PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES |
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Observation and Simulation of $n=1$ Reversed Shear Alfvén Eigenmode on the HL-2A Tokamak |
P. W. Shi1, Y. R. Yang2, W. Chen1, Z. B. Shi1*, Z. C. Yang1, L. M. Yu1, T. B. Wang1, X. X. He1, X. Q. Ji1, W. L. Zhong1, M. Xu1, and X. R. Duan1 |
1Southwestern Institute of Physics, Chengdu 610041, China 2State Key Laboratory of Intense Pulsed Radiation Simulation and Effect, Northwest Institute of Nuclear Technology, Xi'an 710024, China
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Cite this article: |
P. W. Shi, Y. R. Yang, W. Chen et al 2022 Chin. Phys. Lett. 39 105201 |
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Abstract A branch of high-frequency Alfvénic modes is observed on the HL-2A tokamak. The electromagnetic mode can be driven unstably in the plasma with an off-axis neutral beam heating. Its mode frequency keeps almost unchanged or presents a slow-sweeping behavior, depending on the detail current evolution. The poloidal and toroidal mode numbers are $m/n=1/1$. The mode has a quite short duration ($\leq$20 ms) and usually appears 5–10 ms after the neutral beam being injected into the plasma. Hybrid simulations based on M3D-K have also been carried out. The result suggests that co-passing energetic particles are responsible for the mode excitation. The simulated mode structures are localized nearby location of minimum safety factor ($q_{\rm min}$) and agree with the structures obtained through tomography of soft x-ray arrays. Further, the modes are localized in the continuum gap and their frequencies increase with variation of $q_{\rm min}$ in a wide range. Last but not least, the characteristic of unchanged frequency on experiment is also reproduced by the nonlinear simulation with a fixed safety factor. All those evidences indicate that the $n=1$ high-frequency mode may belong to a reversed shear Alfvén eigenmode.
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Received: 06 July 2022
Editors' Suggestion
Published: 20 September 2022
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PACS: |
52.35.Mw
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(Nonlinear phenomena: waves, wave propagation, and other interactions (including parametric effects, mode coupling, ponderomotive effects, etc.))
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52.35.Bj
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(Magnetohydrodynamic waves (e.g., Alfven waves))
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52.35.Py
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(Macroinstabilities (hydromagnetic, e.g., kink, fire-hose, mirror, ballooning, tearing, trapped-particle, flute, Rayleigh-Taylor, etc.))
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