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25th IAEA FUSION ENERGY CONFERENCE OV/4-1 Ov Over ervie view of of Rec ecent ent Experi periments ments on on HL HL-2A A M. Xu on behalf of HL-2A team & collaborators Southwestern Institute of Physics, Chengdu, China In

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SLIDE 1

HL HL-2A

  • M. Xu on behalf of HL-2A team & collaborators

Southwestern Institute of Physics, Chengdu, China

Ov Over ervie view of

  • f Rec

ecent ent Experi periments ments on

  • n HL

HL-2A A

25th IAEA FUSION ENERGY CONFERENCE OV/4-1

In collaboration with

USTC, ASIPP, Hefei, China CEA\IRFM, Cadarache, France University of California, San Diego, USA MPI für Plasmaphysik, IPP-Juelich, Germany NIFS, Toki, Japan CCFE, Abingdon, UK

Acknowledgements

GA, PPPL, LLNL, UCI, UCLA, UCSD, USA JAEA, Kyushu Uni., Japan FOM Institute DIFFER, The Netherlands ENEA, Frascati, Italy Kurchatov Institute, Russia WCI, NFRI, Korea HUST, IOP, Tsinghua Uni.,PKU,SCU, China

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SLIDE 2

HL HL-2A

  • R:

1.65 m

  • a:

0.40 m

  • Bt:

1.2~2.7 T

  • Configuration:

Limiter, LSN divertor

  • Ip:

150 ~ 480 kA

  • ne:

1.0 ~ 6.0 x 1019 m-3

  • Te:

1.5 ~ 5.0 keV

  • Ti:

0.5 ~ 2.8 keV Heating: ECRH/ECCD: 5 MW

(6 X 68 GHz/0.5MW/1s, 2 X 140 GHz/1W/1s)

NBI (tangential): 3 MW LHCD: 2 MW (4/3.7 GHz/500 kW/2 s) Diagnostics: over 30, e.g. CXRS, MSE, ECEI… Fuelling system (H2/D2): Gas puffing (LFS, HFS, divertor) Pellet injection (LFS, HFS) SMBI /CJI (LFS, HFS)

LFS: f =1~80 Hz, pulse duration > 0.5 ms gas pressure < 3 MPa

HL-2A tokamak-present status

2

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SLIDE 3

HL HL-2A

Outline

 H-mode physics and pedestal dynamics

  • Two types of LCO in the I-phase of L-I-H transition
  • Role of MHD modes in triggering I-H transition
  • Role of impurities in H-I transition
  • Quasi-coherent mode before and between ELMs

 MHD & energetic particle physics

  • Shear Alfven wave & nonlinear interaction with TMs
  • Transitions among low-frequency MHD modes
  • Energetic particle loss induced by MHD instabilities
  • Interaction b/w NTMs & non-local transport

 ELM mitigation  Impurity transport  Summary & outlook

3

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SLIDE 4

HL HL-2A

4

Two types of LCO during L-I-H

0.2 0.4 0.6 0.8 1.0 0.2 0.4 0.6 0.8 e|Er|/<Te> Envelope of ne(a.u.) 500 505 510 515 520 525 530 0.5 1 1.5 t(ms) D(a.u.) 1 3 H I-phase L 2 2 1 2 3 1 3

 Two types of LCO (type-Y and type-J) observed during L-I-H  Type-Y: turbulence leads Er, Type-J: Er leads turbulence  P is the key, and jumps before I-H

1 2 D(a.u.) f (kHz) 5 10 15 40 80

2 3 4 5 6

rPe

f (kHz) 5 10 15 50 100 150 200 510 520 3 4 5 6 t (ms)

  • <Er>(kvm
  • 1)

100 150

500 505 510 515 520 525 530 0.2 0.4 0.6 t (ms) RMS (ne)

H I

  

Vf

1021 (eVm-4)

B/t

L (a) (b) (d) (e) (f)

(c)

  • J. Cheng, PRL 2013; J. Dong, FEC 2014, EX/11-3; Y. Xu, EPS 2014
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SLIDE 5

HL HL-2A

5

Possible interpretation of different LCOs

Turbulence (prey) Zonal flow (predator) Turbulence (predator) P (prey)

Er oscillation

For the change of type-Y to type-J, It seems that P must be large enough !

Type-Y Type-J

  • Y. Xu, EPS 2014
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SLIDE 6

HL HL-2A

6

Outward propagation w/ MHD crash

After the mode crash, plasma profile becomes flat:  Edge P increases !  ErxB shear flow increases  suppress turbulence  H-mode

500 502 504 506 508 510 512 512 0.4 0.6 0.8

Te (keV)

t (ms) 0.5 1

D(a.u.) f (kHz)

10 15 2 4 6 8 10 0.2 0.4 0.6

RMS

1.8 1.9 2

nel (1019m-3)

500 502 504 506 508 510 512 0.3 0.4 0.5 0.6 0.7 0.8 0.9 t (ms)

Te (keV) r=3.5 cm r=10.5 cm r=17.5 cm r=20 cm B/t B/t r=11 cm

(b) (c) (d) (e)

r= 14 cm

(f)

Radial outward propgagation of thermal flux observed in ECE signals H

(a)

I-phase r= 16.5 cm r= 26.5 cm r= 8 cm r= 11 cm r=8 cm r= 20 cm r= 22.5 cm

  • 0.6-0.4-0.2 0 0.2 0.4 0.6

1.5 2.0 2.5 Normalized R ne (10

19 m

  • 3)

before crash after crash

# 19385

# 19391

140 160 180 200 0.2 0.4 0.6 0.8 1 1.2 #19385

R (cm) Te (keV)

before crash after crash

  • Y. Xu, EPS 2014 & PPCF 2014
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SLIDE 7

HL HL-2A

7

 H-mode physics and pedestal dynamics

 Two types of LCO in the I-phase of L-I-H transition  Role of MHD modes in triggering I-H transition

  • Role of impurities in H-I transition
  • Quasi-coherent mode before and between ELMs

 MHD & energetic particle physics

  • Shear Alfven wave & nonlinear interaction with TMs
  • Transitions among low-frequency MHD modes
  • Energetic particle physics loss by MHD instabilities
  • Interaction b/w NTMs & non-local transport

 ELM mitigation  Impurity transport  Summary & outlook

Outline

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SLIDE 8

HL HL-2A

8

Impurity induced H-I-H transitions

Oscillations lead to: Considerable particle loss； Reduce the pedestal gradient； Reduce impurity density.  Impurity induced H-I transition

W.L. Zhong, EPS 2014

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SLIDE 9

HL HL-2A

9

  • Quasi-coherent modes observed during ELM-free period & b/w ELMs;
  • Quasi-coherent mode: 50-100kHz; kθ~0.43 cm-1 (electron diamagnetic

direction ~8km/s), kr~1 cm-1 (inward) , n =7 (counter Ip );

  • Mode excitation relates to pedestal saturation.

Pedestal density gradient Mode intensity Density fluctuation

  • W. Zhong, FEC 2014, EX/P7-23

Quasi-coherent mode before and between ELMs

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SLIDE 10

HL HL-2A

10

 H-mode physics and pedestal dynamics

 Two types of LCO in the I-phase of L-I-H transition  Role of MHD modes in triggering I-H transition  Role of impurities in H-I transition  Quasi-coherent mode before and between ELMs

 MHD & energetic particle physics

  • Shear Alfven wave & nonlinear interaction with TMs
  • Transitions among low-frequency MHD modes
  • Energetic particle loss induced by MHD instabilities
  • Interaction b/w NTMs & non-local transport

 ELM mitigation  Impurity transport  Summary & outlook

Outline

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SLIDE 11

HL HL-2A

11 Auto-bicoherence & summed auto- bicoherence of Mirnov signals, indicating nonlinear interaction among low-frequency fluctuations and AEs.

Generation of n=0 mode by coupling

  • Axis-symmetric n=0 MHD mode

was observed in the presence strong AEs & TMs;

  • Nonlinearly generated via

i) BAE & TM coupling  EGAM ii) TAE & TM coupling

  • Could be one of the

mechanisms for energy cascade in EP driven turbulence.

  • W. Chen, FEC 2014, EX/P7-27
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SLIDE 12

HL HL-2A

12

Down sweeping Down sweeping Up sweeping Up sweeping BAE BAE MAG MAG

Typical discharges with the sweeping modes on HL-2A. The blue and red lines are corresponding to shot I and shot II, respectively. Spectrogram of Mirnov signal for shot I (top) and shot II (bottom).

  • Down-sweeping frequency MHD modes during Ip ramp-up (NBI+ECRH); up-

sweeping frequency MHD modes before sawtooth crash during Ip plateau and NBI.

  • Both propagate poloidally in ion diamagnetic drift direction and toroidally co-

current direction in the lab frame, with n=2-5, and m=n.

  • By kinetic Alfven eigenmode simulation, down-sweeping identified to be KRSAE,

and up-sweeping is RSAE in ideal or kinetic MHD limit.

Shot I Shot II

Up- and down sweeping RSAEs

  • W. Chen, NF, 2014
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SLIDE 13

HL HL-2A

13

Transitions b/w fishbone & LLM

Transition from LLM to fishbone Transition from fishbone to LLM

  • L. Yu, FEC 2014, EX/P7-25

 Transition from LLM to fishbone and backward transition from fishbone to LLM were

  • bserved during NBI heating;

 fLLM is higher than toroidal rotation frequency, but close to the precessional frequency of trapped energetic ions generated by NBI.  This observed LLM is energetic particle mode or saturated fishbone excited by the trapped energetic ions.

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SLIDE 14

HL HL-2A

14

 H-mode physics and pedestal dynamics

 Two types of LCO in the I-phase of L-I-H transition  Role of MHD modes in triggering I-H transition  Role of impurities in H-I transition  Quasi-coherent mode before and between ELMs

 MHD & energetic particle physics

 Shear Alfven wave & nonlinear interaction with TMs  Transitions among low-frequency MHD modes

  • Energetic particle loss induced by MHD instabilities
  • Interaction b/w NTMs & non-local transport

 ELM mitigation  Impurity transport  Summary & outlook

Outline

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SLIDE 15

HL HL-2A

15  Fast-ion loss induced by MHD instabilities measured by a fast-ion loss probe (SLIP).  Compared with long-lived mode (LLM), the spot induced by sawtooth crash has a broad range in energy and pitch.  Interactions between MHD instabilities and energetic ions causes the fast-ion losses with the wide range of energy and pitch angle.

Observation of fast ion loss by SLIP

  • Y. Zhang, FEC 2014, EX/P7-24 & RSI 2014
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SLIDE 16

HL HL-2A

400 600 800 1000 0.5 1 1.5 400 600 800 1,000 0.5 1 1.5 2 Time (ms)

(b)

No: 19455 (a) PECRH (MW) <ne> (1019m-3) SMBI Te (keV)

0.01 0.25 0.32

=

0.46 0.53 0.65 0.76

3/2 mode onset NTM onset 16

 NTMs driven by the transient perturbation of local Te induced by non-local transport.

NTM onset during non-local transport

─ The NTM is located at the inversion surface of non-locality. ─ The NTM onset is related to largest ▽Te around the reversion surface.

  • X. Ji, FEC 2014, EX/6-4
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SLIDE 17

HL HL-2A

17

Avalanche characteristics for non-locality

During non-local transport Before non-local transport

 Enhanced-avalanche characteristics during non-local transport

─ During non-locality, larger decorrelate time lag and Hurst parameters

─ Longer range of inward and outward radial heat flux propagation ─ Long radial propagation broken near the q=3/2 surface (NTM)

  • X. Ji, FEC 2014, EX/6-4

520 530 540 550 560 570 580 0.5 1 1.5 2 Time (ms) Te (keV) No:18938 0.51 0.24 0.45 0.70 0.81

 =

SMBI During Before

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SLIDE 18

HL HL-2A

18

 H-mode physics and pedestal dynamics

 Two types of LCO in the I-phase of L-I-H transition  Role of MHD modes in triggering I-H transition  Role of impurities in H-I transition  Quasi-coherent mode before and between ELMs

 MHD & energetic particle physics

 Shear Alfven wave & nonlinear interaction with TMs  Transitions among low-frequency MHD modes  Energetic particle loss induced by MHD instabilities  Interaction b/w NTMs & non-local transport

 ELM mitigation  Impurity transport  Summary & outlook

Outline

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SLIDE 19

HL HL-2A

19

2.7 3.0 0.5 1 150 200 460 560 660 1.5 3.0 t (ms)

33%

D (a.u.)

19% 20% Ti/Ti=31%

Ti (eV) (b) (c) 1/ELM (kHz) <ne> (1019m-3) shot 22497 (a) (d)

0.24 0.48 0.72 1 3 5 7 Ti/Ti fpost/fpre (a)

0.12 0.24 0.36 1 3 5 7 Vt/Vt fpost/fpre (b)

 ELM mitigation only induced by significant amount of SMBI injection. NO mitigation for first 2 SMBI (Ti dropped by ~20%) and mitigation for the last 3 SMBI (Ti dropped by ~ 30%);  Seems that thresholds of ~20% on δTi/Ti and 13% on δVT/VT are associated with successful mitigation

Ti & VT decrease associated with ELM mitigation

  • D. Yu, FEC 2014, EX/P7-20
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SLIDE 20

HL HL-2A

20

Vertical profile of CIV and CIII measured in HL-2A

1.2 1.4 1.6 1.8 2 2.2 2.4

  • 0.8
  • 0.6
  • 0.4
  • 0.2

0.2 0.4 R (m) Z (m) Targets Baffles Throat Dome Moveable limiter Viewing area of spectrometer Fixed limiters R (m)

2 4 6 8 10 12 1 2 3 4 5 6 #14158 #14181 CIV/ne (arb.) ne (x1013 cm-3) (a) Exp. 1 2 3 4 5 1 2 3 4 5 6 CIV/ne (10-19 W cm) ne (1013 cm-3) (b) Chem+Phys Chem+ Enhanced Phys Model.

0.2 0.4 0.6 0.8 1.0 1.2

  • 10
  • 20
  • 30
  • 40
  • 50

Divertor source Baffle source Wall source CIV Z (cm) Model.

2 4 6 8

  • 10 -20 -30 -40 -50

CIV (X104 Counts/ch) Z (cm) Limiter source Baffle source Exp. 0.5 1.0 1.5 2.0

  • 10 -20 -30 -40 -50

Z (cm) CIV(x104Counts/ch)

  • Div. plate source

Baffle source Exp.

Impurity profile changes for different source locations 3D modeling suggests that both poloidal asymmetry of impurity flow profile and an enhanced physical sputtering play important role in impurity distribution and its screening efficiency in SOL

Impurity transport studies in SOL

  • Z. Cui, FEC 2014, EX/P7-26
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SLIDE 21

HL HL-2A

21

 H-mode physics and pedestal dynamics

 Two types of LCO in the I-phase of L-I-H transition  Role of MHD modes in triggering I-H transition  Role of impurities in H-I transition  Quasi-coherent mode before and between ELMs

 MHD & energetic particle physics

 Shear Alfven wave & nonlinear interaction with TMs  Transitions among low-frequency MHD modes  Energetic particle loss induced by MHD instabilities  Interaction b/w NTMs & non-local transport

 ELM mitigation  Impurity transport  Summary & outlook

Outline

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SLIDE 22

HL HL-2A

22

Summary

 H-mode physics and pedestal dynamics

 Two types of LCO, type-Y & type-J observed, P is the key for LCO transition.  MHD mode crash  edge P increases  triggering I-H transition  LCOs lead to particle loss, reduce grad_n & impurity, impurity induced I-H-I

transition

 Quasi-coherent mode relates to pedestal saturation.

 MHD & energetic particle physics

 BAEs and TAEs can interact with TMs and generate n=0 axi-symmetric mode;  Up- and down sweeping RSAEs were identified.  Transitions between fishbone and LLM observed.  Energetic particle loss by MHD was measured by SLIP.  SMBI induced non-locality can be explained by avalanche, and NTM at q=3/2

breaks non-local transport  ELM mitigation & impurity transport

Ti & VT reduction associated by ELM mitigation was measured Impurity profiles found to be sensitive to different impurity source locations.

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SLIDE 23

HL HL-2A

23

Outlook

 HL-2A

  • Heating upgrade: 2MW LHCD, 5MW ECRH, 3MW NBI,
  • Diagnostics development: ECEI, MSE, BES, GPI, DBS, CXRS …
  • Transport: H-mode physics, impurity transport, momentum transport
  • MHD instability (RWM, NTM), NTM & saw tooth control by ECRH;
  • 3D effects: on ELM control, plasma flow, ZF and turbulence, L-H transition

threshold, plasma displacement;

  • Energetic particles: EP driven mode identification, EP loss and control of EP

induced instabilities  HL-2M (upgrade of HL-2A)

  • Parameters: R=1.78m, a=0.65m, Bt=2.2T, Ip=2.5MA, Heating~ 25MW,

triangularity=0.5, elongation=1.8-2.0

  • Mission: advanced divertor (snowflake, tripod), PWI at high heat flux, high

performance, high beta, and high bootstrap current plasma

  • Commission planned end of 2015
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SLIDE 24

HL HL-2A

24

HL-2A Contributions to this conference

Xu, Y. EX/P8-18 Fri. PM Xu, Yuan EX/P7-19 Fri. AM Yu, D.L. EX/P7-20 Fri. AM Nie, L. EX/P7-22 Fri. AM Wang, A. TH/P5-5 Thu. AM

  • Wang. Z. TH/P7-30 Thu. AM

He, H. TH/P2-13 Tue. PM Zheng, G. TH/3-1Rb Wed. 17:00 PM .... Dong, J. EX/11-3 Sat. 11:30 AM Ji, X. EX/6-4 Thu. 3:20 PM Zhong, W. EX/P7-23 Fri. AM Yu, L. EX/P7-25 Fri. AM Cheng, J. EX/P7-32 Fri. AM Chen, W. EX/P7-27 Fri. AM Cui, Z. EX/P-26 Fri. AM Zhang, Y. EX/P7-24 Fri. AM Liu, Y. EX/P7-18 Fri. AM Dong, Y. EX/P7-31 Fri. AM

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SLIDE 25

HL HL-2A

25

Thanks for your attention!

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SLIDE 26

HL HL-2A

26

  • Spec. of DBS signal

f=34GHz, X-mode

  • Spec. of DBS signal

f=17GHz, O-mode

  • Spec. of DBS signal

f=23GHz, O-mode

  • Spec. of DBS signal

f=48GHz, X-mode Density fluctuations of BAEs and EGAM measured by Doppler back scattering (DBS). Experimental results indicate the EGAM structure is global and frequencies are constant (eigenmode) in the radial direction. Internal fluctuations of EGAM observed by different diagnostic methods.

BAE1

Low density Ohmic heating

Backup: Why is EGAM?

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SLIDE 27

HL HL-2A

27

Backup: Why is EGAM?

fEGAM/fGAM<1 in core plasma. Consistent with theory and simu. predictions.

Fu, PRL08; Nazikian, PRL08; Wang, PRL13

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SLIDE 28

HL HL-2A

28

Multi-transition between I-phase and H-mode

LCOs cause considerable particle loss and reduce the pedestal gradient and the impurity density.  The radiation power is increasing during the H-mode phase . Impurity density and radiation power continually increases for around 2 ms after the H-I transition. LCOs Type-J LCO W.L. Zhong, and et. al. 2014 EPS, Berlin, Germany A A co counter-clockwise e di direction bet between |V |VE

E ×B|

| an and ne

RMS,

, LCO rad adial ally pr propagates outw

  • utward in

n ped pedes estal l region.

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SLIDE 29

HL HL-2A

29

Mode intensity vs. pedestal gradient during statistic ELM cycle

 The mode is also observed during inter- ELMs by reflectometers.  n =7 (counter current direction), kθ ~ 0.43 cm-1(Electron diamagnetic direction)  Mode excitation is related to the saturation of the pedestal

Pedestal top Mid pedestal Pedestal base Three ELMs

Pedestal instabilities during Inter-ELMs

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SLIDE 30

HL HL-2A

30

The radial eigenfunction of a RSAE is obtained by a kinetic Alfvén eigenmode code (KAEC), which is a non-perturbative kinetic MHD eigenvalue code. By solving the vorticity equation using the finite element method, The KAEC can calculate the mode structures in general tokamak geometry with finite pressure. KAEC calculations of the eigenfunction of n=2 and n=3 down- sweeping RSAEs with the two different qmin. The RSAEs are highly localized near qmin. The m=n poloidal harmonic are dominant. The mode frequency drops as qmin decreasing. If ignoring the FLR effects, the modes do not

  • ccur. So the RSAEs are

kinetic, but not ideal instabilities. In the same case, the ideal MHD code, NOVA-K, does not find the down- sweeping modes.

Simulation for DS-RSAE Activities

Simulation of RSAE by KAEC

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SLIDE 31

HL HL-2A

31

Impact of NTM on non-local transport

Without NTM during non-locality With NTM during non-locality

3/2 NTM

The damping effect of NTM on non-local transport Reduction of avalanche features with NTM in non-locality

─ With NTM, lower intensity of avalanches ─ H parameter much smaller than without NTM in plasma core ─ Long radial propagation clearly broken near the q=3/2 surface (NTM)