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Observation of bi-directional global Alfvén eigenmodes in the MAST-U tokamak

M.B. Dreval, H.J.C. Oliver, S.E. Sharapov, J.F. Rivero-Rodriguez, M. Fitzgerald, C. Michael, R. Ochoukov, L. Velarde, M. Cecconello, D. Ryan2025年1月Nuclear FusionIF 3出版社

The first observations and classification of deuterium beam-driven sub-cyclotron frequency range Alfvén eigenmodes (AEs) are presented for the MAST-Upgrade tokamak. Sets of observed eigenmodes are separated in frequency by approximately 200 kHz. We observe a lower frequency separation of ∼10 kHz within each set, and the toroidal mode number n increases with frequency sequentially. The ∼200 kHz step between the sets coincides with the interval between successive curves of the Shear Alfvén continuum according to linear ideal MHD modeling. The sub-cyclotron frequency AEs can be identified as the global AEs (GAEs) localized at the continuum extrema regions. Each set contains the same range of n. These observations are consistent with our GAE modeling. In low plasma current (Ip) discharges, we observe only GAEs propagating counter to the plasma current and the beam direction. These GAEs are located near the magnetic axis. We observe counter and co-propagating GAEs simultaneously in higher Ip discharges. The co-propagating GAEs occur because of the formation of second continuum minima. Very flat safety factor profiles in higher Ip MAST-U discharges give rise to these minima. They are located at around half of the plasma radius. The GAEs have properties that are very different to those of compressional AEs previously reported for the MAST tokamak with low magnetic fields (Sharapov et al 2014 Phys. Plasmas21 082501) before the upgrade.

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Alfvén waveAlfvén eigenmodeMASTMAST Upgrade

AIによる論文要約

MAST-Uトカマクにおける双方向グローバルアルフベン固有モードの観測
JAプラズマ物理、核融合研究に興味のある学生や研究者が対象です。トカマク装置におけるアルフベン固有モードの振る舞いを理解することは、プラズマ加熱や安定性を向上させるうえで重要です。#プラズマ物理 #核融合 #アルフベン固有モード #MAST-Uトカマク
LLM向け: {'Title': 'MAST-Uトカマクにおける双方向グローバルアルフベン固有モードの観測', 'Author(s)': '不明', 'Research Ob…

この論文では、MAST-Uトカマクにおける重水素ビーム駆動の亜サイクロトロン周波数範囲のアルフベン固有モード(AE)の初観測と分類が報告されています。観測されたエイゲンモードは周波数で約200 kHzの間隔で分離しており、各セットの中で約10 kHzの間隔で順次トロイダルモード数nが増加しています。これらの特性は線形理想MHDモデリングによる剪断アルフベン連続体の極値領域に局在するグローバルAE(GAE)として一致しています。

Observation of bi-directional global Alfvén eigenmodes in the MAST-U tokamak
ENThis paper should be read by fusion researchers and students interested in the behavior of Alfvén eigenmodes in tokamak plasmas, particularly the effects of plasma current and safety factor profiles on the propagation of these modes.#AlfvénEigenmodes #GlobalAlfvénEigenmodes #MagntohydrodynamicInstabilities #MASTPlusUpgrade #FusionPlasmas
LLM向け: {'Title': 'Observation of bi-directional global Alfvén eigenmodes in the MAST-U …

This paper reports the first observations of deuterium beam-driven sub-cyclotron frequency Alfvén eigenmodes (AEs) in the MAST-U tokamak. The AEs are classified as global AEs (GAEs) and are localized at the continuum extrema regions. The authors observe counter and co-propagating GAEs, with the co-propagating GAEs occurring due to the formation of second continuum minima in higher plasma current discharges.

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