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Edge turbulence dynamics across electron–ion root transitions during ECRH modulation experiments in the TJ–II stellarator

Arnold A Alvarez, Boudewijn Ph van Milligen, Igor Voldiner, Iberê L Caldas, Zwinglio O Guimarães-Filho, Oleksandr S Kozachok, Oleksandr O Chmyga, the TJ-II Team2026年6月Plasma Physics and Controlled FusionIF 2.2出版社

In this work, we report an experimental study of electron-to-ion (e–i) root transitions in the TJ-II stellarator, a confinement transition associated with the formation of a sheared radial electric field in the plasma edge. The line-averaged electron density, , was kept close to the value at which such transitions are typically observed, while the electron cyclotron resonance heating (ECRH) power was modulated in order to investigate how changes in heating conditions affect the transition. We find that the density at which the e–i transition occurs depends on the applied ECRH power. This indicates that alone does not determine the transition, and supports the view that the relevant control parameter is linked to the edge plasma potential profile, or equivalently to the radial electric field and its shear. Long-range correlation analysis using spatially separated Langmuir probes reveals a clear change in the nature of edge turbulence across the transition. Below the threshold, correlations are consistent with radially propagating filamentary structures, while above the threshold they are localized in a narrow radial region, consistent with the presence of a zonal-flow-like structure of width about 1.5 cm. In the high confinement state, wavelet spectra show a strong suppression of low frequency fluctuations (below 50 kHz) together with a significant reduction of the turbulence correlation time, indicating effective turbulence decorrelation by shear flows. In addition, intermittency is reduced, suggesting a decrease in multifractality and an increased role of turbulence dominated by a low-order mode. Measures of entropy and statistical complexity suggest that this transition can be considered a phase transition. Altogether, these observations show that the plasma edge dynamics during the e–i root transition cannot be understood as a purely profile-driven process, but involve nonlinear interactions between profiles and turbulence.

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tj-ii中精度(概要文一致)

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StellaratorElectron cyclotron heatingTJ-IIEdge turbulence

AIによる論文要約

TJ-IIステラレータにおけるECRH変調実験中の電子-イオン根遷移に伴うエッジ乱流のダイナミクス
JA核融合研究やプラズマ物理を学ぶ学生、特に乱流と閉じ込め遷移の関係に興味がある研究者#プラズマ物理 #核融合 #乱流 #ステラレータ #閉じ込め遷移
LLM向け: {"Title": "TJ-IIステラレータにおける電子-イオン根遷移とエッジ乱流のダイナミクス", "Authors": "未記載", "Research O…

この研究では、TJ-IIステラレータのプラズマ端で起こる電子-イオン根遷移(e-i遷移)を実験的に調べました。電子サイクロトロン共鳴加熱(ECRH)のパワーを変調し、加熱条件の変化が遷移にどう影響するかを調べました。その結果、遷移が起こる密度は加熱パワーに依存することが分かりました。また、プラズマ端の乱流の性質が遷移を境に変化することを、ラングミュアプローブを用いた長距離相関解析で明らかにしました。遷移前は放射状に伝搬するフィラメント構造が観測されるのに対し、遷移後は約1.5cm幅の帯状流(ゾーナルフロー)様構造が現れ、低周波数(50kHz以下)のゆらぎが抑制され、乱流の相関時間が短くなります。これはシア流による乱流の非相関化を示しています。また、間欠性が減少し、低次のモードが支配的になることも分かりました。これらの結果は、e-i遷移が単純なプロファイル駆動ではなく、プロファイルと乱流の非線形相互作用を含むことを示しています。

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