 2-4 tangential PINIs.H-modes at low collisionality. Clear modulation of toroidal rotation is measured by CX with 12 channels and Dt=10 ms. Torque deposition has broad profile. This case has been modelled to extract Pr and V assuming the torque source from TRANSP. In some cases a modulation in antiphase of the normal PINIs has been added to compensate the tangential PINI modulation in order to minimize Te, Ti, position modulation and to have regions in the plasma where the torque modulation is also minimized. This case has not yet been modelled.

12. Modulated torque source collisional All JxB JxB From TRANSP NUBEAM using 160.000 monte carlo particles

13. Rotation modulation Very good signal at 1st harmonic and also for some channelsvisible peak at 3rd harmonic Phase measured with respect to NBI power

14. Rotation modulation

15. JETTO simulation Simulated w,Ti for 9 cycles ne, Te and J from experiment ci either Bohm-gyroBohm or parabolic type adjusted to fit Ti profile cj = Prci Vj=uniform and constant From steady-state momentum and ion heat balance: Preff ~0.25 Try simulations with low Pr and no pinch or Pr~1 and pinch

16. JETTO simulation Pr=1 v=15 m/s Best results to fit both steady-state and modulation cj / ci = 1 Vj= 15 m/s

17. JETTO simulation Pr=0.25 no pinch Simulation with Pr=0.25 and no pinch fits steady-state equally but fails to reproduce modulation data Similar modelling of compensated case is in progress

18. Conclusions from NBI modulation • NBI modulation allows to conclude that the low effective Pr is due to the presence of a signifcant inward momentum pinch • Pr=1 and 15 m/s gives best reproduction of data • Result more in line with gyrokinetic predictions. Comparison with linear gyrokinetic predictions is in progress • Weiland and GLF23 will also be used to simulate modulation. Expected to fail as they predicted low Pr and no significant pinch in steady-state simulations.

19. Effect of TF Ripple on Plasma Rotation P.C. de Vries, A. Salmi, V. Parail, G Saibene and JET EFDA Contributors • The 32 Toroidal Field coil system at JET can be re-configured such that 2 sets of 16 coils can be charged independently. The TF ripple can be increased by different TF currents in the two coil sets. • To accurately predict rotation in ITER a better understanding of the effect of TF Ripple on plasma rotation is required. • TF Ripple Experiments were carried out at JET in January/March 2007 in which the TF ripple at the outer separatrix was increased from d=0.08% to 1.5%. • Plasma rotation was measured by means of CXRS.

20. TF ripple and plasma rotation • The Toroidal Field ripple induces particle losses by • Trapping of particles in the TF ripple • Stochastic (radial) diffusion of the banana-orbits • Calculations have shown that the second process is dominant in JET plasmas for TF ripple amplitudes >0.5-1%. • The induced particle (ion) loss flow (in JET predominantly NBI particles) provides a counter current torque to the bulk plasma. • The co-current NBI at JET provides a co-current Torque. • Hence, TF Ripple is thought to reduce the toroidal (co-current) rotation. • The exact mechanism is under investigation • TF Ripple experiments have been carried out and are being analysed. • Particle losses simulations by ASCOT have been carried out.

21. General trend • Database of all discharges done during the TF Ripple Experiment • General trend: Mach number decreases as a function of TF ripple • Negative (or counter current) edge rotation is observed (with co-NBI) • The edge Mach number at JET can become negative when>0.7-1% • For some discharges the counter rotation extends up to r=0.6.

22. Normal versus Tangential JET NBI • The JET NBI system has two sets of PINIs: one slightly more normal than the other. • With normal NBI a larger fraction of NBI particles will be trapped in banana orbits. Hence a larger fraction will be affected by the TF ripple • For the same total torque input discharges with “normal” NBI will have a smaller rotation compared to more tangential NBI. different input power (But same absorbed power) same NBI torque different momentum! For =0.5%

23. Ripple Scan in identical H-mode plasmas • Mach number/total angular momentum decreases with TF ripple. • Negative (or counter current) edge rotation is observed >0.8%. • Momentum confinement time decreases with TF ripple. T = +18.8Nm T = +13.9Nm T = +3.5Nm By A. Salmi, et al. • The j x B torque due to the TF ripple induced particle loss flow can be calculated. • ASCOT calculates ripple induced losses and ripple counter torque. • The total torque is reduced but up to a ripple of d=1% stays positive. • ASCOT calculated total torque can be used to determine tf. • Still decrease of tf with d observed: Extra losses (not incl. in ASCOT)?

24. Same TF ripple but different rotation • The negative rotation at the edge can be affected by the edge conditions • For identical TF ripple amplitude the density is increased by gas dosing • The ‘torque’ on the plasma is reduced for higher densities (lower T) • Similarly, the counter edge rotation for discharge with high TF ripple (d=1%) seem to follow the edge temperature.

25. Observed trend • Comparing edge Mach numbers of discharges with the same d=1%, one finds that the edge rotation scales with the local temperature. • Higher edge temperature means a stronger reduction of edge rotation.

26. Summary • TF ripple amplitudes of d=0.5-1% have a strong effect on the plasma rotation. • The use of NBI PINIs with more normal orientation at larger ripple causes a larger reduction of the rotation. • Normal NBI creates more trapped particles • Mechanism likely to be associated with ripple induce banana orbit diffusion • At JET counter rotating plasma was observed at the edge with co-rotation in the core. • ASCOT calculations of the ripple induced particle losses and consequential torque show that for these cases the calculated total torque on the plasma is still positive.

27. Spontaneous toroidal rotation studies in RF-heated JET plasma • TFH L.-G. Eriksson, T. Hellsten, F. Nave, J. Brzozowski, K. Holmström, T. Johnson, J. Ongena, K.-D. Zastrow, JET-EFDA Contributors*

28. Spontaneous rotation measured in pure RF L-mode plasmas using NBI blips and MHD Both LH and ICRH explored 66310

29. LH Ip=1.5 MA …but depends on plasma current Ip=2.6 MA LH+ICRH The presence of counter-rotation in the core region is clearly linked to the presence of ICRH… Ip=1,5 MA

30. Low Ip is a necessary but not sufficient condition for a hollow rotation profile. LHCD only plasmas at low current do not have counter core rotation Co-rotation in the edge region of the plasma scales fairly well with the diamagnetic stored energy, WDIA, divided by the line-averaged density.

31. Simulation using torque from ICRH as calculated by SELFO and simple momentum transport model with tj=tE Torque from fast ion losses very small - not enough to make negative core rotation given the positive boundary condition from experiment

32. SUMMARY • Good set of data of spontaneous rotation profiles in ICRH or LH or ICRH+LH L-mode plasmas • Core counter rotation observed with ICRH but not with LH and only at low plasma current • Torque due to fast ions does not seem sufficient to explain measured rotation • No transport modelling yet performed to explore transport based explanations of the observed rotation

33. Jetto simulation using ASCOT torque Torque calculated by ASCOT, taking into account the fast ion losses Negative at the edge c=ci yields best reproduction of expt rotation profile c/ ci seems to be higher than without ripple (c=0.3 ci in most JET plasmas), or torque not correct? missing torque due to thermal ion losses vtor Pulse 69648 c=0.3 ci c=0.7 ci c= ci torque T.Tala preliminary!