The role of Doppler shift in ICRH: Majority D experiments in JET & ITER perspectives

1. The role of Doppler shift in ICRH: Majority D experiments in JET & ITER perspectives D. Van Eester, E. Lerche, A. Krasilnikov, … 09/03/08

2. Outline • Intro: generalities on majority heating • A. Krasilnikov JET D majority experiments: • experimental results • modeling • D tail formation in (3He)-D MC experiments • H beam heating in non-activated ITER phase • Equivalent Maxwellian distribution • Accounting for actual beam source • Accounting for actual distribution • JET experiments to test ITER heating scenario’s?

3. RF heating basics Heating / QL diffusion efficiency: N=1 IF “ << “ Polarization: Majority Minority heating 1 ion species:

4. Using the Doppler shift to diminish the impact of adverse polarization on ICRH efficiency w= WH+k//v // location w= WH 1MeV 10keV 500keV 100keV 500keV 100keV 10keV 1MeV ITER H majority scenario

5. D majority heating in JET: Combined NBI + RF heating dipole dipole

6. D majority heating in JET: parameters • Bo=3.3T or 3.6T; Ip=2MA • f=25MHz; PRF up to 2MW; dipole phasing • ENBI=80keV or 80+130keV; PNBI~6MW; normal and tangential • Neo=2.5 x 1019m-3 • Pure D up to traces of H (~5%) + Be evaporation ( 1%) & Ar gas puff (<0.5%)

7. D majority heating in JET: performance ~4 ~2

8. D majority heating in JET: performance ~50% Dedicated efforts RF pilots allowed to couple PRF~2MW. ~40%

9. D majority heating in JET: neutron camera NBI+RF NBI RF (NBI+RF) > NBIonly + RFonly horizontal vertical

10. D majority heating in JET: Synergistics & (weak) tail formation NPA TOFOR NBI+RF NBI late NBI+RF NBI early NBI

11. D majority modeling: PSTELION (V. Vdovin) e D beam D • Bo=3.6T; Neo=2.5 1019m-3; Teo=Tio=5.5keV • D beam modeled as 52keV Maxwellian, shifted in velocity space • 1000 poloidal modes: scenario dominated by FW • PAr@0.5% ~9%PRF: impurities could absorb a fraction of RF power

12. D majority modeling: CYRANO-BATCH Coupled full wave propagation/damping + quasi-linear diffusion simulations Counter-streaming xn v Co-streaming Non-Maxwellian (active) dielectric response from CYRANO (adaptive grid) Source trapped region Pitch angle scattering D beam BATCH energy distribution for 130keV

13. D majority modeling: CYRANO-BATCH Coupled full wave propagation/damping + quasilinear diffusion simulation X[Dbeam]=6.2% ~0.5m Doppler shift Pbeam/Ptot~40%

14. RF heated beam distribution:poloidal dependence Thermal subpopulation mv2/2 Fo(xn,v) Source RF induced tail Pitch angle scattering mv2/2 Fo HFS midplane mv2/2 Fo LFS midplane trapped co- passing co- passing counter- passing counter- passing

15. RF heated beam distribution: radial dependence Increased slowing down particle density ( 130keV) at inner surfaces Increased tail particle density (>130keV) at outer surfaces (Weak) tail formation r=0.4m r=0.1m ps: change in slowing down time due to Te increase was NOT accounted for in the iterations

16. D tail formation in (3He)-D MC expts f=33MHz & Bo=3.35/3.45T D tail observed (Ttail~300keV); evidence already discussed in 2004; supplementary info now 69388: 11% 3He 69392: 18% 3He 69393: 18% 3He 69392 69393 69388 PRF=4MW Gamma ray energy [MeV]

17. (3He)-D MC experiments: D tail evidence 69388 NPA 69388 TOFOR 5-6s 7-8s NPA 69392 TOFOR 69392 7-8s 7-8s 5-6s 5-6s 6-7s

18. (3He)-D MC experiments in JET: D beam modeling rho=0.02m, LFS midplane Cold cyclotron layer (Max.) Source rho=0.5m, LFS midplane 0.6 rho [m]

19. (3He)-D min-MC experiments in JET: Fuchs-Bers “beating” ~ idem total absorption: finite machine size effect T3He=10keV More points needed to complete the curve!! T3He=100keV

20. Preliminary conclusions from JET experiments • Synergistic effects NBI - RF: NBI preheating enhances RF heating efficiency • Doppler shifted resonance of beam D is important absorption mechanism even at low X[Dbeam] • Detailed distribution info from modeling suggests various diagnostics may see different aspects of same physics • Influence of 80keV vs. 130keV on D majority heating performance not yet clarified! • Influence of NBI characteristics on D tail formation in (3He)-D to be studied further Further investigation needed …

21. H beam heating in ITER • In search for heating scenario’s for non-activated phase ITER at half nominal field (2.65T) • H minority in 4He • Balanced H-4He • H majority • Preliminary computations only! • Beam modeled as Maxwellian with equivalent T • Simple FP modeling of beam (non-looped CYRANO-BATCH)

22. ITER half field scenario’s Main parameters (L-mode ITER case at half field from P.U.Lamalle): • B0 = 2.65T • IP = 7.5MA • T(0) = 6.2keV • T(a) = 0.2keV • aT = 2.0 • n(0) = 4.9 x 1019/m3 • n(a) = 3.2 x 1019/m3 • an = 0.55 • R0 = 6.2m • Z0 = 0 • D0 = 0.1m (parab.) •  = 1.5 (const.) • d = 0.1 (const.) • f = 40MHz • N = 33 • H-beam: Maxw@150keV

23. H minority in 4He (47.5% 4He + 5% thermal H) @ 6.2keV single pass scenario

24. Balanced H-4He: Doppler broadening To=6.2keV; 33.33%He4; 28.33%H@6.2keV; 5%H@150keV w= WH w= WH H beam

25. H majority (no beam) (thermal) H @ 6.2keV 30% single pass absorption

26. 5% H beam in H H @ 150keV H beam 60% single pass absorption

27. ITER NBI heating: source 500keV 8MW H beam L mode H mode Power density

28. H beam assisted H minority in 4He in ITER TH,beam=150keV Significant beam heating Doppler broadening ~1.4m Source: X[Hbeam]=0%, 0.5%, 1%, 2%, 3%, 4%, 5%

29. H beam assisted H majority in ITER TH,beam=150keV Significant beam heating Doppler broadening ~1m Source: X[Hbeam]=0%, 0.5%, 1%, 2%, 3%, 4%, 5%, 7%, 10%, 20%

30. ITER (Hbeam)-H H beam TH,beam= 150keV • Non-efficient single pass absorption (~30%) • Beam enhances RF efficiency • Beam heating dominates from very modest concentration onwards (~2%)

31. (BATCH) ITER H Beam distribution H minority in 4He PRFlaunched=20MW PRFtotH=17MW X[H]=5% modest source density -> modest RF power density H beam in 4He PRFlaunched =40MW PRFtotHbeam=7MW tauE=1.54s (X[H]~1%) Density profiles:

32. JET expts to test RF heating in non-activated ITER ? • Continue majority D experiments at higher freq? • Role Doppler shift being identified, retry Krasilnikov expts at33MHz (better coupling than at 25MHz + beam absorption on-axis) • Can we test the ITER H majority heating scenario in JET? • 42MHz @2.7T (or 51MHz @ 3.3T) • Fast ion diagnostics to identify tail (higher Ttail than D majority heating for same RF power) • No neutrons (+: no activation, -: less diagnostics) • (Re-)address H-3He heating • (H)-3He, balanced H-3He, H-(3He) • As (D)-T but more energetic tails • H beam and/or 3He beam (fake ITER’s D or T tail) • (Re-)address (3He)-D heating? • Investigate role of ICRH on D tail formation • Optimize D heating: beating effect, 3He conc. Scan, 80keV vs. 130keV beams

33. H beam assisted H majority in JET TH,beam=55keV Significant beam heating Doppler broadening ~0.5m Source shape X[Hbeam]=0%, 0.5%, 1%, 2%, 3%, 4%, 5%, 7%, 10%, 20%

34. Conclusions • A. Krasilnikov JET D majority experiments: • Combined NBI+RF heating beneficial; ICRH only nontrivial • RF+NBI synergism clearly demonstrated (Neut. camera, NPA, TOFOR) • Significant absorption at beam’s Doppler shifted cyclotron resonance • D tail formation in (3He)-D MC experiments • Evidence of D strong tail (gamma’s, NPA, TOFOR) • Likely thanks to Doppler-shifted D cyclotron resonance • Role of beating effect and MC efficiency not yet clarified! • Due to Doppler shift: “isolated” heating nontrivial • H beam heating in non-activated ITER phase: modeling • (H)-4He : good single pass absorption (even without beam) • H majority : NBI necessary to enhance single pass absorption • Beam heating starts to dominate at low concentrations • ITER’s volume requires significant power to ensure significant power densities to create hot populations (Max NBI/RF power in ITER?) • JET experiments to test non-activated ITER heating? • Continuation of majority D at higher frequency • H beam assisted majority H heating: similar performance to D heating but faster tails formed (& no neutrons)