九州大学-研究者情報 [井戸毅 (教授) 応用力学研究所附属高温プラズマ理工学研究センター]

1.	T. Ido, M. Hasegawa, R. Ikezoe, T. Onchi, K. Hanada, H. Idei, K. Kuroda, Y. Nagashima, Conceptual design of a heavy ion beam probe for the QUEST spherical tokamak, Review of Scientific Instruments, 10.1063/5.0101770, 2022.11.
2.	Conway, G.D., Smolyakov, A.I., Ido, T., Geodesic acoustic modes in magnetic confinement devices, Nuclear Fusion, https://doi.org/10.1088/1741-4326/ac0dd1, 62, 1, 013001-1-013001-149, vol.62, No.1, 013001, 2022.01, [URL], Geodesic acoustic modes (GAMs) are ubiquitous oscillatory flow phenomena observed in toroidal magnetic confinement fusion plasmas, such as tokamaks and stellarators. They are recognized as the non-stationary branch of the turbulence driven zonal flows which play a critical regulatory role in cross-field turbulent transport. GAMs are supported by the plasma compressibility due to magnetic geodesic curvature—an intrinsic feature of any toroidal confinement device. GAMs impact the plasma confinement via velocity shearing of turbulent eddies, modulation of transport, and by providing additional routes for energy dissipation. GAMs can also be driven by energetic particles (so-called EGAMs) or even pumped by a variety of other mechanisms, both internal and external to the plasma, opening-up possibilities for plasma diagnosis and turbulence control. In recent years there have been major advances in all areas of GAM research: measurements, theory, and numerical simulations. This review assesses the status of these developments and the progress made towards a unified understanding of the GAM behaviour and its role in plasma confinement. The review begins with tutorial-like reviews of the basic concepts and theory, followed by a series of topic orientated sections covering different aspects of the GAM. The approach adopted here is to present and contrast experimental observations alongside the predictions from theory and numerical simulations. The review concludes with a comprehensive summary of the field, highlighting outstanding issues and prospects for future developments..
3.	T. Ido, A. Fujisawa, K. Takemura, T.-K. Kobayashi, D. Nishimura, N. Kasuya, A. Fukuyama, C. Moon, K. Yamasaki, S. Inagaki, Y. Nagashima, and T. Yamada, Conceptual design of heavy ion beam probes on the PLATO tokamak, Review of Scientific Instruments , 10.1063/5.0041814, 92, 053553, 2021.05, [URL], Heavy ion beam probe (HIBP) systems have been designed for the new tokamak, PLATO [A. Fujisawa, AIP Conf. Proc. 1993, 020011 (2018)]. The designs have been completed, and the installations are in progress. Two HIBPs are being installed in toroidal sections 180○ apart to investigate long-range correlations in the toroidal direction. Each HIBP consists of an injection beamline and a detection beamline as usual. Yet, one of the HIBPs is equipped with an additional detection beamline; the measurement positions of its two detection beamlines can be placed on almost the same magnetic surface yet at poloidal angles that differ by ∼180○. The use of three detection beamlines allows us to investigate spatial asymmetry and long-range correlations in both the toroidal and poloidal directions, simultaneously. The detected beam intensity is expected to be enough for turbulence measurements in almost the entire plasma region when the electron density is up to 1 × 10^19 m−3 by selecting appropriate ion species for the probe beam. Each detector has three channels 10 mm apart, allowing measurement of local structures of micro-scale turbulence. Therefore, using the HIBPs on the PLATO tokamak will enable both local and global properties of plasma turbulence to be investigated, simultaneously..
4.	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..
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.	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..
7.	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..
8.	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..

主要総説, 論評, 解説, 書評, 報告書等

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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

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1.	井戸毅, 清水昭博, 西浦正樹, 田窪英法, 西澤章光, LHDにおいて垂直NBIにより形成される電位及び密度の空間構造, 第39回プラズマ・核融合学会年会, 2022.11, 近年不純物ホール等、不純物輸送の解明を契機として磁気面上における電位の非一様性の影響が注目されている。この非一様性を形成する要因の一つとして、高エネルギーの中性粒子入射（NBI)に起因する捕捉高速イオンの影響が数値シミュレーションに指摘されている（H. Yamaguchi and S. Murakami, Nucl. Fusion 58 016029 (2018)）。本研究では、核融合科学研究所のLHDにおいて垂直NBIに対するプラズマ内部における電位分布及び密度分布の応答の計測を行った。図1に垂直NBIの有無に対する電位分布及び重イオンビームプローブ（HIBP）の信号強度分布の違いを示す。ここでHIBPの信号強度はプラズマの密度及び高速イオンの密度を反映する。電位分布、信号強度分布ともにNBI時に特徴的な空間構造が形成されることが観測された。この構造はNBが入射されている間は維持されており、再現性があることも確認された。また、LHDには2基の垂直NBIが設置されているが、上記の特徴的な構造は、計測位置からトロイダル方向に近い位置でのNBI時には顕著であるが、遠い位置でのNBI時には観測されない。この結果は、垂直NBI時にトロイダル方向に局在した電位構造が形成されており、磁気面上の非一様性の存在を示唆している。ただし、この構造は上記数値シミュレーションとは異なり、磁気軸近傍で顕著に現れる。今後この2次元構造や高速イオンの分布の解析を含め、物理機構を検討する必要がある。.
2.	T. Ido, M. Hasegawa, R. Ikezoe, T. Onchi, K. Hanada, H. Idei, K. Kuroda, Y. Nagashima, Conceptual Design of a Heavy Ion Beam Probe for the QUEST spherical tokamak, 24th Topical Conference on High Temperature Plasma Diagnostics, 2022.05, A heavy ion beam probe (HIBP) has been designed for the QUEST spherical tokamak to measure plasma turbulence and the electric potential profiles. By using a cesium ion beam with the energy of several keV, the observable region covers most of the upper half of the plasma. Although the probe beam is deflected by the poloidal magnetic field produced by plasma current and poloidal coil currents, it can be detected under the plasma current up to 150 kA by modifying the trajectories with two electrostatic sweepers. According to numerical estimation of the detected beam intensity, sufficient signal intensity for measuring plasma turbulence can be obtained over almost the measurable region when the electron density is up to 1×10^19 m^(-3) which is larger than the cut-off density of ECH in QUEST. The performance of the designed HIBP is sufficient for the QUEST project..
3.	Takeshi Ido, Dynamics of energetic particle-driven oscillatory zonal flow in toroidal plasmas, 第38回　プラズマ・核融合学会, 2021.11.
4.	井戸毅，長谷川真，池添竜也，恩地拓己，出射浩，黒田賢剛，吉田直亮，永島芳彦, QUEST用重イオンビームプローブの設計, プラズマ・核融合学会, 2020.12.
5.	Takeshi Ido, Akihide Fujisawa, Keiji Takemura, Naohiro Kasuya, Shigeru Inagaki, Atsushi Fukuyama, Yoshihiko Nagashima, Chanho Moon, Kotaro Yamasaki, Takuma Yamada, Yusuke Kosuga, Makoto Sasaki , Design of Heavy Ion Beam Probes on the PLATO tokamak, High-Temperature Plasma Diagnostics Conference, 2020.12, Plasma turbulence plays a decisive role in determining dynamics of plasmas not only in laboratories but also in the space. Especially, recent studies have indicated the importance of not only local but also global properties of the turbulence such as symmetry breaking and multi-scale interaction. In order to explore dynamics of plasmas through measuring plasma turbulence precisely and globally, a new tokamak named Plasma Turbulence Observatory (PLATO) is being constructed in Kyushu University. One of the key diagnostic systems for the PLATO project is Heavy Ion Beam Probe (HIBP), by which the electric potential, its fluctuations, density fluctuations, and magnetic fluctuations are measured directly and simultaneously without any perturbation to the plasmas. The HIBPs are installed in two toroidal sections to observe long range correlation in the toroidal direction. In addition, two energy analyzers in a poloidal cross section to observe the poloidal asymmetry and the correlation in the poloidal direction. The measurable area covers almost the whole plasma with a circular poloidal cross section and approximately 80 % of a poloidal cross section of the plasma with \kappa of 1.5 and \delta of 0.5, where \kappa is the ellipticity and \delta is the triangularity. The beam energy is 10 – 50 keV for Rubidium (Rb) beam or 50 – 150 keV for Sodium (Na) beam. According to a numerical calculation under the condition in which the central electron density is 1x10^19 (m^-3) and the density profile is parabolic, the detected beam intensity will be sufficient for micro-turbulence measurement in the region from the normalized minor radius(rho) of 0.2 to the plasma edge by Rb beam and in whole measurable region by Na beam. Therefore, we will be able to investigate nature of turbulence through multi-scale and simultaneous measurement. .
6.	井戸毅，清水昭博，西浦正樹，濱田泰司，新配位創成研究チーム, 乱流抑制配位創成に向けたHIBP設置可能性の検討, プラズマ・核融合学会, 2020.11.
7.	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..
8.	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。.

学会活動

所属学会名

プラズマ・核融合学会

日本物理学会

学協会役員等への就任

2013.10～2016.09, 日本物理学会, 運営委員.

学会大会・会議・シンポジウム等における役割

2020.10.26～2020.10.31, 4th Asia Pacific Conference on Plasma Physics (AAPPS-DPP2020), プログラム委員，座長.

学会誌・雑誌・著書の編集への参加状況

2021.07～2023.06, プラズマ・核融合学会誌, 国内, 編集委員.

2018.10～2022.09, Plasma and Fusion Research, 国際, 編集委員.

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
2022年度	4				4
2021年度	3	0	0	0	3
2020年度	5	0	0	0	5
2019年度	3	0	0	0	3

受賞

第15回技術進歩賞, プラズマ・核融合学会, 2010.11.

自然科学研究機構若手研究者賞, 自然科学研究機構, 2012.06.

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.

競争的資金(受託研究を含む)の採択状況

2018年度～2021年度, 科学研究費補助金 (文部科学省）, 代表, 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.

共同研究、受託研究(競争的資金を除く)の受入状況

2022.04～2023.03, 代表, LHDプラズマにおける熱・粒子輸送への高速イオン駆動電磁場の影響.

2022.04～2023.03, 代表, 磁場閉じ込め高温プラズマ内部における2次元電磁揺動計測手法の開発.

2021.04～2022.03, 代表, 磁場閉じ込め高温プラズマ内部における2次元電磁揺動計測手法の開発.

2021.04～2022.03, 代表, LHDプラズマにおける熱・粒子輸送への高速イオン駆動電磁場の影響.

九大関連コンテンツ

pure2017年10月2日から、「九州大学研究者情報」を補完するデータベースとして、Elsevier社の「Pure」による研究業績の公開を開始しました。

QIR　九州大学学術情報リポジトリシステム情報科学研究院

応用力学研究所


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