Observation of beta-induced Alfvén Eigenmode in J-TEXT tokamak

Liu, Linzi; He, Junyu; Hu, Qiming; Zhuang, G.

doi:10.1088/0741-3335/57/6/065007

Cited by 29 publications

(32 citation statements)

References 29 publications

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“…Investigations of BAEs are abundant, since they are ubiquitous in tokamak plasmas. Experimentally, the BAE was discovered on DIII-D [11] during neutral beam heating, and then it was also reported in FTU [14], HL-2A [15,16], EAST [17], and J-TEXT [18,19]. There are also many theoretical investigations [4,[20][21][22][23] and numerical simulations [24][25][26][27][28][29] of BAE.…”

Section: Introductionmentioning

confidence: 93%

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

Duan¹,

Fu²,

Cai³

2022

Nucl. Fusion

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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.

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Section: Introductionmentioning

confidence: 93%

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

Duan¹,

Fu²,

Cai³

2022

Nucl. Fusion

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“…The experimental results show that the BAEs are related not only to the population of the energetic electrons, but also to their energy and pitch angles. The BAEs excited by the static resonant magnetic perturbation have been found on JTEXT [13]. Recently, the double BAE pairs inter acting with tungsten impurities that induced m/n = 2/1 snake fluctuations are mapped out for the first time on EAST [14].…”

Section: Introductionmentioning

confidence: 97%

Beta induced Alfvén eigenmode driven by energetic ions on the HL-2A tokamak

et al. 2019

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Research on beta induced Alfvén eigenmodes (BAEs) driven by energetic ions has been carried out on the HL2A tokamak. The BAEs can be observed in the cases of q min being beyond or below unity. The mode frequencies are around 60-95 kHz. The radial mode structures have been detected by the multichannel microwave reflectometer and soft xray arrays. The results suggest that the BAEs are highly localized at the normalized radius of ρ = 0.07-0.26. Theoretical analyses based on the general fishbonelike dispersion relation and Alfvén mode code support the experimental measurements in both mode frequencies and locations. The BAEs are found to be excited more easily in low electron density discharges. The coexistence of BAEs and reversed shear Alfvén eigenmodes enables the estimation of q min directly from experiments.

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“…Thus, they would interact with each other strongly. Recently, some experiments [9][10][11][12][13][14][15][16] have shown that BAEs can be excited in the presence of magnetic islands. BAEs were observed during tearing modes in FTU [9], TEXTOR [10], HL-2A [11,12] and J-TEXT [13,17] Ohmic plasmas, EAST with lower hybrid wave plasmas, HL-2A [18] and TJ-II stellarator [15] with energetic ions plasmas.…”

Section: Introductionmentioning

confidence: 99%

Excitation of beta-induced Alfvén eigenmodes by the coupling between geodesic acoustic mode and magnetic island

Cai

Gao

et al. 2021

Nucl. Fusion

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The mechanism of excitation of beta-induced Alfvén eigenmodes (BAEs) with magnetic islands larger than a threshold without energetic ions is studied. It is found that the nonlinear coupling between geodesic acoustic mode and magnetic islands can drive the pair of BAEs. The phase of BAEs to island should be π/2 to excite the BAEs and the magnetic island is larger than a threshold. The results are consistent with the experimental results shown in EAST(#86309). It implies that similar experimental results in other tokamaks, that BAEs excitation by magnetic islands without energetic ions, may be from the nonlinear coupling between islands and waves. It also implies that the existence of magnetic islands can make the excitation of BAEs easier in plasma with energetic ions, since the magnetic island can also increase the pressure gradient of energetic ions near the island separatrix. This predicts that BAEs may appear more frequently in the presence of magnetic islands in ITER.

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Observation of beta-induced Alfvén Eigenmode in J-TEXT tokamak

Cited by 29 publications

References 29 publications

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

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

Beta induced Alfvén eigenmode driven by energetic ions on the HL-2A tokamak

Excitation of beta-induced Alfvén eigenmodes by the coupling between geodesic acoustic mode and magnetic island

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