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Gyrokinetic analysis of low-n shear Alfvén and ion sound wave spectra in a high-beta tokamak plasma
https://repo.qst.go.jp/records/48866
https://repo.qst.go.jp/records/48866e022a7dc-3ea4-4535-8539-aaead10ca7cb
| Item type | 学術雑誌論文 / Journal Article(1) | |||||
|---|---|---|---|---|---|---|
| 公開日 | 2018-05-08 | |||||
| タイトル | ||||||
| タイトル | Gyrokinetic analysis of low-n shear Alfvén and ion sound wave spectra in a high-beta tokamak plasma | |||||
| 言語 | ||||||
| 言語 | eng | |||||
| 資源タイプ | ||||||
| 資源タイプ識別子 | http://purl.org/coar/resource_type/c_6501 | |||||
| 資源タイプ | journal article | |||||
| アクセス権 | ||||||
| アクセス権 | metadata only access | |||||
| アクセス権URI | http://purl.org/coar/access_right/c_14cb | |||||
| 著者 |
ビアワーゲ, アンドレアス
× ビアワーゲ, アンドレアス× Lauber, Philipp× ビアワーゲ アンドレアス |
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| 抄録 | ||||||
| 内容記述タイプ | Abstract | |||||
| 内容記述 | Using the linear gyrokinetic code LIGKA, we study the structure of the continuous spectra Ω(ρ) = ω(ρ) + iγ(ρ) of shear Alfvén waves (SAW) and ion sound waves (ISW) in a high-beta JT60U tokamak plasma and look for evidence of Alfvén acoustic couplings or mode conversion. Here, Ω is the complex local eigenfrequency, ρ is a radial coordinate, and we consider waves with low toroidal mode number n = 3 . We focus on the frequency range ω[BAE] <= ω <= ω[TAE] between the beta-induced and toroidicity-induced Alfvén frequency gaps. The real frequencies ω(ρ) of the gyrokinetic ISW continua are remarkably similar to MHD results. The kinetic damping rates are of order −γ/ω ~ 30% for Te /Ti ≈ 1.7 , and reduce to 15% when the temperature ratio is raised to Te /Ti ≈ 4.8 . It is shown that SAW and ISW continua can be simultaneously excited with an antenna and that the global response of the ISWs is significantly enhanced when the on-axis beta value is raised from β0 = 1.7% to 3.6% while keeping Te /Ti > 1 . In contrast, when the ion temperature is increased such that Te /Ti ≈ 0.4 , ISW branches become undetectable in spite of higher β0 . At the same time, a large part of the SAW continuum is locally destabilized by ion temperature gradients and a set of discrete global modes was found, some of which are weakly damped or unstable and interpreted as kinetic beta-induced Alfvén eigenmodes. It is estimated that the kinetic damping of such low-n Alfvénic modes contributes much more to the anomalous bulk ion heating than the excitation of nearby ISW continua, so that Alfvén acoustic couplings in the frequency band ω[BAE] <= ω <= ω[TAE] are irrelevant within the scope of the model used. |
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| 書誌情報 |
Nuclear Fusion 巻 57, p. 116063-1-116063-21, 発行日 2018-05 |
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| DOI | ||||||
| 識別子タイプ | DOI | |||||
| 関連識別子 | 10.1088/1741-4326/aa80fe | |||||
