An overview of the energetic electron induced instabilities with high-power ECRH on HL-2A

Ding, X.T.; Chen, W.; Yu, Lu; Chen, S.Y; Dong, J. Q.; Ji, Xia; Shi, Z.B.; Zhou, Yadong; Dong, Y.B.; Huang, Xianli; Li, J.X.; Zhang, Y.P.; Song, Xiao Yan; Zhou, J.; Rao, Jun; Cao, Jianyong; Huang, M.; Feng, B.B.; Cui, Z.Y.; Huang, Yusheng; Liu, Yi; Yan, L.W.; Yang, Qingwei; Duan, X.R.; Liu, Y.

doi:10.1088/0029-5515/53/4/043015

Cited by 30 publications

(36 citation statements)

References 26 publications

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“…A careful experimental analysis to characterize the direction of propagation of the electron fishbone mode has been performed on HL-2A tokamak [25][26][27][28][29], where mode frequency of energetic electron driven fishbones during off-axis ECRH on both HFS and low field side (LFS) was studied. In particular, in [25] barely circulating energetic electrons were considered responsible to drive electron fishbones during off-axis ECRH on the LFS, whereas both barely circulating and barely trapped energetic electrons were considered responsible to drive electron fishbones during HFS heating.…”

Section: Experimental Evidences Of Energetic Electron Driven Fishbonesmentioning

confidence: 99%

Theory and modeling of electron fishbones

et al. 2016

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Internal kink instabilities exhibiting fishbone like behavior have been observed in a variety of experiments where a high energy electron population, generated by strong auxiliary heating and/or current drive systems, was present. After briefly reviewing the experimental evidences of energetic electrons driven fishbones, and the main results of linear and nonlinear theory of electron fishbones, the results of global, self-consistent, nonlinear hybrid MHD-Gyrokinetic simulations will be presented. To this purpose, the extended/hybrid MHD-Gyrokinetic code XHMGC will be used. Linear dynamics analysis will enlighten the effect of considering kinetic thermal ion compressibility and diamagnetic response, and kinetic thermal electrons compressibility, in addition to the energetic electron contribution. Nonlinear saturation and energetic electron transport will also be addressed, making extensive use of Hamiltonian mapping techniques, discussing both centrally peaked and offaxis peaked energetic electron profiles. It will be shown that centrally peaked energetic electron profiles are characterized by resonant excitation and nonlinear response of deeply trapped energetic electrons. On the other side, off-axis peaked energetic electron profiles are characterized by resonant excitation and nonlinear response of barely circulating energetic electrons which experience toroidal precession reversal of their motion.

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Section: Experimental Evidences Of Energetic Electron Driven Fishbonesmentioning

confidence: 99%

Theory and modeling of electron fishbones

et al. 2016

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“…In particular, TAE modes driven by EP beam with a one-third Alfven speed are extensively observed in experiment. In many auxiliary heating experiments, for example, NBI, ECRH/ICRH (electron/ion cyclotron resonant heating), LH (lower hybrid wave heating) and so on, TAE modes are extensively observed [11][12][13]. The TAE instabilities often induce large fast particles loss and eject a great amount of EPs which can damage first wall of vacuum cell of tokamak.…”

Section: Nuclear Fusionmentioning

confidence: 99%

Simulation of toroidicity-induced Alfven eigenmode excited by energetic ions in HL-2A tokamak plasmas

Cheng

Dong

et al. 2018

Nucl. Fusion

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The toroidicity-induced Alfven eigenmode (TAE) excited by energetic (fast) ions was first simulated using the GTC code for HL-2A experiments. The simulation results indicate that the fraction of energetic ions is about 3% in the experiments. The critical density of energetic ions to excite the TAE mode is around 0.023, which is in good agreement with the theoretical expectation of 0.026. The real frequency of TAE with toroidal mode number n = 3 is around 211 kHz and is inversely proportional to the square root of electron density, which is quantitatively in agreement with the experimental observation (Ding et al 2013 Nucl. Fusion 53 043015). The frequency is in resonance with the summations of toroidal precession frequency and transit frequency of passing energetic ions, indicating that resonance with passing energetic ions is dominant for the excitation of the modes in the experiment. It is also checked by the phase space structures of |δf h | 2 (strength of energetic particle distribution function) that the TAE modes are mainly induced by passing energetic ions in HL-2A. The growth rates of TAE modes increase with fast ion density and its gradient. In addition, lower n TAE modes, such as n = 1 can also be driven by energetic ions when off-axis heating with higher beam energy is employed in the experiment. The width of radial mode structures for lower n modes is usually wider than those for higher n modes. The perpendicular wave vector of the modes and Larmor radius of ions satisfy the relation |k ⊥ ρ Li | 2 1. Finally, the polarization of the mode shows that the perturbed parallel electric field is much smaller than the electrostatic parallel electric field.

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“…Recently, new experimental phenomena, e.g. coexistence of multi-Alfvenic modes [6] induced by energetic electrons and the frequency jump of electron fishbone (e-fishbone) modes [29] during high-power ECRH, have been observed. These new results may contribute to the understanding of the underlying physics mechanism for the excitation of the low-frequency (LF) Alfvenic and acoustic fluctuations.…”

Section: Ep Physicsmentioning

confidence: 99%

An overview of recent HL-2A experiments

Duan¹,

Ding²,

Dong³

et al. 2013

Nucl. Fusion

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For the firsttime supersonic molecular beam injection (SMBI) and cluster jet injection (CJI) were applied to mitigate edge-localized modes (ELMs) in HL-2A successfully. The ELM frequency increased by a factor of 2-3 and the heat flux on the divertor target plates decreased by 50% on average after SMBI or CJI. Energetic particle induced modes were observed in different frequency ranges with high-power electron cyclotron resonance heating (ECRH). The high frequency (200-350kHz) of the modes with a relatively small amplitude was close to the gap frequency of the toroidicity-induced Alfven eigenmode. The coexistent multi-mode magnetic structures in the high temperature and low-collision plasma could affect the plasma transport dramatically. Long-lived saturated ideal magnetohydrodynamic instabilities during strong neutral beam injection heating could be suppressed by high-power ECRH. The absolute rate of nonlinear energy transfer between turbulence and zonal flows was measured and the secondary mode competition between low-frequency (LF) zonal flows (ZFs) and geodesic acoustic modes (GAMs) was identified, which demonstrated that ZFs played an important role in the L-H transition. The spontaneously generated E × Bshear flow was identified to be responsible for the generation of a large-scale coherent structure (LSCS), which provided unambiguous experimental evidence for the LSCS generation mechanism. New meso-scale electric potential fluctuations (MSEFs) at frequency f ∼ 10.5 kHz with two components of n = 0 and m/n = 6/2were also identified in the edge plasmas for the first time. The MSEFs coexisted and interacted with magnetic islandsof m/n = 6/2, turbulence and LF ZFs.

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An overview of the energetic electron induced instabilities with high-power ECRH on HL-2A

Cited by 30 publications

References 26 publications

Theory and modeling of electron fishbones

Theory and modeling of electron fishbones

Simulation of toroidicity-induced Alfven eigenmode excited by energetic ions in HL-2A tokamak plasmas

An overview of recent HL-2A experiments

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