Article
Physics, Multidisciplinary
Shuai Jiang, Zheng-Xiong Wang, Lai Wei, Tong Liu
Summary: The effects of plasma radiation on the nonlinear evolution of neo-classical double tearing modes (NDTMs) in tokamak plasmas with reversed magnetic shear are numerically investigated. It is found that plasma radiation destabilizes the NDTMs and promotes kinetic energy growth in the late nonlinear phase. Moreover, plasma radiation induces a broad spectrum of MHD perturbations and a radially broadened region of MHD turbulence. Plasma radiation can also advance the explosive burst of kinetic energy in the presence of fast driven reconnection between rational surfaces. Furthermore, plasma radiation can induce explosive burst in the reversed magnetic shear configuration.
Article
Physics, Fluids & Plasmas
Ming Xu, Ruirui Ma, Liqing Xu, Yingying Li, Hailin Zhao, Wei Chen, Shouxin Wang, Guoqiang Li, Guoqiang Zhong, Fudi Wang, Yifei Jin, Juan Huang, Qing Zang, Haiqing Liu, Liqun Hu, Xianzu Gong, Guosheng Xu, Jiansheng Hu, Baonian Wan
Summary: Mode structures and excitation conditions for LFMs were investigated in EAST plasmas, revealing two stages of instabilities and analyzing the frequency characteristics and factors affecting their excitation.
Article
Multidisciplinary Sciences
Minjun J. Choi, Laszlo Bardoczi, Jae-Min Kwon, T. S. Hahm, Hyeon K. Park, Jayhyun Kim, Minho Woo, Byoung-Ho Park, Gunsu S. Yun, Eisung Yoon, George McKee
Summary: The authors provide comprehensive observations and analysis on the evolution of magnetic islands and plasma turbulence in tokamak plasmas, revealing the intricate effects of turbulence on the evolution of magnetic islands.
NATURE COMMUNICATIONS
(2021)
Article
Physics, Multidisciplinary
M. Li, X. Q. Wang, B. Zhang, X. Su, Y. Xu
Summary: The effects of energetic particles (EPs) on m/n = 3/1 magnetohydrodynamic (MHD) instabilities in reversed magnetic shear configurations are investigated through hybrid simulations. It is found that a global instability, known as energetic particle modes (EPMs), can be excited by strong energetic particle drive within the Alfven continuum. In the linear growth stage, EPs not only cause radial broadening of mode structures but also enhance toroidal mode coupling when EP beta exceeds a certain threshold. In the nonlinear saturation stage, the good flux surfaces are maintained throughout the plasma region over a prolonged time evolution of EPMs. The nonlinear saturation amplitude of EPMs is studied in detail, considering the effects of EP beta values, particle distribution width, beam energy, and initial pitch angle. It is also observed that MHD nonlinearity reduces the saturation level of EPMs compared to the linear MHD case, while high-n harmonics have a minor impact.
EUROPEAN PHYSICAL JOURNAL PLUS
(2023)
Article
Physics, Fluids & Plasmas
Tong Liu, Zheng-Xiong Wang, Lai Wei, Jialei Wang
Summary: An explosive burst excited by neoclassical tearing mode in reversed magnetic shear tokamak plasmas has been investigated. Numerical investigations have identified a threshold in electron cyclotron driven current, below which the NTM islands are not effectively suppressed and a deleterious explosive burst can be triggered. Three control strategies have been attempted, and two of them have been recognized as effective in preventing explosive bursts.
Article
Physics, Fluids & Plasmas
Ming Xu, Liqun Hu, Tianfu Zhou, Ling Zhang, Liqing Xu, Yanmin Duan, Qing Zang, Haiqing Liu, Xianzu Gong, Guosheng Xu
Summary: The annular/central collapses of electron temperature in the EAST tokamak have been studied, with precursor modes being excited before these events. Multiple magnetic island chains coexist for high-Z impurity concentrations. Reproduction of annular/central collapse events is achieved through magnetic reconnection of m/n = 2/1 double tearing modes. Different penetration depths of high-Z impurity density play a key role in exciting these events, along with the establishment of reversed magnetic shear.
Article
Physics, Fluids & Plasmas
Shuai Jiang, Weikang Tang, Lai Wei, Tong Liu, Haiwen Xu, Zhengxiong Wang
Summary: The effects of plasma radiation on the nonlinear evolution of neo-classical tearing modes are investigated, and it is found that the radiation can reduce the pressure near the rational surface and enhance the perturbed bootstrap current during the nonlinear evolution. Additionally, the radiation can increase the growth rate of magnetic islands by diminishing the pressure, thus preventing the islands from saturating.
PLASMA SCIENCE & TECHNOLOGY
(2022)
Article
Physics, Multidisciplinary
Ding-Zong Zhang, Xu-Ming Feng, Jun Ma, Wen-Feng Guo, Yan-Qing Huang, Hong-Bo Liu
Summary: The linear behavior of the dominant unstable mode and its high order harmonics in a reversed magnetic shear cylindrical plasma were numerically investigated. The dominant mode is a classical double tearing mode with low beta, but is driven mainly by plasma pressure with sufficiently large beta. The mode undergoes a transition from DTM to pressure-driven mode with the increase of pressure, and the distance between two rational surfaces has an important influence on the mode transition.
Article
Physics, Fluids & Plasmas
H. Y. Wang, T. Liu, Y. Q. Liu, Z. X. Wang
Summary: The study investigates the effect of plasma boundary shape on the beta(N) threshold in toroidal tokamak plasmas, showing that the critical value of beta(Nc) is influenced by the boundary shape, especially under different separations between rational surfaces with the same helicity. Moreover, significant changes in the critical value of beta(Nc) are observed in cases with large elongation.
PLASMA PHYSICS AND CONTROLLED FUSION
(2022)
Article
Physics, Multidisciplinary
Ruibo Zhang, Lei Ye, Yang Chen, Nong Xiang, Xiaoqing Yang
Summary: We study the effects of kinetic ions on double-tearing modes using the GEM gyrokinetic particle-in-cell simulation code with a gyrokinetic ion/fluid electron hybrid model. Our results show that ion kinetic effects can decrease the growth rate of these modes, with a stronger effect for modes coupled to rational surfaces at smaller distances. Kinetic ions also enhance the coupling effect between the rational surfaces. Energy transfer analyses reveal that the stabilizing effect of kinetic ions is mainly attributed to the perpendicular magnetic drift of ions in the coupling region and around the outer rational surface.
Article
Physics, Fluids & Plasmas
Wanling Ge, Jialei Wang, Feng Wang, Zheng-Xiong Wang
Summary: Hybrid simulations investigate the dependence of downward-sweeping reversed shear Alfven eigenmodes (RSAEs) on key parameters in tokamaks, finding that the occurrence of downward-sweeping RSAEs strongly depends on bulk plasma profiles, especially the pressure gradient at q (min). The study also shows that increasing the pressure gradient at q (min) can enhance the likelihood of destabilizing downsweeping RSAEs.
Article
Physics, Multidisciplinary
Y. Yao, Zhihong Lin, J. Q. Dong, P. Shi, S. F. Liu, Jingchun Li
Summary: The investigation showed that increasing the separation of the rational surfaces enhances the growth rates of DTMs and leads to the decoupling of the DTM system into two single-tearing modes. Additionally, the presence of thermal ions destabilizes the DTM, and the toroidal effect has a mild destabilizing effect on the growth of DTMs.
Article
Physics, Fluids & Plasmas
A. Kryzhanovskyy, D. Bonfiglio, S. Cappello, M. Veranda, M. Zuin
Summary: This paper discusses the properties and triggering mechanisms of Alfven waves in the reversed-field pinch (RFP) and circular tokamak configurations using nonlinear 3D magnetohydrodynamics (MHD) modeling. Numerical simulations and comparisons with analytical solutions are performed, providing consistent results with experimental observations.
Article
Physics, Fluids & Plasmas
Zhenghao Ren, Feng Wang, Huishan Cai, Jinyuan Liu
Summary: This study investigates the nonlinear evolution of the tearing mode instability with toroidal rotation using a three-dimensional toroidal geometry magnetohydrodynamic code. It is found that toroidal rotation significantly stabilizes the magnetic island, regardless of the direction. The stabilizing effect of toroidal rotation is stronger in the nonlinear phase compared to the linear phase.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Multidisciplinary
B. M. Alotaibi, Haifa A. Al-Yousef, R. E. Tolba, W. M. Moslem
Summary: Different nonlinear dynamical behaviors of dust-acoustic modes in a homogeneous plasma were examined using a 3D-NLS equation. Various methods, including bifurcation analysis and factorization method, were employed to explore the solutions of the equation, including periodic, shocklike, and explosive waves. Additionally, the study also investigated the rogue wave solution and its dependence on nonextensivity parameters, which can have implications for electrostatic structures in dusty plasmas like Saturn's E-ring.