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 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 HL-2A HL
HL-2A tokamak-present status • R: 1.65 m • a: 0.40 m • B t : 1.2~2.7 T • Configuration: Limiter, LSN divertor • I p : 150 ~ 480 kA • n e : 1.0 ~ 6.0 x 10 19 m -3 • T e : 1.5 ~ 5.0 keV • T i : 0.5 ~ 2.8 keV Diagnostics: over 30, e.g. CXRS, MSE, ECEI… Heating: Fuelling system (H 2 /D 2 ): ECRH/ECCD: 5 MW Gas puffing (LFS, HFS, divertor) (6 X 68 GHz/0.5MW/1s, 2 X 140 GHz/1W/1s) Pellet injection (LFS, HFS) NBI (tangential) : 3 MW SMBI /CJI (LFS, HFS) LFS: f =1~80 Hz, pulse duration > 0.5 ms LHCD: 2 MW (4/3.7 GHz/500 kW/2 s) gas pressure < 3 MPa HL HL-2A 2
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 HL HL-2A 3
Two types of LCO during L-I-H 2 I L H D (a.u.) 1.5 D (a.u.) 1 (a) 1 f (kHz) 15 80 0.5 V f 10 (b) 40 5 500 505 510 515 520 525 530 200 f (kHz) 150 15 t(ms) B / t 150 100 10 100 50 5 (c) I-phase H L 0.8 6 10 21 (eVm -4 ) Envelope of ne(a.u.) (d) r P e 5 3 4 0.6 2 3 2 1 -1 ) 0.4 (e) -<E r >(kvm 6 2 3 5 2 1 4 0.2 1 3 0.6 510 520 3 RMS (n e ) t (ms) 0.4 (f) 0.2 0.4 0.6 0.8 1.0 0.2 e |E r |/<T e > 500 505 510 515 520 525 530 t (ms) Two types of LCO (type-Y and type-J) observed during L-I-H Type-Y: turbulence leads E r, Type-J: E r leads turbulence P is the key, and jumps before I-H J. Cheng, PRL 2013; J. Dong, FEC 2014, EX/11-3; Y. Xu, EPS 2014 HL-2A HL 4
Possible interpretation of different LCOs Type-Y Zonal flow Turbulence (predator) (prey) Type-J P Y. Xu, EPS 2014 Turbulence (prey) (predator) For the change of type-Y to type-J, It seems that P must be large enough ! E r oscillation HL-2A HL 5
Outward propagation w/ MHD crash After the mode crash, plasma profile becomes flat: Edge P increases ! E r xB shear flow increases suppress turbulence H-mode # 19391 I-phase H D (a.u.) # 19385 1 (a) 2.5 -3 ) 0.5 19 m 2.0 n e ( 10 10 8 f (kHz) 15 B / t (b) 6 before crash 4 1.5 10 2 after crash 0.6 B / t Radial outward propgagation of (c) -0.6-0.4-0.2 0 0.2 0.4 0.6 0.4 RMS thermal flux observed in ECE signals Normalized R 0.2 (f) 0.9 r= 8 cm n el (10 19 m -3 ) 1.2 2 r=3.5 cm 0.8 r= 11 cm #19385 1.9 1 0.7 r=10.5 cm T e (keV) (d) r= 14 cm 1.8 T e (keV) r=17.5 cm 0.8 0.6 r= 16.5 cm 0.6 0.5 r= 20 cm r=8 cm 0.4 T e (keV) 0.8 0.4 before crash r= 22.5 cm after crash 0.2 r=11 cm 0.3 (e) 0.6 r= 26.5 cm r=20 cm 0 140 160 180 200 500 502 504 506 508 510 512 0.4 R (cm) 500 502 504 506 508 510 512 512 t (ms) t (ms) Y. Xu, EPS 2014 & PPCF 2014 HL-2A HL 6
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 physics loss by MHD instabilities • Interaction b/w NTMs & non-local transport ELM mitigation Impurity transport Summary & outlook HL-2A HL 7
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 HL HL-2A 8
Quasi-coherent mode before and between ELMs Density fluctuation Pedestal density gradient Mode intensity Quasi-coherent modes observed during ELM-free period & b/w ELMs; Quasi-coherent mode: 50-100kHz; k θ ~0.43 cm -1 (electron diamagnetic direction ~8km/s), k r ~1 cm -1 (inward) , n =7 (counter I p ); Mode excitation relates to pedestal saturation. W. Zhong, FEC 2014, EX/P7-23 HL HL-2A 9
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 HL-2A HL 10
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. Auto-bicoherence & summed auto- bicoherence of Mirnov signals, indicating nonlinear interaction among low-frequency fluctuations and AEs. W. Chen, FEC 2014, EX/P7-27 HL-2A HL 11
Up- and down sweeping RSAEs Up sweeping Down sweeping Shot I BAE MAG Shot II Up sweeping Down Typical discharges with the sweeping modes on Spectrogram of Mirnov signal for shot I (top) BAE sweeping HL-2A. The blue and red lines are and shot II (bottom). W. Chen, NF, 2014 corresponding to shot I and shot II, respectively. Down-sweeping frequency MHD modes during I p ramp-up (NBI+ECRH); up- sweeping frequency MHD modes before sawtooth crash during I p 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. MAG By kinetic Alfven eigenmode simulation, down-sweeping identified to be KRSAE, and up-sweeping is RSAE in ideal or kinetic MHD limit. HL-2A HL 12
Transitions b/w fishbone & LLM Transition from LLM to fishbone Transition from fishbone to LLM Transition from LLM to fishbone and backward transition from fishbone to LLM were observed during NBI heating; f LLM 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. L. Yu, FEC 2014, EX/P7-25 HL HL-2A 13
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 HL-2A HL 14
Observation of fast ion loss by SLIP 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. Y. Zhang, FEC 2014, EX/P7-24 & RSI 2014 HL HL-2A 15
NTM onset during non-local transport No: 19455 1.5 P ECRH (MW) (a) 1 0.5 <n e > (10 19 m -3 ) 0 400 600 800 1000 (b) NTM onset 3/2 mode onset T e (keV) 2 SMBI 1.5 = 0.01 1 0.25 0.32 0.46 0.5 0.53 0.65 0.76 0 400 600 800 1,000 Time (ms) NTMs driven by the transient perturbation of local T e induced by non-local transport. ─ The NTM is located at the inversion surface of non-locality. ─ The NTM onset is related to largest ▽ T e around the reversion surface. X. Ji, FEC 2014, EX/6-4 HL HL-2A 16
Avalanche characteristics for non-locality Before SMBI During No:18938 = 2 0.24 T e (keV) 1.5 0.45 0.51 1 0.70 0.81 0.5 520 530 540 550 560 570 580 Time (ms) Before non-local transport During non-local transport Enhanced-avalanche characteristics during non-local transport ─ During non-locality, larger decorrelate time lag and Hurst parameters X. Ji, FEC 2014, EX/6-4 ─ Longer range of inward and outward radial heat flux propagation ─ Long radial propagation broken near the q=3/2 surface (NTM) HL-2A HL 17
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