Global kinetic-MHD simulations of downward-sweeping reversed shear Alfvén eigenmodes in tokamak plasmas

Ge, Wanling; Wang, Rui; Wang, Jialei

doi:10.1088/1741-4326/ac21f8

Cited by 3 publications

(2 citation statements)

References 69 publications

(131 reference statements)

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“…For the MHD part in code M3D-K, the dissipative MHD model consists of the full resistive MHD equations and the additional dissipative terms including viscosity and heat conduction. The M3D-K code has been widely used to analyze the linear and nonlinear behaviors of energetic particle modes and Alfvén eigenmodes in tokamak plasmas [42][43][44].…”

Section: Experimental Observation and Simulation Setupmentioning

confidence: 99%

Multiple interactions between fishbone instabilities and internal transport barriers in EAST plasmas

Wang

et al. 2022

Nucl. Fusion

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The fishbone instabilities and internal transport barriers (ITBs) are frequently and sequentially observed in tokamak plasmas. Recently, the relationship between fishbone and ITB was numerically studied mainly on the basis of experimental results (Z. X. Liu et al., 2020 Nucl. Fusion 60 122001). It was identified that a radial electric field can be generated by fishbone itself, which may act as a trigger of ITB formation. To gain a deeper understanding of this subject, in this work, we further demonstrate the multiple interactions between fishbone instability and ITB in Experimental Advanced Superconducting Tokamak (EAST) experiment (discharge #56933) using hybrid kinetic-MHD code M3D-K. In the multiple-n simulations, it is found that the zonal electric field can be induced in the nonlinear stage of fishbone, leading to a relatively large E×B zonal flow that is sufficient to suppress the dominant microinstability before ITB formation, which should account for the trigger of ITB. After the ITB is triggered, the equilibrium pressure gradient increases and the fast ions from the neutral beam injection accumulate in ITB region. Then, the linear simulations are performed to analyze the effect of ITB formation on fishbone instability. It is shown that due to the change of the pressure gradient during ITB expansion, the change of bootstrap current density profile modifies the q profile, and then stabilizes the fishbone mode. Additionally, the accumulation of the fast ions leads to a broadening of fast ion distribution around the ITB region, which also has a stabilizing effect on the fishbone mode.

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Section: Experimental Observation and Simulation Setupmentioning

confidence: 99%

Multiple interactions between fishbone instabilities and internal transport barriers in EAST plasmas

Wang

et al. 2022

Nucl. Fusion

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“…The M3D-K code has been extensively applied to investigate the interaction between EP and MHD instabilities, e.g. tearing mode [31][32][33], fishbone [34,35], BAE [36,37], TAE [38,39], reversed shear Alfvén eigenmode [40,41].…”

Section: The Physic Model Of M3d-k and Parameters Setupmentioning

confidence: 99%

Simulations of beta-induced Alfvén eigenmode mitigation by off-axis energetic particle distribution

Duan,

Zhu,

Cai

2024

Nucl. Fusion

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The effect of different off-axis energetic particle (EP) slowing down distribution on beta-induced Alfven eigenmode (BAE), driven by the on-axis EP distribution, is systematically studied using kinetic-magnetohydrodynamic code M3D-K. The aim is to analyze the optimal parameter region for controlling AEs via varying EP distribution parameters. The simulation results reveal that by modifying the gradients of the EP distribution, the off-axis EP can further destabilize or mitigate the on-axis EP driven BAE, depending on the off-axis EP distribution's parameters: deposition profile, EP beta, pitch angle, injection velocity and direction. When the off-axis EP is deposited outside the mode center, and its injection velocity is sufficiently large to satisfy the resonance with BAE, the stabilization of BAE is achieved. This stabilizing effect is directly proportional to the off-axis EP beta, while excessive off-axis EP beta can trigger a new EP-driven instability located outside the BAE. Furthermore, to achieve a stronger stabilizing effect, the pitch angle distribution and velocity direction of the off-axis EP should be close to those of the on-axis EP. For instance, compared to the counter-passing off-axis EP, the co-passing off-axis EP can lead to a more effective mitigation of the BAE driven by the co-passing on-axis EP.

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Hybrid numerical simulation on fast particle transport induced by synergistic interaction of low- and medium- frequency magnetohydrodynamic instabilities in tokamak plasma

Zhu¹,

Chen²,

Feng³

et al. 2023

Acta Phys. Sin.

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In tokamak experiments, various MHD instabilities usually co-exist and interact with fast particles. It can cause significant fast particle transport and loss, and pose damage to the first wall, leading to discharge quench in tokamak. Therefore, understanding the physical mechanism of fast particle transport caused by MHD instabilities is a crucial but urgently solved physical issue for the steady-state long pulse operation of future reactor-graded devices. Based on the experimental phenomenon of synergy between nonresonant internal kink mode and tearing mode observed on NSTX, a spherical tokamak device, this paper utilizes the global nonlinear hybrid-kinetic simulation code M3D-K to compare the characteristics of fast particle loss, transport and redistribution in the two cases: I) only non-resonant internal kink modes; II) the synergy between the non-resonant internal kink mode and tearing mode. The physical mechanism of fast particle transport, loss and redistribution caused by such synergy is studied. The results show that the synergy between the non-resonant internal kink mode and the tearing mode can significantly enhance the loss and transport of fast particles. The main reason is that such synergy can provide a radial channel for fast particles to mitigate from the plasma core to the plasma boundary accompanied with the total stochasticity of the magnetic topology. These results can help understand the physical mechanism of the transport and loss of fast particles caused by the synergy of low-frequency MHD instabilities in future fusion reactors, and provide some new ideas for finding strategies to control and mitigate the loss and transport level of fast particles in future fusion reactors.

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Global kinetic-MHD simulations of downward-sweeping reversed shear Alfvén eigenmodes in tokamak plasmas

Cited by 3 publications

References 69 publications

Multiple interactions between fishbone instabilities and internal transport barriers in EAST plasmas

Multiple interactions between fishbone instabilities and internal transport barriers in EAST plasmas

Simulations of beta-induced Alfvén eigenmode mitigation by off-axis energetic particle distribution

Hybrid numerical simulation on fast particle transport induced by synergistic interaction of low- and medium- frequency magnetohydrodynamic instabilities in tokamak plasma

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