Influence of trapped energetic ions on low-frequency magnetohydrodynamic instabilities with reversed shear profile

2021 ◽  
Vol 28 (1) ◽  
pp. 012104
Author(s):  
Baofeng Gao ◽  
Huishan Cai ◽  
Feng Wang ◽  
Xiang Gao ◽  
Yuanxi Wan
Keyword(s):  
Low Frequency ◽  
Energetic Ions ◽  
Reversed Shear

scholarly journals Effect of the electron redistribution on the nonlinear saturation of Alfvén eigenmodes and the excitation of zonal flows

2020 ◽  
Vol 86 (3) ◽  
Author(s):  
A. Biancalani ◽  
A. Bottino ◽  
P. Lauber ◽  
A. Mishchenko ◽  
F. Vannini
Keyword(s):  
Magnetic Field ◽  
Zonal Flow ◽  
Large Aspect Ratio ◽  
Nonlinear Saturation ◽  
Energetic Ions ◽  
Electron Population ◽  
Zonal Flows ◽  
Particle In Cell ◽  
Alfven Eigenmodes ◽  
Reversed Shear

Numerical simulations of Alfvén modes driven by energetic particles are performed with the gyrokinetic (GK) global particle-in-cell code ORB5. A reversed shear equilibrium magnetic field is adopted. A simplified configuration with circular flux surfaces and large aspect ratio is considered. The nonlinear saturation of beta-induced Alfvén eigenmodes (BAE) is investigated. The roles of the wave–particle nonlinearity of the different species, i.e. thermal ions, electrons and energetic ions are described, in particular for their role in the saturation of the BAE and the generation of zonal flows. The nonlinear redistribution of the electron population is found to be important in increasing the BAE saturation level and the zonal flow amplitude.

Hybrid simulations of beta-induced Alfvén eigenmode with reversed safety factor profile

2021 ◽  
Author(s):  
Sizhe Duan ◽  
Guoyong Fu ◽  
Huishan Cai
Keyword(s):  
Nonlinear Dynamics ◽  
Rational Surface ◽  
Injection Velocity ◽  
Nonlinear Simulation ◽  
Energetic Ions ◽  
Radial Gradient ◽  
Nonlinear Phase ◽  
Simulation Results ◽  
Reversed Shear ◽  
Hybrid Simulations

Abstract Based on the experimental parameters in HL-2A tokamak, hybrid simulations have been carried out to investigate the linear stability and nonlinear dynamics of BAE. It is found that the (m/n=3/2) beta-incuced Alfvén eigenmode (BAE) is excited by co-passing energetic ions with qmin=1.5 in linear simulation, and the mode frequency is consistent with experimental meuasurement. The simulation results show that the energetic ions βh, the injection velocity v0 and orbit width parameter ρh of energetic ions are important parameters determining the drive of BAE. Furthermore, the effect of qmin (with fixed shape of q profile) is studied, and it is found that: when qmin ≤ 1.50, the excited modes are BAEs, which are located near q=1.50 rational surfaces; when qmin > 1.50, the excited modes are simillar to the reversed-shear Alfvén eigenmodes (RSAEs), which are mainly localized around q=qmin surfaces. Nonlinear simulation results show that the nonlinear dynamics of BAE is sensitive to the EP drive. For strongly driven case, firstly, redistribution and transport of engetic ions are trigged by (m/n=3/2) BAE, which raised the radial gradient of energetic ions distribution function near q=2 rational surface, and then an EPM (m/n=4/2) is driven in nonlinear phase. Finally, these two instabilities triggered significant redistribution of energetic ions, which results in the twice-repeated and mostly-downward frequency chirping of (m/n=3/2) BAE. For weakly driven case, there are no (m/n=4/2) EPM being driven and twice-repeated chirping in nonlinear phase, since the radial gradient near q=2 rational surface is small and almost unchanged.

scholarly journals Observation of Reversed-Shear Alfvén Eigenmodes Excited by Energetic Ions in a Helical Plasma

2010 ◽  
Vol 105 (14) ◽  
Author(s):  
K. Toi ◽  
F. Watanabe ◽  
T. Tokuzawa ◽  
K. Ida ◽  
S. Morita ◽  
...  
Keyword(s):  
Energetic Ions ◽  
Alfven Eigenmodes ◽  
Reversed Shear

Destabilization of reversed shear Alfvén eigenmodes driven by energetic ions during NBI in HL-2A plasmas withqmin∼ 1

2014 ◽  
Vol 54 (10) ◽  
pp. 104002 ◽  
Author(s):  
W. Chen ◽  
LiMin Yu ◽  
Yi. Liu ◽  
X.T. Ding ◽  
H.S. Xie ◽  
...  
Keyword(s):  
Energetic Ions ◽  
Alfven Eigenmodes ◽  
Reversed Shear

Low-frequency waves and associated energetic ions downstream of Saturn

1985 ◽  
Vol 90 (A11) ◽  
pp. 10791 ◽  
Author(s):  
K. W. Behannon ◽  
M. L. Goldstein ◽  
R. P. Lepping ◽  
H. K. Wong ◽  
B. H. Mauk ◽  
...  
Keyword(s):  
Low Frequency ◽  
Energetic Ions ◽  
Low Frequency Waves

Low-frequency global Alfvén eigenmodes in low-shear tokamaks with trapped energetic ions

2009 ◽  
Vol 16 (9) ◽  
pp. 092502 ◽  
Author(s):  
V. S. Marchenko ◽  
Ya. I. Kolesnichenko ◽  
S. N. Reznik
Keyword(s):  
Low Frequency ◽  
Energetic Ions ◽  
Alfven Eigenmodes ◽  
Low Shear

Theoretical studies of low-frequency Alfvén modes in tokamak plasmas

2021 ◽  
Author(s):  
R R Ma ◽  
Liu Chen ◽  
Fulvio Zonca ◽  
Yueyan Li ◽  
Zhiyong Qiu
Keyword(s):  
Low Frequency ◽  
Acoustic Mode ◽  
Frequency Region ◽  
Physical Parameters ◽  
Linear Wave ◽  
Tokamak Plasmas ◽  
High Frequency Region ◽  
Energetic Ions ◽  
Ballooning Mode ◽  
Spectral Patterns

Abstract Linear wave properties of the low-frequency Alfvén modes (LFAMs) observed in the DIII-D tokamak experiments with reversed magnetic shear [Nucl. Fusion 61, 016029 (2021)] are theoretically studied and delineated based on the general fishbone-like dispersion relation. By adopting the representative experimental equilibrium parameters, it is found that, in the absence of energetic ions, the LFAM is a kinetic ballooning mode instability of reactive-type with a dominant Alfvénic polarization. More specifically, due to diamagnetic and trapped particle effects, the LFAM can be coupled with the beta-induced Alfvén-acoustic mode in the low-frequency region (frequency much less than the thermal-ion transit and/or bounce frequency); or with the beta-induced Alfvén eigenmode in the high frequency region (frequency higher than or comparable to the thermal-ion transit frequency); resulting in reactive-type instabilities. Moreover, the ‘Christmas light’ and ‘mountain peak’ spectral patterns of LFAMs as well as the dependence of instability drive on the electron temperature observed in the experiments can be theoretically interpreted by varying the relevant physical parameters. Conditions when dissipative-type instabilities may set in are also discussed.

Effects of energetic ions on double tearing modes in reversed shear plasmas

2016 ◽  
Vol 57 (1) ◽  
pp. 016039 ◽  
Author(s):  
Xian-Qu Wang ◽  
Xiao-Gang Wang
Keyword(s):  
Energetic Ions ◽  
Tearing Modes ◽  
Reversed Shear

Low-Frequency Sheath Instability in a Non-Maxwellian Plasma with Energetic Ions

2004 ◽  
Vol 92 (4) ◽  
Author(s):  
Mikhail Starodubtsev ◽  
Md. Kamal-Al-Hassan ◽  
Hiroaki Ito ◽  
Noboru Yugami ◽  
Yasushi Nishida
Keyword(s):  
Low Frequency ◽  
Energetic Ions ◽  
Maxwellian Plasma
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