Article
Physics, Fluids & Plasmas
L. Bardoczi, N. J. Richner, N. C. Logan
Summary: Analysis of a multi-scenario database of over 13,000 DIII-D H-mode discharges shows that magnetic islands are predominantly pressure gradient driven and stochastically triggered non-linear instabilities. The observations suggest that the majority of the analyzed 2,1 tearing modes are non-linear, neoclassically driven instabilities, with classical stability not playing a dominant role in their onset.
Article
Physics, Fluids & Plasmas
Ruirui Ma, Liu Chen, Fulvio Zonca, Yueyan Li, Zhiyong Qiu
Summary: This study theoretically investigates the linear wave properties of low-frequency Alfven modes (LFAMs) observed in DIII-D tokamak experiments and finds that LFAM is a reactive-type kinetic ballooning mode instability under certain experimental conditions. The study also explains the observed spectral patterns and the dependence of instability drive on electron temperature in the experiments.
PLASMA PHYSICS AND CONTROLLED FUSION
(2022)
Article
Physics, Fluids & Plasmas
J. Kim, J. Kang, T. Rhee, J. Jo, H. Han, M. Podesta, J. H. Lee, S. Lee, J. G. Bak, M. J. Choi, R. Nazikian, H. Jhang, J. Ko, M. Joung, Y-M Jeon, Y-S Na, K. Shinohara, C. Z. Cheng
Summary: Recent experiments have shown that electron cyclotron current drive (ECCD) can suppress Alfvenic activity, enhance the confinement of fast ions, and improve the performance of fusion plasmas.
Article
Physics, Fluids & Plasmas
Enzo Lazzaro, Luca Bonalumi, Silvana Nowak, Daniele Brunetti
Summary: In tokamak operation, the robust diagnostics of MHD instabilities rely on magnetic signals and fast B perturbation signals. By analyzing the relationship between ZSSW moments and stability index, stability boundaries under different rotation conditions can be identified, providing insights for real-time monitoring and control in fusion reactors.
IEEE TRANSACTIONS ON PLASMA SCIENCE
(2021)
Article
Physics, Fluids & Plasmas
I. G. Miron
Summary: The paragraph discusses the limitations of pressure-driven instabilities on the plasma normalized beta value and presents a multi-mode model for describing NTM evolution. By solving the perturbed equations in various spaces and making approximations, a linear model is proposed to provide a clear, quasi-analytic NTM solution, which has been tested against different discharges at JET.
Article
Physics, Fluids & Plasmas
A. Gude, M. Maraschek, V Igochine, B. Sieglin, M. Willensdorfer, H. Zohm
Summary: Tearing modes are a major concern for large tokamak devices, and their detection and characterization are crucial to avoid impact on discharge or machine damage. The phase difference between different modes affects mode detection and identification, while phase-locked tearing modes can be in phase at any poloidal position.
PLASMA PHYSICS AND CONTROLLED FUSION
(2021)
Article
Physics, Fluids & Plasmas
L. Bardoczi, R. J. La Haye, E. J. Strait, N. C. Logan, S. P. Smith, N. J. Richner, J. D. Callen
Summary: We have successfully achieved preemptive direct stabilization of m, n = 2, 1 neoclassical tearing modes (NTMs) in DIII-D low-torque ITER baseline scenario plasmas using electron cyclotron waves. The experiments demonstrate that the observed stabilization is achieved by replacing the missing bootstrap current in the island with electron cyclotron current drive (ECCD). These findings are significant as they provide the first demonstration of disruptive NTM control by ECCD in the plasma scenario planned for ITER.
Article
Physics, Fluids & Plasmas
M. Jiang, Y. Xu, W. Chen, W. L. Zhong, P. W. Shi, Z. B. Shi, X. T. Ding, R. Ke, H. F. Liu, Y. R. Zhu, Y. P. Zou, Z. J. Li, T. B. Wang, Y. P. Zhang, L. M. Yu, Z. C. Yang, L. Z. Liu, N. Wu, X. Q. Ji, Yi Liu, M. Xu
Summary: This study investigates the coupling among various MHD modes in high beta H-mode plasmas and finds that the interactions between these modes play a crucial role in determining the plasma behavior. The coupling in the core region regulates the edge transport and the ELM crash results in changes in mode width.
Review
Multidisciplinary Sciences
Huishan Cai, Ding Li
Summary: This review focuses on the interaction between energetic particles and tearing modes in magnetically confined fusion plasmas. The influence of energetic particles on tearing modes and the transport of energetic particles by tearing modes are discussed. The effects of energetic particles on tearing modes are described based on a general dispersion relation, while the transport of energetic particles is reviewed for both circulating and trapped particles. The importance of this interaction and open issues are also discussed.
NATIONAL SCIENCE REVIEW
(2022)
Article
Chemistry, Multidisciplinary
Alexander Yashin, Anna Ponomarenko, Ivan Balachenkov, Gleb Kurskiev, Evgenii Kiselev, Vladimir Minaev, Alexander Petrov, Yury Petrov, Nikolay Sakharov, Nikita Zhiltsov
Summary: In this study, we observed magnetohydrodynamic (MHD) activity of the spherical tokamak Globus-M2, which resulted in a deterioration in plasma confinement and a transition from H-mode to L-mode or disruption. The observed instability was identified as tearing modes caused by the formation of magnetic islands in plasma, which impose limits on plasma pressure. The width and velocity of the islands play crucial roles in their impact on plasma confinement. The Doppler backscattering (DBS) method combined with magnetic probes was used to study tearing modes in the spherical tokamak Globus-M2. Comparative analysis of the observed tearing modes and the influence of different plasma parameters on their development was conducted.
APPLIED SCIENCES-BASEL
(2023)
Article
Physics, Fluids & Plasmas
Z. S. Qu, M. J. Hole
Summary: The shear Alfven continuum spectrum is studied for a tokamak with a single island chain using the ideal magnetohydrodynamics theory. The results show that the asymmetry of the island leads to new frequency gaps, and the width of the combined TAE/MAE gap narrows as the island grows. Additionally, the eigenfunction of the continuum mode near the island exhibits highly localized structures.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Fluids & Plasmas
H. J. C. Oliver, S. E. Sharapov, Z. Stancar, M. Fitzgerald, E. Tholerus, B. N. Breizman, M. Dreval, J. Ferreira, A. Figueiredo, J. Garcia, N. Hawkes, D. L. Keeling, P. G. Puglia, P. Rodrigues, R. A. Tinguely
Summary: The Joint European Torus conducted an experimental campaign using a mixture of deuterium (D) and tritium (T) plasma and observed a high-frequency mode known as the toroidal Alfven eigenmode (TAE). Through simulations and calculations, it was found that the TAE can be driven by beam ions with high toroidal mode numbers, while alpha particles contribute less to the driving force. Radiative damping was identified as the dominant damping mechanism. The observed TAE matched the calculated results.
Article
Physics, Fluids & Plasmas
A. V. Dudkovskaia, J. W. Connor, D. Dickinson, P. Hill, K. Imada, S. Leigh, H. R. Wilson
Summary: This study adopts an improved model of drift island theory to address the boundary layer of drift island separatrix and investigate the contribution of polarization current around the magnetic island separatrix. By considering the dissipation caused by collisions in the distribution function, the radial discontinuity on both sides of the separatrix is eliminated, resulting in a smoother density distribution. The overall effect of polarization current on the NTM threshold is quantified by combining the contributions from outside and inside the separatrix layer, and it self-consistently accounts for the electrostatic potential reconstructed from plasma quasi-neutrality.
Article
Physics, Fluids & Plasmas
Deng Zhou, Xiaoqing Yang, Yue Ming, Chenxiao Gan
Summary: The axisymmetric Alfven modes in the presence of energetic ions are studied using the MHD-kinetic hybrid model in tokamak plasmas. The dispersion relation of continuous spectra is derived for the coupled m = 0, +/- 2 poloidal harmonics. In addition to the conventional axisymmetric Alfven modes, the energetic ions can induce axisymmetric Alfven modes if certain conditions are met.
PHYSICS OF PLASMAS
(2022)
Article
Physics, Fluids & Plasmas
M. Dreval, S. E. Sharapov, Ye O. Kazakov, J. Ongena, M. Nocente, R. Calado, R. Coelho, J. Ferreira, A. Figueiredo, M. Fitzgerald, J. Garcia, C. Giroud, N. C. Hawkes, V. G. Kiptily, F. Nabais, M. F. F. Nave, H. Weisen, T. Craciunescu, M. Salewski, Z. Stancar
Summary: Various types of Alfven eigenmodes (AEs) destabilized by fast ions over a broad frequency range have been identified in JET experiments. Through detailed numerical investigations, the high-frequency Alfven cascade (AC) modes localized in the central regions of the plasma exhibit characteristics consistent with experimental measurements. The resonant conditions for mode excitation are found to be determined by passing ions of high energy, similar to JT-60U experiments.
Article
Physics, Fluids & Plasmas
Kaijun Zhao, Yoshihiko Nagashima, Zhibin Guo, Patrick H. Diamond, Jiaqi Dong, Longwen Yan, Kimitaka Itoh, Sanae-I Itoh, Xiaobo Li, Jiquan Li, Akihide Fujisawa, Shigeru Inagaki, Jun Cheng, Jianqiang Xu, Yusuke Kosuga, Makoto Sasaki, Zhengxiong Wang, Huaiqiang Zhang, Yuqian Chen, Xiaogang Cao, Deliang Yu, Yi Liu, Xianming Song, Fan Xia, Shuo Wang
Summary: Enhancements of edge zonal flows, radial electric fields, and turbulence are observed in electron cyclotron resonance heating-heated plasmas. The effects of sawtooth heat pulses on flows and turbulence are presented. The delay time of the maximal intensity of the electric fields, zonal flows, and turbulence with respect to the sawtooth crashes is estimated as similar to 1 ms and comparable to that of the sawtooth-triggered intermediate phases.
PLASMA SCIENCE & TECHNOLOGY
(2023)
Article
Physics, Fluids & Plasmas
G. Z. Hao, G. Q. Dong, B. T. Cui, Y. Q. Liu, Y. H. Xu, T. F. Sun, X. Q. Ji, S. Wang, Y. F. Zhao, J. Q. Xu, X. Bai, N. Zhang, C. Y. Li, L. Wang, H. D. He, J. M. Gao, Yi Liu, W. L. Zhong, M. Xu, X. R. Duan
Summary: The divertor biasing technique, which uses divertor biasing current filaments to create field perturbations, offers a promising alternative for controlling the edge localized mode (ELM) and divertor heat load in tokamaks. Simulation results reveal that the technique can be applied to ELM control and reduce the chance of mode locking associated with core perturbations.
Article
Physics, Fluids & Plasmas
Guoliang Xia, Yueqiang Liu, T. C. Hender, K. G. McClements, E. Trier, E. Tholerus
Summary: This study uses the MARS-F/K codes to simulate the passive and active control of the n=1 resistive wall mode in a spherical tokamak. Passive control relies on plasma flow and drift kinetic resonance damping, while active control requires a flux-to-voltage control scheme with proportional and derivative controllers. The results show that the RWM can be fully stabilized with axial plasma flow at 5% of the Alfven speed, with success rates exceeding 90% in the presence of sensor signal noise.
Article
Physics, Fluids & Plasmas
Y. Q. Wang, G. Z. Hao, Y. P. Zou, Y. Q. Liu, W. Chen, G. M. Yang, G. Meng, Y. T. Miao, Y. F. Zhao, Y. B. Xia
Summary: The transport and loss of beam injected energetic particles due to three-dimensional perturbations in plasma with external kink instability and fishbone-like mode were studied numerically in HL-2A tokamak. The simulation results showed that when the XK-induced radial magnetic field perturbation exceeded a threshold value of about 10(-2), the profile of energetic particles experienced a significant change. The transport of energetic particles was dominated by diffusion instead of convection. Furthermore, when the resonance between the FLM and energetic particles occurred at a frequency above a threshold value of approximately 2 kHz, the redistribution and loss of energetic particles were substantially enhanced.
Article
Physics, Multidisciplinary
J. Gonzalez-Martin, M. Garcia-Munoz, J. Galdon-Quiroga, Y. Todo, J. Dominguez-Palacios, M. Dunne, A. Jansen van Vuuren, Y. Q. Liu, L. Sanchis, D. Spong, W. Suttrop, X. Wang, M. Willensdorfer
Summary: The suppression and excitation of Alfve'n eigenmodes in a tokamak plasma have been experimentally achieved for the first time using externally applied 3D perturbative fields with different spatial spectra. These perturbations cause a redistribution of fast ions in the plasma, altering the phase-space gradients that drive the modes and ultimately determining their existence. Simulations indicate that a resonant transport layer activated by the 3D perturbative field plays a role in the fast-ion redistribution. These findings are significant for controlling fast-ion driven Alfve'nic instabilities in future fusion plasmas.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Fluids & Plasmas
Lina Zhou, Yueqiang Liu, Hanqing Hu, Mattia Siccinio, Maviglia Francesco, Hartmut Zohm, Leonardo Pigatto, Yong Wang, Li Li, Guangzhou Hao, Xu Yang, Hanyu Zhang, Ping Duan, Long Chen
Summary: A systematic investigation is conducted on the plasma response to an externally applied RMP field in an EU DEMO reference plasma with the aim of controlling edge localized modes. The study focuses on the role of kinetic effects associated with both thermal particles and fusion-born alphas. The results show that the single fluid, resistive model predicts a large peak amplification of the plasma response, while a more advanced response model including kinetic resonances between RMP perturbation and drift motions of particles finds a strong suppression of the field amplification.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Fluids & Plasmas
Guanming Yang, Yueqiang Liu, Zhibin Wang, Yongqin Wang, Yutian Miao, Guangzhou Hao
Summary: The redistribution of neutral beam injection (NBI) fast ions in ITER is studied, and it is found that both the internal kink and fishbone instabilities can cause transport of fast ions in real space. The transport of fast ions increases with the amplitude of the internal kink perturbation and the frequency of the fishbone instability. Perturbations with higher toroidal mode number lead to outward excursion of the fast ion transport regions.
PLASMA SCIENCE & TECHNOLOGY
(2023)
Article
Nanoscience & Nanotechnology
J. W. Li, L. Li, Y. Q. Liu, Y. F. Wang, P. Qin, Q. B. Luan, X. J. Huang, L. J. Guo, F. C. Zhong
Summary: A systematic numerical study using the MARS-F code is conducted to investigate the plasma response to the resonant magnetic perturbation (RMP) field applied for controlling edge localized modes (ELMs) in tokamak plasmas with varying aspect ratio. The results show a non-monotonic dependence of the resonant response field near the plasma edge with changing aspect ratio, indicating that certain aspect ratios are more favorable for ELM control. The optimal aspect ratio depends on the toroidal and poloidal spectra of the applied RMP field.
Article
Physics, Fluids & Plasmas
N. Zhang, Y. Q. Liu, D. L. Yu, Yi Liu, G. Z. Hao, L. Liu, X. X. He, T. F. Sun, X. Q. Ji, S. Wang, G. Q. Dong, X. Bai, Y. L. Wei, W. J. Chen, Y. W. Sun, M. Jiang, Y. P. Zhang, Z. B. Shi, W. L. Zhong, M. Xu
Summary: The effects of predominantly n=1 resonant magnetic perturbation (RMP) on plasma density and toroidal flow speed in the HL-2A tokamak were investigated. Simulation results showed that neoclassical toroidal viscosity (NTV) played a key role in modifying plasma momentum and particle transport. The electron NTV particle flux model, combined with free-boundary condition, yielded the best agreement with experimental results.
Article
Physics, Fluids & Plasmas
Xu Yang, Yueqiang Liu, Wei Xu, Yuling He, Guoliang Xia
Summary: The influence of negative triangularity (NT) on the stability of the n = 1 tearing mode (TM) has been investigated numerically. The TM near the plasma edge is found to be more unstable in NT plasmas compared to positive triangularity (PT) plasmas, due to the lack of favorable average curvature stabilization in NT configurations. However, in the core-localized TM, larger Shafranov shift in the plasma core associated with NT configuration results in more stable TM.
Article
Physics, Fluids & Plasmas
Cheng Ye, You-Wen Sun, Hui-Hui Wang, Yue-Qiang Liu, Tong-Hui Shi, Qing Zang, Tian-Qi Jia, Qun Ma, Shuai Gu, Nan Chu, Kai-Yang He, Man-Ni Jia, Xue-Min Wu, Peng-Cheng Xie, Hui Sheng, Hua Yang, Lian-Sheng Huang, Biao Shen, Miao-Hui Li, Jin-Ping Qian, EAST Team
Summary: The plasma-beta effect on the n=1 resonant magnetic perturbation (RMP) field penetration in purely radio-frequency (RF) wave heated discharges has been investigated. The experimental results show that the error-field tolerance is improved with increasing RF power, benefiting from the increased electron perpendicular flow dominated by a counter-current electron diamagnetic flow. However, the theoretical scaling overestimates the power index, and the degradation effect of plasma beta is observed.
Article
Physics, Fluids & Plasmas
V Igochine, M. Bonotto, A. Gude, M. Maraschek, L. Pigatto, P. Bettini, Y. Q. Liu, L. Piron, D. Voltolina, H. Zohm
Summary: Tokamak plasmas can amplify small resonant components of error fields near the ideal MHD limits. ASDEX Upgrade experiments demonstrate the necessity of EF correction considering plasma effect for optimal compensation, even for small resonant EFs. Such correction improves the achievable characteristics and stability of discharges.
PLASMA PHYSICS AND CONTROLLED FUSION
(2023)
Article
Physics, Fluids & Plasmas
G. Q. Dong, Y. Q. Liu, G. Z. Hao, S. Wang, N. Zhang, Y. Q. Wang, Y. T. Miao, C. Y. Li, Y. F. Zhao
Summary: A systematic investigation is carried out to study the effect of the neutral beam injection induced energetic particles (EPs) on the internal kink instability in the HL-2M tokamak. Non-perturbative MHD-kinetic hybrid computations show a generally stabilization effect on the internal kink, primarily due to drift kinetic resonances associated with EPs. Both the bounce resonance and transit resonance of passing EPs have minor influence on the mode stability.
PHYSICS OF PLASMAS
(2023)
Article
Nanoscience & Nanotechnology
G. Q. Dong, Y. Q. Liu, G. Z. Hao, S. Wang, N. Zhang, Y. Q. Wang, Y. T. Miao, C. Y. Li, Y. F. Zhao
Summary: This study systematically investigates the effects of 3D perturbations caused by an unstable n = 1 internal kink on the energetic particles in HL-2M tokamak. It is found that the 3D perturbation affects the EP drift orbit, confinement, and loss in HL-2M. The instability-induced EP loss is typically less than 10%, but the prompt orbit loss associated with the 2D equilibrium field reaches about 16% in HL-2M.
Article
Physics, Multidisciplinary
Zhou Li-Na, Hu Han-Qing, Liu Yue-Qiang, Duan Ping, Chen Long, Zhang Han-Yu
Summary: It is well known that large-scale type-I edge localized modes (ELMs) pose risks to machine components in future large fusion devices. Recent experiments have shown that resonant magnetic perturbations (RMPs) can suppress or mitigate ELMs. This study focuses on the roles played by the edge safety factor, RMP coil current, and particle drift kinetic effects. Computational simulations show that the plasma response exhibits periodic amplification as q95 varies and that the number of peaks is positively correlated with the toroidal number. The optimal/worst current phase difference and the optimal coil current amplitude can be well fitted by simple analytical models.
ACTA PHYSICA SINICA
(2023)
