Experimental observation and simulation analysis of the relationship between the fishbone and ITB formation on EAST tokamak

Liu, Z.X.; Ge, Wanling; Wang, F.; Liu, Y.J.; Yang, Yong; Wu, Muquan; Wang, Z.X.; Zhang, Xiaoxi; Li, H.; Xie, Jinlin; Lan, Tao; Mao, Wenzhe; Liu, A.D.; Zhou, Chu; Ding, Weixing; Zhuang, G.; Liu, W.D.

doi:10.1088/1741-4326/abb146

Cited by 19 publications

(33 citation statements)

References 24 publications

(27 reference statements)

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“…Further, even after minor adjustment of the q-profile in this work, the frequency behavior of the fishbone is similar to that in a previous simulation study by Liu et al [19], which was confirmed to be consistent with experimental observations [34]. The successful reproduction of a fishbone in this work forms the basis for the further analyses of fishbone instability during ITB expansion.…”

Section: The Stabilizing Effect Of Itb Expansion On the Fishbonesupporting

confidence: 90%

“…Generally, the formation of an ITB is often accompanied by magnetohydrodynamic (MHD) instability, acting as a trigger for ITB formation, such as m/n = 1/1 fishbone activities [16] and double tearing modes [17,18]. In particular, a strong relationship between fishbone instability driven by energetic particles and ITB formation has been observed in both EAST [19,20] and ASDEX Upgrade [16]. In these discharges, onset of the ITB occurs immediately after the fishbone oscillation and is radially located around q min , accompanied by a decrease in turbulent transport levels [16].…”

Section: Introductionmentioning

confidence: 99%

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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: The Stabilizing Effect Of Itb Expansion On the Fishbonesupporting

confidence: 90%

Section: Introductionmentioning

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 non-perturbative effects of energetic particles are included on the mode in our self-consistent model. The M3D-K code has been widely applied to analyze magnetohydrodynamics, energetic particle modes, and Alfvénic activities in tokamak plasmas [48][49][50][51][52].…”

Section: M3d-k Modelmentioning

confidence: 99%

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

Ge¹,

Wang²,

Wang³

2021

Nucl. Fusion

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Hybrid simulations are performed to investigate the dependence of downward sweeping reversed shear Alfvén eigenmodes (RSAEs) on key parameters in tokamaks. The investigation is mainly focused on downsweeping RSAEs with a toroidal number 3 n  . It is found that the occurrence of downward sweeping RSAEs strongly depends on the bulk plasma profiles, including pressure profile and safety factor profile. The influence of bulk plasma pressure value and pressure gradient at min q on downsweeping RSAEs are studied, respectively. It is shown that the excitation of downsweeping RSAE is more associated with the plasma pressure gradient at min q than that with the pressure value. The enhancement of pressure gradient at min q improves the likelihood of the destabilization of downsweeping RSAEs. Moreover, the downsweeping RSAEs only occur in a weak magnetic shear configuration in our simulations. By increasing magnetic shear strength of central plasmas, it is numerically verified that the downsweeping RSAE activities are suppressed and eventually replaced by toroidal Alfvén eigenmodes (TAEs). Following this process, the transition region from TAEs to RSAEs is shifted to a region with lower min q values. In this work, the downsweeping RSAE, which has been confirmed that the mode is in the nonperturbative regime, has a twisted mode structure in the poloidal plane, while the upsweeping RSAE, which is in the perturbative regime, has an up-down symmetry mode structure (no shearing). Further, downward sweeping RSAEs, showing a relatively narrow mode spatial profile, are generally more stable than the upward sweeping ones, which can be a reason why the downsweeping RSAEs are rare in experiments. Finally, it is found that the kinetic effect of energetic ion central pitch angle does not affect the excitation of downward sweeping RSAEs, but affects the mode stability.

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“…2017; Liu et al. 2020). It is identified that ITB formation in the ion thermal channel strongly correlates to the excitation of the fishbone (Chu et al.…”

Section: Introductionmentioning

confidence: 99%

“…In addition, it has been revealed that fishbone instability is often excited after the ITB formation, and it plays no role in triggering ITB; however, ITBs with fishbone are stronger than without fishbone (He et al 2022). In EAST tokamak, ITB formation is stepwise and always appears after the fishbone instability (Yang et al 2017;Liu et al 2020). It is identified that ITB formation in the ion thermal channel strongly correlates to the excitation of the fishbone (Chu et al 2021;Zhang et al 2022).…”

Section: Introductionmentioning

confidence: 99%

A simple model for internal transport barrier induced by fishbone in tokamak plasmas

Liu,

2023

J. Plasma Phys.

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Fishbone bursts have been observed to strongly correlate to internal transport barrier (ITB) formation in a number of tokamak devices. A simple model incorporating the fishbone dynamics and ion pressure gradient evolution is proposed in order to investigate the key physics parameters assisting the triggering of ITB. The time evolution of fishbone is described by the well-known predator–prey model. For each burst cycle, the energetic particles (EPs) resonantly interact with fishbone and are radially expelled from inner region leading to a radial current. A compensating bulk plasma return current and, hence, poloidal flow can be induced if the fishbone cycle frequency is greater than the poloidal flow damping rate. When the shear of the poloidal flow exceeds a critical value, the turbulent fluctuations are suppressed and the bulk ion pressure gradient transits to the high-confinement state. It is shown that this process is only sensitive to the deposition rate of the trapped EPs within the $q=1$ surface, but not sensitive to other parameters. A quantitative formula for the shearing rate of poloidal flow induced by fishbone bursts is derived and verified numerically.

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Experimental observation and simulation analysis of the relationship between the fishbone and ITB formation on EAST tokamak

Cited by 19 publications

References 24 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

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

A simple model for internal transport barrier induced by fishbone in tokamak plasmas

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