Observation of toroidal Alfvén eigenmode excited by energetic electrons induced by static magnetic perturbations in the EAST tokamak

Chu, Nan; Sun, Yuan; Gu, Shuai; Wang, H.H.; Hu, Yuan; Shi, Tonghui; Chen, D.L.; Gu, Xiaoxia; He, Kang; Jia, M.; Lin, Shiyao; Liu, H.Q.; Qian, J.; Ren, Jie; Shen, Biao; Ti, Ang; Wang, S.X.; Xie, Jinlin; Xu, M.; Xue, Minmin; Niu, Y.; Zang, Qing; Zeng, Long; Zhang, J.Z.; Zhang, Tonggang; Zhang, Y.; Zhong, Guoqiang; Zhou, Chu; Zhou, Ruo

doi:10.1088/1741-4326/aad70c

Cited by 26 publications

(29 citation statements)

References 44 publications

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“…In EAST LHW experiment [26], the observed AEs can propagate in either ion or electron diamagnetic drift direction. In addition, it was recently reported that energetic electrons induced by static magnetic perturbations can also drive a TAE propagating in the ion diamagnetic drift direction [27]. These experimental studies revealed some properties of energetic-electron driven AE, including its frequency, mode number and propagation direction.…”

Section: Introductionmentioning

confidence: 89%

Simulation of Alfvén eigenmodes destabilized by energetic electrons in tokamak plasmas

Todo

Wang

2020

Nucl. Fusion

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Alfvén eigenmodes (AEs) driven by energetic electrons were investigated via hybrid simulations of an MHD fluid interacting with energetic electrons. The investigation focused on AEs with the toroidal number n = 4. Both energetic electrons with centrally peaked beta profile and off-axis peaked profile are considered. For the centrally peaked energetic electron beta profile case, a toroidal Alfvén eigenmode (TAE) propagating in the electron diamagnetic drift direction is found. The mode is mainly driven by deeply trapped energetic electrons. It is also found that a few passing energetic electrons spatially localized around rational surfaces can resonate with the mode. For the off-axis peaked energetic electron beta profile case, an AE propagating in the ion diamagnetic drift direction is found when a q − p r o f i l e with weak magnetic shear is adopted. The destabilized mode is an elliptical-Alfvén-eigenmode-type (EAE-type) mode which has a spatial profile peaking at the rational surface and a frequency close to the second Alfvén frequency gap. It is found that passing energetic electrons and barely trapped energetic electrons are responsible for this EAE-type mode destabilization. The saturation levels are compared for a TAE with the same linear growth rate among energetic electron driven mode and energetic ion driven mode with isotropic and anisotropic velocity space distributions. The saturation level of TAE driven by trapped energetic electrons is comparable to that driven by energetic electrons with isotropic velocity space distribution where the contribution of trapped particles is dominant. It is found that the trapped energetic ion driven TAE has a larger saturation level than the passing energetic ion driven TAE, which indicates the difference in particle trapping by the TAE between trapped and passing energetic ions.

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Section: Introductionmentioning

confidence: 89%

Simulation of Alfvén eigenmodes destabilized by energetic electrons in tokamak plasmas

Todo

Wang

2020

Nucl. Fusion

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“…This provides an approximate boundary between instabilities that act on REs in real space (< 30 MHz) and those that act on REs in phase space (> 30 MHz). Consequently both few MHz instabilities, 10-100s kHz MHD instabilities, and stationary applied 3-D fields can deconfine REs in effectively the same manner [42,8,82,70,43,16,41].…”

Section: General Prospects For Kinetic Instabilitiesmentioning

confidence: 99%

Recent DIII-D advances in runaway electron measurement and model validation

Paz-Soldan¹,

Eidietis²,

Hollmann³

et al. 2019

Nucl. Fusion

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Novel measurements and modeling of runaway electron (RE) dynamics in DIII-D have resolved experimental discrepancies and validated predictions for ITER, improving confidence that RE avoidance and mitigation can be predictably achieved. Considering RE formation, first experimental assessments of the RE seed current demonstrates that present hot-tail theories are not yet accurate and require improved treatment of the pellet dynamics. Novel measurements of kinetic instabilities in the MHz-range have been made in the RE formation phase, with the intensity of these modes correlated with previously unexplained empirical thresholds for RE generation. Controlled RE dissipation experiments in quiescent regimes have validated RE distribution function dependencies on collisional and synchrotron damping, both in terms of distribution function shape and dissipation rates. Measurements of RE bremsstrahlung and synchrotron emission are now used in tandem to resolve energy and pitch-angle effects. A resolution to long-standing dissipation anomalies in the quiescent regime is offered by taking into account kinetic instability effects on RE phase-space dynamics. Kinetic instabilities in the 100-200 MHz range are directly observed, though modeling finds the largest dissipation arises from GHz range instabilities that are beyond the reach of existing diagnostics. Kinetic instabilities are also observed in the mature post-disruption RE plateau phase, so long as the collisional damping rate is reduced with low-Z injection. Experiments with high-Z injection find that the dissipation rate saturates with injection quantity, likely due to neutral diffusion rates being slower than vertical instability rates in DIII-D. Considering the final loss, a 0D model for first-wall Joule heating is found to be in agreement with experiment, and controlled access to RE equilibria with edge safety factor of two identifies novel dynamics brought about by large-scale kink instabilities. These dynamics are typified by fast (tens of microseconds) RE loss rates without RE beam regeneration. The above measurements and comparison with theory represent significant advances in the understanding of RE dynamics and indicate possible new opportunities for RE avoidance or mitigation via kinetic instabilities.

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“…(Experimental Advanced Superconducting Tokamak)上观测到环效应引起的阿尔芬本征模(Toroidicity-Induced Alfvén Eigenmodes, TAEs) [10,11] 、比压阿尔芬本征模(Beta-Induced Alfvén Eigenmodes, BAEs) [12,13] 以及反磁剪切阿尔芬本征模(Reverse Shear Alfvén Eigenmodes, RSAEs) [14,15] 等. 这些模式在不同装置的不同放电条件下呈现出不同特性, 如在HL-2A上高能离子激发的BAE具有频率啁啾特性 [16] , 而在EAST上BAE的存在依赖于低杂波功率, 并且磁重联对其有很大影响等 [11] .…”

Section: 引言unclassified

Discrete Alfvén eigenmodes excited by energetic particles in China Fusion Engineering Test Reactor

Zhao¹,

Hu²,

He³

et al. 2020

Sci. Sin.-Phys. Mech. Astron.

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In burning plasmas, discrete Alfvén eigenmodes (αTAEs, where α denotes a parameter of plasma pressure gradient) can be readily destabilized by energetic particles under the wave-particle resonance condition. In this study, we theoretically analyze the physical features of αTAEs in the China Fusion Engineering Test Reactor (CFETR), which is viewed as the next generation device in the Chinese magnetic confinement fusion program. One of the scientific objectives of the device is to achieve steady-state operation. There are three reference schemes for baseline steady-state operation, namely Case 1: NB+EC, Case 2: NB+EC+LH, and Case 3: EC+LH, where NB, EC, and LH represent neutral beam, electron cyclotron wave, and lower hybrid wave, respectively. Within the ideal magnetohydrodynamic (MHD) description, we focus on the physical characteristics of αTAEs and correlation between the radial profile of total current density and αTAEs for the three scenarios of CFETR operation with the help of a MHD eigenvalue code. The numerical results indicated that multiple branches of αTAEs can be trapped in potential wells of the ballooning drive under the CFETR operation condition. In the inner region, the bootstrap current density is large, and the total current density profile, defined by the peak of the radial profile of total plasma current density is relatively flat. Therefore, there are abundant αTAEs in this region. However, in the outer region, the bootstrap current is relatively small, and the total current density decreases gradually. So, αTAEs are hardly seen in this region. The αTAEs in the inner region are quasi-marginally stable within the ideal MHD description. In the CFETR operations, the energetic particles generated can destablize the MHD αTAEs under the wave-particle resonance conditions. We study the stability features of αTAEs interacting with energetic particles by employing linear gyrokinetic-MHD hybrid eigenvalue codes. The multiple branches of αTAEs are excited under the various resonance conditions. Moreover, the multiple branches of αTAEs can also be excited by energetic particles with virial energy. Furthermore, higher-frequency αTAEs may be destabilized by energetic particles with higher energy. These αTAEs could change the distribution of energetic particles in phase space and cause the loss of a large number of particles, which may affect the plasma confinement.

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Observation of toroidal Alfvén eigenmode excited by energetic electrons induced by static magnetic perturbations in the EAST tokamak

Cited by 26 publications

References 44 publications

Simulation of Alfvén eigenmodes destabilized by energetic electrons in tokamak plasmas

Simulation of Alfvén eigenmodes destabilized by energetic electrons in tokamak plasmas

Recent DIII-D advances in runaway electron measurement and model validation

Discrete Alfvén eigenmodes excited by energetic particles in China Fusion Engineering Test Reactor

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Observation of toroidal Alfvén eigenmode excited by energetic electrons induced by static magnetic perturbations in the EAST tokamak

Cited by 26 publications

References 44 publications

Simulation of Alfvén eigenmodes destabilized by energetic electrons in tokamak plasmas

Simulation of Alfvén eigenmodes destabilized by energetic electrons in tokamak plasmas

Recent DIII-D advances in runaway electron measurement and model validation

Discrete Alfv&eacute;n eigenmodes excited by energetic particles in China Fusion Engineering Test Reactor

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Discrete Alfvén eigenmodes excited by energetic particles in China Fusion Engineering Test Reactor