1. ASIPP Overview of EAST H-mode Plasma Liang Wang*, J. Li, B.N. Wan, H.Y. Guo, Y. Liang, G.S. Xu, L.Q. Hu for EAST Team & Collaborators Institute of Plasma Physics, Chinese Academy of Sciences *Email: wliang@ipp.ac.cn 2 nd A3 Foresight Workshop on Spherical Torus, January 6 - 8, Tsinghua University, 2013 Beijing, China

2. ASIPP 2 Outline 2  Introduction  H-mode access & power threshold  ELM characteristics, energy loss and divertor power load  Active control of giant ELMs  Long pulse H-mode over 30 s in EAST  Summary and conclusion

3. ASIPP Experimental Advanced Superconducting Tokamak 3  Major radius: R 0 = 1.9 m  Minus radius: a = 0.5 m  Plasma duration: t=1000 s  Plasma current: I p = 1 MA  Toroidal field: B T = 3.5 T  Triangularity: δ = 0.3-0.65  SN/DN divertor configuration  Commenced operation on 26 Sept. 2006  First H mode on 7 Nov. 2010  H-mode duration over 30s on 28 May 2012  Divertor operation over 400s on 21 June 2012

4. ASIPP EAST Upgrade Capacity & Near-term Plan 4 RMP Coils (n=4)

5. ASIPP 5 Outline 5  Introduction  H-mode access & power threshold  ELM characteristics, energy loss and divertor power load  Active control of giant ELMs  Long pulse H-mode over 30 s in EAST  Summary and conclusion

6. ASIPP Lithium wall conditionings 6 Increasing Li Coverage (85% @2012 vs 30% @2010) Active Li injection to help operate long pulse H-mode Need one more oven for full surface coating.  Reduce recycling  Suppress impurities  Benefit ICRF &LHCD coupling  Mitigate ELMs

7. ASIPP H-mode threshold power 7 Threshold power of EAST H modes is aligned with predictions of the international tokamak scaling 2010 campaign 2012, dithering L  H transition  Threshold power shows no dependence on heating method  Appears to have a roll- over ne ~ 2.2  10 19 /m 3  Low density limit for H- mode access B.N. Wan et al., Nucl. Fusion 53, 104006 (2013)

8. ASIPP Unfavorable B  B facilitates H-mode access in EAST 8  H-mode access in EAST favors the divertor configuration with ion B× ∇ B drift away from the X-point, in contrast to other tokamaks.  Thus, LSN with reversed Bt facilitates access to H-modes  Type I ELMy H- mode in EAST was only achieved in LSN. Reversed Bt, 2010 campaign Normal Bt, 2012 H.Y. Guo et al., Nucl. Fusion 54, 013002 (2014) B  B ↓ B  B ↑

9. ASIPP 9 Outline 9  Introduction  H-mode access & power threshold  ELM characteristics, energy loss and divertor power load  Active control of giant ELMs  Long pulse H-mode over 30 s in EAST  Summary and conclusion

10. ASIPP Type-I ELMs in EAST 10  LSN with LHW+ICRH  Heating power: P heat ~1.5P LH  Good confinement: H 98 ~1  Lower density : n e /n G < 0.5  Repetition freq.: f ELM < 50 Hz  Peak heat flux: ~10 MWm -2 Contours of j s at UI (a), UO (b), LI (c) and LO (d) divertor targets for a typical Type-I ELMy H-mode. Divertor particle fluxes L. Wang et al., Nucl. Fusion 53, 073028 (2013)

11. ASIPP Type-I ELM power load, pedestal energy loss 11  Pedestal energy loss: ~ 8.5%  Divertor power load: ~ 5%  Most of Type I ELM ejected power is deposited on the outboard divertor Characteristics of divertor power load and peak heat flux for a Type I ELM. ELM energy loss and divertor heat load for two groups of coherent type-I ELMs in #41200 & #42556

12. ASIPP Compound ELMs in EAST 12  Characteristic: an initial ELM spike followed by a number of small ELMs.  Achieved in DN (δ=0.46) with LHW+ICRH, P heat ~1.3MW  Good confinement: H 98 ~1  Density: n e /n G >0.5  ELM frequency: f ELM ~50Hz  The plasma energy loss & div. power load: both ~ 4.5%.  Peak heat flux : between that of type-I and type-III ELMs.

13. ASIPP Essential difference between compound ELMs & ELM filaments: different time scale 13 Type-III ELM filaments observed by divertor LPs (left) and visible camera w/ BOUT++ (right).  The time scale of a compound ELM: a few ms  The interval time betw. adjacent ELM filaments: 150-250μs X.Q. Xu et al 24 th IAEA FEC

14. ASIPP Type-III ELMs in EAST 14  The most common ELMs observed in EAST up to now.  Achieved USN, DN, LSN   P heat ~P LH : LHW only, ICRF only, LHW+ICRF  f ELM =0.2-0.8kHz  n e /n G = 0.2-0.65  Confinement: H 98 = 0.5-0.8  No ∆ W dia was observed  ∆W div /W dia : 1-2%.  Peak heat flux: ~2MW/m 2. G. S. Xu et al., NF 51, 072001 (2011); L. Wang et al., NF 52, 063024 (2012)

15. ASIPP 15  Three diagnostics (Divertor LPs + IR camera + LFS Reciprocating LPs) independently demonstrated. L. Wang et al., submitted to Nucl. Fusion, December 2013 Scaling of divertor power footprint width in RF- heated type-III ELMy H-mode  In addition, the systematic experiments of EAST shows the inverse scaling is independent div-configuration (LSN, DN, USN).

16. ASIPP Very small ELMs in EAST (type-II like) 16  Achieved with LHW+ICRH, P heat ~1.7MW, q 95 ≥ 4.5  H 98 = 0.8-0.9, between type-I and type-III ELM regimes  High δ: very small ELMs  type-I ELMs when δ was reduced to ~ 0.4.  High density: n e /n G = 0.5 - 0.6  High freq: f ELM = 0.8-1.5kHz  Peak heat flux: < 1MWm -2 largely  No ∆W dia was observed  Broadband MHD mode: 20-50kHz L. Wang et al., Nucl. Fusion 53, 073028 (2013)

17. ASIPP 17 Outline 17  Introduction  H-mode access & power threshold  ELM characteristics, energy loss and divertor power load  Active control of giant ELMs  Long pulse H-mode over 30 s in EAST  Summary and conclusion

18. ASIPP Demonstrated for the 1 st time Edge magnetic topology change by LHCD 18 Helical Radiation Belts (helical current sheets) induced by LHCD Y. Liang, …, L. Wang et al., PRL 110, 235002 (2013)

19. ASIPP Strong mitigation of ELMs with LHCD 19  ICRF-dominated + 10Hz LHW modulation (LHW-off: 50ms ~ ½τ E )  H 98 =0.8; W dia | L  H : 50  100kJ  LHW off: f ELM ~150Hz  LHW on: ELMs disappear or sporadically appear w/ f ELM ~600Hz  Peak particle flux: ↓ by 2-4  W dia varied slightly: within ±5%  A quick reduction of Г i,div during inter-ELM can be seen when LHW was switched off. Y. Liang, …, L. Wang et al., PRL 110, 235002 (2013)

20. ASIPP 20 Collaborated with PPPL Demonstrated for the 1 st time ELM Pacing by Innovative Li-granule Injection  Triggering ELMs (~25 Hz) with 0.7 mm Li granules @ ~45 m/s.  ELM trigger efficiency after L-H transition: ~100%.  Much lower divertor particle/heat loads than intrinsic type-I ELMs. D. Mansfield et al., Nucl. Fusion 53, 113023 (2013) Li

21. ASIPP ELM control by SMBI 21 SMBI: Supersonic Molecular Beam Injection, Initially developed by SWIP.CN, successfully applied on HL-2A, KSTAR & EAST X. L. Zou et al., 24 th IAEA FEC, San Diego

22. ASIPP SHF can be actively controlled with SMBI 22  Striated Heat Flux (SHF ) region in the far-SOL can be actively controlled with SMBI.  Characteristic of LHCD heating scheme  SMBI significantly enhancing SHF, while reducing peak heat fluxes near strike point.  Achieving similar results with conventional gas puff or Ar seeding.

23. ASIPP SHF can be actively controlled by regulating edge particle fluxes 23  For SHF: q SHF ~ Γ i T ped, T ped ~ 350 eV  q SHF increases with Γ i.  At OST: q OST ~ Γ i T div, T div ~ Γ i -1,  q OST remains similar.  A unique physics feature of ergodized plasma edge by LHCD.  Allowing control of the ratio of q SHF /q OST, thus divertor power deposition area via control of divertor plasma conditions. J. Li, …, L. Wang et al., Nature Phys. 9, 817 (2013) L. Wang et al., submitted to PSI - 2014, invited talk

24. ASIPP 24 Achieved long pulse H-mode over 30s w/ small ELMs to minimize transient heat load  Predominantly small ELMs with H 98 ~ 0.9, between type-I and type-III ELMy H-modes.  Target heat flux is largely below 2 MW/m 2.  Accompanied by QCM, continuously removing heat and particles. J. Li, …, L. Wang et al., Nature Physics 9, 817 (2013)

25. ASIPP 25 Outline 25  Introduction  H-mode access & power threshold  ELM characteristics, energy loss and divertor power load  Active control of giant ELMs  Long pulse H-mode over 30 s in EAST  Summary and conclusion

26. ASIPP  Significant progress has been made on H-mode & ELMs toward long pulse operations in EAST on both technol. & phys. fronts. Various ELM dynamics and their behaviors have been characterized. LHCD leads to edge plasma ergodization, mitigating ELM transient heat load and broadening the divertor footprint. LHCD + SMBI allows control of SS target heat flux distribution by regulating divertor conditions. H-mode access in EAST favors the divertor configuration with ion B×  B drift away from the X-point, in contrast to other tokamaks. Achieved repeatable, long-pulse H-mode over 30 s successfully.  EAST is being upgraded with ITER-like W mono-block divertor and more than 20 MW CW H&CD, offering an exciting opportunity and great challenge for H-mode studies. Summary & Conclusion 26

27. ASIPP 27 Thank you! Welcome to join EAST experiments! We will be right here waiting for you … EAST – Test Bed for ITER

28. ASIPP Back up 28

29. ASIPP  Mo first wall  Water-cooled  Cryo-pump LFS & HFS wall: Graphite  Molybdenum 2012: Mo + graphite div. 2010: full graphite

30. ASIPP Type-III ELMs in EAST 30  The most common ELMs observed in EAST up to now.  Achieved in DN, LSN, USN  LHW only, ICRF only, LHW+ICRH, P heat ~P LH  Frequency: f ELM =0.2-0.8kHz  Density: n e /n G = 0.2-0.65  Confinement: H 98 =0.5-0.8  No ∆ W dia was observed  Divertor power load: 1-2%.  Peak heat flux: ~2MW/m 2.

31. ASIPP The very small ELMs are type-II like 31  Operation space of Type II ELMs: high δ, high κ, high n e, and high q 95  Confinement of Type II ELMs: H 98 being 10% less than Type I ELMs  Unique feature of Type II ELMs: w/ broadband MHD mode ( 30±10kHz@ASDEX-Upgrade; 10-40kHz@JET) ( 30±10kHz@ASDEX-Upgrade; 10-40kHz@JET) Time-frequency spectrum of Mirnov magnetic signal.

32. ASIPP Flexible boundary control with LHCD 32  The long pulse H-mode was achieved with dominant LHCD, with additional ICRH.  LHCD induces drives n=1 helical currents at edge, leading to 3D distortion of magnetic topology, similar to RMP  LHCD appears to be effective at controlling ELMs over a broad range q 95, in contrast to fixed RMP coils.