九州大学 研究者情報
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基本情報 研究活動
井戸 毅(いど たけし) データ更新日:2020.07.02



主な研究テーマ
磁場閉じ込めプラズマにおける電位分布形成機構の解明
キーワード:磁場閉じ込めプラズマ、電位分布、重イオンビームプローブ
2004.04.
大型ヘリカル装置(LHD)用重イオンビームプローブの開発
キーワード:重イオンビームプローブ, 電位計測
2000.04.
JFT-2Mトカマクにおける重イオンビームプローブの開発
キーワード:重イオンビームプローブ
1997.10~2004.03.
JFT-2MトカマクにおけるL-H遷移における電位の時空間構造の解明
キーワード:磁場閉じ込めプラズマ、L-H遷移、電場、乱流輸送、重イオンビームプローブ
1999.04~2006.03.
従事しているプロジェクト研究
PLATOプロジェクト
2017.04~2022.03, 代表者:藤澤彰英, 九州大学, 九州大学.
研究業績
主要原著論文
1. T. Ido, Y. Miura, K. Hoshino, K. Kamiya, Y. Hamada, A. Nishizawa, Y. Kawasumi, H. Ogawa, Y. Nagashima, K. Shinohara, Y. Kusama, JFT-2M group, Observation of the interaction between the geodesic acoustic mode and ambient fluctuation in the JFT-2M tokamak, Nuclear Fusion, 10.1088/0029-5515/46/5/003, 46, 5, 512, 2006.03, [URL], The electrostatic and density fluctuation are measured simultaneously with a heavy ion beam probe. The electrostatic fluctuation with the geodesic acoustic mode (GAM) frequency is observed in L-mode plasmas and not in H-mode plasmas. The poloidal and radial structure is consistent with the GAM. So the fluctuation is concluded to be the GAM. The amplitude of the GAM changes in the radial direction; it is small near the separatrix, has a maximum at 3 cm inside the separatrix and decreases again to 5 cm inside the separatrix. The GAM and the temporal behaviour of the ambient density fluctuation show a significant coherence, and the phase of modulation of the ambient density fluctuation tends to delay the potential oscillation of the GAM. It is clearly verified that the GAM affects ambient fluctuation and also the local particle transport through modulation of the amplitude of the ambient fluctuation..
2. T Ido, Y Miura, K Kamiya, Y Hamada, K Hoshino, A Fujisawa, K Itoh, S-I Itoh, A Nishizawa, H Ogawa, Y Kusama and JFT-2M group, Geodesic–acoustic-mode in JFT-2M tokamak plasmas, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/48/4/S04, 48, S41, 2006.03, [URL], The characteristics of geodesic–acoustic-mode (GAM) are investigated through direct and simultaneous measurement of electrostatic and density fluctuations with a heavy ion beam probe. The amplitude of the GAM changes in relation to the radial position; it is small near the separatrix, reaches a local maximum at 3 cm inside the separatrix and then decreases again to 5 cm inside the separatrix. The frequency is constant in the range, though the predicted GAM frequency varies according to the temperature gradient. The correlation length is about 6 cm and comparable to the structure of the amplitude of the GAM. The results indicate the GAM has a radial structure which reflects the local condition at about 3 m inside the separatrix. The phase relation between the GAM oscillation indicates that the GAM is a radial propagating wave.
The interaction between the GAM and the ambient density fluctuation is shown by the high coherence between the GAM oscillation and the temporal behaviour of the ambient density fluctuation. Moreover, the phase relation between the electric field fluctuation of the GAM (E˜r,GAM) and the amplitude of the density fluctuation indicates that the modulation of the ambient density fluctuation delays the E˜r,GAM. The causality between the GAM and the modulation of the density fluctuation is revealed..
3. Takeshi IDO, Akihiro SHIMIZU, Masaki NISHIURA, Shinji KATO, Haruhisa NAKANO, Akimitsu NISHIZAWA, Yasuji HAMADA, Mitsuhiro YOKOTA, Kiwamu TSUKADA, Hideki OGAWA, Tomoyuki INOUE, Katsumi IDA, Mikiro YOSHINUMA, Sadayoshi MURAKAMI, Kenji TANAKA, Kazumichi NARIHARA, Ichihiro YAMADA, Kazuo KAWAHATA, Naoki TAMURA and the LHD Experimental Group, Electrostatic Potential Measurement by Using 6-MeV Heavy Ion Beam Probe on LHD, Plasma and Fusion Research, 10.1585/pfr.3.031, 3, 031, 2008.04, [URL], A heavy ion beam probe (HIBP) using a 3 MV tandem accelerator was installed in Large Helical Device (LHD). It is designed to measure the electrostatic potential in the core region directly. It is calibrated and can be used to measure the electrostatic potential profiles in LHD plasmas. The radial electric field (Er) obtained from the potential profiles measured using the HIBP agrees with that measured by charge exchange spectroscopy (CXS). Er predicted by the neoclassical theory is also compared to that measured using the HIBP, and is in good agreement with the experimental results in the core region..
4. T. Ido, K. Kamiya, Y. Miura, Y. Hamada, A. Nishizawa, and Y. Kawasumi, Observation of the Fast Potential Change at L-H Transition by a Heavy-Ion-Beam Probe on JFT-2M, Physical Review Letters, 10.1103/PhysRevLett.88.055006 , 88, 5, 055006, 2002.01, [URL], The fast potential change near the separatrix is measured directly at the L-H transition by a heavy-ion-beam probe. The potential changes with two different time scales at the L-H transition triggered by a sawtooth crash: it drops at first with the time scale of 10 100 ms just after the arrival of the heat pulse due to the sawtooth crash. Then, it decreases again at a few 100 ms after the first drop at a time scale of about 200 ms..
5. T. Ido, K. Itoh, M. Osakabe, M. Lesur, A. Shimizu, K. Ogawa, K. Toi, M. Nishiura, S. Kato, M. Sasaki, K. Ida, S. Inagaki, S.-I. Itoh, the LHD Experiment Group, Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device, Physical Review Letters, 10.1103/PhysRevLett.116.015002, 116, 015002, 2016.01, [URL], Abrupt and strong excitation of a mode has been observed when the frequency of a chirping energetic-particle driven geodesic acoustic mode (EGAM) reaches twice the geodesic acoustic mode (GAM) frequency. The frequency of the secondary mode is the GAM frequency, which is a half-frequency of the primary EGAM. Based on the analysis of spatial structures, the secondary mode is identified as a GAM. The phase relation between the secondary mode and the primary EGAM is locked, and the evolution of the growth rate of the secondary mode indicates nonlinear excitation. The results suggest that the primary mode (EGAM) contributes to nonlinear destabilization of a subcritical mode..
6. T. Ido, K. Itoh, M. Lesur, M. Osakabe, A. Shimizu, K. Ogawa, M. Nishiura, I. Yamada, R. Yasuhara, Y. Kosuga, M. Sasaki, K. Ida, S. Inagaki, S.-I. Itoh and the LHD Experiment Group, Observation of subcritical geodesic acoustic mode excitation in the large helical device, Nuclear Fusion, 10.1088/1741-4326/aa665a, 57, 072009 , 2017.04, [URL], The abrupt and strong excitation of the geodesic acoustic mode (GAM) has been found in the
large helical device (LHD), when the frequency of a chirping energetic particle-driven GAM
(EGAM) approaches twice that of the GAM frequency. The temporal evolution of the phase
relation between the abrupt GAM and the chirping EGAM is common in all events. The result
indicates a coupling between the GAM and the EGAM. In addition, the nonlinear evolution
of the growth rate of the GAM is observed, and there is a threshold in the amplitude of the
GAM for the appearance of nonlinear behavior. A threshold in the amplitude of the EGAM for
the abrupt excitation of the GAM is also observed. According to one theory (Lesur et al 2016
Phys. Rev. Lett. 116 015003, Itoh et al 2016 Plasma Phys. Rep. 42 418) the observed abrupt
phenomenon can be interpreted as the excitation of the subcritical instability of the GAM. The excitation of a subcritical instability requires a trigger and a seed with sufficient amplitude. The observed threshold in the amplitude of the GAM seems to correspond with the threshold in the seed, and the threshold in the amplitude of the EGAM seems to correspond with the threshold in the magnitude of the trigger. Thus, the observed threshold supports the interpretation that the abrupt phenomenon is the excitation of a subcritical instability of the GAM..
主要総説, 論評, 解説, 書評, 報告書等
1. 井戸 毅,浜田泰司,三浦幸俊,星野克道, ゾーナルフロー研究の現状と展望 3.ゾーナルフローの最近の実験研究 3.3 重イオンビームプローブによるゾーナルフロー研究 II, プラズマ・核融合学会, doi.org/10.1585/jspf.81.987, 2005.12, [URL], The Heavy ion beam probe (HIBP) is a powerful tool to investigate the potential anddensityfluctuationof hightemperature plasmas. The observations using HIBPs have contributed substentially to the recent rapid progressin the study of zonal flow. In this article, the characteristic of the Geodesic Acoustic Mode (GAM), which is a typeof the zonal flow, isintroducedonthe basisof experimental resultsusingHIBPs.Theobservedfrequencyandspacestructure are quite similarto the theoretical predictions. The influence of the GAMflow onthe background fluctua-tion, including the causality, is also observed..
2. 井戸 毅,清水昭博,西浦正樹, LHD における 6 MeV 重イオンビームプローブ(HIBP)による電位分布・揺動計測の現状と将来展望, プラズマ・核融合学会, 2010.09, [URL], 磁場閉じ込めプラズマ中に形成される電位分布および揺動の振る舞いとその閉じ込めへの影響を調べるために,大型ヘリカル装置(LHD)用重イオンビームプローブ(HIBP)の開発を行ってきた.HIBP としては過去最大規模となるため,長期の開発期間を要したが,本計測装置を設置した結果,LHD で生成される高温プラズマ内部において初めて直接電位計測が行えるようになった.この結果,電位分布のパラメータ依存性,GeodesicAcoustic Mode(GAM)やアルヴェン固有モードの特性などが明らかになりつつある..
3. 井戸 毅, 高温プラズマにおける測地線音波の周期倍分岐, パリティ (丸善), 2018.12.
主要学会発表等
1. 井戸毅、一ノ瀬薫、清水昭博、佐々木真、王 灏、西浦正樹, LHDにおける高速イオン励起測地線音波バーストが電位分布に及ぼす影響
, 第36回プラズマ・核融合学会年会, 2019.11, LHDにおいてNBI時に高速イオン励起測地線音波(EGAM)がバースト的に発生する。この時、GAMの周期より十分長く、バースト継続時間より短い時間で平均した平均電位の変動が観測された。電位はプラズマ中心領域で負に、規格化小半径0.2より外では正に変動しており、中心近傍で負電場が形成されている。この電場形成は高速イオンの損失を示唆している。中心近傍においてはEGAM発生時に電位揺動及び密度揺動も減少しており、負電場形成との関連が考えられる。.
2. Takeshi Ido, Akihiro Shimizu, Masaki Osakabe, Kimitaka Itoh, Maxime Lesur, Kunihiro Ogawa, Hao Wang, Makoto Sasaki, Yusuke Kosuga, Shigeru Inagaki, Sanae.–I. Itoh, and the LHD Experiment Group , Nonlinear wave-particle interaction in magnetized high temperature plasmas confined in Large Helical Device, 3rd Asia-Pacific Conference on Plasma Physics, 2019.11, Wave-particle interactions are ubiquitous in plasmas, and they are observed as interesting phenomena. In this presentation, observed subcritical instability driven by nonlinear wave-particle interaction in magnetized plasmas will be shown.
In magnetized high temperature plasmas confined in the Large Helical Device (LHD), it is observed that an instability named geodesic acoustic mode(GAM) is excited abruptly by energetic particles existing through the inverse Landau damping. The frequency of this instability usually increases with the time scale of a few milliseconds, and the temporal evolution of the frequency reflects the evolution of the velocity distribution which is a result of wave-particle interaction.
When the frequency of the GAM reaches twice the ordinary GAM frequency and the amplitude of the GAM exceeds a threshold, another GAM is abruptly excited with the shorter time scale of 1 ms or less. The phase relation between the originally-existing GAM, hereinafter referred to as the primary mode, and the abruptly excited GAM, hereinafter referred to as the secondary mode, is locked, and the evolution of the growth rate of the secondary mode indicates nonlinear excitation. These behaviors can be interpreted as the excitation of the subcritical instability of the secondary mode through nonlinear wave-particle interaction triggered by the primary mode. Abrupt excitation phenomena have been wildly observed in laboratory plasmas (e.g. sawtooth oscillation and disruption) and astro-plasmas(e.g. solar flare), and subcritical instabilities are one of the working hypotheses of the onset of abrupt phenomena. The finding of the abrupt excitation of the GAM and the understanding of the phenomena as the subcritical instability demonstrate an experimental path to the understanding of the physical mechanism of the onset of the abrupt phenomena.
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学会活動
所属学会名
プラズマ・核融合学会
日本物理学会
学術論文等の審査
年度 外国語雑誌査読論文数 日本語雑誌査読論文数 国際会議録査読論文数 国内会議録査読論文数 合計
2019年度
研究資金
科学研究費補助金の採択状況(文部科学省、日本学術振興会)
2017年度~2021年度, 特別推進研究, 分担, 統合観測システムで解き明かす乱流プラズマの構造形成原理と機能発現機構.
2008年度~2010年度, 若手研究(A,B), 代表, 多チャンネル重イオンビームプローブの開発による電位構造形成過程の研究.
2012年度~2014年度, 基盤研究(C), 代表, 高効率多チャンネル重イオン検出器の開発による電場形成とプラズマ乱流の研究.
2015年度~2017年度, 基盤研究(C), 代表, 微視的乱流と大域的揺らぎの同時計測による磁場閉じ込めプラズマにおける熱輸送の研究.
2018年度~2020年度, 基盤研究(C), 代表, 高エネルギー粒子駆動揺動場とプラズマ乱流場のスケール間相互作用の検証.
共同研究、受託研究(競争的資金を除く)の受入状況
2019.04~2020.03, 分担, 高速イオン励起不安定性がプラズ閉じ込めに及ぼす影響.

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