Advancements in Tokamak Physics: Heating, Current Drive, and Wave Heating

1. Tokamak Physics • Jan Mlynář • 8. Heating and current drive Neutral beam heating and current drive, ... to be continued 1: Úvod, opakování

2. Neutral Beam Injection: principle Beam duct Ion source Accellerator Neutraliser Neutral beam Magnetic filter Ionisation Thermalisation Electricity -> other form (kinetic energy of particles) Transport to plasma (outside part) (inside part)

3. NBI Principle, in more detail I E Day

4. Size matters – ITER beamlinevs Torus

5. Evolution from Present Status - ITER I E Day

6. Neutral beam heating = 2.9.1017 8: Heating and current drive

7. Neutral beam heating 8: Heating and current drive

8. Neutral beam heating 8: Heating and current drive

9. Beam slowing 8: Heating and current drive

10. Distribution function 8: Heating and current drive

11. Beam current drive 8: Heating and current drive

12. R Resonance zone Wave heating Antenna Wave to particles Electricity -> other form (electromagnetic oscillations) Transport to plasma (outside part) transmission lines antenna (inside part) waves Thermalisation

13. phase velocity fast slow direction of propagation k parallel to B0: according to polarisation (with respect to B0, in other fields of science –e.g. optics- wrt propagation direction) right -> direction of rotation of electrons left -> direction of rotation of ions k perpendicular to B0 ordinary: E1 // B0 extraordinary: E1 perp to B0 Classification of waves

14. Wave Heating Review of Plasma Waves 8: Heating and current drive

15. Wave Heating Dielectric Tensor 8: Heating and current drive

16. Wave Heating Classification of waves 8: Heating and current drive

17. Wave Heating Resonances, Cut-offs 8: Heating and current drive

18. Wave Heating Resonances, Cut-offs 8: Heating and current drive

19. Wave Heating Energy flow 8: Heating and current drive

20. Wave Heating: Ray tracing 8: Heating and current drive

21. Wave Heating: Ray tracing ASDEX-U 8: Heating and current drive

22. Wave Heating: Ray tracing Mode conversion Boundary conditions 8: Heating and current drive

23. Wave Heating: CMA diagram In each region, the topological form of thephase velocity remain unchanged. Fast wave is outside (the wave front in vacuum which would always be a circle) slow wave is inside. E.g. in the top left region (high B, low n) the X/L wave is slow, the O/R wave is fast(X and O have k || B, L and R have k ┴ B) 8: Heating and current drive

24. Ion Cyclotron Heating fast wave ~ tens of MHz Plasma edge cutoff below on harmonic frequencies heating on minorities (e.g. on H in D plasmas) Resonant layer is vertical at Heating on harmonics  energies often higher than Ec  relaxation is mostly due to heating of electrons 8: Heating and current drive

25. Ion Cyclotron Heating 8: Heating and current drive

26. Ion Cyclotron Heating Heating on minorities: Decreases with increasing concentration, however, new “ion-ion” hybrid resonance emerges. May result in IBW (Ion Bernstein Wave)  can drive electrons Disadvantage: strongly sensitive on minority concentration ICRH advantages: Economic, powerful, important ion heating disadvantages: high E, problems with reflected power (ELMs), (“coupling of waves to plasma”, in particular problems with ELMs), non-directional. 8: Heating and current drive

27. Lower Hybrid Resonance Slow wave at a small angle to B ~ GHz  long path to the resonant region  Landau damping along the path turns out to be more important than LH itself Plasma edge – evanescent region (cutoff below ) i.e. “waves tunnels through” The antenna produces a wide spectrum  wide spectrum of fast electrons due to the Landau damping  current drive Reminder: The current drive would not exist if distribution of velocities of plasma particles were flat. However, Maxwellian distribution is not flat, which means wave can locally flatten the distribution in the direction of the wave propagation. 8: Heating and current drive

28. Lower Hybrid Resonance 8: Heating and current drive

29. Mode converter • Equally split the RF power in 3 in the poloidal direction • 1 input & 3 outputs WR-229 • Conversion efficiency: 98.65 % • Return Loss: -20.5dB J. Hilairet

30. LH - Wave Propagation Depends on ne and B Antenna structure

31. Electron Cyclotron Resonance Advantages : no evanescent region highly directional highest achievable power density Disadvantages: acts only on electrons expensive new technology (less reliable) Highly directional  profile control e.g. suppression of NTMs (mg. islands) 8: Heating and current drive

32. Electron Cyclotron Resonance 8: Heating and current drive

33. Electron Cyclotron Resonance 8: Heating and current drive

34. Electron Cyclotron Resonance Current Drive (ECCD) • Fisch – Boozer • directional increase of decreases n • Ohkawa • increase of pushes passing particles • into the trapped region (opposite direction to the Fisch - Boozer)  lower momentum loss Other applications of ECR: • plasma heating • current profile control for advanced regimes • transport studies via modulated ECRH • plasma start-up assistance • wall conditioning (ITER) 8: Heating and current drive

35. Bulk and Tail Current Drive 8: Heating and current drive

36. ITER ECR system 24 x 1 MW, 170 GHz gyrotrons 3 x 1 MW, 120 GHz gyrotrons for SUA wave guide switch to … equatorial or upper launcher 8: Heating and current drive

37. ITER ECR Upper Port • 3 ports with 8 beams in two rows • Main function: NTM (and sawtooth) control • Front steering • In vertical direction to scan radial deposition • Well focussed for optimised localization at q=3/2 and 2 8: Heating and current drive