2025/01/06 更新

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写真a

フジサワ アキヒデ
藤澤 彰英
fujisawa akihide
所属
応用力学研究所 核融合力学部門 教授
極限プラズマ研究連携センター (併任)
総合理工学府 総合理工学専攻(併任)
職名
教授
連絡先
メールアドレス
電話番号
0925837709
プロフィール
プラズマ乱流の実験的研究を主に行っている。現在は、伊藤プラズマ乱流研究センターおよび高温プラズマ力学センターを 拠点として、直線装置PANTAにおける実験指導およびプラズマ乱流実験全体におけるデータ解析法の開発などを 手がけている。またプラズマ乱流実験を試行したトーラス型磁場プラズマ閉じ込め装置の設計を行っている。
外部リンク

学位

  • 理学博士

経歴

  • 自然科学研究機構 核融合科学研究所   

研究テーマ・研究キーワード

  • 研究テーマ: 非平衡極限プラズマ全国共同連携ネットワーク研究計画

    研究キーワード: 極限プラズマ

    研究期間: 2014年4月 - 2023年3月

  • 研究テーマ: プラズマ乱流及び分岐の実験的研究

    研究キーワード: プラズマ乱流、分岐、輸送、核融合

    研究期間: 2014年4月 - 2023年3月

  • 研究テーマ: 非平衡極限プラズマ全国共同連携ネットワーク研究計画

    研究キーワード: 極限プラズマ

    研究期間: 2010年10月 - 2016年9月

受賞

  • プラズマ核融合学会論文賞

    2013年12月   プラズマ核融合学会   プラズマ学融合学会のPlasma and Fusion Research誌に掲載されたLong Range Temperature Fluctuation in LHDと題する論文が平成25年度の論文賞を受賞した。 プラズマ乱流が創成する巨視的な揺らぎ構造の発見に関する論文で、これまで謎であった非局所輸送の解明につながるなど、磁場閉じ込めプラズマの構造形成原理の理解を大きく進める論文である。

  • 日本物理学会論文賞

    2012年3月   日本物理学会  

  • 仁科記念賞

    2011年12月   仁科記念財団   藤澤彰英、居田克巳の両氏は、高温磁場閉じ込めプラズマにおいて、自発的に形成される巨視的・メゾスケールの電磁場構造(自発流、自発電場界面、帯状流、帯状磁場等)を世界に先駆けて次々と実験で観測し、電磁場構造が微視的乱流から形成される機構を実証した。プラズマ乱流にかかわる輸送と非線形相互作用の解明に決定的進歩をもたらした。微視的熱乱流が大域的磁場を形成する、乱流ダイナモ仮説の素過程の一つも実証した。これらは、プラズマ物理学の新しい研究領域を開拓する傑出した業績である。核融合実験炉のコスト減や信頼性向上につながる等核融合研究にも多大な貢献をした。

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    磁場閉じ込めプラズマにおける乱流による帯状流、および帯状磁場形成の実験研究であり、磁場閉じ込めプラズマの性能予測の向上と、歴史的な物理学上の問題であるダイナモ過程の解明に迫る研究業績である。

  • 平成22年度科学技術分野の文部科学大臣表彰科学技術賞

    2010年4月   文部科学省   磁場閉じ込めプラズマにおける回転流の発見と炉心改善研究

  • 第26回井上学術賞

    2009年12月   財団法人 井上科学振興財団   研究題目「磁場閉じ込めプラズマの乱流輸送の実験的研究と帯状流の発見」

  • JPSJ注目論文

    2007年2月   日本物理学会   論文 'Causal Relationship between Zonal Flow and Turbulence in a Toroidal Plasma' A. Fujisawa et al., J. Phys. Soc. Jpn, 76 p. 033501 (2007)

  • プラズマ・核融合学会論文賞受賞

    2000年11月   プラズマ・核融合学会   論文 'Experimental Observation of Bifurcation Nature of Radial Electric Field in CHS Heliotron/Torsatron' A. Fujisawa et al., J. Plasma Fusion Res. 75 604 (1999)

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論文

  • Turbulence in Toroidal Plasma 査読 国際誌

    Akihide Fujisawa

    Proceedings of the 12th Asia Pacific Physics Conference   2014年4月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    A new paradigm for plasma turbulence has been made; plasma turbulence is regarded as nonlinear system of drift waves and their generated structures, zonal flows, streamers, and large scale modes. New paradigm provides ways to clarify unsolved problems in magnetically confined plasma, for example, confinement improvement, nonlocal transport, isotope effect, and so on. Identification of these structures should contribute to establishing the first principle laws of transport. Full scale measurement covering the whole plasma is essential for further understanding of plasma turbulence in laboratory experiments. Special toroidal device should be made for further physical understanding of turbulence.

  • Experimental studies of mesoscale structure and its interactions with microscale waves in plasma turbulence 査読 国際誌

    Fujisawa, Akihide

    PLASMA PHYSICS AND CONTROLLED FUSION   53.0 ( 12.0 )   2011年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The modern view of plasma turbulence has been established due to the discovery of zonal flows and other structures which drift-waves generate, and contributes to exploring new manners of understanding turbulence-driven transport and structural formation in magnetized plasmas and astronomic objects. This paper presents the recent development of laboratory experiments, in particular, for drift-wave turbulence which have advanced understanding and have made the paradigm shift. The topics include the discovery of mesoscale structures, such as zonal flows and streamers, the recent development of analyzing techniques to quantify the couplings between different scale structures and methods to elucidate energy transfer direction, and turbulence transport and barrier formation. Finally, future experiments are suggested for establishing the first-principle laws of turbulence transport and structural formation.

    DOI: 10.1088/0741-3335/53/12/124015

  • Observation of Long-Distance Radial Correlation in Toroidal Plasma Turbulence 査読 国際誌

    Inagaki, S.; Tokuzawa, T.; Itoh, K.; Ida, K.; Itoh, S. -I.; Tamura, N.; Sakakibara, S.; Kasuya, N.; Fujisawa, A.; Kubo, S.; Shimozuma, T.; Ido, T.; Nishimura, S.; Arakawa, H.; Kobayashi, T.; Tanaka, K.; Nagayama, Y.; Kawahata, K.; Sudo, S.; Yamada, H.; Komori, A.

    PHYSICAL REVIEW LETTERS   107.0 ( 11.0 )   0.0 - 0.0   2011年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This Letter presents the discovery of macroscale electron temperature fluctuations with a long radial correlation length comparable to the plasma minor radius in a toroidal plasma. Their spatiotemporal structure is characterized by a low frequency of similar to 1-3 kHz, ballistic radial propagation, a poloidal or toroidal mode number of m/n = 1/1 (or 2/1), and an amplitude of similar to 2% at maximum. Nonlinear coupling between the long-range fluctuations and the microscopic fluctuations is identified. A change of the amplitude of the long-range fluctuation is transmitted across the plasma radius at the velocity which is of the order of the drift velocity.

    DOI: 10.1103/PhysRevLett.107.115001

  • Equilibrium reconstruction of axisymmetric plasmas by combining Gaussian process regression and Markov chain Monte Carlo sampling

    Nishizawa, T; Tokuda, S; Sanpei, A; Hasegawa, M; Yamasaki, K; Fujisawa, A

    PLASMA PHYSICS AND CONTROLLED FUSION   67 ( 1 )   2025年1月   ISSN:0741-3335 eISSN:1361-6587

  • On the Nonlinear Coupling of the High Wavenumber Fluctuations Exhibiting the Discrete Spectra Observed in PANTA

    Kawachi, Y; Sasaki, M; Nishizawa, T; Kosuga, Y; Terasaka, K; Inagaki, S; Yamada, T; Kasuya, N; Moon, C; Nagashima, Y; Fujisawa, A

    PLASMA AND FUSION RESEARCH   19 ( 0 )   n/a - 2   2024年11月   ISSN:1880-6821 eISSN:18806821

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    記述言語:英語   出版者・発行元:一般社団法人 プラズマ・核融合学会  

    We report on the nonlinear coupling properties of high-wavenumber fluctuation, which exhibits discrete frequency spectra with a frequency span comparable to the ion cyclotron frequency observed in PANTA. Bicoherence analysis is used to investigate this nonlinear coupling. The results indicate a finite coupling between individual discrete peaks but no coupling between the ion cyclotron frequency components of these discrete peaks. This suggests that the observed turbulence with a discrete spectrum is destabilized linearly rather than through nonlinear coupling.

    DOI: 10.1585/pfr.1201031

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  • Preparatory study of feasibility for a vertical viewing electron cyclotron emission diagnostic for the JT-60SA tokamak 査読 国際誌

    Tokuzawa, T; Yoshida, M; Imazawa, R; Nakagawa, S; Inagaki, S; Kin, F; Chiba, S; Suzuki, N; Nasu, T; Fujisawa, A; Ida, K

    REVIEW OF SCIENTIFIC INSTRUMENTS   95 ( 8 )   2024年8月   ISSN:0034-6748 eISSN:1089-7623

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Review of Scientific Instruments  

    A preparatory study is underway to investigate the feasibility study of high-energetic, non-thermal electron distribution function measurements using a vertical-viewing electron cyclotron emission (ECE) diagnostic on JT-60SA. The system is designed to detect broad ECE spectra (70-260 GHz) due to the second, third, and fourth harmonics using a focusing optics system with four quasi-optical mirrors in the upper port of JT-60SA. A Gaussian beam optics design is performed in vacuum, and ray tracing calculations are performed in plasma using the TRAVIS code to investigate density characteristics. A ceramic viewing dump is also designed to reduce the effects of multiple reflections from the opposing vacuum vessel surface.

    DOI: 10.1063/5.0218359

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  • Identification of nonlinear effects of background asymmetry on solitary oscillations in a cylindrical plasma 査読 国際誌

    Kobayashi, T; Fujisawa, A; Nagashima, Y; Moon, C; Yamasaki, K; Nishimura, D; Inagaki, S; Shimizu, A; Tokuzawa, T; Ido, T

    SCIENTIFIC REPORTS   14 ( 1 )   12175   2024年5月   ISSN:2045-2322

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Scientific Reports  

    A symmetry-breaking in rotational spatial pattern of quasi-periodic solitary oscillations is revealed with tomography measurement of plasma emission, simultaneously with background asymmetry in stationary plasma structure. Although the oscillatory pattern deformation is a natural course in the presence of asymmetry, elaborate analyses identify existence unfeatured nonlinear effects of the background asymmetry, i.e., its nonlinear couplings with harmonic modes of rotational symmetry, to produce non-harmonic mode to break the symmetry and cause the oscillatory pattern to be chaotic. The findings suggest the unrecognized fundamental process for plasmas to be turbulent.

    DOI: 10.1038/s41598-024-62969-1

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  • Mass dependency of high-wavenumber turbulence in a linear partially magnetized plasma 査読 国際誌

    Kawachi, Y; Sasaki, M; Nishizawa, T; Kosuga, Y; Terasaka, K; Inagaki, S; Yamada, T; Kasuya, N; Moon, C; Nagashima, Y; Fujisawa, A

    PHYSICS OF PLASMAS   31 ( 4 )   2024年4月   ISSN:1070-664X eISSN:1089-7674

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Plasmas  

    We investigated the mass dependency of the high-wavenumber turbulence, which occurs at scales smaller than the ion effective Larmor radius, in a partially magnetized plasma column. In this system, two different types of fluctuations were observed: one exhibiting a coherent discrete spectrum, while the other displaying a broadband continuous spectrum. The phase velocities of both types showed a similar mass dependency, approximately matching the ion sound velocity or electron diamagnetic drift velocity. Additionally, we found that the discrete spectrum has a peak interval frequency comparable to the ion cyclotron frequency, which is consistent with ion cyclotron ranges of fluctuations, including ion Bernstein waves.

    DOI: 10.1063/5.0187997

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  • A Method to Analyze Plasma Images Using Modified Fourier-Bessel Functions 査読 国際誌

    Nishimura, Y; Fujisawa, A; Nagashima, Y; Moon, C; Nishizawa, T; Kobayashi, T; Shimizu, A; Tokuzawa, T; Ido, T; Nishimura, D; Kobayashi, T

    PLASMA AND FUSION RESEARCH   19 ( 0 )   1201014 - 1201014   2024年3月   ISSN:1880-6821 eISSN:18806821

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 プラズマ・核融合学会  

    A new method is proposed to analyze plasma image of tomography using modified Fourier-Bessel Functions (FBF) instead of the original FBF analysis. The application of the method to an assumed plasma image shows that the difference between the original and the fitting image is improved considerably to that of FBF, owing to giving a better fitting inside the plasma and eliminating the ghost values outside the plasma, without any disadvantages in analysis of plasma structures and patterns.

    DOI: 10.1585/pfr.19.1201014

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  • Velocity Field Estimation using Tomography in a Cylindrical Plasma 査読 国際誌

    Nishimura, D; Fujisawa, A; Nagashima, Y; Moon, C; Yamasaki, K; Nishizawa, T; Kobayashi, T; Kobayashi, T; Shimizu, A; Tokuzawa, T

    PLASMA AND FUSION RESEARCH   19 ( 0 )   1201005 - 1201005   2024年1月   ISSN:1880-6821 eISSN:18806821

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 プラズマ・核融合学会  

    This article presents a new method, called extended Rotational Movement Analysis (e-RoMA), to estimate the velocity field of a cylindrical plasma from its two-dimensional images based on Fourier-Bessel function expansion. The proposed method is applied to tomography images of a plasma produced in a linear cylindrical device PANTA and succeeded in obtaining the two- dimensional velocity field. The first results suggest an issue to be investigated, that is, the presence of azimuthal asymmetry in the velocity field.

    DOI: 10.1585/pfr.19.1201005

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  • Estimation of plasma parameter profiles and their derivatives from linear observations by using Gaussian processes 査読 国際誌

    Nishizawa, T; Tokuda, S; Kobayashi, T; Tanaka, K; Funaba, H; Yamada, ; Takemura, Y; Tokuzawa, T; Yasuhara, R; Uehara, H; Ida, K; Takahashi, H; Kawachi, Y; Inagaki, S; Kado, S; Sasaki, M; Fujisawa, A

    PLASMA PHYSICS AND CONTROLLED FUSION   65 ( 12 )   2023年12月   ISSN:0741-3335 eISSN:1361-6587

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Plasma Physics and Controlled Fusion  

    Gaussian process regression (GPR) has been utilized to provide fast and robust estimates of plasma parameter profiles and their derivatives. We present an alternative GPR technique that performs profile regression analyses based on arbitrary linear observations. This method takes into account finite spatial resolution of diagnostics by introducing a sensitivity matrix. In addition, the profiles of interest and their derivatives can be estimated in the form of a multivariate normal distribution even when only integrated quantities are observable. We show that this GPR provides meaningful measurements of the electron density profile and its derivative in a toroidal plasma by utilizing only ten line-integrated data points given that the locations of magnetic flux surfaces are known.

    DOI: 10.1088/1361-6587/ad074a

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  • Identification of trapping finer-scale fluctuations in a solitary vortex in linear magnetized plasma 査読 国際誌

    Arakawa, H; Sasaki, M; Inagaki, S; Lesur, M; Kosuga, Y; Kobayashi, T; Kin, F; Yamada, T; Nagashima, Y; Fujisawa, A; Itoh, K

    PLASMA PHYSICS AND CONTROLLED FUSION   65 ( 11 )   2023年11月   ISSN:0741-3335 eISSN:1361-6587

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Plasma Physics and Controlled Fusion  

    The mutual interaction of drift wave-type modes and zonal flows causes the formation of higher-order nonlinear structures. This study focuses on the spatio-temporal behavior of these higher-order structures in a linear magnetized plasma. The structures include a solitary vortex, a long-lived circumnavigating motion localized both radially and azimuthally, and a short-lived packet of finer-scale fluctuations excited at the position of the solitary vortex. Observing the time evolution of the two-dimensional cross-sectional structures revealed that the packet of finer-scale fluctuations is trapped in the solitary vortex. The trapping times found are consistent with the theoretical evaluation.

    DOI: 10.1088/1361-6587/acfbb3

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  • Transition between continuous and discrete spectra of high-wavenumber turbulence in neutral gas pressure scan experiments on a linear magnetized plasma 査読 国際誌

    Kawachi, Y; Sasaki, M; Nishizawa, T; Kosuga, Y; Terasaka, K; Inagaki, S; Yamada, T; Kasuya, N; Moon, C; Nagashima, Y; Fujisawa, A

    PLASMA PHYSICS AND CONTROLLED FUSION   65 ( 11 )   2023年11月   ISSN:0741-3335 eISSN:1361-6587

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Plasma Physics and Controlled Fusion  

    Spectral transition between continuous and discrete spectra has been observed in high-wavenumber turbulence excitation experiments. The transition appeared in neutral gas scanning, which shows that continuous spectra dominate at low gas pressures and discrete spectra dominate at high gas pressures. Both spectra have well smaller spatial scale than the ion effective Larmor radius. The discrete spectra have 6-11 peaks and maximum peak values at 4th or 5th peak. Correlation length analysis reveals that the continuous component is turbulent and the discrete component is coherent. The bicoherence analysis shows that the turbulent spectra have finite nonlinear coupling, whereas the discrete spectra have no corresponding coupling.

    DOI: 10.1088/1361-6587/acfbf7

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  • Observation of Quasi-Periodic Two-Dimensional Velocity Fields in Plasma Using Tomographic Laser-Induced Fluorescence Spectroscopy 査読 国際誌

    Arakawa, H; Sasaki, M; Inagaki, S; Terasaka, K; Kawachi, Y; Kin, F; Yamada, T; Nagashima, Y; Fujisawa, A

    PLASMA AND FUSION RESEARCH   18 ( 0 )   1201086 - 1201086   2023年10月   ISSN:1880-6821 eISSN:18806821

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 プラズマ・核融合学会  

    Recently, a new method that applies vector tomography to laser-induced fluorescence has been introduced, enabling the measurement of quasi-periodic two-dimensional velocity field in plasma [H. Arakawa et al., Plasma Fusion Res. 18, 1401032 (2023)]. In this study, we experimentally demonstrated this method in a linear magnetized plasma and presented the initial measurement results. The observed two-dimensional velocity field allowed the evaluation of Reynolds force and its energy transfer.

    DOI: 10.1585/pfr.18.1201086

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  • Rotational movement analysis based on Fourier-rectangular function transform for cylindrical plasma 査読 国際誌

    Nishimura, D; Fujisawa, A; Yamasaki, K; Nagashima, Y; Moon, C; Nishizawa, T; Kobayashi, TK; Kobayashi, T; Shimizu, A; Tokuzawa, T; Ido, T

    JOURNAL OF APPLIED PHYSICS   134 ( 11 )   113302   2023年9月   ISSN:0021-8979 eISSN:1089-7550

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Journal of Applied Physics  

    This article presents a method to estimate the rotational velocity of a cylindrical plasma from its two-dimensional images by an extended use of the Fourier-rectangular function transform, which was proposed to analyze the structure and dynamics of a cylindrical plasma [K. Yamasaki e t a l ., J. Appl. Phys. 126 , 043304 (2019)]. The proposed method is applied to tomography images of plasmas produced in a linear cylindrical device and succeeds in obtaining the radial distribution of rotational velocity and its fluctuations, providing an interesting finding, that is, the existence of flow modulation associated with m = 1 mode fluctuations.

    DOI: 10.1063/5.0165318

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  • Nonlinear simulation of resistive drift waves in cylindrical magnetized plasmas in the presence of symmetry breaking particle source 査読 国際誌

    Kasuya, N; Sasaki, M; Kawachi, Y; Kobayashi, T; Nishizawa, T; Arakawa, H; Yamada, T; Fujisawa, A

    PHYSICS OF PLASMAS   30 ( 8 )   82302   2023年8月   ISSN:1070-664X eISSN:1089-7674

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Physics of Plasmas  

    Nonlinear fluid simulation of drift wave turbulence in the presence of symmetry breaking particle source is performed for the cylindrical magnetized plasmas. It is demonstrated that the symmetry breaking of the system directly affects the selection rule of structure formations, the streamers disappear, and the zonal flows are enhanced in the case with the symmetry breaking. The symmetry breaking is introduced in the flux-driven simulation by inducing the particle source whose amplitude depends on the azimuthal angle. The symmetry breaking mode is driven stationarily, and the nonlinear process of the drift waves is significantly modified. By scanning the amplitude of the symmetry breaking source, the structure formation processes are systematically investigated. In addition, the nonlinear forces of the turbulence show the relaxation of the density gradient and the drive of the perpendicular/parallel flows in a two-dimensional manner.

    DOI: 10.1063/5.0150748

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  • Analysis of Turbulence Driven Particle Transport in PANTA by Using Multi-Field Singular Value Decomposition 査読 国際誌

    Kodahara, T; Sasaki, M; Kawachi, Y; Jajima, Y; Kobayashi, T; Yamada, T; Arakawa, H; Fujisawa, A

    PLASMA AND FUSION RESEARCH   18 ( 0 )   1202036 - 1202036   2023年6月   ISSN:1880-6821 eISSN:18806821

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 プラズマ・核融合学会  

    Multi-field singular value decompositions (SVDs) is applied to turbulence obtained in a cylindrical magnetized plasma, PANTA. This method enables us to obtain the spatial mode structures with common temporal evolution of different physical quantities, such as the fluctuations of density and flows. Turbulence driven particle transport is evaluated by the method. It is shown that only the coupling of the same mode drives the transport, which stems from the orthogonality of the SVD. Thanks to this characteristics, the number of degrees of freedom which plays roles for the transport dynamics could be significantly reduced.

    DOI: 10.1585/PFR.18.1202036

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  • Reynolds Force Evaluation of Quasi-Coherent Structure by Tomographic Laser-Induced Fluorescence Spectroscopy 査読 国際誌

    Arakawa, H; Sasaki, M; Inagaki, S; Fujisawa, A

    PLASMA AND FUSION RESEARCH   18 ( 0 )   1401032 - 1401032   2023年5月   ISSN:1880-6821 eISSN:18806821

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 プラズマ・核融合学会  

    A new method of vector tomography by laser-induced fluorescence (LIF) spectroscopy is proposed for the evaluation of the velocity field of quasi-coherent structure in linear magnetized plasma. Here, the two-dimensional velocity field was reconstructed with measuring synchronization of azimuthal reference probes and line-integrated LIF. The laser installation condition is designed to move in a radial direction perpendicular to the laser path. We applied the proposed method to a quasi-coherent flow obtained from a direct numerical turbu-lence simulation and demonstrated that the Reynolds stress and its force can be evaluated if its flow structure is maintained.

    DOI: 10.1585/PFR.18.1401032

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  • Sanae-Inoue Itoh 1952–2019: a memorial note for a pioneer researcher of plasma bifurcation 国際誌

    Fujisawa, A; Kasuya, N; Kosuga, Y; Nagashima, Y; Sasaki, M; Yamada, T

    REVIEWS OF MODERN PLASMA PHYSICS   7 ( 1 )   21   2023年5月   ISSN:2367-3192

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Reviews of Modern Plasma Physics  

    This memorial note for Professor Sanae-I Itoh presents her specific achievements in physics research alongside her wider record of accomplishment in the field of magnetically confined plasmas. The topics include bifurcation phenomena (e.g., H-mode and improved confinement modes), turbulence-generated structures (e.g., zonal flows and streamers), and fundamental concepts and processes in plasma turbulence (e.g. nonlinear couplings and energy transfer. The note focuses initially on results obtained through her integration of theory, simulation, and experiment, particularly those arising from a low temperature plasma facility at Kyushu University. We then describe contemporary challenges in plasma turbulence which Sanae addressed with great interest, and consider some of the perspectives that were opened by her achievements.

    DOI: 10.1007/s41614-023-00123-6

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    Scopus

  • A Proposal to Evaluate Electron Temperature and Electron Density Fluctuations Using Dual Wavelength Emission Intensity Tomography in a Linear Plasma 査読 国際誌

    永島 芳彦, 藤澤 彰英, 稲垣 滋, 文 贊鎬, 金 史良, カワチ ユウイチ, 荒川 弘之, 山田 琢磨, 小林 達哉, 糟谷 直宏, 小菅 佑輔, 佐々木 真, 井戸 毅

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   92 ( 3 )   33501 - 033501-4   2023年3月   ISSN:00319015 eISSN:13474073

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:The Physical Society of Japan  

    A procedure to calculate normalized electron temperature and electron density fluctuations using dual wavelength emission intensity tomography in a linear magnetized plasma is proposed. Expression of emission intensity is modeled as ϵk ∞ Tαke n2e where ϵk is emission intensity, Te is electron temperature, ne is electron density, k = 1 for ArI, and k = 2 for ArII. Using the model, normalized Te and ne fluctuations can be expressed as linear function of both the normalized emission intensity fluctuations. To calculate αk, we perform least squares method between real ϵk measured with a tomography system and artificial ϵk reconstructed using Te and ne measured with a Langmuir probe located downstream of the tomography system. The results show that α1 = 2.2 and α2 = 2.6, and normalized Te and ne fluctuations are preliminarily evaluated from emission intensity tomography data.

    DOI: 10.7566/JPSJ.92.033501

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    Scopus

    CiNii Research

  • Formation Process of a Solitary Vortex in a Zonal Flow – Drift-Wave Dynamics 査読 国際誌

    Arakawa, H; Sasaki, M; Inagaki, S; Lesur, M; Kosuga, Y; Kobayashi, T; Kin, F; Yamada, T; Nagashima, Y; Fujisawa, A; Itoh, K

    PLASMA AND FUSION RESEARCH   17 ( 0 )   1301106 - 1301106   2022年11月   ISSN:1880-6821 eISSN:18806821

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:一般社団法人 プラズマ・核融合学会  

    A solitary vortex organization process in drift-wave type fluctuations interacting with the zonal flow was identified experimentally in a linear magnetized plasma. An azimuthal probe array was used to evaluate temporal changes in the amplitude and phase in the density fluctuations. Excitation/damping of the solitary vortex is synchronized with zonal perturbation, and the waveform of drift-wave type fluctuation and its harmonics also changes synchronously. The solitary vortex is formed primarily through the phase modulation of the fundamental drift-wave type fluctuation and its harmonics.

    DOI: 10.1585/pfr.17.1301106

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    Scopus

    CiNii Research

  • Effects of sawtooth heat pulses on edge flows and turbulence in a tokamak plasma 査読 国際誌

    Zhao, KJ; Nagashima, Y; Guo, ZB; Diamond, PH; Dong, JQ; Yan, LW; Itoh, K; Itoh, SI; Li, XB; Li, JQ; Fujisawa, A; Inagaki, S; Cheng, J; Xu, JQ; Kosuga, Y; Sasaki, M; Wang, ZX; Zhang, HQ; Chen, YQ; Cao, XG; Yu, DL; Liu, Y; Song, XM; Xia, F; Wang, S

    PLASMA SCIENCE & TECHNOLOGY   25 ( 1 )   15101   2022年1月   ISSN:1009-0630 eISSN:2058-6272

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Plasma Science and Technology  

    Enhancements of edge zonal flows, radial electric fields, and turbulence are observed in electron cyclotron resonance heating-heated plasmas (Zhao et al 2013 Nucl. Fusion 53 083011). In this paper, the effects of sawtooth heat pulses on flows and turbulence are presented. These experiments are performed using multiple Langmuir probe arrays in the edge plasmas of the HL-2A tokamak. The edge zonal flows, radial electric fields, and turbulence are all enhanced by sawteeth. Propagation of the zonal flow and turbulence intensities is also observed. The delay time of the maximal intensity of the electric fields, zonal flows, and turbulence with respect to the sawtooth crashes is estimated as ∼1 ms and comparable to that of the sawtooth-triggered intermediate phases. Not only the zonal flows but also the radial electric fields lag behind the turbulence. Furthermore, the intensities of both the zonal flows and electric fields nearly linearly increase/decrease with the increase/decrease of the turbulence intensity. A double-source predator-prey model analysis suggests that a relatively strong turbulence source may contribute to the dominant zonal flow formation during sawtooth cycles.

    DOI: 10.1088/2058-6272/ac7c60

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  • Dynamic interaction between fluctuations with different origins in a linear magnetized plasma 査読 国際誌

    Kawachi Y., Inagaki S., Sasaki M., Kosuga Y., Yamasaki K., Kobayashi T., Kin F., Yamada T., Arakawa H., Nagashima Y., Moon C., Kasuya N., Fujisawa A.

    Physics of Plasmas   28 ( 11 )   112302   2021年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/5.0065887

  • Transport Simulation of PLATO Tokamak Plasma Using Integrated Code TASK 査読 国際誌

    Mochinaga S., Kasuya N., Fukuyama A., Nagashima Y., Fujisawa A.

    Plasma and Fusion Research   16   1403093   2021年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1585/pfr.16.1403093

  • Effects of Electron Temperature Fluctuation on Turbulence Measurement by Langmuir Probe in a Magnetized Helicon Plasma 査読 国際誌

    Kawachi Y., Inagaki S., Sasaki M., Kosuga Y., Yamada T., Nagashima Y., Moon C., Kasuya N., Fujisawa A.

    Plasma and Fusion Research   16   1202081   2021年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1585/PFR.16.1202081

  • Fourier-Rectangular Function Analysis of Spatiotemporal Structure of Bursting Phenomenon in a Cylindrical Plasma 査読 国際誌

    Daiki NISHIMURA, Akihide FUJISAWA, Yoshihiko NAGASHIMA, Chanho MOON, Kotaro YAMASAKI, Taiki KOBAYASHI and Shigeru INAGAKI

    Plasma and Fusion Research   16   1201075   2021年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1585/pfr.16.1201075

  • Proposal of Analysis Method for Pattern Recognition of Two-Dimensional Structure of Plasma 査読 国際誌

    Taiki KOBAYASHI, Akihide FUJISAWA, Yoshihiko NAGASHIMA, Chanho MOON,Daiki NISHIMURA, Kotaro YAMASAKI and Shigeru INAGAKI

    Plasma and Fusion Research   16   1201082   2021年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1585/pfr.16.1201082

  • Conceptual design of heavy ion beam probes on the PLATO tokamak 査読 国際誌

    Ido T., Fujisawa A., Takemura K., Kobayashi T.-K., Nishimura D., Kasuya N., Fukuyama A., Moon C., Yamasaki K., Inagaki S., Nagashima Y., Yamada T.

    Review of Scientific Instruments   92 ( 5 )   53553   2021年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/5.0041814

  • Correlation-estimated conditional average method and its application on solitary oscillation in PANTA 査読 国際誌

    Kobayashi, T.-K., Fujisawa, A. Nagashima, Y., Moon, C., Yamasaki, K., Nishimura, D., Inagaki, S., Yamada, T., Kasuya, N., Kosuga, Y., Sasaki, M., Kawachi, Y.

    Plasma Physics and Controlled Fusion   63 ( 3 )   32001   2021年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1361-6587/abd980

  • Review of plasma turbulence experiments 国際誌

    Akihide FUJISAWA

    Proceedings of the Japan Academy, Series B   97 ( 3 )   103 - 119   2021年3月

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    記述言語:英語   掲載種別:研究論文(大学,研究機関等紀要)  

    DOI: 10.2183/pjab.97.006

  • Modal polarization analysis using Fourier- rectangular function transform in a cylindrical plasma 査読 国際誌

    D. Nishimura, A. Fujisawa, Y. Nagashima, C. Moon, K. Yamasaki, T.-K. Kobayashi, S. Inagaki, T. Yamada, Y. Kawachi, N. Kasuya, Y. Kosuga, and M. Sasaki

    Journal of Applied Physics   129 ( 9 )   93301   2021年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/5.0037352

  • The first observation of 4D tomography measurement of plasma structures and fluctuations 査読 国際誌

    Moon, C., Yamasaki, K., Nagashima, Y., Inagaki, S., Ido, T., Yamada, T., Kasuya, N., Kosuga, Y., Sasaki, M., Kawachi, Y., Nishimura, D., Kobayashi, T., Fujisawa, A.

    Scientific Reports   11 ( 1 )   3720   2021年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1038/s41598-021-83191-3

  • Comparison between Tomography and Langmuir Probe Data in PANTA 査読 国際誌

    Nagashima Y., Fujisawa A., Yamasaki K., Inagaki S., Moon C., Kin F., Kawachi Y., Arakawa H., Yamada T., Kobayashi T., Kasuya N., Kosuga Y., Sasaki M., Ido T.

    Journal of the Physical Society of Japan   89 ( 9 )   93501   2020年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7566/JPSJ.89.093501

  • Simulation of Co-Existence of Ballooning and Kink Instabilities in PLATO Tokamak Plasma 査読 国際誌

    Shuhei TOMIMATSU, Naohiro KASUYA, Masahiko SATO, Atsushi FUKUYAMA, Masatoshi YAGI, Yoshihiko NAGASHIMA and Akihide FUJISAWA

    Plasma and Fusion Research   15   1403052   2020年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1585/pfr.15.1403052

  • Observation of spatiotemporal structures of temperature fluctuations by using of a statistical phase detection method in a linear magnetized plasma 査読 国際誌

    Kawachi Y., Inagaki S., Kin F., Yamasaki K., Kosuga Y., Sasaki M., Nagashima Y., Yamada T., Arakawa H., Kasuya N., Moon C., Hasamada K., Fujisawa A.

    Plasma Physics and Controlled Fusion   62 ( 5 )   55011   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1361-6587/ab8132

  • Magnetic field dependence of plasma properties observed with tomography in PANTA 査読 国際誌

    Marui I., Fujisawa A., Nagashima Y., Moon C., Yamasaki K., Inagaki S., Yamada T.

    Plasma and Fusion Research   15   1201018   2020年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1585/PFR.15.1201018

  • Tomography system for two-dimensional observation of fluctuation in magnetized plasma 査読 国際誌

    Yamasaki K., Fujisawa A., Nagashima Y., Moon C., Inagaki S., Yamada T.

    Review of Scientific Instruments   91 ( 3 )   33502   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.5144480

  • Design and Implementation of DC Pulsed Power Supply Employing Self-Excited Induction Generators and Flywheels for Toroidal Field Coils of a Tokamak Device, PLATO 査読 国際誌

    Murayama M., Kato S., Fujisawa A., Matsuoka K., Tsutsui H., Tsuji-Iio S., Shimada R.

    IEEE Transactions on Applied Superconductivity   30 ( 4 )   9042294   2020年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1109/TASC.2020.2981075

  • Study of turbulence intermittency in linear magnetized plasma 査読 国際誌

    Boyu Zhang, Shigeru Inagaki, Kazunobu Hasamada, Kotaro Yamasaki, Fumiyoshi Kin, Yoshihiko Nagashima, Takuma Yamada and Akihide Fujisawa

    Plasma Physics and Controlled Fusion   61 ( 11 )   115010   2019年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1361-6587/ab434f

  • Spatial structure of low-frequency fluctuations throughout the transition of poloidal flow velocity in edge plasmas of LHD 査読 国際誌

    C. Moon, T. Kobayashi, K. Ida, T. Tokuzawa, C. Hidalgo, M. Yoshinuma, K. Ogawa, K. Itoh, A. Fujisawa, and LHD Experiment Group

    Physics of Plasmas   26 ( 9 )   092302   2019年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.5098954

  • 特別推進研究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(プロジェクトレビュー)

    藤澤彰英, 稲垣滋, 井戸毅, 飯尾俊二

    プラズマ・核融合学会誌   95 ( 8 )   391-397   2019年8月

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    記述言語:日本語  

  • Ion temperature measurement by laser-induced fluorescence spectroscopy in panta 査読 国際誌

    Arakawa H., Inagaki S., Kosuga Y., Sasaki M., Kin F., Hasamada K., Yamasaki K., Kobayashi T., Yamada T., Nagashima Y., Fujisawa A., Kasuya N., Itoh K., Itoh S.-I.

    IEEJ Transactions on Electrical and Electronic Engineering   14 ( 10 )   1450-1454   2019年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1002/tee.22962

  • Fourier-rectangular function analysis for cylindrical plasma images 査読 国際誌

    K. Yamasaki, A. Fujisawa, Y. Nagashima, C. Moon, S. Inagaki, N. Kasuya, Y. Kosuga, M. Sasaki, and T. Yamada

    Journal of Applied Physics   126 ( 4 )   043304   2019年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.5108717

  • Comparison of Conditional Average Using Threshold and Template Methods for Quasi-Periodic Phenomena in Plasmas 査読 国際誌

    Fumiyoshi KIN, Kimitaka ITOH, Tim HAPPEL, Gregor BIRKENMEIER, Akihide FUJISAWA, Sigeru INAGAKI, Sanae-I. ITOH, Ulrich STROTH and ASDEX Upgrade Team

    Plasma and Fusion Research   2019年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Roles of solitary eddy and splash in drift wave-zonal flow system in a linear magnetized plasma 査読 国際誌

    H. Arakawa, Makoto Sasaki, Inagaki Shigeru, Yusuke Kosuga, T. Kobayashi, Naohiro Kasuya, Takuma Yamada, Yoshihiko Nagashima, F. Kin, akihide fujisawa, K. Itoh, S. I. Itoh

    Physics of Plasmas   26 ( 5 )   2019年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We experimentally investigate the roles of drift wave type fluctuations interacting with zonal flow. The drift wave type fluctuations examined in this paper are characterized by nonlinear solitary wave, splash, and solitary eddy [Arakawa et al., Sci. Rep. 6, 33371 (2016)]. Compared to the nonlinear solitary wave, splash has a short lifetime, while solitary eddy has a long lifetime. Excitation/damping of the splash and the solitary eddy are synchronized with zonal perturbation. The roles of the splash and the solitary eddy in transport processes are also discussed. Solitary eddy contributes to momentum transport and accelerates zonal flow. The particle flux driven by the solitary eddy and the splash is in the inward and outward directions, respectively, with similar magnitudes.

    DOI: 10.1063/1.5094577

  • Estimation of particle flux driven by coherent mode using of statistical conditional averaging 査読 国際誌

    Kawachi Y., Inagaki S., Hasamada K., Yamasaki K., Kin F., Kosuga Y., Sasaki M., Nagashima Y., Kasuya N., Yamada T., Zhang B., Fujisawa A.

    Plasma and Fusion Research   14   1402090   2019年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1585/PFR.14.1402090

  • Observations of radially elongated particle flux induced by streamer in a linear magnetized plasma 査読 国際誌

    F. Kin, akihide fujisawa, K. Itoh, Yusuke Kosuga, Makoto Sasaki, Inagaki Shigeru, Yoshihiko Nagashima, Takuma Yamada, Naohiro Kasuya, K. Yamasaki, K. Hasamada, B. Y. Zhang, Y. Kawachi, H. Arakawa, T. Kobayashi, S. I. Itoh

    Physics of Plasmas   26 ( 4 )   2019年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The streamer-driven particle flux is evaluated experimentally in a linear cylindrical plasma. The streamers, a radially elongated and azimuthally localized structure created in turbulent plasma, really induce ballistic transport, and directly connect the plasma core to the edge within one order faster time scale than that of turbulence. The occurrence of large transport deviates from a Gaussian distribution and is likely to obey a power law. The fundamental plasma experiment clearly shows the significant and essential contributions of streamers to cross-field transport and structural formation of turbulent plasmas.

    DOI: 10.1063/1.5093218

  • Combined methods of moment vectors and Stokes parameters to analyze tomographic image of plasma turbulence 査読 国際誌

    akihide fujisawa, Yoshihiko Nagashima, K. Yamasaki, Inagaki Shigeru, Takuma Yamada, Makoto Sasaki

    Physics of Plasmas   26 ( 1 )   2019年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Plasma turbulence tomography is now working to show a two dimensional structure and dynamics of plasma turbulence in a cylindrical plasma device, PANTA. A new method, the Stokes parameter analysis on moment vectors, is being developed to treat the image of plasma turbulence and extract hidden characteristics of polarization or rotation of spatial patterns created in turbulent plasmas. The article presents the explanation of the method and the application results obtained from a PANTA plasma.

    DOI: 10.1063/1.5048970

  • Density profile measurement with a heavy ion beam probe in a toroidal plasma of the compact helical system 査読 国際誌

    A. Shimizu, akihide fujisawa, S. Ohshima, H. Nakano, T. Minami, M. Isobe, S. Okamura, K. Matsuoka

    Review of Scientific Instruments   89 ( 11 )   2018年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A possibility of electron density measurements with heavy ion beam probes (HIBPs) has been demonstrated, along with their capability to measure the potential and magnetic field. A method has been proposed to reconstruct the electron density profile [A. Fujisawa et al., Rev. Sci. Instrum. 74, 3335 (2003)]. In the method, the profile of secondary beam currents is converted into a local density profile by taking into account local brightness and so-called path integral effects which mean the effect of beam attenuation along the beam orbit. Here the article presents the HIBP measurement of the electron density profile after the proposed method was first applied on the real experimental data of compact helical system plasmas. In the real application, the hollow density and the peaked profiles are successfully obtained with sufficiently high temporal resolution (a few ms), in accordance with the electron density profile measured with Thomson scattering for electron cyclotron resonance heating and neutral beam injection plasmas.

    DOI: 10.1063/1.5039571

  • Propagation direction of geodesic acoustic modes driven by drift wave turbulence 査読 国際誌

    Makoto Sasaki, K. Itoh, T. Kobayashi, Naohiro Kasuya, akihide fujisawa, Sanae Itoh

    Nuclear Fusion   58 ( 11 )   2018年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Selection rule of the radial propagation direction of geodesic acoustic modes (GAMs) is investigated. Here, we study the influence of nonlinear coupling with drift wave turbulence on the propagation direction of GAMs. Based on wave-kinetic equation for the turbulence, the phase-space dynamics is numerically solved and the nonlinear saturated states are obtained, where the phase-space consists of the real space and the wavenumber space. A wave pattern of the GAM in a nonlinear saturated state varies to form a standing wave, outward and inward propagating waves, depending on the peak radial wavenumber of the turbulence. The impact of nonlinear coupling with turbulence is discussed by deriving the GAM dispersion relation that includes the effect of the turbulence.

    DOI: 10.1088/1741-4326/aad251

  • Experimental research plan of nonlinearity of tokamak edge turbulence in plasma turbulence observatory 国際誌

    Yoshihiko Nagashima, akihide fujisawa

    Front-runners� Symposium on Plasma Physics in Honor of Professors Kimitaka Itoh and Sanae-I. Itoh, 2018 Front-runners' Symposium on Plasma Physics in Honor of Professors Kimitaka Itoh and Sanae-I. Itoh   2018年8月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    A set of experimental works based on nonlinear data analysis in the JFT-2M is planned in order to verify nonlinearity of edge turbulence in PLAsma Turbulence Observatory (PLATO) tokamak. In this paper, we introduce the preceding experimental works of the JFT-2M tokamak, and show how the revisited works are applied to progress of turbulence research in the new tokamak.

    DOI: 10.1063/1.5048716

  • Determination of Spatiotemporal Structure of Fluctuations by Statistical Averaging Method 査読 国際誌

    Yuichi KAWACHI, Sigeru INAGAKI, Kentaro TOMITA, Kotaro YAMASAKI, Fumiyoshi KIN, Yusuke KOSUGA, Makoto SASAKI, Yoshihiko NAGASHIMA, Naohiro KASUYA, Kazunobu HASAMADA, Boyu ZHANG, Akihide FUJISAWA

    Plasma and Fusion Research   2018年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Past and present experiments toward PLATO project 国際誌

    akihide fujisawa

    Front-runners� Symposium on Plasma Physics in Honor of Professors Kimitaka Itoh and Sanae-I. Itoh, 2018 Front-runners' Symposium on Plasma Physics in Honor of Professors Kimitaka Itoh and Sanae-I. Itoh   2018年8月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    Plasma turbulence has been intensively studied in the research of magnetic confinement for realizing a nuclear fusion reactor, and the international research has provided various discoveries of and physics insights into turbulent plasmas, such as turbulence-driven transport, effects of electric field on confinement, generation of flows and fields, and so on, although the research has been performed with a strong weight on achieving fusion-relevant performance plasma. However, at present a project to construct a physics-oriented device, named PLAsma Turbulence Observatory (PLATO), in Kyushu University, aiming at essential physics understanding of turbulent plasmas. The article reviews the major physics achievements up to data, and the steps to reach the concept of a new toroidal device with the major purpose for physics understanding of plasma turbulence.

    DOI: 10.1063/1.5048721

  • Effect of magnetic shear on edge turbulence in SOL-like open field line configuration in QUEST 査読 国際誌

    Santanu Banerjee, H. Zushi, N. Nishino, Kazuaki Hanada, Hiroshi Idei, K. Nakamura, Makoto Hasegawa, akihide fujisawa, Yoshihiko Nagashima, K. Mishra, S. Tashima, Takumi Onchi, A. Kuzmin, K. Matsuoka

    Plasma Physics and Controlled Fusion   60 ( 8 )   2018年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Intensity fluctuations are investigated using the fast camera imaging technique in the slab annular plasma as a function of magnetic shear and connection length in the spherical tokamak QUEST. Note that here QUEST is operated as a simple magnetized torus with a tight aspect ratio. Slab annular plasmas feature open magnetic field lines and can mimic the tokamak edge-scrape off layer (SOL)-like plasma attributes reasonably well. Three magnetic shear regimes are realized using three poloidal magnetic field (PF) coil pairs. A whole range of connection lengths (∼∞ ≥ L c ≥ 5.5 m) is scanned by varying the PF strength for a given toroidal field for each magnetic shear regime. For the first time a systematic study of the effect of magnetic shear and field line pitch together on edge-SOL-like plasma fluctuations is being reported. Slab plasmas with intermediate magnetic shear are observed to be more susceptible to generate distinct blobs when L c is reduced by increasing the PF strength. A distinct coherent mode appears only at the lowest magnetic shear slab featuring a deep potential well. Such mode is not apparent at other magnetic shear cases even at the same L c. Finally, with a combination of PF coil pairs, both the features of intermediate and low magnetic shear slabs are shown to be realizable simultaneously. Significantly stronger blobs are observed with such combination of PF mirror ratios in the presence of a coherent mode. This study may provide better insight into the effect of magnetic configuration in the tokamak edge and SOL turbulence and can help in searching for better tools to control cross-field convective intermittent transport in tokamaks.

    DOI: 10.1088/1361-6587/aacb69

  • Extraction of nonlinear waveform in turbulent plasma 査読 国際誌

    F. Kin, K. Itoh, akihide fujisawa, Yusuke Kosuga, Makoto Sasaki, Takuma Yamada, Inagaki Shigeru, Sanae Itoh, T. Kobayashi, Yoshihiko Nagashima, Naohiro Kasuya, H. Arakawa, K. Yamasaki, K. Hasamada

    Physics of Plasmas   25 ( 6 )   2018年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Streamers and their mediator have been known to exist in linear cylindrical plasmas [Yamada et al., Nat. Phys. 4, 721 (2008)]. Conditional averaging is applied to extract the nonlinear characteristics of a mediator, which has been simply treated as a linear wave. This paper reports that a mediator should have higher harmonic components generated by self-couplings, and the envelope of a streamer should be generated with not only fundamental but also higher harmonic components of the mediator. Moreover, both the mediator and the envelope of the streamer have common features with solitary waves, i.e., the height should increase inversely as the square of their localization width.

    DOI: 10.1063/1.5027124

  • Three-dimensional structure of the streamer in linear plasmas 査読 国際誌

    Yamada, T., Inagaki, S., Sasaki, M., Nagashima, Y., Kin, F., Arakawa, H., Kobayashi, T., Yamasaki, K., Kasuya, N., Kosuga, Y., Fujisawa, A., Itoh, K., Itoh, S.-I.

    Journal of the Physical Society of Japan   87 ( 3 )   034501   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.7566/JPSJ.87.034501

  • Evaluation of Measurement Signal of Heavy Ion Beam Probe of Energetic-Particle Driven Geodesic Acoustic Modes 査読 国際誌

    Makoto SASAKI, Kimitaka ITOH, Takeshi IDO, Akihiro SHIMIZU, Tatsuya KOBAYASHI, Hiroyuki ARAKAWA, Naohiro KASUYA, Akihide FUJISAWA, Sanae-I. ITOH

    Plasma and Fusion Research   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Symmetry-Breaking of Turbulence Structure and Position Identification in Toroidal Plasmas 査読 国際誌

    Kimitaka ITOH, Sanae-I. ITOH, Yoshihiko NAGASHIMA, Takuma YAMADA, Yusuke KOSUGA, Akihide FUJISAWA

    Plasma and Fusion Research   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Spatio-temporal dynamics of turbulence trapped in geodesic acoustic modes 査読 国際誌

    Sasaki, M., Kobayashi, T., Itoh, K., Kasuya, N., Kosuga, Y., Fujisawa, A., Itoh, S.-I.

    Physics of Plasmas   25 ( 1 )   012316   2018年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1063/1.5008541

  • Quantification of Turbulent Driving Forces for the Geodesic Acoustic Mode in the JFT-2M Tokamak 査読 国際誌

    Kobayashi, T., Sasaki, M., Ido, T., Kamiya, K., Miura, Y., Nagashima, Y., Ida, K., Inagaki, S., Fujisawa, A., Itoh, S.-I., Itoh, K.

    Physical Review Letters   120   045002   2018年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1103

  • Position identification of measurement for the study of symmetry-breaking of turbulence structure in toroidal plasmas 招待 査読 国際誌

    Itoh, K., Itoh, S.I., Nagashima, Y., Yamada, T., Fujisawa, A.

    Journal of the Physical Society of Japan   87 ( 2 )   025002   2018年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.7566

  • Nonlinear characteristics of mediator and streamer in linear magnetized plasmas 国際誌

    F. Kin, akihide fujisawa, K. Itoh, Yusuke Kosuga, Makoto Sasaki, Takuma Yamada, Inagaki Shigeru, S. I. Itoh, T. Kobayashi, Yoshihiko Nagashima, Naohiro Kasuya, H. Arakawa, K. Yamasaki, K. Hasamada

    45th EPS Conference on Plasma Physics, EPS 2018 45th EPS Conference on Plasma Physics, EPS 2018   565 - 568   2018年1月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Model validation for radial electric field excitation during L-H transition in JFT-2M tokamak 招待 査読 国際誌

    Kobayashi, T., Itoh, K., Ido, T., Kamiya, K., Itoh, S.-I., Miura, Y., Nagashima, Y., Fujisawa, A., Inagaki, S., Ida, K., Hoshino, K.

    Nuclear Fusion   57 ( 7 )   72005   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1741-4326/aa5d03

  • Turbulent transport reduction induced by transition on radial electric field shear and curvature through amplitude and cross-phase in torus plasma 査読 国際誌

    Kobayashi, T., Itoh, K., Ido, T., Kamiya, K., Itoh, S.-I., Miura, Y., Nagashima, Y., Fujisawa, A., Inagaki, S., Ida, K.

    Scientific Reports   7 ( 1 )   14971   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1038/s41598-017-14821-y

  • Topological bifurcation of helical flows in magnetized plasmas with density gradient and parallel flow shear 査読 国際誌

    Sasaki, M., Kasuya, N., Itoh, K., Toda, S., Yamada, T., Kosuga, Y., Nagashima, Y., Kobayashi, T., Arakawa, H., Yamasaki, K., Fujisawa, A., Inagaki, S., Itoh, S.-I.

    Physics of Plasmas   24 ( 11 )   112103   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1063/1.5000343

  • Plasma equilibrium based on RF-driven current profile without assuming nested magnetic surfaces on QUEST 査読 国際誌

    Nakamura, K., Alam, M.M., Jiang, Y.Z., Mitarai, O., Kurihara, K., Kawamata, Y., Sueoka, M., Takechi, M., Hasegawa, M., Tokunaga, K., Araki, K., Zushi, H., Hanada, K., Fujisawa, A., Idei, H., Nagashima, Y., Kawasaki, S., Nakashima, H., Higashijima, A., Nagata, T., Fukuyama, A.

    Fusion Engineering and Design   123   532 - 534   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Investigation of hydrogen recycling in long-duration discharges and its modification with a hot wall in the spherical tokamak QUEST 査読 国際誌

    Hanada, K., Yoshida, N., Honda, T., Wang, Z., Kuzmin, A., Takagi, I., Hirata, T., Oya, Y., Miyamoto, M., Zushi, H., Hasegawa, M., Nakamura, K., Fujisawa, A., Idei, H., Nagashima, Y., Watanabe, O., Onchi, T., Kuroda, K., Long, H., Watanabe, H., Tokunaga, K., Higashijima, A., Kawasaki, S., Nagata, T., Takase, Y., Fukuyama, A., Mitarai, O.

    Nuclear Fusion   57 ( 12 )   126061   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Fully non-inductive second harmonic electron cyclotron plasma ramp-up in the QUEST spherical tokamak 査読 国際誌

    Idei, H., Kariya, T., Imai, T., Mishra, K., Onchi, T., Watanabe, O., Zushi, H., Hanada, K., Qian, J., Ejiri, A., Alam, M.M., Nakamura, K., Fujisawa, A., Nagashima, Y., Hasegawa, M., Matsuoka, K., Fukuyama, A., Kubo, S., Shimozuma, T., Yoshikawa, M., Sakamoto, M., Kawasaki, S., Nakashima, H., Higashijima, A., Ide, S., Maekawa, T., Takase, Y., Toi, K.

    Nuclear Fusion   57 ( 12 )   126045   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1088/1741-4326/aa7c20

  • Temporal-spatial structures of plasmas flows and turbulence around tearing mode islands in the edge tokamak plasmas 査読 国際誌

    Zhao, K.J., Nagashima, Y., Li, F.M., Shi, Y., Diamond, P.H., Dong, J.Q., Itoh, K., Itoh, S.-I., Zhuang, G., Liu, H., Chen, Z.P., Cheng, J., Nie, L., Ding, Y.H., Hu, Q.M., Chen, Z.Y., Rao, B., Cheng, Z.F., Gao, L., Zhang, X.Q., Yang, Z.J., Wang, N.C., Wang, L., Jin, W., Yan, W., Xu, J.Q., Wu, Y.F., Yan, L.W., Fujisawa, A., Inagaki, S., Kosuga, Y., Sasaki, M.

    Nuclear Fusion   5 ( 12 )   126006   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • A proposal of Fourier-Bessel expansion with optimized ensembles of bases to analyse two dimensional image 招待 査読 国際誌

    Yamasaki, K., Fujisawa, A., Nagashima, Y.

    Review of Scientific Instruments   88 ( 9 )   093507   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1063/1.5000744

  • Measurement of thickness of film deposited on the plasma-facing wall in the QUEST tokamak by colorimetry 招待 査読 国際誌

    Wang, Z., Hanada, K., Yoshida, N., Shimoji, T., Miyamoto, M., Oya, Y., Zushi, H., Idei, H., Nakamura, K., Fujisawa, A., Nagashima, Y., Hasegawa, M., Kawasaki, S., Higashijima, A., Nakashima, H., Nagata, T., Kawaguchi, A., Fujiwara, T., Araki, K., Mitarai, O., Fukuyama, A., Takase, Y., Matsumoto, K.

    Review of Scientific Instruments   88 ( 9 )   093502   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1063/1.5000739

  • Spatial distribution of atomic and ion hydrogen flux and its effect on hydrogen recycling in long duration confined and non-confined plasmas 招待 査読 国際誌

    Kuzmin, A., Zushi, H., Takagi, I., Sharma, S.K., Kobayashi, M., Hirooka, Y., Onchi, T., Hanada, K., Yoshida, N., Nakamura, K., Fujisawa, A., Idei, H., Nagashima, Y., Hasegawa, M., Mutoh, T., Mishra, K., Ohwada, H.

    Nuclear Materials and Energy   12   627 - 632   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1016/j.nme.2017.03.027

  • Mesoscale electric fluctuations interacting with zonal flows, magnetic fluctuations and turbulence 査読 国際誌

    Zhao, K.J., Nagashima, Y., Diamond, P.H., Dong, J.Q., Itoh, K., Itoh, S.-I., Yan, L.W., Cheng, J., Fujisawa, A., Inagaki, S., Kosuga, Y., Sasaki, M., Huang, Z.H., Yu, D.L., Li, Q., Ji, X.Q., Song, X.M., Huang, Y., Liu, Y., Yang, Q.W., Ding, X.T., Duan, X.R.

    Nuclear Fusion   57 ( 7 )   076036   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Permutation entropy and statistical complexity in characterising low-aspect-ratio reversed-field pinch plasma 招待 査読 国際誌

    Onchi, T., Fujisawa, A., Sanpei, A., Himura, H., Masamune, S.

    Physica Scripta   92 ( 5 )   55601   2017年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1402-4896/aa6689

  • Analysis of plasma equilibrium based on orbit-driven current density profile in steady-state plasma on QUEST 招待 査読 国際誌

    Nakamura, K., Alam, M.M., Jiang, Y.Z., Mitarai, O., Kurihara, K., Kawamata, Y., Sueoka, M., Takechi, M., Hasegawa, M., Tokunaga, K., Araki, K., Zushi, H., Hanada, K., Fujisawa, A., Idei, H., Nagashima, Y., Kawasaki, S., Nakashima, H., Higashijima, A., Nagata, T., Fukuyama, A.

    Fusion Engineering and Design   109-111   1528 - 1533   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Power Balance Estimation in Long Duration Discharges on QUEST 査読 国際誌

    Hanada, K., Zushi, H., Idei, H., Nakamura, K., Ishiguro, M., Tashima, S., Kalinnikova, E.I., Nagashima, Y., Hasegawa, M., Fujisawa, A., Higashijima, A., Kawasaki, S., Nakashima, H., Mitarai, O., Fukuyama, A., Takase, Y., Gao, X., Liu, H., Qian, J., Ono, M., Raman, R.

    Plasma Science and Technology   18 ( 11 )   1069 - 1075   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1088/1009-0630/18/11/03

  • Current status and prospect of plasma control system for steady-state operation on QUEST 招待 査読 国際誌

    Hasegawa, M., Nakamura, K., Zushi, H., Hanada, K., Fujisawa, A., Tokunaga, K., Idei, H., Nagashima, Y., Kawasaki, S., Nakashima, H., Higashijima, A.

    Fusion Engineering and Design   112   699 - 702   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1016/j.fusengdes.2016.04.016

  • Structure formation in parallel ion flow and density profiles by cross-ferroic turbulent transport in linear magnetized plasma 査読 国際誌

    Kobayashi, T., Inagaki, S., Kosuga, Y., Sasaki, M., Nagashima, Y., Yamada, T., Arakawa, H., Kasuya, N., Fujisawa, A., Itoh, S.-I., Itoh, K.

    Physics of Plasmas   23   102311   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1063/1.4965915

  • Synchronization of Geodesic Acoustic Modes and Magnetic Fluctuations in Toroidal Plasmas 査読 国際誌

    Zhao, K.J., Nagashima, Y., Diamond, P.H., Dong, J.Q., Itoh, K., Itoh, S.-I., Yan, L.W., Cheng, J., Fujisawa, A., Inagaki, S., Kosuga, Y., Sasaki, M., Wang, Z.X., Wei, L., Huang, Z.H., Yu, D.L., Hong, W.Y., Li, Q., Ji, X.Q., Song, X.M., Huang, Y., Liu, Y., Yang, Q.W., Ding, X.T., Duan, X.R.

    Physical Review Letters   117   145002   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Eddy, drift wave and zonal flow dynamics in a linear magnetized plasma 査読 国際誌

    Arakawa, H., Inagaki, S., Sasaki, M., Kosuga, Y., Kobayashi, T., Kasuya, N., Nagashima, Y., Yamada, T., Lesur, M., Fujisawa, A., Itoh, K., Itoh, S.-I.

    Scientific Reports   6   33371   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1038/srep33371

  • Response of the far scrape-off layer plasma to strong gas puffing in the high poloidal beta configuration of the QUEST spherical tokamak 査読 国際誌

    Onchi, T., Zushi, H., Mishra, K., Oyama, Y., Nagashima, Y., Hanada, K., Idei, H., Hasegawa, M., Kuzmin, A., Miura, H., Nakamura, K., Fujisawa, A., Nagaoka, K.

    Plasma Physics and Controlled Fusion   58   115004   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1088/0741-3335/58/11/115004

  • Changes of particle flux during end-plate biasing experiment in PANTA 査読 国際誌

    Kin, F., Yamada, T., Inagaki, S., Nagashima, Y., Arakawa, H., Kobayashi, T., Miwa, Y., Kasuya, N., Sasaki, M., Kosuga, Y., Fujisawa, A., Itoh, K., Itoh, S.-I.

    Journal of the Physical Society of Japan   85   093501   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.7566/JPSJ.85.093501

  • Guiding Center Orbit Calculation for Evaluating the Current Density Distributions of the Electrons in Electron Cyclotron Heating on QUEST 招待 査読 国際誌

    Alam, Md.M., Nakamura, K., Idei, H., Hasegawa, M., Tokunaga, K., Araki, K., Hanada, K., Fujisawa, A., Nagashima, Y., Kawasaki, S., Nakashima, H., Higashijima, A., Xia, F., Mitarai, O.

    IEEE Transactions on Plasma Science   44   7482769   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1109/TPS.2016.2570815

  • Experimental Identification of Electric Field Excitation Mechanisms in a Structural Transition of Tokamak Plasmas 査読 国際誌

    Kobayashi, T., Itoh, K., Ido, T., Kamiya, K., Itoh, S.-I., Miura, Y., Nagashima, Y., Fujisawa, A., Inagaki, S., Ida, K., Hoshino, K.

    Scientific Reports   30720   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1038/srep30720

  • Observation of an edge coherent mode and poloidal flow in the electron cyclotron wave induced high β<inf>p</inf>plasma in QUEST 招待 査読 国際誌

    Banerjee, S., Zushi, H., Nishino, N., Mishra, K., Mahira, Y., Tashima, S., Ejiri, A., Yamaguchi, T., Onchi, T., Nagashima, Y., Hanada, K., Nakamura, K., Idei, H., Hasegawa, M., Fujisawa, A., Kuzmin, A., Matsuoka, K.

    23   082507   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1063/1.4960117

  • Hydrogen flux measurements with permeation probes in spherical tokamak QUEST 査読 国際誌

    Kuzmin, A., Zushi, H., Takagi, I., Sharma, S.K., Hirooka, Y., Kobayashi, M., Sakamoto, M., Hanada, K., Onchi, T., Oyama, Y., Youshida, N., Nakamura, K., Fujisawa, A., Idei, H., Nagashima, Y., Hasegawa, M., Mishra, K.

    Vacuum   129   178 - 182   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1016/j.vacuum.2016.04.025

  • Current density calculation from particle orbit in RF-driven divertor plasma on QUEST 招待 査読 国際誌

    Alam, M.M., Nakamura, K., Hasegawa, M., Tokunaga, K., Araki, K., Zushi, H., Hanada, K., Fujisawa, A., Idei, H., Nagashima, Y., Kawasaki, S., Nakashima, H., Higashijima, A., Xia, F., Mitarai, O.

    Proceedings - Symposium on Fusion Engineering   7482308   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1109/SOFE.2015.7482308

  • Adaptive-Array electron cyclotron emission diagnostics using data streaming in a software defined radio system 招待 査読 国際誌

    Idei, H., Mishra, K., Yamamoto, M.K., Hamasaki, M., Fujisawa, A., Nagashima, Y., Hayashi, Y., Onchi, T., Hanada, K., Zushi, H.

    Journal of Instrumentation   11 ( 4 )   C04010   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1088/1748-0221/11/04/C04010

  • A Concept of Cross-Ferroic Plasma Turbulence 招待 査読 国際誌

    Inagaki, S., Kobayashi, T., Kosuga, Y., Itoh, S.-I., Mitsuzono, T., Nagashima, Y., Arakawa, H., Yamada, T., Miwa, Y., Kasuya, N., Sasaki, M., Lesur, M., Fujisawa, A., Itoh, K.

    Scientific Reports   6   22189   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1038/srep22189

  • Improvement of the reynolds stress probe for end-plate biasing experiments in a cylindrical laboratory plasma 招待 査読 国際誌

    Kanzaki, T., Nagashima, Y., Inagaki, S., Kin, F., Miwa, Y., Sasaki, M., Yamada, T., Fujisawa, A., Kobayashi, T., Kasuya, N., Kosuga, Y., Itoh, S.-I., Itoh, K.

    Plasma and Fusion Research   11   1201091   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1585/pfr.11.1201091

  • Comparison of current density profiles based on particle orbit-driven current in steady-state plasma on QUEST 招待 査読 国際誌

    Alam, M.M., Nakamura, K., Xia, F., Mitarai, O., Hasegawa, M., Tokunaga, K., Araki, K., Zushi, H., Hanada, K., Fujisawa, A., Idei, H., Nagashima, Y., Kawasaki, S., Nakashima, H., Higashijima, A., Nagata, T.

    Fusion Engineering and Design   109-111   1624 - 1630   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1016/j.fusengdes.2015.11.007

  • Comparative studies of inner and outer divertor discharges and a fueling study in QUEST 招待 査読 国際誌

    Mitarai, O., Nakamura, K., Hasegawa, M., Onchi, T., Idei, H., Fujisawa, A., Hanada, K., Zushi, H., Higashijima, A., Nakashima, H., Kawasaki, S., Matsuoka, K., Koike, S., Takahashi, T., Tsutsui, H.

    Fusion Engineering and Design   109-111   1365 - 1370   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1016/j.fusengdes.2015.12.022

  • A calibration of setting of mach probes by observing GAM oscillations 招待 査読 国際誌

    Itoh, K., Zhao, K., Dong, J., Itoh, S.-I., Fujisawa, A., Inagaki, S., Sasaki, M., Nagashima, Y., Kosuga, Y., Cheng, J., Kobayashi, T.

    Plasma and Fusion Research   11   1402002   2016年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: DOI: 10.1585/pfr.11.1402002

  • Change in Edge Fluctuations Synchronized with Heat Pulse in the JFT-2M Tokamak 査読 国際誌

    Nagashima Yoshihiko, K. Itoh, Sanae-I. Itoh, Fujisawa Akihide, K. Hoshino

    Journal of Physical Society of Japan, Japanese Physics Society   85   063501-1 - 063501-4   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7566/JPSJ.85.063501

  • Tomography as a promising diagnostic tool for plasma turbulence 査読 国際誌

    Akihide Fujisawa, 永島 芳彦, 稲垣 滋, 恩地 拓己, 大島伸介, 清水昭博

    Institute of Physics   58   025005-1 - 025005-10   2016年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A system for plasma turbulence tomography has been developed in a linear cylindrical plasma
    as a prototype with aiming at future application on toroidal plasma of higher temperature. This paper describes the diagnostic system in both aspects of the soft- and hardware, and reports the first results of tomographic reconstruction that can successfully produce local emission and its fluctuations. In the reconstruction process, two dimensional view of plasma is obtained for approximately 0.6 ms in every sampling time of 1 μs using parallel processing of 120 cores with 10 personal computers. The results include the steady state analysis of local fluctuation power spectra using fast Fourier transform, analysis of temporal behavior of fluctuation power spectra with wavelet transform, and analyses of the structural deformation or pattern of local plasma emission, demonstrating that the success of tomography as a promising diagnostic tool for plasma turbulence.

    DOI: 10.1088/0741-3335/58/2/025005

  • On the Study of Higher Harmonics of Heat Pulse Propagation in the Modulated-Heating Experiments 査読 国際誌

    K. Itoh, Sanae-I. Itoh, S. Inagaki, Naohiro Kasuya, Fujisawa Akihide

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   85 ( 1 )   2016年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.7566/JPSJ.85.014501

  • Multiple wall-reflection effect in adaptive-array differential-phase reflectometry on QUEST 査読 国際誌

    H.Idei, MISHRA KISHORE KANTI, Yamamoto, M., Fujisawa Akihide, Nagashima Yoshihiko, Hamasaki, M., Hayashi, Y., Takumi Onchi, K.Hanada, zushi hideki

    JOURNAL OF INSTRUMENTATION   11   2016年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/1748-0221/11/01/C01014

  • Tomography for Local Plasma Turbulence Measurements 査読 国際誌

    Akihide Fujisawa, 永島 芳彦, 稲垣 滋

    プラズマ核融合学会 Plasma and Fusion Research   10   1201080-1 - 1201080-2   2015年12月

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    記述言語:日本語   掲載種別:研究論文(学術雑誌)  

    A prototype system for plasma turbulence tomography was tested in linear plasma with aiming at future application to toroidal plasma. The line-integrated plasma emission lines of ArI and ArII were measured with sufficiently high signal-to-noise ratios, and the signals were reconstructed using the maximum likelihood expectation maximization (MLEM) algorithm and parallel computing. Here, the first results for local plasma emissions and fluctuation spectra obtained with the prototype system are reported.

    DOI: 10.1585/pfr.10.1201080

  • Comparative studies of inner and outer divertor discharges and a fueling study in QUEST 査読 国際誌

    O.Mitarai, Kazuo Nakamura, Makoto Hasegawa, Takumi Onchi, H.Idei, Fujisawa Akihide, K.Hanada, zushi hideki, A.Higashijima, H.Nakashima, S.Kawasaki, K.Matsuoka, S.Koike, T.Takahashi, H.Tsutsui

    Fusion Engineering and Design   2015年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.fusengdes.2015.12.022

  • Analysis of plasma equilibrium based on orbit-driven current density profile in steady-state plasma on QUEST 査読 国際誌

    Kazuo Nakamura, M M Alam, YZ Jiang, O Mitarai, K Kurihara, Y Kawamata, M Sueoka, M Takech, Makoto Hasegawa, K. Tokunaga, K Araki, zushi hideki, K.Hanada, Fujisawa Akihide, H.Idei, Nagashima Yoshihiko, S Kawasaki, H Nakashima, A Higashijima

    Fusion Engineering and Design   1 - 6   2015年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.fusengdes.2015.11.035

  • Azimuthal inhomogeneity of turbulence structure and its impact on intermittent particle transport in linear magnetized plasmas 査読 国際誌

    Kobayashi, T., S. Inagaki, M. Sasaki, Kosuga, Y., Arakawa, H., Yamada, T., Nagashima Yoshihiko, Miwa, Y., Naohiro Kasuya, Fujisawa Akihide, Sanae-I. Itoh, Itoh, K.

    PHYSICS OF PLASMAS   22 ( 11 )   112301-1 - 112301-8   2015年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1063/1.4934537

  • Comparison of current density profiles based on particle orbit-driven current in steady-state plasma on QUEST 査読 国際誌

    Md Mahbub Alam, Kazuo Nakamura, Fan Xia, Osamu Mitarai, Makoto Hasegawa, K. Tokunaga, Kuniaki Araki, zushi hideki, Fujisawa Akihide, H.Idei, Nagashima Yoshihiko, Shoji Kawasaki, Hisatoshi Nakashima, ki Higashijima, Takahiro Nagata

    Fusion Engineering and Design   1 - 7   2015年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.fusengdes.2015.11.007

  • Development of a high-performance control system by decentralization with reflective memory on QUEST 査読 国際誌

    Makoto Hasegawa, Kazuo Nakamura, zushi hideki, K.Hanada, Fujisawa Akihide, Mitarai, Osamu, K. Tokunaga, H.Idei, Nagashima Yoshihiko, Kawasaki, Shoji, Nakashima, Hisatoshi, Higashijima, Aki

    FUSION ENGINEERING AND DESIGN   96-97   629 - 632   2015年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.fusengdes.2015.06.054

  • Global gas balance and influence of atomic hydrogen irradiation on the wall inventory in steady-state operation of QUEST tokamak 査読 国際誌

    Aleksandrovich Arseniy Kuzmin, zushi hideki, Takagi, I., Sharma, S. K, RUSINOV ALEKSANDR, Inoue, Y., Y.; Hirooka, Zhou, H, Kobayashi, M., Mizuki Sakamoto, K.Hanada, Naoaki Yoshida, Kazuo Nakamura, Fujisawa Akihide, Matsuoka, K., H.Idei, Nagashima Yoshihiko, Makoto Hasegawa, Takumi Onchi

    JOURNAL OF NUCLEAR MATERIALS   463   1087 - 1090   2015年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jnucmat.2014.12.092

  • Particle balance in long duration RF driven plasmas on QUEST 査読 国際誌

    K.Hanada, zushi hideki, Naoaki Yoshida, Yugami, N., Honda, T., Makoto Hasegawa, MISHRA KISHORE KANTI, Aleksandrovich Arseniy Kuzmin, Kazuo Nakamura, Fujisawa Akihide, H.Idei, Nagashima Yoshihiko, Osamu Watanabe, Takumi Onchi, H. Watanabe, K. Tokunaga, Higashijima, A., Kawasaki, S., Nakashima, H.

    JOURNAL OF NUCLEAR MATERIALS   463   1084 - 1086   2015年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jnucmat.2015.01.013

  • Observation of heat flux and plasma flow in scrape off layer in QUEST 査読 国際誌

    Takumi Onchi, Mahira, Y., Nagaoka, K., Tashima, S., BANERJEE SANTANU, MISHRA KISHORE KANTI, H.Idei, K.Hanada, Kazuo Nakamura, Fujisawa Akihide, Nagashima Yoshihiko, Makoto Hasegawa, Matsuoka, K., Aleksandrovich Arseniy Kuzmin, Osamu Watanabe, Kawasaki, S., Nakashima, H., Higashijima, A.

    JOURNAL OF NUCLEAR MATERIALS   463   428 - 431   2015年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1016/j.jnucmat.2014.11.136

  • Self organization of high beta_p plasma equilibrium with an inboard poloidal magnetic field null in QUEST 査読 国際誌

    Kishore Mishra, zushi hideki, Fujisawa Akihide, H.Idei, Makoto Hasegawa, Takumi Onchi, Nagashima Yoshihiko, Saya Taslima, S Banerjee, K.Hanada

    IAEA Nuclear Fusion   55   2015年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Successful production of high βp plasmas (εβp ≥ 1) fully non-inductively (NI) and their long pulse sustainment with the help of modest power (<100 kW) of electron cyclotron waves is demonstrated. High βp plasmas are found for the first time to be naturall

    DOI: 10.1088/0029-5515/55/8/083009

  • Comparison between Non-Inductive Plasma Current Start-Up Using ECRH with and without Fundamental Resonance on QUEST 招待 査読 国際誌

    Hiroki Miura, K.Hanada, zushi hideki, Kazuo Nakamura, Fujisawa Akihide, H.Idei, Nagashima Yoshihiko, Makoto Hasegawa, Hisatoshi Nakashima, Shoji Kawasaki, Aki Higashijima, Osamu Mitarai, Atsushi Fukuyama, Yuichi Takase

    Plasma and Fusion Research   ( 10 )   3402066-1 - 3402066-4   2015年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1585

  • Heat flux and plasma flow in the far scrape-off layer of the inboard poloidal field null configuration in QUEST 査読 国際誌

    Takumi Onchi, Kishore Mishra, Fujisawa Akihide, zushi hideki, H.Idei, K.Hanada, Makoto Hasegawa, Nagashima Yoshihiko

    Phys. Plasmas   55 ( 22 )   082513 - 082513   2015年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Heat flux and plasma flow in the scrape-off layer (SOL) are examined for the inboard poloidal field null (IPN) configuration of the spherical tokamak QUEST. In the plasma current (I p) ramp-up phase, high heat flux (>1 MW/m2) and supersonic flow (Mach num

    DOI: http://dx.doi.org/10.1063/1.4928878

  • Observation of Parallel Force Balance for Drift Wave Fluctuation by a Fast Voltage Sweeping Method in a Linear Plasma 査読 国際誌

    Nagashima Yoshihiko, S. Inagaki, Fujisawa Akihide, Hiroyuki Arakawa, Takuma Yamada, Yudai Miwa, Tatsuya Kobayashi,, Sanae-I. Itoh, Kimitaka Itoh

    Journal of the Physical Society of Japan   84 ( 6 )   063501-1 - 063501-3   2015年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Edge plasma dynamics during L-H transition in the JFT-2M tokamak 査読 国際誌

    T. Kobayashi, K. Itoh, T. Ido, K. Kamiya, 伊藤 早苗, Y. Miura, 永島 芳彦, Akihide Fujisawa, 稲垣 滋, K. Ida, K. Hoshino

    Nucl. Fusion   55   2015年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    DOI: 10.1088/0029-5515/55/6/063009

  • Dynamical programming based turbulence velocimetry for fast visible imaging of tokamak plasma 査読 国際誌

    Takumi Onchi, Kishore Mishra, Fujisawa Akihide, zushi hideki, H.Idei, K.Hanada, Makoto Hasegawa, Nagashima Yoshihiko

    Rev. Sci. Instrum   86   033505-1 - 033505-8   2015年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    An orthogonal dynamic programming (ODP) based particle image velocimetry (PIV) technique is developed to measure the time resolved flow field of the fluctuating structures at the plasma edge and scrape
    off layer (SOL) of tokamaks.

    DOI: 10.1063/1.4914838

  • Study of non-linear coupling of fluctuations at long distance in LHD 招待 査読 国際誌

    稲垣 滋, T. Tokuzawa, T. Kobayashi, 伊藤 早苗, K. Itoh, K. Ida, Akihide Fujisawa, S. Kubo, T. Shimozuma, N. Tamura, N. Kasuya, H. Tsuchiya, Y. Nagayama

    ( 54 )   114014-1 - 114014-6   2014年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Non-linear coupling between fluctuations at different radial locations is observed on the Large Helical Device (LHD) plasma. The summed bi-coherence between the low frequency macro-scale fluctuation (frequency is f = 2.75 kHz) at ρ = reff/a99 = 0.63 (wher

    DOI: 10.1088/0029-5515/54/11/114014"

  • A Prototype diagnostics sytem to detect ultraviolet emission for plasma turbulence 査読 国際誌

    Akihide Fujisawa, 恩地 拓己, A. Sanpei

    Review of Scientific Instruments   85   113502-1 - 113502-3   2014年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A system to detect ultraviolet emissions from plasma is developed for multi-point measurement, the target of which is the imaging of turbulence with a high temporal resolution. A fluorescent glass, which converts ultraviolet emissions to visible light with a wavelength of approximately 540 nm, is utilized in the system. Following the conversion, the fluorescent light is transferred with fibre optics, and is converted to electric signals in a location that is sufficiently distant from an electrically noisy environment around the plasma device. This paper describes a prototype system of this diagnostic method and discusses the spectral analysis obtained using a low-aspect-ratio reversed field pinch RELAX

    DOI: 10.1063/1.4900660

  • End plate biasing experiments in linear magnetized plasmas 査読 国際誌

    T. Yamada, S. Inagaki, T. Kobayashi, Y. Nagashima, T. Mitsuzono, Y. Miwa, K. Nakanishi, H. Fujino, M. Sasaki, N. Kasuya, M. Lesur, Y. Kosuga, A. Fujisawa, S.-I. Itoh and K. Itoh

    NUCLEAR FUSION   54.0 ( 11.0 )   2014年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Investigation of progression from low to high hydrogen recycling during long duration discharges on a spherical tokamak, QUEST 国際誌

    K. Hanada, N. Yoshida, H. Zushi, K. Nakamura, A. Fujisawa, H. Idei, Y. Nagashima, H. Watanabe, M. Hasegawa, S. Kawasaki, H. Nakashima, A. Higashijima, O. Watanabe, Y. Takase, A. Fukuyama, O. Mitarai, M. Peng and the QUEST team

    Proc.25th Fusion Energy Conference (FEC 2014), 2014.10.13-18, St. Petersburg Russian Federation   2014年10月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    Progression from low (LR) to high recycling (HR) was observed in full non-inductive long duration discharges up to 12 minutes on QUEST. Repetitive transition between LR and HR was induced by periodic gas puffing and the period to recover to LR, rec, was gradually prolonged with the plasma duration. The period, rec, normalized by gas rate has a linear relation to time-integrated H. This indicates hydrogen recycling induced an intentional gas puffing is increasing with time-integrated H which an indicator of hydrogen (H) fluence to the wall. To understand the dependence, deuterium (D) storing capability of the specimen exposed to QUEST plasmas was investigated by implantation of D2+
    ions of 1keV and subsequent thermal desorption spectroscopy (TDS) as a post-mortem analysis. A diffusion-trap model, reconstructing the obtained the results of TDS, shows a clear dependence of recycling ratio on fluence and a time evolution of wall-stored H can be reconstructed. The model calculation indicates surface recombination on the deposition layer plays an essential role in QUEST wall behaviour. Wall temperature dependence on the number of injected H to keep density is experimentally investigated and is agreed with the model calculation. This result is quite helpful to execute hot wall experiments on QUEST.

  • Investigation of Non-inductive Plasma Current Start-up by RF on QUEST 査読 国際誌

    Ishiguro, Masaki; Hanada, Kazuaki; Liu, Hiqing; Ogata, Ryota; Isobe, Mitsutaka; Tashima, Saya; Zushi, Hideki; Sato, Khonosuke; Fujisawa, Akihide; Nakamura, Kazuo; Idei, Hiroshi; Sakamoto, Mizuki; Hasegawa, Makoto; Takase, Yuichi; Maekawa, Takashi; Kishimoto, Yasuaki; Mitarai, Osamu; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki

    15TH INTERNATIONAL CONGRESS ON PLASMA PHYSICS (ICPP2010) & 13TH LATIN AMERICAN WORKSHOP ON PLASMA PHYSICS (LAWPP2010)   511.0 ( 0.0 )   0.0 - 0.0   2014年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Formations of a closed flux surface (CFS) on QUEST are achieved by fully non-inductive current start-up driven by RF, which is 8.2GHz in frequency and more than 40kW in power. It found that appropriate magnetic configuration with positive n-index and reduction of particle recycling was crucial to achieve the non-inductive plasma current start-up (PCS) successfully. Especially the controllability of particle recycling should be improved by wall conditioning based on successive plasma production and wall cleaning with electron cyclotron resonance heating (ECR) plasmas induced by RF in frequency of 2.45GHz.

    DOI: 10.1088/1742-6596/511/1/012041

  • Shape Reconstruction of RF-Driven Divertor Plasma on QUEST 査読 国際誌

    Nakamura, Kazuo; Fujita, H.; Liu, X. L.; Xue, E. B.; Xia, Fan; Mitarai, Osamu; Kurihara, Kenichi; Kawamata, Y.; Sueoka, M.; Hasegawa, Makoto; Tokunaga, Kazutoshi; Zushi, H.; Hanada, K.; Fujisawa, A.; Matsuoka, K.; Idei, H.; Nagashima, Y.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Araki, Kuniaki; Fukuyama, A.

    IEEE TRANSACTIONS ON PLASMA SCIENCE   42.0 ( 9.0 )   2309.0 - 2312.0   2014年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In the present RF-driven plasma with a lot of high-energy electrons, there may be anisotropic plasma pressure, which makes the usual equilibrium analysis difficult, but the Cauchy condition surface method can reconstruct the plasma shape precisely regardless of the anisotropy. In addition, the plasma current effect in the open magnetic surfaces outside of the closed magnetic surfaces is considered in the RF-driven divertor plasma. In the reconstruction process, singular value (SV) decomposition is used and optimal criterion function for generalized cross validation is estimated concerning truncation or reduction of the small-SV components.

    DOI: 10.1109/TPS.2014.2341616

  • Thermal imaging of plasma with a phased array antenna in QUEST 査読 国際誌

    Kishore Mishra, Hiroshi Idei, hideki zushi, K. Nagata, R. Akimoto, M. K. Yamamoto, Kazuaki Hanada, makoto hasegawa, Kazuo Nakamura, Akihide Fujisawa, Yoshihiko Nagashima, S. Banerjee, 恩地 拓己, KUZMIN ARSENIY ALEKSANDROVI

    REVIEW OF SCIENTIFIC INSTRUMENTS   85.0   2014年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Role of stochasticity in turbulence and convective intermittent transport at the scrape off layer of Ohmic plasma in QUEST 査読 国際誌

    Banerjee, Santanu; Zushi, H.; Nishino, N.; Hanada, K.; Ishiguro, M.; Tashima, S.; Liu, H. Q.; Mishra, K.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A.; Nagashima, Y.; Matsuoka, K.

    PHYSICS OF PLASMAS   21.0 ( 7.0 )   0.0 - 0.0   2014年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Statistical features of fluctuations are investigated using the fast camera imaging technique in the scrape of layer (SOL) of electron cyclotron resonance heated Ohmic plasma. Fluctuations in the SOL towards low field side are dominated by coherent convective structures (blobs). Two dimensional structures of the higher order moments (skewness s and kurtosis k) representing the shape of probability density function (PDF) are studied. s and k are seen to be functions of the magnetic field lines. s and k are consistently higher towards the bottom half of the vessel in the SOL showing the blob trajectory along the field lines from the top towards bottom of the vessel. Parabolic relation (k = As-2 + C) is observed between s and k near the plasma boundary, featuring steep density gradient region and at the far SOL. The coefficient A, obtained experimentally, indicates a shift of prominence from pure drift-wave instabilities towards fully developed turbulence. Numerical coefficients characterizing the Pearson system are derived which demonstrates the progressive deviation of the PDF from Gaussian towards gamma from the density gradient region, towards the far SOL. Based on a simple stochastic differential equation, a direct correspondence between the multiplicative noise amplitude, increased intermittency, and hence change in PDF is discussed. (C) 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4890359

  • Dynamics of edge limit cycle oscillation in the JFT-2M Tokamak 査読 国際誌

    Kobayashi, T.; Itoh, K.; Ido, T.; Kamiya, K.; Itoh, S. -I.; Miura, Y.; Nagashima, Y.; Fujisawa, A.; Inagaki, S.; Ida, K.; Kasuya, N.; Hoshino, K.

    NUCLEAR FUSION   54.0 ( 7.0 )   2014年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In the JFT-2M tokamak (JFT standing for JAERI Fusion Torus), the limit cycle oscillation (LCO), together with several variables, i.e., the electrostatic potential, radial electric field, electron density, turbulence intensity, and D-alpha emission from the divertor region, is observed before the L-to-H transition. The spatiotemporal dynamics of the LCO is analysed in detail. Zonal flows are not seen, while modulation is observed in the edge-localized poloidal flow and density gradient. Modulation is also seen in the Reynolds stress, caused by that in the turbulence intensity and turbulence wavenumber. However, flow acceleration cannot be explained by the modulation in the Reynolds stress. Rapid inward propagation is also observed for the density gradient and turbulence packet. The characteristics of the propagation are verified by means of turbulence spreading theory and diffusion theory.

    DOI: 10.1088/0029-5515/54/7/073017

  • Analytical Solution of High βp Equilibria with Natural Inboard Poloidal Null Configuration Obtained in the Spherical Tokamak QUEST 査読 国際誌

    Kishore MISHRA, Hideki ZUSHI, Hiroshi IDEI, Saya TASHIMA, Santanu BANERJEE, Makoto HASEGAWA, Kazuaki HANADA, Kazuo NAKAMURA, Akihide FUJISAWA, Yoshihiko NAGASHIMA, Keisuke MATSUOKA, Arseny KUZMIN, Takumi ONCHI and QUEST Team

    Plasma and Fusion Research   9.0 ( RA )   2014年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Particle balance in long duration RF driven plasmas on QUEST 国際誌

    K. Hanada, H. Zushi, N. Yoshida, M. Hasegawa, K. Mishra, Kuzumina, K. Nakamura, A. Fujisawa, H. Idei, Y. Nagashima, O. Watanabe, T. Onchi, H. Watanabe, K. Tokunaga, A. Higashijima, S. Kawasaki, H. Nakashima, Y. Takase, A. Fukuyama, O. Mitarai, T. Maekawa and M. Peng

    21st International Conference on Plasma Surface Interactions 2014   2014年6月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Identification of Quasi-Periodic Nonlinear Waveforms in Turbulent Plasmas 査読 国際誌

    Shigeru INAGAKI, Yudai MIWA, Tatsuya KOBAYASHI, Takuma YAMADA, Yoshihiko NAGASHIMA, Tomohiro MITSUZONO, Hiromitsu FUJINO, Makoto SASAKI, Naohiro KASUYA, Maxime LESUR, Yusuke KOSUGA, Akihide FUJISAWA, Sanae-I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   9.0 ( RC )   2014年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A new method is presented for identifying waveforms of fluctuations in turbulent plasmas. The method is based on heartbeat analysis in which the convolution of a waveform is obtained by employing the phase tracking method. Phase tracking is performed by correlating raw time-series data with a template waveform; the template is evaluated through iteration procedure. The method is applied to fluctuations in a PANTA plasma, and the nonlinear waveform and its distribution of periods are obtained.

  • Scrape Off Layer Flow Characteristics in the Spherical Tokamak QUEST 国際誌

    Santanu Banerjee, H. Zushi, N. Nishino, Y. Mahira, K. Nagaoka, K. Mishra, S. Tashima, Y. Nagashima, K. Hanada, K. Nakamura, H. Idei, M. Hasegawa, A. Fujisawa, K. Matsuoka

    Proceedings of the 12th Asia Pacific Physics Conference   2014年3月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Role of energetic electrons during current ramp-up and production of high poloidal beta plasma in non-inductive current drive on QUEST 査読 国際誌

    Tashima, Saya; Zushi, H.; Isobe, M.; Hanada, K.; Idei, H.; Nakamura, K.; Fujisawa, A.; Matsuoka, K.; Hasegawa, M.; Nagashima, Y.; Okamura, S.; Banerjee, S.; Kawasaki, S.; Nakashima, H.; Higashijima, A.

    NUCLEAR FUSION   54.0 ( 2.0 )   0.0 - 0.0   2014年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A scenario for non-inductive current ramp-up has been demonstrated using electron cyclotron waves in the spherical tokamak QUEST. The configuration was characterized by a high toroidal magnetic mirror ratio of 2 and a steady vertical magnetic field of more than 10% of the toroidal magnetic field. The generation and confinement of energetic electrons having energy greater than 10 keV were studied using hard x-rays. Because of the energetic electron pressure, a natural divertor formed with an inboard poloidal field null at the high poloidal beta (approximately 3-4).

    DOI: 10.1088/0029-5515/54/2/023010

  • An Assessment of Limit Cycle Oscillation Dynamics Prior to L-H Transition 査読 国際誌

    Kimitaka ITOH, Sanae-I. ITOH and Akihide FUJISAWA

    Plasma and Fusion Research   8.0 ( Rev )   2013年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In this article, experimental observations of limit cycle oscillations (LCO) that precede L-to-H transition are discussed. Issues are: (1) the existence of zonal flows, (2) spatio-temporal evolutions of turbulence intensity, and (3) periodic generations/decays of mean radial electric field and density. The role of Reynolds stress to accelerate the LCO flow is also addressed. The propagation of changes of the density gradient and turbulence amplitude into the core is commented. Varieties in experimental reports on these issues are explained, and possible origins of different interpretations are discussed. Problem definitions for the future research for resolution are presented.

  • Sawtooth-triggered limit-cycle oscillations and I-phase in the HL-2A tokamak 査読 国際誌

    Zhao, K. J.; Cheng, J.; Diamond, P. H.; Dong, J. Q.; Yan, L. W.; Hong, W. Y.; Xu, M.; Tynan, G.; Miki, K.; Huang, Z. H.; Itoh, K.; Itoh, S-I; Fujisawa, A.; Nagashima, Y.; Inagaki, S.; Wang, Z. X.; Wei, L.; Song, X. M.; Lei, G. J.; Li, Q.; Ji, X. Q.; Liu, Yi; Yang, Q. W.; Ding, X. T.; Duan, X. R.

    NUCLEAR FUSION   53.0 ( 12.0 )   0.0 - 0.0   2013年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Transitions between low (L-mode) and intermediate (I-phase) confinement regimes triggered by sawteeth are investigated using multiple Langmuir probe arrays in the edge plasmas of the HL-2A tokamak. The I-phase is characterized by limit-cycle oscillations (LCOs). Repeated L-I-L transitions induced by sawtooth heat pulses are also observed. Statistical analyses show that the delay time of the L-I transition relative to sawtooth crashes is less than similar to 1 ms. The intensity of turbulence bursts in the I-phase is stronger than those observed in L-mode plasmas. Measurements are consistent with zonal flow reducing turbulence intensity in the frequency band similar to 20-100 kHz, while the LCO turbulence of frequency higher than 100 kHz has more power than that in the L-mode. The analyses of time-resolved power transfers between turbulence and zonal flows suggest that power transfers exist between turbulence and zonal flows. The direction of the power transfers is from turbulence into geodesic acoustic modes in ohmic plasmas.

    DOI: 10.1088/0029-5515/53/12/123015

  • New Method of Analysis for Dynamical Transport 査読 国際誌

    Shigeru INAGAKI, Tokihiko TOKUZAWA, Tatsuya KOBAYASHI, Sanae-I. ITOH, Kimitaka ITOH, Katsumi IDA, Shin KUBO, Takashi SHIMOZUMA, Naoki TAMURA, Akihide FUJISAWA, Naohiro KASUYA, Hayato TSUCHIYA, Yoshio NAGAYAMA, Kazuo KAWAHATA, Hiroshi YAMADA, Akio KOMORI and LHD Experiment Group

    Plasma and Fusion Research   8.0 ( RC )   2013年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    By employing a new method for studying dynamical transport, hysteresis in the flux-gradient relation was recently discovered for modulated heating. In this paper, the new method is compared to the conventional heat-pulse propagation method. We also demonstrate integration of results from the new method with the power balance thermal conductivity.

  • Measurement of Dynamical Density Profiles Using a Microwave Frequency Comb Reflectometer 査読 国際誌

    Shigeru INAGAKI, Kimitaka ITOH, Takuma YAMADA, Sanae-I. ITOH, Tokihiko TOKUZAWA, Akihide FUJISAWA, Naohiro KASUYA, Makoto SASAKI, Yoshihiko NAGASHIMA and Hiroyuki ARAKAWA

    Plasma and Fusion Research   8.0 ( RC )   2013年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We propose the use of a microwave comb for measuring the density profile as a continuous function of radius with high temporal resolution. The analysis focuses on phase-sensitive convolution of the reflected waves: convolution of pulses can eliminate statistical noise. The time resolution for constructing the density profile is also discussed.

  • Higher Harmonics in a Perturbative Transport Experiment 査読 国際誌

    Shigeru INAGAKI, Sanae-I. ITOH, Kimitaka ITOH, Naohiro KASUYA, Tatsuya KOBAYASHI, Akihide FUJISAWA, Tokihiko TOKUZAWA, Katsumi IDA, Shin KUBO, Takashi SHIMOZUMA, Naoki TAMURA, Hayato TSUCHIYA, Yoshio NAGAYAMA, Kazuo KAWAHATA, Hiroshi YAMADA, Akio KOMORI and LHD Experiment Group

    Plasma and Fusion Research   8.0 ( RC )   2013年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We have used the convolution method to obtain higher harmonics of the temperature perturbation in a heating modulation experiment on LHD plasma. In comparison with predictions based on the diffusive model, amplitudes of higher harmonics (such as the seventh) decayed much more slowly as they propagated radially. Changes in the time derivative of temperature at the onset and turning-off of heating power remained much sharper after radial propagation than those predicted by the diffusion model.

  • How is turbulence intensity determined by macroscopic variables in a toroidal plasma? 査読 国際誌

    Inagaki, S.; Tokuzawa, T.; Tamura, N.; Itoh, S. -I.; Kobayashi, T.; Ida, K.; Shimozuma, T.; Kubo, S.; Tanaka, K.; Ido, T.; Shimizu, A.; Tsuchiya, H.; Kasuya, N.; Nagayama, Y.; Kawahata, K.; Sudo, S.; Yamada, H.; Fujisawa, A.; Itoh, K.

    NUCLEAR FUSION   53.0 ( 11.0 )   0.0 - 0.0   2013年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report observations of the dynamic response of micro-fluctuations and turbulent flux to a low-frequency heating power modulation in the Large Helical Device. The responses of heat flux and micro-fluctuation intensity differ from that of the change in temperature gradient. This result violates the local transport model, where turbulence is determined by the local temperature gradient. A new relationship between flux, gradient and turbulence is found. In addition to the temperature gradient, the heating rate is proposed as a new, direct controlling parameter of turbulence to explain the fast response of turbulence against periodic modulation of heating power.

    DOI: 10.1088/0029-5515/53/11/113006

  • Development of plasma control system for divertor configuration on QUEST 査読 国際誌

    Hasegawa, M.; Nakamura, K.; Zushi, H.; Hanada, K.; Fujisawa, A.; Matsuoka, K.; Mitarai, O.; Idei, H.; Nagashima, Y.; Tokunaga, K.; Kawasaki, S.; Nakashima, H.; Higashijima, A.

    FUSION ENGINEERING AND DESIGN   88.0 ( 6.0 )   1074.0 - 1077.0   2013年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A plasma control system to sustain divertor configurations is developed on QUEST (Q-shu university experiment with steady-state spherical tokamak). Magnetic fluxes are numerically integrated at 100 kHz using FPGA (Field-Programmable Gate Array) modules and transferred to a main calculation loop at 4 kHz. With these signals, plasma shapes are identified in real time at 2 kHz under the assumption that the plasma current can be represented as one filament current. This calculation is done in another calculation loop in parallel by taking advantage of a multi-core processor of the plasma control system. The inside and outside plasma edge positions are controlled to their target positions using PID (proportional-integral-derivative) control loops. Whereas the outside edge position can not be controlled by the outer PF coil current, the inside edge position can be controlled by the inner PF coil current. (C) 2013 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.fusengdes.2013.03.035

  • クォターニオンによるマトリクスコンバータの解析

    中村 一男, 藤田 広樹, 劉 暁龍, 薛 二兵, 御手洗 修, 長谷川 真, 德永 和俊, 荒木 邦明, 図子 秀樹, 花田 和明, 藤澤 彰英, 松岡 啓介, 出射 浩, 永島 芳彦, 川崎 昌二, 中島 寿年, 東島 亜紀

    電気学会研究会資料 電子デバイス/半導体電力変換研究会 合同研究会 大阪大学   2013年10月

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    記述言語:日本語   掲載種別:研究論文(その他学術会議資料等)  

  • 28pKB-2 On formation of a natural inboard separatrix in ECW heated Ohmic plasma on the spherical tokamak QUEST

    Kishore, Mishra; Zushi, H; Idei, H; Tashima, S; Banerjee, S; Hasegawa, M; Hanada, K; Nakamura, K; Fujisawa, A; Nagashima, Y;

    日本物理学会講演概要集   68.0 ( 2.0 )   208.0   2013年9月

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    記述言語:英語   掲載種別:研究論文(その他学術会議資料等)  

  • Non-Inductive Current Drive by EC Waves in an Inboard Poloidal Magnetic Field Null Configuration on the Spherical Tokamak QUEST 査読 国際誌

    Saya TASHIMA, Hideki ZUSHI, Mitsutaka ISOBE, Hiroshi IDEI, Shoichi OKAMURA, Kazuaki HANADA, Kazuo NAKAMURA, Akihide FUJISAWA, Keisuke MATSUOKA, Makoto HASEGAWA, Yoshihiko NAGASHIMA, Shoji KAWASAKI, Hisatoshi NAKASHIMA, Aki HIGASHIJIMA and QUEST Team

    Plasma and Fusion Research   8.0 ( RA )   2013年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    To investigate the effects of confinement of fast electrons on poloidal beta equilibrium, experiments under different toroidal magnetic mirror ratios, MOMFC, were performed in electron cyclotron heated plasma in the spherical tokamak QUEST. The proportional constants of the relation between plasma current and vertical magnetic fields decreased with increase in MOMFC. The poloidal field null point appeared in the chamber for MOMFC > 1.8 at a plasma current value of ∼15 kA. Poloidal beta and temperature of hard X-rays increased with MOMFC. This suggests that high poloidal beta equilibrium plasma is produced by better confinement of energetic trapped particles.

  • Evaluation of Excitation Conditions of ITG Modes in the PANTA 査読 国際誌

    Yudai MIWA, Naohiro KASUYA, Makoto SASAKI, Shigeru INAGAKI, Kimitaka ITOH, Masatoshi YAGI, Akihide FUJISAWA, Yoshihiko NAGASHIMA, Maxime LESUR, Tatsuya KOBAYASHI, Soutarou YAMADA, Tetsuo YAMASHITA, Satoshi OTSUBO, Shinsuke KAKIGAWA, Tomohiro MITSUZONO, Hirofumi FUJINO and Sanae-I. ITOH

    Plasma and Fusion Research   8.0 ( RA )   2013年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    To study the nonlinear saturation mechanism in turbulent plasmas, we plan to obseve ion temperature gradient (ITG) modes in the Plasma Assembly for Nonlinear Turbulence Analysis (PANTA). Linear growth rates of ITG modes in the linear device are analyzed to determine their excitation conditions using a three-field fluid model to describe the ion motion. Parameter scans of the linear growth rate show the threshold for ITG mode excitation, and the typical plasma parameters of the PANTA are found in the unstable domain.

  • Measurement of Dynamical Density Profiles Using a Microwave Frequency Comb Reflectometer 査読 国際誌

    Shigeru Inagaki, Akihide Fujisawa, Naohiro Kasuya, Sanae Itoh, Kimitaka Itoh

    Plasma and Fusion Research   8.0 ( RC )   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Turbulence Velocimetry of Tangential Fast Imaging Data on QUEST 査読 国際誌

    Santanu BANERJEE, Hideki ZUSHI, Nobuhiro NISHINO, Yoshihiko NAGASHIMA, Kazuaki HANADA, Saya TASHIMA, Tsubasa INOUE, Kazuo NAKAMURA, Hiroshi IDEI, Makoto HASEGAWA, Akihide FUJISAWA and Keisuke MATSUOKA

    Plasma and Fusion Research   8.0 ( RA )   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A particle image velocimetry technique based on orthogonal dynamic programming is developed to measure the time resolved flow field of the fluctuating structures at the plasma edge and scrape off layer. This non-intrusive technique can provide two dimensional velocity fields at high spatial and temporal resolution from a fast framing image sequence and hence can provide better insights in plasma flow as compared to conventional probe measurements. Applicability of the technique is tested with simulated image pairs. Finally, it is applied to tangential fast visible images of QUEST as a test case to estimate the scrape off layer flow in Ohmic and ECRH driven plasma discharges.

  • Spatial structures and interaction of multiple sheared flow populations in tokamak edge turbulence 査読 国際誌

    Zhao, K. J.; Dong, J. Q.; Yan, L. W.; Diamond, P. H.; Cheng, J.; Hong, W. Y.; Huang, Z. H.; Xu, M.; Tynan, G. R.; Itoh, K.; Itoh, S. -I.; Fujisawa, A.; Nagashima, Y.; Inagaki, S.; Wang, Z. X.; Wei, L.; Li, Q.; Ji, X. Q.; Huang, Y.; Liu, Yi.; Zhou, J.; Song, X. M.; Yang, Q. W.; Ding, X. T.; Duan, X. R.

    NUCLEAR FUSION   53.0 ( 8.0 )   0.0 - 0.0   2013年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The radial structures of multiple sheared flow populations and fluctuations are simultaneously measured using combinations of Langmuir probe arrays in the edge plasmas of the HL-2A tokamak with ohmic and electron cyclotron resonance heating (ECRH). The maximum of geodesic acoustic mode (GAM) amplitude locates at similar to 2-3 cm inside the last close flux surface (LCFS). The low-frequency zonal flow (LFZF) and GAM tend to coexist in the inner region. The dependences of the amplitudes of the multiple sheared flows and turbulence on ECRH heating power are also investigated. The measured turbulent Reynolds stresses are shown to be strongly correlated with the sheared flows, as predicted by theory. The turbulence is modulated at the each frequency of the multiple sheared flows simultaneously, and the particle fluxes induced by the turbulence are significantly reduced near the LCFS and in the GAM peaking region. The analyses also show that the spatial structures of the turbulent envelopes at the LFZF and GAM frequencies are similar to those observed in LFZF and GAM.

    DOI: 10.1088/0029-5515/53/8/083011

  • Characteristics of High Poloidal Beta (β p) Plasma Formed by Electron Cyclotron Waves in Spherical Tokamak QUEST 国際誌

    Kishore Mishra, Hiroshi Idei, Hideki Zushi, Saya Tashima, Santanu Banerjee, Makoto Hasegawa, Kazuaki Hanada, Kazuo Nakamura, Akihide Fujisawa, Keisuke Matsuoka, Yoshihiko Nagashima, S. Kawasaki, A. Higashijima, H. Nakashima, and Quest Group

    Proceedings of the 12th Asia Pacific Physics Conference (APPC12)   1.0   2013年7月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Spatiotemporal Structures of Edge Limit-Cycle Oscillation before L-to-H Transition in the JFT-2M Tokamak 査読 国際誌

    Kobayashi, T.; Itoh, K.; Ido, T.; Kamiya, K.; Itoh, S. -I.; Miura, Y.; Nagashima, Y.; Fujisawa, A.; Inagaki, S.; Ida, K.; Hoshino, K.

    PHYSICAL REVIEW LETTERS   111.0 ( 3.0 )   0.0 - 0.0   2013年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In this Letter, we report analyses of spatiotemporal dynamics of turbulence and structure in the limit-cycle oscillation (LCO) that precedes an L-to-H transition. Zonal flows are not observed during LCO, and the oscillation is the periodic generations or decays of barrier with edge-localized mean flow. Oscillatory Reynolds stress is found to be too small to accelerate the LCO flow, by considering the dielectric constant in magnetized toroidal plasmas. Propagation of changes of the density gradient and turbulence amplitude into the core is also observed.

    DOI: 10.1103/PhysRevLett.111.035002

  • Quaternion Concept in Matrix Converter Design for Feedback Stabilization by Magnetic Field Coil 国際誌

    NAKAMURA Kazuo, FUJITA Hiroki, LIU Xiaolong, XUE Erbing, MITARAI Osamu, HASEGAWA Makoto, TOKUNAGA Kazutoshi, ZUSHI Hideki, HANADA Kazuaki, FUJISAWA Akihide, IDEI Hiroshi, NAGASHIMA Yoshihiko, KAWASAKI Shoji, NAKASHIMA Hisatoshi, HIGASHIJIMA Aki, ARAKI Kuniaki

    Proc. International Conference on Electrical Engineering (ICEE 2013),Xiamen,July 2013   2013年7月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Cross-field motion of plasma blob-filaments and related particle flux in an open magnetic field line configuration on QUEST 査読 国際誌

    Liu, H. Q.; Hanada, K.; Nishino, N.; Ogata, R.; Ishiguro, M.; Gao, X.; Zushi, H.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.

    JOURNAL OF NUCLEAR MATERIALS   438.0   S513 - S517   2013年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Blob-filaments have been observed by combined measurement with a fast camera and a movable Langmuir probe in an open magnetic field line configuration of electron cyclotron resonance (ECR) heating plasma in QUEST. Blob-filaments extended along field lines do correspond to over-dense plasma structures and propagated across the field lines to the outer wall. The radial velocity of the blob structure, Vb, was obtained by three methods and was dominantly driven by the E x B force. The radial velocity, size of the blob showed good agreements with the results obtained by sheath-connected interchange theoretical model. Vb corresponds to roughly 0.02-0.07 of the local sound speed (Cs) in QUEST. The higher moments (skewness S and kurtosis K) representing the shape of PDF of density fluctuation are studied. Their least squares fitting with quadratic polynomial is K = (1.60 +/- 0.27) S-2 - (0.46 +/- 0.20). The larger blob structures, occurring only 10% of the time, can carry more than 60% loss of the entire radial particle flux. (C) 2013 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jnucmat.2013.01.106

  • SHAPE RECONSTRUCTION OF RF-DRIVEN DIVERTOR PLASMA ON QUEST 国際誌

    NAKAMURA Kazuo, FUJITA Hiroki, LIU Xiaolong, XUE Erbing, XIA Fan, MITARAI Osamu, KURIHARA Kenichi, KAWAMATA Yoichi, SUEOKA Michiharu, HASEGAWA Makoto, TOKUNAGA Kazutoshi, ZUSHI Hideki, HANADA Kazuaki, FUJISAWA Akihide, IDEI Hiroshi, NAGASHIMA Yoshihiko, KAWASAKI Shoji, NAKASHIMA Hisatoshi, HIGASHIJIMA Aki, ARAKI Kuniaki

    Proc. Third Meeting for A3 Foresight Program Workshop on Critical Physics Issues Specific to Steady State Sustainment of High-Performance Plasmas,19-24 May 2013,Beijing,China,NIFS-PROC-95   2013年5月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • On turbulence-correlation analysis based on correlation reflectometry 査読 国際誌

    Teplova (Kosolapova), N.; Itoh, K.; Itoh, S-I; Gusakov, E.; Heuraux, S.; Inagaki, S.; Sasaki, M.; Kobayashi, T.; Nagashima, Y.; Oldenbuerger, S.; Fujisawa, A.

    PHYSICA SCRIPTA   87.0 ( 4.0 )   0.0 - 0.0   2013年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Drift wave micro-turbulence is the main source of anomalous transport in a tokamak. Correlation reflectometry is a powerful diagnostic tool which provides information on plasma turbulence and subsequently on underlying instability. In this paper, theoretical expressions for the analysis of radial correlation reflectometry (RCR) data are derived. Integral kernels, which convert the correlation function of two microwave reflectometry signals into a correlation function of plasma turbulence and inverse, are discussed. The analytical expression and the method of combining the RCR diagnostic and another local density fluctuation (e.g. Doppler enhanced scattering or heavy ion beam probe) is proposed. The correlation between reflectometry signals and those from other local fluctuation measurements is analysed. The long-range tail of the correlation decays much more gradually than the turbulence correlation, however, it decays faster than that of two microwave reflectometry signals. The way to calculate turbulence wave number spectrum for this case is also proposed.

    DOI: 10.1088/0031-8949/87/04/045502

  • Streamer Structures in Experiment and Modeling 査読 国際誌

    Takuma YAMADA, Makoto SASAKI, Naohiro KASUYA, Yoshihiko NAGASHIMA, Shigeru INAGAKI, Tatsuya KOBAYASHI, Masatoshi YAGI, Akihide FUJISAWA, Sanae-I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   8.0 ( RA )   2013年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Validation of modeling in meso-scale structure formation is undergoing by using multi-channel probe measurements and advanced analyzing techniques such as bispectrum. Study of meso-scale structures including streamers is important for understanding anomalous transports in magnetized plasmas. A streamer structure and its mediator mode were observed in the Large Mirror Device-Upgrade linear plasma. The mediator mode nonlinearly coupled with many other drift wave modes and generated a streamer structure by phase locking. The radial biphase profiles indicating the phase locking showed the radial elongation of the streamer structure. Modes having similar characteristics to the mediator were also found in a theoretical work based on the Hasegawa-Mima model and a numerical simulation code.

  • H∞ Loop Shaping Control for Plasma Vertical Position Instability on QUEST 査読 国際誌

    Liu Xiaolong, Kazuo Nakamura, Tatsuya Yoshisue, Osamu Mitarai, Makoto Hasegawa, Kazutoshi Tokunaga, Xue Erbing, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Kuniaki Araki

    PLASMA SCIENCE & TECHNOLOGY   15.0 ( 3.0 )   295.0   2013年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    QUEST has a divertor configuration with a high and a negative n-index, and the problem of plasma vertical position instability control in QUEST is still under extensive study for achieving high efficiency plasma. The instability we considered is that the toroidal plasma moves either up or down in the vacuum chamber until it meets the vessel wall and is extinguished. The actively controlled coils (HCU and HCL) outside the vacuum vessel are serially connected in feedback with a measurement of the plasma vertical position to provide stabilizing control. In this work, a robust controller is employed by using the loop synthesis method, and provides robust stability over a wide range of n-index. Moreover, the gain of the robust controller is lower than that of a typical proportional derivative (PD) controller in the operational frequency range; it indicates that the robust controller needs less power consumption than the PD controller does.

  • H-infinity Loop Shaping Control for Plasma Vertical Position Instability on QUEST 査読 国際誌

    Liu Xiaolong; Nakamura, Kazuo; Yoshisue, Tatsuya; Mitarai, Osamu; Hasegawa, Makoto; Tokunaga, Kazutoshi; Xue Erbing; Zushi, Hideki; Hanada, Kazuaki; Fujisawa, Akihide; Idei, Hiroshi; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki; Araki, Kuniaki

    PLASMA SCIENCE & TECHNOLOGY   15.0 ( 3.0 )   295.0 - 299.0   2013年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    QUEST has a divertor configuration with a high and a negative n-index, and the problem of plasma vertical position instability control in QUEST is still under extensive study for achieving high efficiency plasma. The instability we considered is that the toroidal plasma moves either up or down in the vacuum chamber until it meets the vessel wall and is extinguished. The actively controlled coils (HCU and HCL) outside the vacuum vessel are serially connected in feedback with a measurement of the plasma vertical position to provide stabilizing control. In this work, a robust controller is employed by using the loop synthesis method, and provides robust stability over a wide range of n-index. Moreover, the gain of the robust controller is lower than that of a typical proportional derivative (PD) controller in the operational frequency range; it indicates that the robust controller needs less power consumption than the PD controller does.

    DOI: 10.1088/1009-0630/15/3/21

  • Statistical features of coherent structures at increasing magnetic field pitch investigated using fast imaging in QUEST 査読 国際誌

    Banerjee, Santanu; Zushi, H.; Nishino, N.; Hanada, K.; Sharma, S. K.; Honma, H.; Tashima, S.; Inoue, T.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A.

    NUCLEAR FUSION   52.0 ( 12.0 )   0.0 - 0.0   2012年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Fluctuations in slab plasma produced by electron cyclotron waves in an open magnetic configuration with vertical (B-z) and toroidal (B-t) fields are investigated as a function of B-z/B-t (field pitch) using a high speed visible camera in the spherical tokamak QUEST. Higher order moments (skewness s and kurtosis k) of spatio- temporal fluctuations are investigated. Background fluctuations, generation of coherent convective structures (blobs) and their propagation are analysed at the intensity gradient (R-im) and the source- free (essentially vacuum on the low- field side) regions, respectively. Parabolic relation (k = As-2 + C) is observed between s and k on the entire R- Z plane for a wide range of B-z/B-t. Progressive shift from the Gaussian statistics beyond R-im is observed with increasing B-z/B-t. From the moments of the probability density functions, possible location for blob generation is inferred to be R-im. Direct correspondence is observed with the prominence of the blobs and increase in stochastic forces with the increase in field pitch. Distribution of waiting time suggests that the blob generation may be a Poisson process. Accelerated cross field transport is observed for reasonably large-sized blobs.

    DOI: 10.1088/0029-5515/52/12/123016

  • Edge turbulence characteristics of the Ohmic-ECRH driven plasma current phase investigated with fast visible imaging in QUEST 国際誌

    Santanu Banerjee, H. Zushi, N. Nishino, Y. Nagashima, K. Hanada, S. Tashima, T. Inoue, K. Nakamura, H. Idei, M. Hasegawa, A. Fujisawa and K. Matsuoka

    Proc. 22nd International Toki Conference November 19- 22,2012   2012年11月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Self-nonlinear coupling of long-range temperature fluctuation in Toroidal plasma 査読 国際誌

    Kobayashi, T.; Inagaki, S.; Itoh, S-I; Itoh, K.; Oldenbuerger, S.; Fujisawa, A.; Nagashima, Y.; Ida, K.; Tsuchiya, H.; Nagayama, Y.; Kawahata, K.; Yamada, H.

    PLASMA PHYSICS AND CONTROLLED FUSION   54.0 ( 11.0 )   0.0 - 0.0   2012年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This paper proposes a clever usage of bispectral analysis for extracting or reconstructing a quasi-coherent and quasi-periodic structural evolution of plasma fluctuations. The method has been applied on electron temperature fluctuation signals measured with a multi-point electron cyclotron emission (ECE) radiometer in the Large Helical Device (LHD). The method successfully reconstructs the averaged spatiotemporal evolution of fluctuating coherent structure (Inagaki et al 2011 Phys. Rev. Lett. 107 115001), while the structure is buried in (or comparable in power to) background fluctuations. The bicoherence analysis has found the faint fluctuating structure consisting of a fundamental mode and the harmonic modes from the existence of significant couplings between them. The reconstructed spatiotemporal structure with the proposed method is compared with that obtained with the lock-in (conditional) average. Three cases of spatiotemporal evolution of the non-sinusoidal waveform are presented.

    DOI: 10.1088/0741-3335/54/11/115004

  • Non-Inductive Current Drive by EC Waves in an Inboard Poloidal Magnetic Field Null Configuration on the Spherical Tokamak QUEST 国際誌

    Saya TASHIMA, Hideki ZUSHI, Mitsutaka ISOBE, Hiroshi IDEI, Shoichi OKAMURA, Kazuaki HANADA, Kazuo NAKAMURA, Akihide FUJISAWA, Keisuke MATSUOKA, Makoto HASEGAWA, Yoshihiko NAGASHIMA, Shoji KAWASAKI, Hisatoshi NAKASHIMA, Aki HIGASHIJIMA and QUEST Team

    Proc. 22nd International Toki Conference November 19- 22, 2012   2012年11月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Configuration of Flows in a Cylindrical Plasma Device 査読 国際誌

    Stella OLDENBÜRGER, Kazuya URIU, Tatsuya KOBAYASHI, Shigeru INAGAKI, Makoto SASAKI, Yoshihiko NAGASHIMA, Takuma YAMADA, Akihide FUJISAWA, Sanae-I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   7.0 ( RA )   2012年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Ion flow is studied in the cylindrical magnetized Argon plasma of the PANTA device using several experimental methods. Time delay estimation technique (TDE) is used to measure the azimuthal propagation of density fluctuations between two electrostatic probes. Ion flux is also studied in azimuthal and axial direction using a newly installed Mach probe. TDE shows velocity profiles qualitatively consistent with expected drift wave propagation and E × B rotation. The Mach probe shows a maximum azimuthal flow and an axial flow shear close to the maximum density gradient and maximum fluctuation position. Striking differences exist in the detected axial ion flows depending on the discharge parameters. In high neutral pressure conditions reversal of axial ion flow was detected in the outer part of the plasma column. Temporal evolution of flows and fluctuations are compared as a first step to assess interplay between plasma turbulence and flows in the radial, axial and azimuthal directions.

  • Spatiotemporal dynamic characteristics and self-nonlinear coupling of long-range temperature fluctuation in Toroidal plasma 査読 国際誌

    T. Kobayashi, Shigeru Inagaki, ITOH INOUE(論文のみ) SANAE, K. Itoh, OLDENBURGER STELLA, Fujisawa Akihide, Nagashima Yoshihiko, K. Ida, H. Tsuchiya, Y. Nagayama, K. Kawahata, H. Yamada

    PLASMA PHYSICS AND CONTROLLED FUSION   2012年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Non-inductive current start-up and plasma equilibrium with an inboard poloidal field null by means of electron cyclotron waves in QUEST 国際誌

    H. Zushi; S. Tashima; M. Ishiguro; M. Hasegawa; S. Banerjee; N. Nishino; M. Isobe; K. Hanada; H. Idei; K. Nakamura; A. Fujisawa; Y. Nagashima; K. Matsuoka, S. K. Sharma; H. Liu; K. Toi; T. Maekawa; A. Ejiri; T. Yamaguchi;J. Hiratsuka; Y. Takase; M. Kikuchi; A. Fukuyama; Y. Ueda; O. Mitarai; S. Okamura;

    Proc. 24th Int. Conf. on Fusion Energy (San Diego, CA, 2012)   2012年10月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Fast visible imaging and edge turbulence analysis in QUEST 査読 国際誌

    Banerjee, Santanu; Zushi, H.; Nishino, N.; Nagashima, Y.; Hanada, K.; Ishiguro, M.; Ryoukai, T.; Tashima, S.; Inoue, T.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A.; Matsuoka, K.

    REVIEW OF SCIENTIFIC INSTRUMENTS   83.0 ( 10.0 )   2012年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A fast visible imaging system is installed on the spherical tokamak QUEST to study edge turbulence. The camera uses a complementary metal-oxide semiconductor detector with a maximum resolution of 1024 x 1024 at 7000 frames/s (fps) and can achieve 775 kfps at a resolution of 128 x 24. In this paper, we present the salient features of the system and its application to study edge turbulence in 8.2 GHz ECRH driven slab plasma, without plasma current. Vertical magnetic field (B-z) topology is varied with three sets of poloidal field (PF) coils and the variation in the edge turbulence is investigated as a function of the B-z strength and curvature. Fluctuation amplitude was highest for the shallow PF well. Cross-correlation coefficient shows distinct coherent mode along z direction at the steep density gradient region and it grows with the PF mirror ratio. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4739080]

    DOI: 10.1063/1.4739080

  • Evaluation of Electron Temperature Fluctuations Using a Conditional Technique 査読 国際誌

    Soutaro YAMADA, Shigeru INAGAKI, Stella OLDENBÜRGER, Tatsuya KOBAYASHI, Katsuyuki KAWASHIMA, Noriko OHYAMA, Yuki TOBIMATSU, Hiroyuki ARAKAWA, Yoshihiko NAGASHIMA, Takuma YAMADA, Makoto SASAKI, Masatoshi YAGI, Naohiro KASUYA, Akihide FUJISAWA, Sanae-I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   7.0 ( RA )   2012年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Electron temperature fluctuation amplitude is evaluated with a single probe using conditional sampling technique on the PANTA (linear magnetic configuration device). Electron temperature fluctuations are extracted as a function of floating potential. Normalized temperature fluctuation amplitude of about 15% is observed in low neutral pressure discharge in PANTA.

  • 18aFA-6 Fluctuation characteristics and flow at the SOL of ECRH driven plasma in QUEST

    Santanu BANERJEE, H ZUSHI, N NISHINO, Y NAGASHIMA, K HANADA, S TASHIMA, T INOUE, K NAKAMURA, H IDEI, M HASEGAWA, A FUJISAWA, K MATSUOKA

    日本物理学会講演概要集   67.0 ( 2.0 )   185.0   2012年9月

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    記述言語:英語   掲載種別:研究論文(その他学術会議資料等)  

  • Plasma Potential in Toroidal Devices: T-10, TJ-II, CHS and LHD 査読 国際誌

    Alexander V. MELNIKOV, Carlos HIDALGO, Takeshi IDO, Akihiro SHIMIZU, Akihide FUJISAWA, Konstantin S. DYABILIN and Sergey E. LYSENKO

    Plasma and Fusion Research   7.0 ( RA )   2012年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Direct measurements of the electric potential φ, using the Heavy Ion Beam Probing, have been undertaken in the T-10 tokamak, and in the helical devices with various magnetic topology: TJ-II, CHS and LHD. L-mode plasmas were considered. Despite the large differences in machine sizes, heating methods and the topology of the magnetic field, the observed φ shows the striking similarities: (i) Similar magnitudes of Er; (ii) For low densities, ne < 0.5 × 1019 m−3, φ is positive, and an increase in ne is associated with the decrease of positive φ and formation of a negative Er; (iii) For higher densities, ne > (0.5-1)× 1019 m−3 , both φ and Er tends to be negative despite the use of different heating methods: Ohmic and ECR heating in T-10, ECRH and/or NBI in TJ-II, CHS and LHD; (iv) Application of ECRH, causing a rise in Te, results in more positive values for φ and Er. The analysis show that the main features of the φ dependences on the ne and Te agree with neoclassical predictions on the four devices within experimental and simulation precisions.

  • On influences of long-range fluctuations on transport in Large Helical Device plasmas 査読 国際誌

    Itoh, K.; Itoh, S-I; Inagaki, S.; Kobayashi, T.; Fujisawa, A.; Nagashima, Y.; Urger, S. Oldenb; Ida, K.; Tokuzawa, T.; Nagayama, Y.; Kawahata, K.; Yamada, H.

    PLASMA PHYSICS AND CONTROLLED FUSION   54.0 ( 9.0 )   0.0 - 0.0   2012年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The competing effects of the long-range fluctuation, which has been found on the Large Helical Device (Inagaki et al 2011 Phys. Rev. Lett. 107 115001), on the net turbulent transport are discussed. The transport, which is driven directly by this mode, is evaluated. Then, the associated reduction of fluctuations in the range of drift wave turbulence is analyzed, by employing the predator-prey model. The transport driven by microscopic turbulence is reduced by the appearance of long-range fluctuations. Comparing these two competing processes, the condition is derived for the net transport to be reduced by the appearance of this long-range fluctuation. In addition, the experimental observations of microscopic fluctuations are discussed. The reduction of high-frequency fluctuations occurs in conjunction with the long-range fluctuations.

    DOI: 10.1088/0741-3335/54/9/095016

  • Electron Bernstein Wave Heating and Current Drive Effects in QUEST 国際誌

    H. Idei, H. Zushi, K. Hanada, E. Kalinnikova, M. Sakaguchi, T. Itado, K. Nakamura, A. Fujisawa, Y. Nagashima, M. Hasegawa, K. Matsuoka, A. Fukuyama, S. Tashima, H. Watanabe, N. Yoshida, K. Tokunaga, A. Ejiri, H. Igami, S. Kubo, K. Toi, M . Isobe, K. Nagaoka, H. Nakanishi, N. Nishino, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Ueda, M. Kikuchi, T. Fujita, O. Mitarai, T. Maekawa and Y. Takase

    FEC 2012: 24. IAEA Fusion Energy Conference; San Diego, CA (United States); 8-13 Oct 2012   217.0   2012年9月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • ECW/EBW Heating and Current Drive Experiment Results and Prospects for CW Operation in QUEST 査読 国際誌

    Hiroshi IDEI, Hideki ZUSHI, Kazuaki HANADA, Evgeniya KALINNIKOVA, Kazuo NAKAMURA, Akihide FUJISAWA, Yoshihiko NAGASHIMA, Makoto HASEGAWA, Keisuke MATSUOKA, Tsuyoshi KARIYA, Tsuyoshi IMAI, Ryutaro MINAMI, Naoaki YOSHIDA, Mizuki SAKAMOTO, Hideo WATANABE, Kazutoshi TOKUNAGA, Akira EJIRI, Masatsugu SAKAGUCHI, Masaki ISHIGURO, Saya TASHIMA, Atsushi FUKUYAMA, Hiroe IGAMI, Shin KUBO, Mitsutaka ISOBE, Kenichi NAGAOKA, Hideya NAKANISHI, Nobuhiro NISHINO, Shoji KAWASAKI, Hisatoshi NAKASHIMA, Aki HIGASHIJIMA, Yuichi TAKASE, Takashi MAEKAWA, Osamu MITARAI, Mitsuru KIKUCHI and Kazuo TOI

    Plasma and Fusion Research   7.0 ( RA )   2012年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A CW phased-array antenna system for electron cyclotron/Bernstein wave heating and current drive (ECWH/CD, EBWH/CD) experiments was developed in the QUEST. The antenna was designed to excite an elliptically polarized pure O-mode wave in oblique injection for the O-X-B mode conversion scenario, and its good performance was confirmed at a high power level. Long pulse discharges with a plasma current of 10 kA and 15 kA were non-inductively attained for 37 s and 20 s, respectively, with only radio frequency (RF) power. Divertor configurations were also obtained in the RF-sustained plasmas. A new operational window for sustained plasma current was observed in the high-density plasma with a higher RF incident power. Two new heating and current drive systems with an 8.56 GHz klystron and a 28 GHz gyrotron are being prepared to conduct CW EBWH/CD experiments in the high-density plasma.

  • 26pYG-2 QUEST 電流駆動における自発的内側 poloidal field null 配位の形成 (26pYG 核融合プラズマ (電流駆動・波動加熱), 領域 2 (プラズマ基礎・プラズマ科学・核融合プラズマ・プラズマ宇宙物理))

    H Zushi, S Tashima, M Ishiguro, M Hasegawa, S Barnejee, H Nishino, M Isobe, K Hanada, H Idei, K Nakamura, A Fujisawa, Y Nagashima, K Matsuoka, I Toi, T Maekawa, Y Takase, M Kikuchi, A Ejin, Y Ueda, O Mitarai, S Okamura

    日本物理学会講演概要集   67.0 ( 1.0 )   280.0   2012年9月

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    記述言語:日本語   掲載種別:研究論文(その他学術会議資料等)  

  • 25pYG-5 Effect of poloidal magnetic field curvature variations on the edge turbulence of 8.2 GHz slab plasma in QUEST

    Santanu BANERJEE, H ZUSHI, N NISHINO, K HANADA, HQ Liu, M ISHIGURO, T RYOUKAI, S TASHIMA, T INOUE, K NAKAMURA, H IDEI, H HASEGAWA, A FUJISAWA, K MATSUOKA, Y NAGASHIMA

    日本物理学会講演概要集   67.0 ( 1.0 )   271.0   2012年9月

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    記述言語:英語   掲載種別:研究論文(その他学術会議資料等)  

  • The role of energetic electrons on non-inductive current start-up and formation of an inboard poloidal field null configuration in the spherical tokamak QUEST 国際誌

    TASHIMA, H ZUSHI, M ISOBE, H IDEI, S OKAMURA, K HANADA, K NAKAMURA, A FUJISAWA, K MATSUOKA, M HASEGAWA, Y NAGASHIMA, M ISHIGURO, S KAWASAKI, H NAKASHIMA, A HIGASHIJIMA

    39th EPS Conference & 16th Int. Congress on Plasma Physics   2012年8月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • A Plasma Shape Identification with Magnetic Analysis for the Real-time Control on QUEST 査読 国際誌

    Makoto Hasegawa, Kazuo Nakamura, Kazutoshi Tokunaga, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima

    IEEJ Transactions on Fundamentals and Materials   132.0 ( 7.0 )   477.0 - 484.0   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In order to identify plasma shape, there is a way to represent the plasma current profile with several parameters, and adjust these parameters with least-square technique in order for calculated magnetic values to accord with measured ones. Here, the plasma shape parameters such as minor radius, elongation, and triangularity are chosen as the fitting parameters to represent plasma shape more directly, and the applicability to the control of the plasma shape are described by evaluating its calculation time. In order to find minimum of an objective function with least-square technique, two methods are compared, namely a linear approximation method and a downhill simplex method. While high accuracies of the measured magnetic signals are required, the good reproducibility is obtained, and the plasma shape identification can be done within several milliseconds in both methods.

  • Three Phase-to-Single Phase Matrix Converter Design for Feedback Stabilization by Magnetic Field Coil 国際誌

    NAKAMURA Kazuo, YOSHISUE Tatsuya, LIU Xiaolong, XUE Erbing, MITARAI Osamu, HASEGAWA Makoto, TOKUNAGA Kazutoshi, ZUSHI Hideki, HANADA Kazuaki, FUJISAWA Akihide, IDEI Hiroshi, NAGASHIMA Yoshihiko, KAWASAKI Shoji, NAKASHIMA Hisatoshi, HIGASHIJIMA Aki, ARAKI Kuniaki

    Proc. International Conference on Electrical Engineering (ICEE 2012),Kanazawa,July 2012   2012年7月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Statistical Analysis of the Convective Intermittent Transport at the Edge Region of QUEST 査読 国際誌

    Santanu Banerjee, Hideki Zushi, Nobuhiro Nishino, Kazuaki Hanada, Sanjeev Kumar Sharma, Tsubasa Inoue, Haiqing Liu, Masaki Ishiguro, Tomofumi Ryokai, Saya Tashima, Kazuo Nakamura, Hiroshi Idei, Makoto Hasegawa, Akihide Fujisawa, Keisuke Matsuoka

    IEEJ Transactions on Fundamentals and Materials   132.0 ( 7.0 )   545.0 - 554.0   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Robust Control on Plasma Vertical Position Instability by a Matrix Converter as Power Supply of QUEST 国際誌

    LIU Xiaolong, YOSHISUE Tatsuya, NAKAMURA Kazuo, XUE Erbing, HASEGAWA Makoto, TOKUNAGA Kazutoshi, ZUSHI Hideki, HANADA Kazuaki, FUJISAWA Akihide, IDEI Hiroshi, NAGASHIMA Yoshihiko, KAWASAKI Shoji, NAKASHIMA Hisatoshi, HIGASHIJIMA Aki, ARAKI Kuniaki

    Proc. International Conference on Electrical Engineering (ICEE 2012),Kanazawa,July 2012   2012年7月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • QUEST Experiments Towards Steady State Operation of Spherical Tokamaks 査読 国際誌

    Kazuaki Hanada, Hideki Zushi, Hiroshi Idei, Kazuo Nakamura, Masaki Ishiguro, Saya Tashima, Evgeniya Kalinnikova, Mizuki Sakamoto, Makoto Hasegawa, Akihide Fujisawa, Konosuke Sato, Naoaki Yoshida, Hideo Watanabe, Kazutoshi Tokunaga, Yoshihiko Nagashima, Aki Higashijima, Shoji Kawasaki, Hisatoshi Nakashima, Haiqing Liu, Osamu Mitarai, Takashi Maekawa, Atsushi Fukuyama, Yuichi Takase, Jinping Qian

    IEEJ Transactions on Fundamentals and Materials   132.0 ( 7.0 )   490.0 - 498.0   2012年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    QUEST計画の大きな目標の一つは、高温プラズマの定常化にかかわる研究である。本論文は、論文は論文は発表時点での長時間維持についての報告(国際球状トカマクワークショップ:平成23年11月於核融合科学研究所)をまとめたものである。特に長時間運転での粒子バランスについてのポイントモデルを用いて、QUESTのパラメータを用いると粒子バランスの定常化に必要な時間が1018秒程度になることを示した。

  • Non-inductive current start-up assisted by energetic electrons in Q-shu University experiment with steady-state spherical tokamak 査読 国際誌

    Ishiguro, Masaki; Hanada, Kazuaki; Liu, Haiqing; Zushi, Hideki; Nakamura, Kazuo; Fujisawa, Akihide; Idei, Hiroshi; Nagashima, Yoshihiko; Hasegawa, Makoto; Tashima, Saya; Takase, Yuichi; Kishimoto, Yasuaki; Mitarai, Osamu; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki

    PHYSICS OF PLASMAS   19.0 ( 6.0 )   2012年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    After intensive discharge cleaning of the chamber wall, non-inductive current start-up experiments have been successfully performed in QUEST in moderate vertical fields of about 1.0-1.5mT with positive n-index. Simultaneously, with increasing plasma current, an asymmetric toroidal flow of energetic electrons was observed and direct measurements of current driven by this asymmetric flow were taken with a newly developed Langmuir probe technique. A numerical study of the energetic electron orbits indicates that the total current is enough to play a dominant role in the formation of a closed flux surface in QUEST. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4731700]

    DOI: 10.1063/1.4731700

  • Time Evolution of Power Spectrum Density in Spontaneous Transition in Cylindrical Magnetized Plasma 査読 国際誌

    Tatsuya KOBAYASHI, Shigeru INAGAKI, Stella OLDENBÜRGER, Katsuyuki KAWASHIMA, Noriko OHYAMA, Yuuki TOBIMATSU, Hiroyuki ARAKAWA, Makoto SASAKI, Yoshihiko NAGASHIMA, Takuma YAMADA, Satoru SUGITA, Masatoshi YAGI, Naohiro KASUYA, Akihide FUJISAWA, Sanae-I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   7.0 ( RA )   2012年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Preliminary observation results are reported for a new discharge regime in the Plasma Assembly for Nonlinear Turbulent Analysis (PANTA), where spontaneous transitions in the equilibrium profile and fluctuation spectra occur. Two different states are defined by using the mean density value. Axial and radial profiles are observed for the two states, and large profile changes are found. The spatiotemporal evolution of the transition front is measured. Changes in the fluctuation spectrum are evaluated using conditional average and lock-in average.

  • Dynamics of particle flux in a cylindrical magnetized plasma 査読 国際誌

    Oldenbuerger, S.; Inagaki, S.; Kobayashi, T.; Arakawa, H.; Ohyama, N.; Kawashima, K.; Tobimatsu, Y.; Fujisawa, A.; Itoh, K.; Itoh, S-I

    PLASMA PHYSICS AND CONTROLLED FUSION   54.0 ( 5.0 )   2012年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Fluctuation-induced cross-field convective particle flux is studied in the cylindrical magnetized plasma assembly for non-linear turbulence analysis (PANTA). The plasma presents a wave turbulence characterized by a limited number of developing modes. To study the link between mode dynamics and particle transport, frequency-dependent time evolution of transport is obtained by applying complex continuous wavelet decomposition on spatio-temporal data from electrostatic probes. The method is shown to recover transport description consistent with other analysis methods for a weakly turbulent state. For a plasma state featuring a large non-sinusoidal structure, the time evolution of transport on the second harmonic of the main fluctuation shows a slow modulation of azimuthal mode number m = 0 with similarities to a zonal perturbation.

    DOI: 10.1088/0741-3335/54/5/055002

  • Observations of Intermittent Structures in the Periphery of a Cylindrical Linear Plasma in PANTA 査読 国際誌

    Noriko OHYAMA, Akihide FUJISAWA, Shigeru INAGAKI, Yoshihiko NAGASHIMA, Stella OLDENBÜRGER, Tatsuya KOBAYASHI, Katsuyuki KAWASHIMA, Yuuki TOBIMATSU, Tetsuo YAMASHITA, Soutaro YAMADA, Hiroyuki ARAKAWA, Takuma YAMADA, Masatoshi YAGI, Naohiro KASUYA, Makoto SASAKI, Sanae-I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   7.0   2012年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Observations of Intermittent Structures in the Periphery of a Cylindrical Linear Plasma in PANTA 査読 国際誌

    Noriko OHYAMA, Akihide FUJISAWA, Shigeru INAGAKI, Yoshihiko NAGASHIMA, Stella OLDENBÜRGER, Tatsuya KOBAYASHI, Katsuyuki KAWASHIMA, Yuuki TOBIMATSU, Tetsuo YAMASHITA, Soutaro YAMADA, Hiroyuki ARAKAWA, Takuma YAMADA, Masatoshi YAGI, Naohiro KASUYA, Makoto SASAKI, Sanae-I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   7.0 ( RC )   2012年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Intermittent pulse events have been observed in the periphery of the linear cylindrical plasmas produced in Plasma Assembly for Nonlinear Turbulence Analysis (PANTA). A novel combination of 32 azimuthal and 3 radial probes enables us to obtain 32 × 3 = 96 pairs of correlations simultaneously. The two-dimensional (2D) correlation analysis shows that the intermittent structure is well correlated with quasi-periodic bursts inside the plasma, and it reveals that the intermittent pulse is caused by the passage of a radially elongated and azimuthally distorted localized structure rotating in the ion diamagnetic direction.

  • Bi-Coherence Analysis of Fluctuations with Long Distance Correlation in Toroidal Plasmas 査読 国際誌

    Inagaki, Shigeru; Kobayashi, Tatsuya; Itoh, Kimitaka; Tokuzawa, Tokihiko; Itoh, Sanae-I.; Ida, Katsumi; Tamura, Naoki; Kasuya, Naoyuki; Fujisawa, Akihide; Kubo, Shin; Shimozuma, Takashi; Yagi, Masatoshi; Tanaka, Kenji; Nagayama, Yoshio; Kawahata, Kazuo; Yamada, Hiroshi

    JOURNAL OF NUCLEAR MATERIALS   81.0 ( 3.0 )   0.0 - 0.0   2012年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Macro-scale temperature fluctuations, which have long radial correlation length (of the order of the plasma radius), have been discovered on Large Helical Device (LHD). In this paper, non-linear coupling between the long-range fluctuations and microscopic fluctuations is investigated using cross bi-coherence analysis. The significant cross bi-coherence between long-range fluctuations and micro-fluctuations is observed in the range of frequency f < 100 kHz, where f is the frequency of microscopic fluctuations. It is found that the squared bi-coherence and bi-phase for this three-wave coupling is weakly dependent on the frequency of microscopic fluctuations. These observations demonstrate that the microscopic fluctuations are coherently interacting with long-range fluctuations.

    DOI: 10.1143/JPSJ.81.034501

  • Fluctuations with long-distance correlation in quasi-stationary and transient plasmas of LHD 査読 国際誌

    Inagaki, S.; Tamura, N.; Tokuzawa, T.; Ida, K.; Kobayashi, T.; Shimozuma, T.; Kubo, S.; Tsuchiya, H.; Nagayama, Y.; Kawahata, K.; Sudo, S.; Fujisawa, A.; Itoh, K.; Itoh, S. -I.

    NUCLEAR FUSION   52.0 ( 2.0 )   2012年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Electron temperature fluctuations with long-distance correlation have been discovered in LHD. This paper reports the extended observations recently made on the spatiotemporal structure of the long-range fluctuations both in quasi-stationary and transient plasmas. The detailed characteristics or spatiotemporal characteristics of long-range temperature fluctuations are revealed successfully using correlation analysis. Particularly, the dynamics of the longrange fluctuations is investigated to find that the amplitude of the fluctuations decreased and their radial correlation lengths shortened during the transient phase induced by pellet injection. Temporal changes of radial correlation structure and amplitude of fluctuations at the onset of change in the plasma state are discussed.

    DOI: 10.1088/0029-5515/52/2/023022

  • Analysis of PWI footprint traces and material damage on the first walls of the spherical tokamak QUEST 査読 国際誌

    Sharma, S. K.; Zushi, H.; Yoshida, N.; Watanabe, H.; Osakabe, M.; Takeri, Y.; Hasegawa, M.; Tanabe, T.; Tokunaga, K.; Hanada, K.; Idei, H.; Sakamoto, M.; Nakamura, K.; Fujisawa, A.; Ishiguro, M.; Tashima, S.

    FUSION ENGINEERING AND DESIGN   87.0 ( 1.0 )   77.0 - 86.0   2012年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    After several non-inductive current startup experimental campaigns in the spherical tokamak QUEST, its metallic first walls have revealed various kinds of damages as a signature of strong plasma wall interaction (PWI). Several types of footprint traces, namely colored regions formed due to material erosion/redeposition, melting of plasma facing components (PFCs) and numerous arc tracks on the chamber walls are recognized. Analysis of the re-deposited materials on collector probes is carried out using Xray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometry (EDS). Redeposition of several impurity materials such as carbon, oxygen and tungsten is identified. The footprint traces are majorly formed on the lower side PFCs, showing a large up/down asymmetry. Both toroidally symmetric and asymmetric footprint traces are formed on the bottoms side divertor plate and the lower part of the outboard side walls, respectively. Localized melting occurred on the outboard side limiters is attributed to the loss of energetic electrons produced via electron cyclotron resonance (ECR) heating. The observed damages are discussed in view of localized PWI, loss of energetic electrons, particle drifts, sputtering, arcing and redeposition of eroded materials. Material analysis and numerically calculated guiding center orbits of the charge particles are used to discuss these damages. (C) 2011 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.fusengdes.2011.10.001

  • Electron Cyclotron / Bernstein Wave Heating and Current Drive Experiments using Phased-array Antenna in QUEST 国際誌

    H. Idei, H. Zushi, K. Hanada, K. Nakamura, A. Fujisawa, M. Hasegawa, N. Yoshida, M. Sakamoto, H. Watanebe, K. Tokunaga, Y. Nagashima, A. Ejiri, M. Sakaguchi, E. Kalinnikova, M. Ishiguro, S. Tashima, A. Fukuyama, H. Igami, S. Kubo, S. K. Sharma, T. Ryokai, H. Q. Liu, M. Isobe, K. Nagaoka, H. Nakanishi, N. Nishino, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Takase, T. Maekawa, O. Mitarai, M. Kikuchi and K. Toi

    AIP Conference Proceedings (Radio Frequency Power in Plasmas)   2011年12月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Direct measurement of energetic electron flow in Q-shu University experiment with steady-state spherical tokamak 査読 国際誌

    Ishiguro, Masaki; Hanada, Kazuaki; Liu, Haiqing; Zushi, Hideki; Yoshida, Naoaki; Tokunaga, Tomonori; Nakamura, Kazuo; Fujisawa, Akihide; Idei, Hiroshi; Sakamoto, Mizuki; Hasegawa, Makoto; Tashima, Saya; Takase, Yuichi; Maekawa, Takashi; Kishimoto, Yasuaki; Mitarai, Osamu; Kawasaki, Shoji; Nakashima, Hisatoshi; Higashijima, Aki

    REVIEW OF SCIENTIFIC INSTRUMENTS   82.0 ( 11.0 )   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In magnetized plasmas, the presence of a significant number of energetic electrons has been observed but quantitative characteristics of these electrons are proving difficult to investigate. A Langmuir probe offers a means to provide quantitative measurement of these energetic electrons that takes into account electron emissions (secondary electron emission and electron reflection) from the probe tips and sheath expansion around the probe tips caused by a considerable negative potential. In this paper, these effects are experimentally confirmed and an analytical means to measure energetic electron characteristics are proposed. An analysis of plasmas produced by a high frequency wave is then applied leading to the successful detection of an asymmetric flow of energetic electrons. The estimated electron temperature and current density were approximately 4-5 keV and 2-3 kA/m(2). (C) 2011 American Institute of Physics. [doi:10.1063/1.3662204]

    DOI: 10.1063/1.3662204

  • Statistical Interpretation of the Density Fluctuations From the High-Speed Visible Images of Edge Turbulence on QUEST 査読 国際誌

    Banerjee, Santanu; Zushi, H.; Nishino, N.; Hanada, K.; Liu, H. Q.; Ishiguro, M.; Ryoukai, T.; Tashima, S.; Nakamura, K.; Idei, H.; Hasegawa, M.; Fujisawa, A.

    IEEE TRANSACTIONS ON PLASMA SCIENCE   39.0 ( 11.0 )   3006.0 - 3007.0   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Edge turbulence has been imaged on QUEST at high temporal resolution (50 kHz) using a fast framing visible camera. Statistical features of fluctuations including blobs are investigated in both open and closed magnetic configurations. Higher order moments of fluctuations including blobs and their mutual relationships are investigated. Close resemblance of the density pdf with Gaussian or beta distributions has earlier been predicted. Hence, an attempt has been made to characterize the density pdf with respect to the Pearson system to ascertain the implications of the stochastic forces.

    DOI: 10.1109/TPS.2011.2163423

  • Optimal Control on Plasma Vertical Position Instability in QUEST 国際誌

    Xiaolong Liu, Kazuo Nakamura, Tatsuya Yoshisue, Osamu Mitarai, Makoto Hasegawa, Kazutoshi Tokunaga, Erbing Xue, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Kuniaki Araki

    Proc. 13th Cross Straits Symposium,Kyushu University,Fukuoka,Nov.,2011   31.0 - 21.0   2011年11月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Dynamic interaction between a solitary drift wave structure and zonal flows in a linear cylindrical device 査読 国際誌

    Arakawa, H.; Kobayashi, T.; Inagaki, S.; Kasuya, N.; Oldenbuerger, S.; Nagashima, Y.; Yamada, T.; Yagi, M.; Fujisawa, A.; Itoh, K.; Itoh, S-I

    PLASMA PHYSICS AND CONTROLLED FUSION   53.0 ( 11.0 )   0.0 - 0.0   2011年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A solitary drift wave structure and its quasi-periodic change are discovered in a linear magnetized plasma. Detailed investigations show that the periodic changes are accompanied by an emission of splash, that is, a short lifetime event characterized by much higher frequencies than that of the fundamental drift waves. Dynamic interaction between the solitary wave and zonal flows is found to cause the emission of splashes since the splashes occur in a particular phase of zonal flows. The findings should give a deep insight into the dynamics and structural formation of magnetically confined plasmas and rotating planets, which are governed by drift and Rossby waves, respectively.

    DOI: 10.1088/0741-3335/53/11/115009

  • Eddy current-adjusted plasma shape reconstruction by Cauchy condition surface method on QUEST 査読 国際誌

    Nakamura, K.; Jiang, Y.; Liu, X. L.; Mitarai, O.; Kurihara, K.; Kawamata, Y.; Sueoka, M.; Hasegawa, M.; Tokunaga, K.; Zushi, H.; Hanada, K.; Fujisawa, A.; Sakamoto, M.; Idei, H.; Kawasaki, S.; Nakashima, H.; Higashijima, A.; Araki, K.

    FUSION ENGINEERING AND DESIGN   86.0 ( 6.0 )   1080.0 - 1084.0   2011年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    CCS (Cauchy Condition Surface) method is a numerical approach to reproduce plasma shape, which has good precision in conventional tokamaks. In order to apply it in plasma shape reproduction of ST (Spherical Tokamak). the calculation precision of the CCS method in a spherical tokamak CPD (Compact PWI experimental Device)(B(t) = 0.25 T, R = 0.3 m, a = 0.2 m) has been analyzed. The precision was confirmed also in ST and decided to be applied to a spherical tokamak QUEST (B(t), = 0.25 T, R = 0.68 m, a = 0.40 m).. In present stage from the magnetic measurement, it is known that the eddy current effect is large in QUEST experiment, and there are no special magnetic measurements for eddy current now, so some proper model should be selected to evaluate the eddy current effect. The eddy current density by not only CS (Center Solenoid) coil but also plasma current is calculated using EDDYCAL (JAEA). The eddy current magnitudes are taken as unknown variables and solved together with plasma shape reconstruction in ohmic discharge and ECCD (Electron Cyclotron Current Drive) discharge. (C) 2011 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.fusengdes.2011.04.045

  • Study of Matrix Converter as a Current-Controlled Power Supply in QUEST Tokamak 査読 国際誌

    Xiaolong LIU, Kazuo NAKAMURA, Yi JIANG, Tatsuya YOSHISUE, Osamu MITARAI, Makoto HASEGAWA, Kazutoshi TOKUNAGA, Hideki ZUSHI, Kazuaki HANADA, Akihide FUJISAWA, Hiroshi IDEI, Shoji KAWASAKI, Hisatoshi NAKASHIMA, Aki HIGASHIJIMA and Kuniaki ARAKI

    Plasma and Fusion Research   6.0 ( RA )   2011年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Because QUEST tokamak has a divertor configuration with a higher κ and a negative n-index, a precise power supply with a rapid response is needed to control the vertical position of the plasma. A matrix converter is a direct power conversion device that uses an array of controlled bidirectional switches as the main power elements for creating a variable-output current system. This paper presents a novel three-phase to two-phase topological matrix converter as a proposed power supply that stabilizes the plasma vertical position and achieves unity input power factor. An indirect control strategy in which the matrix converter is split into a virtual rectifier stage and a virtual inverter stage is adopted. In the virtual rectifier stage, the instantaneous active power and reactive power are decoupled on the basis of system equations derived from the DQ transformation; hence, unity power factor is achieved. Space vector pulse width modulation is adopted to determine the switching time of each switch in the virtual rectifier; the output voltage of the virtual rectifier is adjusted by the virtual inverter stage to obtain the desired load current. Theoretical analyses and simulation results are provided to verify its feasibility.

  • 25pGW-5 Effect of TF ripples on plasma wall interaction and localized damages due to loss of energetic electrons in QUEST

    SK Sharma, H Zushi, N Yoshida, H Watanabe, M Osakabe, Y Takeiri, M Hasegava, K Tokunaga, K Hanada, H Idei, M Sakamoto, K Nakamura, A Fujisawa, M Ishiguro, S Tashima, Team QUEST

    日本物理学会講演概要集   66.0 ( 1.0 )   240.0   2011年9月

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    記述言語:英語   掲載種別:研究論文(その他学術会議資料等)  

  • Verification of wavelet analysis for a heat pulse propagation experiment 査読 国際誌

    Kobayashi, T.; Inagaki, S.; Itoh, S-I; Ida, K.; Oldenbuerger, S.; Tsuchiya, H.; Nagayama, Y.; Kawahata, K.; Yamada, H.; Sasaki, M.; Fujisawa, A.; Itoh, K.

    PLASMA PHYSICS AND CONTROLLED FUSION   53.0 ( 9.0 )   0.0 - 0.0   2011年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A new wavelet analysis method is used to study heat pulse propagation in magnetic confinement plasmas. The wavelet transform is applied to estimate the time evolution of the phase delay in heat pulse propagation with a fine temporal resolution. The procedure of analysis is explained in detail. The method is examined by taking an exemplary heat pulse propagation in the Large Helical Device. Various wavelet parameters are tested and the parameter region where relevant results are obtained is identified. Temporal resolution of the phase variation is evaluated from a convergence study.

    DOI: 10.1088/0741-3335/53/9/095012

  • Study of Matrix Converter as Stabilizing Power Supply for Vertical Position Instability on QUEST Tokamak 国際誌

    Xiaolong Liu, Kazuo Nakamura, Tatsuya Yoshisue, Osamu Mitarai, Makoto Hasegawa, Kazutoshi Tokunaga, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima, Kuniaki Araki

    Proc. 2011 Annual Conference of I.E.E. of Japan,Industry Applications Society,Okinawa,Sept. 6-8,2011   2011年9月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Investigations of the radial propagation of blob-like structure in a non-confined electron cyclotron resonance heated plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak 査読 国際誌

    Ogata, R.; Hanada, K.; Nishino, N.; Liu, H. Q.; Zushi, H.; Ishiguro, M.; Ikeda, T.; Nakamura, K.; Fujisawa, A.; Idei, H.; Hasegawa, M.; Kawasaki, S.; Nakashima, H.; Higashijima, A.

    PHYSICS OF PLASMAS   18.0 ( 9.0 )   0.0 - 0.0   2011年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A study of radial propagation and electric fields induced by charge separation in blob-like structures has been performed in a non-confined cylindrical electron cyclotron resonance heating plasma on Q-shu University Experiment with a Steady-State Spherical Tokamak using a fast-speed camera and a Langmuir probe. The radial propagation of the blob-like structures is found to be driven by E x B drift. Moreover, these blob-like structures were found to have been accelerated, and the property of the measured radial velocities agrees with the previously proposed model [C. Theiler et al., Phys. Rev. Lett. 103, 065001 (2009)]. Although the dependence of the radial velocity on the connection length of the magnetic field appeared to be different, a plausible explanation based on enhanced short-circuiting of the current path can be proposed. (C) 2011 American Institute of Physics. [doi:10.1063/1.3640494]

    DOI: 10.1063/1.3640494

  • 26pGW-13 Experimental observation and Statistical Analysis of Blob-like Structures in QUEST

    HQ Liu, K Hanada, N Nishino, R Ogata, M Ishiguro, H Zushi, K Nakamura, A Fujisawa, H Idei, M Hasegawa

    日本物理学会講演概要集   66.0 ( 1.0 )   256.0   2011年9月

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    記述言語:英語   掲載種別:研究論文(その他学術会議資料等)  

  • 26pGW-12 B_Z dependence of the higher order moments of density fluctuations in slab geometry plasma in QUEST

    Santanu Banerjee, H Zushi, N Nishino, K Hanada, H Honma, HQ Liu, M Ishiguro, T Ryoukai, S Tashima, K Nakamura, H Idei, M Hasegawa, A Fujisawa

    日本物理学会講演概要集   66.0 ( 1.0 )   256.0   2011年9月

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    記述言語:英語   掲載種別:研究論文(その他学術会議資料等)  

  • Evaluation of Electron Temperature Fluctuations Using Two Different Probe Techniques in Plasma Assembly for Nonlinear Turbulence Analysis (PANTA) 査読 国際誌

    Katsuyuki KAWASHIMA, Yasuhiro MIYOSHI, Stella OLDENBÜRGER, Shigeru INAGAKI, Hiroyuki ARAKAWA, Yoshihiko NAGASHIMA, Takuma YAMADA, Makoto SASAKI, Tatsuya KOBAYASHI, Kazuya URIU, Satoru SUGITA, Masatoshi YAGI, Naohiro KASUYA, Akihide FUJISAWA, Sanae -I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   6.0 ( RA )   2011年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Electron temperature fluctuations are measured with a rotatable triple probe in PANTA. Effects of fluctuation phase are cancelled by aligning the probe pins in the propagation direction of fluctuations. Evaluated electron temperature fluctuations normalized by average electron temperature are much smaller than normalized density fluctuations and normalized floating potential fluctuations in low electron temperature PANTA plasma. Additionally conditional sampling technique is applied to a single probe measurement.

  • Study of blob-like structures in QUEST 査読 国際誌

    Liu, H. Q.; Hanada, K.; Nishino, N.; Ogata, R.; Ishiguro, M.; Zushi, H.; Nakamura, K.; Sakamoto, M.; Idei, H.; Fujisawa, A.; Hasegawa, M.; Higashizono, Y.; Kawasaki, S.; Nakashima, H.; Higashijima, A.

    JOURNAL OF NUCLEAR MATERIALS   415.0 ( 1.0 )   S620 - S623   2011年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Blob-like structures are observed in an open magnetic field line configuration of electron cyclotron resonance (ECR) heating plasma in QUEST. The combined measurement with a fast camera and a movable Langmuir probe show that visible filamentary structures extended along field lines do correspond to over-dense plasma structures. Ion saturation current time trace shows a front-like asymmetric burst when a visible structure reaches the probe during its outward propagation. The typical radial velocity of the blob-like structure, V-b, was measured as similar to 1 km/s with the fast camera at the intermediate area. V-b increased as the blob-like structure moved along major radius, R (outward). The average velocity of E x B drift derived from the probe measurement, slightly larger than V-b, was also increased as the blob-like structure propagated to larger R. (C) 2010 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jnucmat.2010.12.225

  • Non-Gaussian properties of global momentum and particle fluxes in a cylindrical laboratory plasma 査読 国際誌

    Nagashima, Yoshihiko; Itoh, Sanae-I.; Inagaki, Shigeru; Arakawa, Hiroyuki; Kasuya, Naohiro; Fujisawa, Akihide; Kamataki, Kunihiro; Yamada, Takuma; Shinohara, Shunjiro; Oldenbuerger, Stella; Yagi, Masatoshi; Takase, Yuichi; Diamond, Patrick H.; Itoh, Kimitaka

    PHYSICS OF PLASMAS   18.0 ( 7.0 )   0.0 - 0.0   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Non-Gaussian statistical properties of the azimuthally averaged momentum and particle fluxes driven by turbulence have been simultaneously observed in inhomogeneous magnetized plasmas for the first time. We identified the stretched Gaussian distribution of the both fluxes and the transition from the point-wise distribution to averaged ones was confirmed. The change of the particle flux precedes that of the momentum flux, demonstrating that the momentum flux is induced by the relaxation of density gradient. (C) 2011 American Institute of Physics. [doi:10.1063/1.3601767]

    DOI: 10.1063/1.3601767

  • Venturini Method and Space Vector Modulation Method in Matrix Converter 国際誌

    K. Nakamura, X. L. Liu, T. Yoshisue, O. Mitarai, K. Tokunaga, M. Hasegawa, H. Zushi, K. Hanada, A. Fujisawa, M. Sakamoto, H. Idei, S. Kawasaki, H. Nakashima, A. Higashijima, K. Araki

    Proc. International Conference on Electrical Engineering (ICEE2011),Hong Kong,July 11-14,2011   2011年7月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Recent experiments and future collaborations on QUEST

    K. Hanada, H. Zushi, H. Idei, K. Nakamura, M. Ishiguro, S. Tashima, E. I.Kalinnikova, M. Sakamoto, M. Hasegawa, A. Fujisawa, A. Higashijima, S. Kawasaki, H. Nakashima, H. Liu, O. Mitarai, T. Maekawa, A. Fukuyama, Y. Takase, J. Qian

    JSPS-CAS Core University Program Seminar on Summary of 10-year Collaborations in Plasma and Nuclear Fusion Research Area 9?11 March 2011,Okinawa,Japan   204.0   2011年7月

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    記述言語:英語  

  • Observation of Nonlinear Coupling between Low Frequency Coherent Modes and Background Turbulence in LMD-U 査読 国際誌

    Tatsuya KOBAYASHI, Shigeru INAGAKI, Hiroyuki ARAKAWA, Stella OLDENBÜRGER, Makoto SASAKI, Yoshihiko NAGASHIMA, Takuma YAMADA, Satoru SUGITA, Masatoshi YAGI, Naohiro KASUYA, Akihide FUJISAWA, Sanae-I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   6.0 ( RA )   2011年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A solitary wave like fluctuating structure is observed in the Large Mirror Device-Upgrade (LMD-U) under relatively high neutral pressure conditions. Ion saturation current fluctuations are measured and Fourier and wavelet power spectra are calculated. Temporal behavior of fluctuation power and strength of nonlinear coupling of low frequency coherent mode and background turbulence in a specific frequency region is analyzed. This is achieved using wavelet spectral and bispectral analyses with conditional averaging.

  • Electron Cyclotron / Bernstein Wave Heating and Current Drive Experiments using Phased-array Antenna in QUEST 国際誌

    H. Idei, H. Zushi, K. Hanada, K. Nakamura, A. Fujisawa, M. Hasegawa, N. Yoshida, M. Sakamoto, H. Watanebe, K. Tokunaga, Y. Nagashima, A. Ejiri, M. Sakaguchi, E. Kalinnikova, M. Ishiguro, S. Tashima, A. Fukuyama, H. Igami, S. Kubo, S. K. Sharma, T. Ryokai, H. Q. Liu, M. Isobe, K. Nagaoka, H. Nakanishi, N. Nishino, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Takase, T. Maekawa, O. Mitarai, M. Kikuchi and K. Toi

    RADIO FREQUENCY POWER IN PLASMAS: Proceedings of the 19th Topical Conference   1406.0 ( 1.0 )   473.0 - 476.0   2011年6月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

    The phased‐array antenna system for Electron Cyclotron/Bernstein Wave Heating and Current Drive experiments has been developed in the QUEST. The antenna was designed to excite a pure O‐mode wave in the oblique injection for the O‐X‐B mode conversion experiments, and its good performances were confirmed at a low power level. The plasma current (<∼15 kA) with an aspect ratio of 1.5 was started up and sustained by only RF injection in the low‐density operations. The long pulse discharge of 10 kA was also attained for 37 s. The new density window to sustain the plasma current was observed in the high‐density plasmas. The single‐null divertor configuration with the high plasma current (<∼25 kA) was attained in the 17 s plasma sustainment.

  • Simulation on Toroidal Field Power Supply of HL-2A Tokamak: Application of Dual DQ0 Transformation for Six-Phase Synchronous Generator Model

    Xiaolong Liu, Kazuo Nakamura, Kazutoshi Tokunaga, Makoto Hasegawa, Kuniaki Araki, Yi Jiang, Tatsuya Yoshisue, Hideki Zushi, Kazuaki Hanada, Akihide Fujisawa, Hiroshi Idei, Shoji Kawasaki, Hisatoshi Nakashima, Aki Higashijima

    Engineering Sciences Reports,Kyushu University   2011年6月

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    記述言語:英語   掲載種別:研究論文(大学,研究機関等紀要)  

  • Non-Inductive Start up of QUEST Plasma by RF Power 査読 国際誌

    Hanada, K.; Zushi, H.; Idei, H.; Nakamura, K.; Ishiguro, M.; Tashima, S.; Kalinnikova, E. I.; Sakamoto, M.; Hasegawa, M.; Fujisawa, A.; Higashijima, A.; Kawasaki, S.; Nakashima, H.; Liu, H.; Mitarai, O.; Maekawa, T.; Fukuyama, A.; Takase, Y.; Qian, J.

    PLASMA SCIENCE & TECHNOLOGY   13.0 ( 3.0 )   307.0 - 311.0   2011年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Both start-up and sustainment of plasma were successfully achieved by fully non-inductive current drive using microwave with a frequency of 8.2 GHz. Plasmas current of 15 kA was implemented for 1 s. Magnetic surface reconstruction exhibited a plasma shape with an aspect ratio of below 1.5. The plasma current was dependent significantly on the launched microwave power and vertical magnetic field, while not affected by the mode of launched wave and the toroidal refractive index. Hard X-ray (HXR) emitted from energetic electrons accelerated by the microwave was observed, and the discharge with a plasma current over 4 kA followed the same trend as the number of photons of 10 keV to 12 keV. This suggests that the plasma current may be driven by energetic electrons. Based on the experimental conditions, alternative explanations of how the plasma current could be driven are discussed.

    DOI: 10.1088/1009-0630/13/3/08

  • Method for Estimating the Wavenumber of Standing Waves Using Three Langmuir Probes 査読 国際誌

    Tatsuya KOBAYASHI, Yoshihiko NAGASHIMA, Shigeru INAGAKI, Hiroyuki ARAKAWA, Makoto SASAKI, Takuma YAMADA, Masatoshi YAGI, Naohiro KASUYA, Akihide FUJISAWA, Sanae-I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   6.0 ( RA )   2011年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A new method for estimating the wavenumber of a standing wave system by using three Langmuir probes is proposed. Analytical formulae are derived from a simple model in which two waves of the same frequency and the same wavenumber propagate in opposite directions. The proposed method can estimate the wavenumber correctly even if the two waves have equal amplitude.

  • Long Range Temperature Fluctuation in LHD 査読 国際誌

    Shigeru INAGAKI, Tokihiko TOKUZAWA, Kimitaka ITOH, Katsumi IDA, Sanae-I. ITOH, Naoki TAMURA, Satoru SAKAKIBARA, Naohiro KASUYA, Akihide FUJISAWA, Shin KUBO, Takashi SHIMOZUMA, Takeshi IDO, Seiya NISHIMURA, Hiroyuki ARAKAWA, Tatsuya KOBAYASHI, Masatoshi YAGI, Kenji TANAKA, Yoshio NAGAYAMA, Kazuo KAWAHATA, Shigeru SUDO, Hiroshi YAMADA, Akio KOMORI and LHD Experiment Group

    Plasma and Fusion Research   6.0 ( RA )   2011年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We report a detailed correlation technique to identify the long-range temperature fluctuation in the Large Helical Device. Correlation hunting has successfully realized the observation of electron temperature fluctuations, which are characterized by their correlation length comparable to the plasma minor radius, with low frequency of ∼ 1-3 kHz, ballistic radial propagation (at a speed of ∼1 km/s, of the order of diamagnetic drift velocity), spatial mode number of m/n = 1/1 (or 2/1), and amplitude of ∼2% at the maximum. Bicoherence analysis confirmed their nonlinear coupling with local microscopic turbulent fluctuations. This long-range temperature fluctuation is a possible carrier of fast propagation in transport processes observed so far. We also comment on the theoretical interpretation.

  • Development of radially movable multichannel Reynolds stress probe system for a cylindrical laboratory plasma 査読 国際誌

    Nagashima, Yoshihiko; Inagaki, Shigeru; Kamakaki, Kunihiro; Arakawa, Hiroyuki; Yamada, Takuma; Shinohara, Shunjiro; Kawai, Yoshinobu; Yagi, Masatoshi; Fujisawa, Akihide; Itoh, Sanae-I; Itoh, Kimitaka; Takase, Yuichi

    REVIEW OF SCIENTIFIC INSTRUMENTS   82.0 ( 3.0 )   2011年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A new radially movable multichannel azimuthal probe system has been developed for measuring azimuthal and radial profiles of electrostatic Reynolds stress (RS) per mass density of microscale fluctuations for a cylindrical laboratory plasma. The system is composed of 16 probe units arranged azimuthally. Each probe unit has six electrodes to simultaneously measure azimuthal and radial electric fields for obtaining RS. The advantage of the system is that each probe unit is radially movable to measure azimuthal RS profiles at arbitrary radial locations as well as two-dimensional structures of fluctuations. The first result from temporal observation of fluctuation azimuthal profile presents that a low-frequency fluctuation (1-2 kHz) synchronizes oscillating Reynolds stress. In addition, radial scanning of the probe system simultaneously demonstrates two-dimensional patterns of mode structure and nonlinear forces with frequency f = 1.5 kHz and azimuthal mode number m = 1. (C) 2011 American Institute of Physics. [doi:10.1063/1.3557384]

    DOI: 10.1063/1.3557384

  • マトリクスコンバータにおけるVenturini法と空間ベクトル法

    中村 一男、劉 暁龍、吉末竜也、御手洗 修、徳永 和俊、長谷川 真、図子 秀樹、花田 和明、藤澤 彰英、坂本 瑞樹、出射 浩、川崎 昌二、中島 寿年、東島 亜紀、荒木 邦明

    半導体電力変換研究会   2011年3月

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    記述言語:日本語   掲載種別:研究論文(その他学術会議資料等)  

  • A Review-Observations of Turbulence and Structure in Magnetized Plasmas 査読 国際誌

    Akihide FUJISAWA

    Plasma and Fusion Research   5.0 ( Rev )   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Magnetized plasma is an non-equilibrium matter rich in nonlinear phenomena; its structural formations are dominated by turbulence. This article provides a brief review of experiments and observations of phenomena occurring in turbulent plasmas, with an emphasis on the methodologies for characterizing turbulence, and visualizing the invisible structure created by turbulence and the internal couplings between the elemental waves that constitute turbulence. Zonal flows, streamers, blobs, and other phenomena are investigated by using analytical methods such as Fourier transformation, wavelet analysis, probabilistic density function analysis, bicoherence, wavelet bicoherence. Finally, the contemporary view of plasma turbulence is presented with discussion of unsolved transport issues in fusion plasmas, such as transport barrier formation and nonlocal transport.

  • Turbulence and zonal flows in edge plasmas of the HL-2A tokamak 査読 国際誌

    Zhao, K. J.; Dong, J. Q.; Yan, L. W.; Hong, W. Y.; Fujisawa, A.; Yu, C. X.; Li, Q.; Qian, J.; Cheng, J.; Lan, T.; Liu, A. D.; Zhao, H. L.; Kong, D. F.; Huang, Y.; Liu, Yi; Song, X. M.; Yang, Q. W.; Ding, X. T.; Duan, X. R.; Liu, Yong

    PLASMA PHYSICS AND CONTROLLED FUSION   52.0 ( 12.0 )   0.0 - 0.0   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Measurements with a toroidally and poloidally displaced three-dimensional set of Langmuir probe arrays have revealed details of turbulence, geodesic acoustic modes (GAMs), zonal flows and their interactions in the edge region of HL-2A tokamak plasmas. The coexistence of intensive low frequency zonal flows (LFZFs) off < 4 kHz and the GAMs of 7 kHz < f(GAM) < 20 kHz has been unambiguously demonstrated. The poloidal and toroidal symmetries of the flows, including the GAMs, are verified experimentally. In particular, the coherency of the flows over a large toroidal scale of 2100 mm at a magnetic flux surface is emphasized. The LFZF packets are shown to propagate outward and inward as equally likely events, whereas the predominantly outward propagation of the GAM packets is analyzed. The nonlinear three-wave coupling of the flows with ambient turbulence is shown with a bicoherency analysis and an envelope modulation of the latter by the former. The intensity of the LFZFs is observed to increase and decrease with increases in ECRH power (similar to 300-700 kW) and safety factor q similar to (3.5-6.2), respectively, whereas the intensity of the GAMs increases with increases in both ECRH power and q.

    DOI: 10.1088/0741-3335/52/12/124008

  • Probability Density Function of Density Fluctuations in Cylindrical Helicon Plasmas 査読 国際誌

    Hiroyuki ARAKAWA, Shigeru INAGAKI, Yoshihiko NAGASHIMA, Takuma YAMADA, Kunihiro KAMATAKI, Tatsuya KOBAYASHI, Satoru SUGITA, Masatoshi YAGI, Naohiro KASUYA, Akihide FUJISAWA, Sanae -I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   5.0 ( RA )   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The turbulence fluctuation spectra of linear magnetized plasmas are measured under various neutral pressure conditions. Strong turbulent waves and symmetric waves are observed in low and high neutral pressure conditions. In this study, we compare the radial structure of the probability density function (PDF) of these fluctuations. The characteristics of the PDFs are related to those of the radial and poloidal turbulent structures.

  • Nonlinear Mode Couplings in a Cylindrical Magnetized Plasma 査読 国際誌

    Takuma YAMADA, Sanae-I. ITOH, Shigeru INAGAKI, Yoshihiko NAGASHIMA, Shunjiro SHINOHARA, Naohiro KASUYA, Kenichiro TERASAKA, Kunihiro KAMATAKI, Hiroyuki ARAKAWA, Masatoshi YAGI, Akihide FUJISAWA and Kimitaka ITOH

    Plasma and Fusion Research   5.0 ( RA )   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Nonlinear mode couplings in plasma turbulence generate mesoscale global structures, such as zonal flows and streamers. A streamer is a poloidally localized structure that is radially elongated. In the Large Mirror Device-Upgrade, a streamer structure was observed in the ion saturation-current fluctuation measured with a 64-channel poloidal Langmuir probe array. The bunching of waves was poloidally localized and rotated slowly in the ion diamagnetic direction. The frequency and poloidal mode number of its envelope corresponded to one particular mode, which was strongly coupled with many other modes. By calculating the radial biphase profile of three pronounced modes, including the particular mode, the streamer structure was confirmed to be radially elongated.

  • Experimental Study of Turbulence and Zonal Flow in Edge Plasmas of the HL-2A Tokamak 査読 国際誌

    Jiaqi DONG, Kaijun ZHAO, Longwen YAN, Wenyu HONG, Changxuan YU, Akihide FUJISAWA, Jun QIAN, Jun CHENG, Adi LIU, Tao LAN, Hailin ZHAO, Defeng KONG, Yi LIU, Yuan HUANG, Qiang LI, Xianming SONG, Qingwei YANG, Xuantong DING, Xuru DUAN and Yong LIU

    Plasma and Fusion Research   5.0 ( RA )   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Measurements with a three dimensional set of Langmuir probe arrays have unambiguously demonstrated the coexistence of intensive low frequency zonal flows (LFZFs), geodesic acoustic modes (GAMs), low frequency fluctuations (LFFs) and high frequency ambient turbulence (HFAT) in the edge of HL-2A tokamak plasmas, by verifying the temporal and spatial characteristics of the electrostatic fluctuations. The intensity of the LFZFs is observed to increase and decrease with increases of ECRH power (∼ 300-700 kW) and safety factor q (∼ 3.5-6.2), respectively, and the intensity of the GAMs increases with the ECRH power as well as q. The radial wave number-frequency spectra of the LFZF show that the LFZF packets propagate outwards and inwards as equally likely events, while the GAM packets propagate predominantly outwards. The three wave coupling of the zonal flows, including the GAMs, and the LFFs with the HFAT is investigated in detail.

  • ECRH Superposition on Linear Cylindrical Helicon Plasma in the LMD-U 査読 国際誌

    Kunihiro KAMATAKI, Sanae-I. ITOH, Shigeru INAGAKI, Hiroyuki ARAKAWA, Yoshihiko NAGASHIMA, Takuma YAMADA, Masatoshi YAGI, Akihide FUJISAWA and Kimitaka ITOH

    Plasma and Fusion Research   5.0 ( RA )   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Electron cyclotron resonance heating (ECRH) is superimposed on a linear cylindrical helicon plasma in the Large Mirror Device-Upgrade (LMD-U) to study the fluctuation characteristics of high density helicon plasma with/without ECRH injection. The radial profiles of electron density and electron temperature rose by < 10 %, and the drift wave frequency decreased with the ECRH injection. Bicoherence analysis reveals that the nonlinear interaction between drift waves and broad frequency band components exists with or without ECRH injection.

  • Bispectral Analysis of Density and Potential Fluctuations in a High Neutral Density Cylindrical Plasma 査読 国際誌

    Tatsuya KOBAYASHI, Shigeru INAGAKI, Hiroyuki ARAKAWA, Kunihiro KAMATAKI, Yoshihiko NAGASHIMA, Takuma YAMADA, Satoru SUGITA, Masatoshi YAGI, Naohiro KASUYA, Akihide FUJISAWA, Sanae -I. ITOH and Kimitaka ITOH

    Plasma and Fusion Research   5.0 ( RA )   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The structure of fluctuations in the Large Mirror Device-Upgrade (LMD-U) depends on the neutral density. In this study, we focus on the high neutral density plasma in which the potential and density fluctuation waveforms are nontrigonometric functions similar to sawtooth waves, and peaks in the power spectrum lie along a straight line when plotted as frequency versus wavenumber. Two-dimentional auto and cross bispectral analyses of Iis and/or Vf, which consider both the matching conditions for both the azimuthal wavenumber and the frequency, have been performed; significant couplings are observed at particular peak frequencies. Similarities and differences between the auto and cross bicoherence of Iis and/or Vf are discussed.

  • Observation of Quasi-Two-Dimensional Nonlinear Interactions in a Drift-Wave Streamer 査読 国際誌

    Yamada, T.; Itoh, S-I; Inagaki, S.; Nagashima, Y.; Kasuya, N.; Kamataki, K.; Arakawa, H.; Kobayashi, T.; Yagi, M.; Fujisawa, A.; Itoh, K.

    PHYSICAL REVIEW LETTERS   105.0 ( 22.0 )   0.0 - 0.0   2010年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A streamer, which is a bunching of drift-wave fluctuations, and its mediator, which generates the streamer by coupling with other fluctuations, have been observed in a cylindrical magnetized plasma. Their radial structures were investigated in detail by using the biphase analysis. Their quasi-two-dimensional structures were revealed to be equivalent with a pair of fast and slow modes predicted by a nonlinear Schrodinger equation based on the Hasegawa-Mima model.

    DOI: 10.1103/PhysRevLett.105.225002

  • Study of Edge Turbulence from the Open to Closed Magnetic Field Configuration during the Current Ramp-up Phase in QUEST, 国際誌

    H. Zushi, N. Nishino, K. Hanada H. Honma, H. Q. Liu, Y. Higashizono, M. Sakamoto, Y. Nakashima, M. Ishiguro, T. Ryoukai, S. Tashima, K. Nakamura, H. Idei, M. Hasegawa, A. Fujisawa, O. Mitarai, A. Fukuyama, Takeiri, Y. Takase, T. Maekawa, Y. Kishimoto

    Proc. 23rd IAEA Fusion Energy Conference, 11-16 October 2010 Daejon, Korea   2010年11月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Bifurcation of the plasma turbulence on LMD-U 査読 国際誌

    Arakawa, H.; Inagaki, S.; Nagashima, Y.; Yamada, T.; Kamataki, K.; Kobayashi, T.; Sugita, S.; Yagi, M.; Kasuya, N.; Fujisawa, A.; Itoh, S-I; Itoh, K.

    PLASMA PHYSICS AND CONTROLLED FUSION   52.0 ( 10.0 )   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Density fluctuation spectra are qualitatively modified depending on filling gas pressure and magnetic field strength in a linear magnetized plasma. Abrupt and spontaneous jumps between fluctuation states during a discharge are observed in the filling gas pressure-magnetic field plane. Those jumps are characterized using a spectrum pattern and have a bifurcation property on the plane.

    DOI: 10.1088/0741-3335/52/10/105009

  • Wavelet analyses using parallel computing for plasma turbulence studies 査読 国際誌

    Fujisawa, A.; Shimizu, A.; Itoh, K.; Nagashima, Y.; Yamada, T.; Inagaki, S.; Matsuoka, K.; Itoh, S-I

    PHYSICS OF PLASMAS   17.0 ( 10.0 )   0.0 - 0.0   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The wavelet analyses have been carried out, using a cluster of personal computer, on the signal of electric field fluctuations measured with heavy ion beam probes in the compact helical system stellarator. The results have revealed the intermittent characteristics of turbulence and of the nonlinear couplings between elemental waves of turbulence. The usage of parallel computing is found to successfully reduce the calculation time as inversely proportional to the CPU number used the cluster, which shows the nature of "embarrassingly parallel computation." The present example of the wavelet analyses clearly demonstrates the importance of the advanced analyzing methods and the parallel computation for the modern studies of plasma turbulence. (C) 2010 American Institute of Physics. [doi:10.1063/1.3488244]

    DOI: 10.1063/1.3488244

  • Study of Edge Turbulence from the Open to Closed Magnetic Field Configuration during the Current Ramp-up Phase in QUEST 国際誌

    H. Zushi, N. Nishino, K. Hanada H. Honma, H. Q. Liu, Y. Higashizono, M. Sakamoto, Y. Nakashima, M. Ishiguro, T. Ryoukai, S. Tashima, K. Nakamura, H. Idei, M. Hasegawa, A. Fujisawa, O. Mitarai, A. Fukuyama, Takeiri, Y. Takase, T. Maekawa, Y. Kishimoto

    Proc.23rd IAEA Fusion Energy Conference   2010年10月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Probability Density Function of Density Fluctuations in Cylindrical Helicon Plasmas 査読 国際誌

    H. Arakawa, S. Inagaki, Y. Nagashima, T. Yamada, K. Kamataki, T. Kobayashi, S. Sugita, M. Yagi, N. Kasuya, A. Fujisawa, K. Itoh and S.-I. Itoh

    Plasma and Fusion Research   5.0 ( RA )   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Observation of edge Reynolds stress increase preceding an L-H transition in Compact Helical System 査読 国際誌

    Yoshihiko NAGASHIMA, Kenichi NAGAOKA, Kimitaka ITOH, Akihide FUJISAWA, Mitsutaka ISOBE, Tsuyoshi AKIYAMA, Chihiro SUZUKI, Shin NISHIMURA, Yasuo YOSHIMURA, Keisuke MATSUOKA, Shoichi OKAMURA, Yuichi TAKASE, Akira EJIRI, Sanae -I. ITOH, Masatoshi YAGI, and CHS Group

    Plasma and Fusion Research   5.0 ( RC )   2010年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Study of Amplitude Correlation Technique in a Cylindrical Magnetized Plasma 査読 国際誌

    Yamada, Takuma; Itoh, Sanae-I.; Inagaki, Shigeru; Nagashima, Yoshihiko; Kamataki, Kunihiro; Arakawa, Hiroyuki; Yagi, Masatoshi; Fujisawa, Akihide; Itoh, Kimitaka

    JOURNAL OF NUCLEAR MATERIALS   79.0 ( 8.0 )   0.0 - 0.0   2010年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    0.0

    DOI: 10.1143/JPSJ.79.085001

  • Internal transport barrier formation induced by edge perturbation on LHD 査読 国際誌

    Inagaki, S.; Tamura, N.; Ida, K.; Kubo, S.; Shimozuma, T.; Nagayama, Y.; Kawahata, K.; Sudo, S.; Fujisawa, A.; Itoh, K.; Itoh, S-I.

    NUCLEAR FUSION   50.0 ( 6.0 )   2010年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The electron internal transport barrier (ITB) is formed by an edge perturbation induced by a tracer encapsulated solid pellet injection in a net-current free LHD plasma. The ITB trigger by an edge perturbation takes place in the low density regime and the ITB is not accompanied by a significant change in the density. At the onset of the core temperature rise, there is a strong correlation between the heat flux in the central region and the temperature gradient at a distance half of the plasma radius away. A radial temperature profile with a concave curvature abruptly appears in the growing phase of temperature gradient. Turbulence suppression mechanisms via flow and magnetic shears are not sufficient to explain these features.

    DOI: 10.1088/0029-5515/50/6/064012

  • Two-dimensional bispectral analysis of drift wave turbulence in a cylindrical plasma 査読 国際誌

    Yamada, T.; Itoh, S. -I.; Inagaki, S.; Nagashima, Y.; Shinohara, S.; Kasuya, N.; Terasaka, K.; Kamataki, K.; Arakawa, H.; Yagi, M.; Fujisawa, A.; Itoh, K.

    PHYSICS OF PLASMAS   17.0 ( 5.0 )   0.0 - 0.0   2010年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Bispectral analysis and multichannel measurement are becoming attractive investigation tools in plasma fluctuation studies. In the Large Mirror Device-Upgrade, the measurement of fluctuations in the ion saturation-current with a 64-channel poloidal Langmuir probe array was performed. The two-dimensional (2D) (poloidal wave number and frequency) power spectrum showed a number of pronounced peaks and broadband fluctuations in the poloidal wave number-frequency space. We applied 2D bispectral analysis, which considers both the matching conditions of poloidal wave number and frequency, to the spatiotemporal waveform, and confirmed the nonlinear couplings between coherent-coherent, coherent-broadband, and broadband-broadband fluctuation components. More than ten peaks were revealed to have as their origins only three original parent modes generated in the plasma. Comparison between the theoretical estimate and experimental observation for the bicoherence showed good agreement. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3429674]

    DOI: 10.1063/1.3429674

  • Development of Phased-array Antenna System and Its Application to EBWH/CD Experiments in QUEST 国際誌

    H. Idei, M. Sakaguchi, E. I. Kalinnikova, K. Nagata, H. Zushi, K. Hanada, S. Tashima, M. Ishiguro, , H. Q. Liu, H. Igami3, S. Kubo, K. Nakamura, A. Fujisawa, M. Sakamoto, M. Hassegawa, Y. Higashizono, R. Ogata, T. Ryokai, S. K. Sharma, S. Kawasaki, H. Nakashima, A. Higashijima, Y. Takase, T. Maekawa, O. Mitarai and Y. Kishimoto

    16th Joint Workshop on Electron Cyclotron Emission and Electron Cyclotron Resonance Heating,Sanya,China   269.0 - 274.0   2010年4月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Experimental Confinement Studies Beyond ITER 査読 国際誌

    Akihide FUJISAWA

    Plasma and Fusion Research   5.0 ( RA )   2010年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The advantages of stellarators are discussed with an emphasis on the high density limit more than 10 times higher than that of tokamaks with the equivalent magnetic field strength. The comparison between stellerators and tokamaks in the light of the new paradigm of plasma turbulence and zonal flows is presented to propose a new optimization principle of magnetic field configuration. The roles of low-temperature devices should be recognized for further understanding of the plasma confinement even in the era of burning state plasmas

  • A review of experimental drift turbulence studies 査読 国際誌

    G R Tynan, A Fujisawa and G McKee

    PLASMA PHYSICS AND CONTROLLED FUSION   51.0 ( 11.0 )   2009年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Experimental drift turbulence and zonal flow studies in magnetically confined plasma experiments are reviewed. The origins of drift waves, transition to drift turbulence and drift turbulence–zonal flow interactions in open field line and toroidal closed flux surface experiments are discussed and the free energy sources, dissipation mechanisms and nonlinear dynamics of drift turbulence in the core, edge and scrape-off layer plasma regions are examined. Evidence that turbulence across these regions is linked and that turbulence-driven zonal flows exist is presented, and evidence that these flows help regulate the turbulent scale lengths, amplitude and fluxes is summarized. Seemingly contradictory reports exist regarding the scale of turbulent transport events; gyro-Bohm behavior of turbulence correlation lengths as well as evidence for long-range transport phenomena both exist. Changes in turbulence during and after transport barrier formation are summarized and compared. The inferred turbulent particle and heat fluxes due to turbulent transport are usually consistent with global confinement, and edge plasma momentum transport appears to be linked to plasma flows at the last-closed flux surface and in the open field line region. However, inconsistencies between observed transport and turbulence have sometimes been reported and are pointed out here. Special attention is given to open issues, and suggestions for future experimental studies are given.

  • Calculation of Beam Trajectories of a Heavy Ion Beam Probe Diagnostic in the TST-2 Spherical Tokamak 査読 国際誌

    Nagashima Yoshihiko, A. Ejiri, Fujisawa Akihide, Y. Takase

    IEEJ Transactions on Fundamentals and Materials   129.0 ( 9.0 )   575.0 - 579.0   2009年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Dynamics of Drift and Flute Modes in Linear Cylindrical ECR Plasma 査読 国際誌

    K. Kamataki, S.-I. Itoh, Y. Nagashima, S. Inagaki, S. Shinohara, M. Yagi, T. Yamada, Y. Kawai, A. Fujisawa, K. Itoh

    JOURNAL OF NUCLEAR MATERIALS   8.0   82.0 - 86.0   2009年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Reynolds Stress Measurements for Investigation of Nonlinear Processes of Turbulence in the Large Mirror Device and in the Large Mirror Device-Upgrade 査読 国際誌

    Yoshihiko NAGASHIMA, Sanae-I. ITOH, Kimitaka ITOH, Akihide FUJISAWA, Shigeru INAGAKI, Yoshinobu KAWAI, Shunjiro SHINOHARA, Masayuki FUKAO, Takuma YAMADA, Kenichiro TERASAKA, Takashi MARUTA, Kunihiro KAMATAK, Hiroyuki ARAKAWA, Masatoshi YAGI, Naohiro KASUYA, George R. TYNAN, Patrick H. DIAMOND, and Yuichi Takase

    JOURNAL OF NUCLEAR MATERIALS   8.0   50.0 - 54.0   2009年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Observations of abrupt changes in the fluctuation spectrum on LMD-U 査読 国際誌

    Arakawa, H.; Kamataki, K.; Inagaki, S.; Maruta, T.; Nagashima, Y.; Yamada, T.; Shinohara, S.; Terasaka, K.; Sugita, S.; Yagi, M.; Kasuya, N.; Fujisawa, A.; Itoh, S-I; Itoh, K.

    PLASMA PHYSICS AND CONTROLLED FUSION   51.0 ( 8.0 )   0.0 - 0.0   2009年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A transition of the fluctuation spectrum of ion saturation current is observed in linear magnetized plasmas. A power spectrum with regular peaks and a broadband spectrum appear alternately during a discharge. The temporal order of changes in the modes is investigated at the transition. The low poloidal mode number components change before the higher modes begin to change. The delay times of change between modes are determined.

    DOI: 10.1088/0741-3335/51/8/085001

  • Measurement of Nonlinear Mode Couplings in the Large Mirror Device-Upgrade 国際誌

    T. Yamada, S.-I. Itoh, S. Inagaki, Y. Nagashima, S. Shinohara, T. Maruta, K. Terasaka, K. Kamataki, N. Kasuya, M. Yagi, Y. Kawai, A. Fujisawa, K. Itoh

    JOURNAL OF NUCLEAR MATERIALS   2009年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Boundary of the geodesic acoustic eigenmode in the vicinity of the magnetic separatrix 査読 国際誌

    Nagashima, Y.; Itoh, K.; Fujisawa, A.; Shinohara, K.; Itoh, S-I; Ido, T.; Yagi, M.; Hoshino, K.; Ejiri, A.; Takase, Y.; Uehara, K.; Miura, Y.

    PLASMA PHYSICS AND CONTROLLED FUSION   51.0 ( 6.0 )   2009年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    We present a detailed investigation of the geodesic acoustic eigenmode(GAEM) profile in the vicinity of the last closed flux surface (LCFS) in the JFT-2M tokamak. Envelope and spectral peak frequency of the GAEM vanish near the LCFS obtained by an equilibrium reconstitution code. Spatial changes in mean plasma gradients (the electron temperature, electron density and floating potential) are correlated with the boundary. This does not contradict that the GAEM can have a node at the LCFS. Discussions of an inverse problem and the application of this GAEM measurement to an experimental test of the LCFS location calculated by the equilibrium reconstitution code are presented.

    DOI: 10.1088/0741-3335/51/6/065019

  • Geodesic Acoustic Mode Spectroscopy II 査読 国際誌

    Sanae-I. ITOH, Seiya NISHIMURA, Kimitaka ITOH, Akihide FUJISAWA, Yoshihiko NAGASHIMA and Shigeru INAGAKI

    Plasma and Fusion Research   4.0 ( RC )   2009年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    An extension of geodesic acoustic mode (GAM) spectroscopy [Plasma Phys. Control. Fusion 49, L7 (2007)] is proposed. The ratio between the lowest frequency of the co-existing ion acoustic mode (IAM) and the frequency of GAM enables us to identify the safety factor of toroidal plasmas. The lowest frequency can be detected by bispectrum analysis when both GAM and IAM are excited. The possibility of measuring the safety factor is discussed.

  • Observation of the parametric-modulational instability between the drift-wave fluctuation and azimuthally symmetric sheared radial electric field oscillation in a cylindrical laboratory plasma 査読 国際誌

    Nagashima, Yoshihiko; Itoh, Sanae-I.; Shinohara, Shunjiro; Fukao, Masayuki; Fujisawa, Akihide; Terasaka, Kenichiro; Kawai, Yoshinobu; Tynan, George R.; Diamond, Patrick H.; Yagi, Masatoshi; Inagaki, Shigeru; Yamada, Takuma; Itoh, Kimitaka

    PHYSICS OF PLASMAS   16.0 ( 2.0 )   0.0 - 0.0   2009年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Observation of the parametric-modulational interaction between the drift-wave fluctuation (7-8 kHz) and azimuthally symmetric sheared radial electric field structure (similar to 0.4 kHz) in a cylindrical laboratory plasma is presented. Oscillation of the sheared radial electric field is synchronized at modulations of the radial wave number and Reynolds stress per mass density of the drift-wave spectrum. Bispectral analysis at the location where the sheared radial electric field has finite radial wave numbers shows that nonlinear energy transfers from the drift wave to the sheared radial electric field occur. Nonlocal energy transfers of fluctuations via "channel of the azimuthally symmetric sheared radial electric field" in spectral space as well as real space are discovered.

    DOI: 10.1063/1.3078075

  • A review of zonal flow experiments 査読 国際誌

    Akihide Fujisawa

    NUCLEAR FUSION   49.0 ( 1.0 )   2009年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The present status of zonal flow experiments is reviewed with the historical process to attain the concept of zonal flows, which provides a new framework for understanding turbulence and transport in toroidal plasmas. The existence of zonal flows is experimentally confirmed to present a new paradigm of plasma turbulence. The paper presents contemporary experiments on zonal flows as major topics with a brief presentation of the zonal flow theories, the diagnostics and data processing techniques for turbulence and zonal flows and the peripheral issues of zonal flow physics. The accumulated experimental results introduced in this review include identification of zonal flows (both stationary zonal flows and geodesic acoustic modes), nonlinear interactions between zonal flows and turbulence, quantification of turbulent Reynolds stress, flow dynamics, energy transfer dynamics between turbulent wave components and the effects of zonal flows on plasma transport. These results have given rise to a new paradigm, namely, that the plasma turbulence is a system of zonal flows and drift waves, with an emphasis on the interaction between the disparate scale structures, e.g. zonal flows (mesoscale) and turbulence (micro-scale).

  • Coexistence of Zonal Flows and Drift-Waves in a Cylindrical Magnetized Plasma 査読 国際誌

    Nagashima, Yoshihiko; Itoh, Sanae-I; Shinohara, Shunjiro; Fukao, Masayuki; Fujisawa, Akihide; Terasaka, Kenichiro; Kawai, Yoshinobu; Kasuya, Naohiro; Tynan, George R.; Diamond, Patrick H.; Yagi, Masatoshi; Inagaki, Shigeru; Yamada, Takuma; Itoh, Kimitaka

    JOURNAL OF NUCLEAR MATERIALS   77.0 ( 11.0 )   2008年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Spatiotemporal structures of fluctuations with frequencies lower than the ion cyclotron frequency in a cylindrical magnetized plasma are investigated. Drift-wave and low-frequency zonal flow coexist. Electrostatic potentials of the zonal flow and the drift-wave are distributed widely in radius. The radial wave number profile of the zonal flow has a shear structure at the radial location where the drift-wave has a maximal normalized fluctuation amplitude. On the other hand, the radial wave number profile of the drift-wave shows vortex tilting, resulting in the generation of stationary turbulence Reynolds stress gradient per mass density. The envelope and bispectral analyses indicate significant nonlinear interactions between the zonal flow and the drift-wave.

    DOI: 10.1143/JPSJ.77.114501

  • Nonlinear energy transfer of drift-wave fluctuation in a cylindrical laboratory plasma 査読 国際誌

    Yoshihiko NAGASHIMA, Sanae -I. ITOH, Shunjiro SHINOHARA, Masayuki FUKAO, Akihide FUJISAWA, Kenichiro TERASAKA, Yoshinobu KAWAI, Naohiro KASUYA, Masatoshi YAGI, Shigeru INAGAKI, Takuma YAMADA and Kimitaka ITOH

    Plasma and Fusion Research   3.0 ( RC )   2008年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Nonlinear energy transfer of the drift-wave spectrum is investigated experimentally in a cylindrical laboratory plasma. Using the Hasegawa-Mima equation, the nonlinear transfer function of electrostatic potential energy in frequency space is estimated by bispectral analysis. The transfer function derived from the drift-wave spectrum indicates a forward cascading of energy transfer from fundamental to higher harmonic modes.

  • Anatomy of plasma turbulence 査読 国際誌

    Yamada, Takuma; Itoh, Sanae-I.; Maruta, Takashi; Kasuya, Naohiro; Nagashima, Yoshihiko; Shinohara, Shunjiro; Terasaka, Kenichiro; Yagi, Masatoshi; Inagaki, Shigeru; Kawai, Yoshinobu; Fujisawa, Akihide; Itoh, Kimitaka

    NATURE PHYSICS   4.0 ( 9.0 )   721.0 - 725.0   2008年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Turbulence is a state of fluids and plasma where nonlinear interactions including cascades to finer scales take place to generate chaotic structure and dynamics(1). However, turbulence could generate global structures(2), such as dynamo magnetic field, zonal flows(3), transport barriers, enhanced transport and quenching transport. Therefore, in turbulence, multiscale phenomena coevolve in space and time, and the character of plasma turbulence has been investigated in the laboratory(4-10) as a modern and historical scientific mystery. Here, we report anatomical features of the plasma turbulence in the wavenumber-frequency domain by using nonlinear spectral analysis including the bi-spectrum(11). First, the formation of the plasma turbulence can be regarded as a result of nonlinear interaction of a small number of irreducible parent modes that satisfy the linear dispersion relation. Second, the highlighted finding here, is the first identification of a streamer ( state of bunching of drift waves(12,13)) that should degrade the quality of plasmas for magnetic confinement fusion(14,15). The streamer is a poloidally localized, radially elongated global structure that lives longer than the characteristic turbulence correlation time, and our results reveal that the streamer is produced as the result of the nonlinear condensation, or nonlinear phase locking of the major triplet modes.

    DOI: 10.1038/nphys1029

  • Observation of Zonal Flow Type Oscillation in Linear Cylindrical ECR Plasmas 査読 国際誌

    Kunihiro KAMATAKI, Sanae -I. ITOH, Yoshihiko NAGASHIMA, Shigeru INAGAKI, Shunjiro SHINOHARA, Masatoshi YAGI, Takuma YAMADA, Yoshinobu KAWAI, Akihide FUJISAWA and Kimitaka ITOH

    Plasma and Fusion Research   3.0 ( L )   2008年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Zonal flow type oscillation, which is driven by a small modulation of the electron cyclotron resonance (ECR) power in a low-frequency band (< 0.1 kHz), and its impact on drift wave turbulence are observed in linear cylindrical ECR plasmas by simultaneous spatiotemporal measurements with a multi-ring probe array. It is found that a potential low-frequency (< 0.1 kHz) oscillation can have a zonal flow type structure. Bicoherence analysis reveals that this zonal flow type oscillation has a nonlinear interaction with the drift mode. These results indicate that an electric field with zonal flow, which is excited externally, can modulate the drift mode amplitude, similar to spontaneous zonal flow.

  • Transport Dynamics and Multi-Scale Coupling of Turbulence in LHD 査読 国際誌

    Shigeru INAGAKI, Naoki TAMURA, Yoshihiko NAGASHIMA, Tokihiko TOKUZAWA, Takuma YAMADA, Katsumi IDA, Takashi MARUTA, Shin KUBO, Kenichi TERASAKA, Takashi SHIMOZUMA, Yoshio NAGAYAMA, Kazuo KAWAHATA, Akio KOMORI, Shunjiro SHINOHARA, Akihide FUJISAWA, Masatoshi YAGI, Yoshinobu KAWAI, Sanae-I. ITOH, Kimitaka ITOH and the LHD experimental group

    Plasma and Fusion Research   3.0 ( RA )   2008年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Spatiotemporal correlation of heat transport and micro- to meso- scale or macro-scale coupling of plasma turbulence are investigated in LHD plasmas, where fast propagation of a cold pulse and a non-local temperature rise are observed. Evidence of a timescale shorter than the diffusion time and a spatial scale longer than the micro-turbulence correlation length between core heat fluxes and edge temperature gradients is found. At the same time, an envelope of turbulent density fluctuations is also found to be modulated. Observation of low frequency (≤ 2 kHz) amplitude modulation of density fluctuation suggests the existence of meso- to macro-scale turbulent structures in the plasma, in which a non-local temperature rise takes place. Relationships between the turbulence with long radial correlation length and the edge-core coupling of heat transport are discussed.

  • Spatiotemporal Behavior of Drift Waves in LMD-U 査読 国際誌

    Takuma YAMADA, Sanae -I. ITOH, Kenichiro TERASAKA, Naohiro KASUYA, Yoshihiko NAGASHIMA, Shunjiro SHINOHARA, Takashi MARUTA, Masatoshi YAGI, Shigeru INAGAKI, Yoshinobu KAWAI, Akihide FUJISAWA and Kimitaka ITOH

    Plasma and Fusion Research   3.0 ( RA )   2008年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In the LMD-U linear magnetized plasma, fluctuation measurements have been performed with multi-channel poloidal Langmuir probe arrays to investigate the spatiotemporal behaviors of drift wave turbulence. Two-dimensional (poloidal mode number-frequency) power spectrum showed not only fluctuation peaks but also the existence of a broadband fluctuation. The broadband fluctuation developed at high poloidal mode number and high frequency regions and not along the linear dispersion relation curve of drift wave modes. It showed shorter correlation time and poloidal length than the peaked fluctuations. Two-dimensional axial coherence was measured with two poloidal probe arrays separated in the axial direction. The axial coherence was strong for both the broadband fluctuation and peak fluctuations, suggesting the quasi-two-dimensional structure of the drift wave turbulence.

  • Observation of Zonal Flow Type Oscillation in Linear Cylindrical ECR Plasmas 査読 国際誌

    Kunihiro KAMATAKI, Sanae -I. ITOH, Yoshihiko NAGASHIMA, Shigeru INAGAKI, Shunjiro SHINOHARA, Masatoshi YAGI, Takuma YAMADA, Yoshinobu KAWAI, Akihide FUJISAWA and Kimitaka ITOH

    Plasma and Fusion Research   9.0 ( RA )   2008年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Experimental Study of Drift Wave Turbulence in Linear Plasmas 査読 国際誌

    Takuma YAMADA, Sanae -I. ITOH, Takashi MARUTA, Naohiro KASUYA, Shunjiro SHINOHARA, Yoshihiko NAGASHIMA, Masatoshi YAGI, Kenichiro TERASAKA, Shigeru INAGAKI, Yoshinobu KAWAI, Masayuki FUKAO, Akihide FUJISAWA and Kimitaka ITOH

    Plasma and Fusion Research   3.0 ( RA )   2008年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Linear plasmas allow multi-point, low-temperature measurements with Langmuir probes. We measured ion saturation-current fluctuations of a Large Mirror Device-Upgrade linear plasma using a poloidal Langmuir probe array. By varying the discharge conditions, the spatiotemporal behavior showed a change from a coherent sine wave to a turbulent waveform through a periodic, modulated sine wave. The two-dimensional (poloidal wave number and frequency) power spectrum for each regime showed a single fluctuation peak, a peak and its harmonics, and a number of peaks in the poloidal wave number-frequency space. Bi-spectral analysis was performed for the turbulent regime, and showed the existence of nonlinear couplings among fluctuation peaks and broadband components.

  • Experimental studies of zonal flow and field in compact helical system plasma 査読 国際誌

    Fujisawa, A.; Itoh, K.; Shimizu, A.; Nakano, H.; Ohshima, S.; Iguchi, H.; Matsuoka, K.; Okamura, S.; Minami, T.; Yoshimura, Y.; Nagaoka, K.; Ida, K.; Toi, K.; Takahashi, C.; Kojima, M.; Nishimura, S.; Isobe, M.; Suzuki, C.; Akiyama, T.; Ido, T.; Nagashima, Y.; Itoh, S. -I.; Diamond, P. H.

    PHYSICS OF PLASMAS   15.0 ( 5.0 )   0.0 - 0.0   2008年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The experimental studies on zonal flows and turbulence have been carried out in Compact Helical System [K. Matsuoka, S. Kubo, M. Hosokawa , in Plasma Physics and Controlled Nuclear Fusion Research, Proc. 12th Int. Conf., Nice, 1988 (International Atomic Energy Agency, Vienna, 1989, Vol. 2, p. 411] using twin heavy ion beam probes. The paper presents the experimental observations of stationary zonal flow, nonlinear couplings between zonal flow and turbulence, and the role of zonal flow in the improved confinement, together with the recent discovery of zonal magnetic field. The presented experimental results strongly support the new paradigm that the plasma transport should be considered as a system of drift wave and zonal flows, and provides the first direct evidence for turbulence dynamo that the structured magnetic field can be really generated by turbulence. (C) 2008 American Institute of Physics.

    DOI: 10.1063/1.2889012

  • Sheared flow generation and mode suppression in a magnetized linear cylindrical plasma 査読 国際誌

    Tsuchiya, H.; Itoh, S-I; Fujisawa, A.; Kamataki, K.; Shinohara, S.; Yagi, M.; Kawai, Y.; Komori, A.; Itoh, K.

    PLASMA PHYSICS AND CONTROLLED FUSION   50.0 ( 5.0 )   0.0 - 0.0   2008年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In a magnetized cylindrical plasma produced with the electron cyclotron resonance (ECR) scheme, a sheared E x B-flow showing zonal flow (ZF) characteristics has been driven by ECR power modulation. This method was used to control the sheared flow, and allowed us to observe that a coherent mode (spontaneously driven in the plasma) becomes stabilized as the induced plasma flow amplitude increases. The stabilization of the mode is caused by the increase in the plasma flow shear; thus, the result demonstrates the fundamental process of the shearing effect of ZFs on turbulence, which is commonly observed in toroidal plasma confinement devices for fusion research.

    DOI: 10.1088/0741-3335/50/5/055005

  • Investigation of competitive oscillations between drift mode and flute mode in linear cylindrical ECR plasma 査読 国際誌

    Kamataki, K.; Itoh, S-I; Nagashima, Y.; Inagaki, S.; Shinohara, S.; Yagi, M.; Yamada, T.; Kawai, Y.; Fujisawa, A.; Itoh, K.

    PLASMA PHYSICS AND CONTROLLED FUSION   50.0 ( 3.0 )   0.0 - 0.0   2008年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A competitive coexistence between a drift mode and a flute mode has been investigated experimentally in a bounded cylindrical electron cyclotron resonance ( ECR) plasma. This competitive cycle was repeated during a whole continuous discharge. Competitive phenomena appeared in plasmas when the density scale length was close to the critical value: the drift mode is dominant and the flute mode is suppressed just below a critical value, but above this value, the flute mode grows abruptly and the drift mode is suppressed. In this phase, the density gradient increases temporally. A small crash takes place when the density scale length reaches a limit value, and then the density profile goes back to the previous states and thus the drift mode is excited and the flute mode is suppressed. The direct nonlinear coupling between the drift mode and the flute mode is weaker than the process of the second harmonic generation of each mode, suggesting that the growth and decay of them are closely related to the modification of the radial density profile.

    DOI: 10.1088/0741-3335/50/3/035011

  • Radial transport characteristics of fast ions due to energetic-particle modes inside the last closed-flux surface in the compact helical system 査読 国際誌

    Nagaoka, Kenichi; Isobe, Mitsutaka; Toi, Kazuo; Shimizu, Akihiro; Fujisawa, Akihide; Ohshima, Shunsuke; Nakano, Haruhisa; Osakabe, Masaki; Todo, Yasushi; Akiyama, Tsuyoshi; Nagashima, Yoshihiko; Suzuki, Chihiro; Nishimura, Shin; Yoshimura, Yasuo; Matsuoka, Keisuke; Okamura, Shoichi

    PHYSICAL REVIEW LETTERS   100.0 ( 6.0 )   0.0 - 0.0   2008年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The internal behavior of fast ions interacting with magnetohydrodynamic bursts excited by energetic ions has been experimentally investigated in the compact helical system. The resonant convective oscillation of fast ions was identified inside the last closed-flux surface during an energetic-particle mode (EPM) burst. The phase difference between the fast-ion oscillation and the EPM, indicating the coupling strength between them, remains a certain value during the EPM burst and drives an anomalous transport of fast ions.

    DOI: 10.1103/PhysRevLett.100.065005

  • Characteristics of high density edge transport barrier with reheat mode on CHS 査読 国際誌

    T. Minami, S. Okamura, T. Akiyama, K. Ida, T. Oishi, M. Isobe, H. Nakano, A. Fujisawa, K. Nagaoka, M. Yoshinura, C. Suzuki, Y. Yoshimura, K. Toi, S. Ohshima, M. Takeuchi, H. Iguchi, S. Nishimura, A. Shimizu, K. Matsuoka, C. Takahashi

    JOURNAL OF NUCLEAR MATERIALS   2008年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Edge transport barrier (ETB) formation and a reheat mode have been simultaneously realized on the Compact Helical System (CHS). The new mode is induced by neutral particle reduction in the edge region, which is caused by shutting off fueling after a strong gas-puffing. When both the reheat mode and the ETB are simultaneously realized, the density reduction is suppressed by the ETB in the peripheral region, and the temperature continues to increase by the reheat mode. This mode provides an enhanced confinement in the high density region (bar ne ~ 1.2 × 1020mr-3) compared to the ETB formation without the reheat mode, because of a large suppression of an anomalous transport, which is confirmed with fluctuation measurements in the edge region.

  • Local observations of fast ion responses to energetic particle modes using a directional probe in the Compact Helical System (CHS) 査読 国際誌

    K. Nagaoka, M. Isobe, K. Toi, K. Goto, T. Ito, Y. Todo, M. Osakabe, S. Ohshima, A. Shimizu, A. Fujisawa, H. Nakano, Y. Takeiri, K. Y. Watanabe, T. Akiyama, Y. Yoshimura, C. Suzuki, S. Nishimura, K. Matsuoka, S. Okamura, CHS group

    NUCLEAR FUSION   48.0 ( 8.0 )   2008年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Detection of Cascading in Drift Wave Turbulence Using Probe Array in Linear Plasmas 査読 国際誌

    Takuma YAMADA, -Sanae -I. ITOH, Takashi MARUTA, Shunjiro SHINOHARA, Naohiro KASUYA, Yoshihiko NAGASHIMA, Masatoshi YAGI, Kenichiro TERASAKA, Masato KAWAGUCHI, Shigeru INAGAKI, Yoshinobu KAWAI, Masayuki FUKAO, Akihide FUJISAWA and Kimitaka ITOH

    Plasma and Fusion Research   2.0 ( RC )   2007年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Measurement of drift wave turbulence using multi-probe systems was performed in the Large Mirror Device-Upgrade linear plasma. We compared a drift wave's two-dimensional (poloidal wave number and frequency) power spectrum with its calculated linear dispersion relation. As a result, a few wave modes that satisfy the linear dispersion relation were observed. Moreover, cascades to non-mode peaks and broadband components that do not satisfy the dispersion relation were identified.

  • Fine positioning of a poloidal probe array 査読 国際誌

    Yamada, T.; Nagashima, Y.; Inagaki, S.; Kawai, Y.; Yagi, M.; Itoh, S. -I.; Maruta, T.; Shinohara, S.; Terasaka, K.; Kawaguchi, M.; Fukao, M.; Fujisawa, A.; Itoh, K.

    REVIEW OF SCIENTIFIC INSTRUMENTS   78.0 ( 12.0 )   2007年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Multipoint detection is an essential requirement for investigating plasma turbulence which is a highly nonlinear phenomenon in space and time. We have fabricated an array of 64-channel poloidal probes surrounding the linear cylindrical plasma named LMD-U in order to study turbulence properties, particularly the nonlinear mode couplings, in the domain of poloidal wave number and frequency. However, misalignments of probe tips produce spurious modes, which do not exist in the real plasma, to distort the precise wave number measurements. The paper presents the description of the 64-channel poloidal probe array with means to adjust the probe positions, with discussion on the effects of the misalignments on the wave number measurements. (C) 2007 American Institute of Physics.

    DOI: 10.1063/1.2818796

  • A Study on Low-Frequency Fluctuations Using New Azimuthal Probe Array in High-Density Helicon Linear Plasma 査読 国際誌

    Kenichiro TERASAKA, Shunjiro SHINOHARA , Yoshihiko NAGASHIMA, Takuma YAMADA, Masato KAWAGUCHI, Takashi MARUTA, Shigeru INAGAKI, Yoshinobu KAWAI, Naohiro KASUYA, Masatoshi YAGI, Akihide FUJISAWA, Kimitaka ITOH and Sanae-I. ITOH

    Plasma and Fusion Research   2.0 ( RC )   2007年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In a high-density plasma produced by helicon waves in a linear device, a change from the coherent to broad-band density fluctuations was observed on increasing the magnetic field. The coherent mode exhibited the drift wave features, and a steady oscillation state was observed. When the magnetic field was increased, the fluctuation level increased, and the higher azimuthal Fourier components were excited. When the spectrum became broad at the higher magnetic field, the behavior of the azimuthal structure became complex and changed rapidly with time. The analysis performed using the movable probe array (48ch.-probe) decomposed the short-lived structure into poloidal mode-frequency space and indicated mode-mode coupling in the broad-band spectrum.

  • Zonal flow driven by energetic particle during magneto-hydro-dynamic burst in a toroidal plasma 査読 国際誌

    Ohshima, S.; Fujisawa, A.; Shimizu, A.; Nakano, H.; Iguchi, H.; Yoshimura, Y.; Nagaoka, K.; Minami, T.; Isobe, M.; Nishimura, S.; Suzuki, C.; Akiyama, T.; Takahashi, C.; Takeuchi, M.; Ito, T.; Watari, T.; Kumazawa, R.; Itoh, S-I; Itoh, K.; Matsuoka, K.; Okamura, S.

    PLASMA PHYSICS AND CONTROLLED FUSION   49.0 ( 11.0 )   1945.0 - 1952.0   2007年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The internal structural measurements of electric field and density using twin heavy ion beam probes have been performed to elucidate the nonlinear evolution of the magneto-hydro-dynamic (MHD) bursty phenomenon driven by the interaction with high-energy particles in a toroidal plasma. The results have given the finest observation of the internal structure of plasma quantities, such as electric field, density and magnetic field distortion, which nonlinearly develop during the MHD phenomenon. In particular, the finding of a new kind of oscillating zonal flow driven by interaction between energetic particles and MHD modes should be emphasized for burning state plasmas.

    DOI: 10.1088/0741-3335/49/11/013

  • Determination of the Major Impurity Radiators in the Reheat Mode Discharges in the Compact Helical System 査読 国際誌

    Chihiro SUZUKI, Tsuyoshi AKIYAMA, Akihide FUJISAWA, Katsumi IDA, Mitsutaka ISOBE, Keisuke MATSUOKA, Takashi MINAMI, Kenichi NAGAOKA, Shin NISHIMURA, Shoichi OKAMURA, Byron J. PETERSON, Akihiro SHIMIZU, Chihiro TAKAHASHI, Kazuo TOI and Yasuo YOSHIMURA

    Plasma and Fusion Research   2.0 ( RA )   2007年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Radiation brightness and impurity behaviors have been studied for reheat mode discharges in the Compact Helical System (CHS) by three different types of impurity diagnostics. Total radiation power measured by a pyroelectric detector significantly reduces after entering the reheat mode, whereas the line-averaged radiation brightness measured by an absolute extreme ultraviolet (AXUV) photodiode array increases especially for a center viewing chord due to the impurity accumulation in the plasma core. One possible reason for this opposite behavior between the two bolometric detectors is the reduced sensitivity of the AXUV photodiode for lower energy photons in vacuum ultraviolet (VUV) region. This speculation is supported by temporal evolutions of VUV spectra measured by a grazing incidence spectrometer. These results demonstrate that the comparison of three impurity diagnostics would be beneficial to the determination of the major impurity radiators and a comprehensive understanding of impurity behaviors in the reheat mode discharges.

  • Experimental progress on zonal flow physics in toroidal plasmas 査読 国際誌

    Fujisawa, A.; Ido, T.; Shimizu, A.; Okamura, S.; Matsuoka, K.; Iguchi, H.; Hamada, Y.; Nakano, H.; Ohshima, S.; Itoh, K.; Hoshino, K.; Shinohara, K.; Miura, Y.; Nagashima, Y.; Itoh, S.-I.; Shats, M.; Xia, H.; Dong, J. Q.; Yan, L. W.; Zhao, K. J.; Conway, G. D.; Stroth, U.; Melnikov, A. V.; Eliseev, L. G.; Lysenko, S. E.; Perfilov, S. V.; Hidalgo, C.; Tynan, G. R.; Holland, C.; Diamond, P. H.; Mckee, G. R.; Fonck, R. J.; Gupta, D. K.; Schoch, P. M.

    NUCLEAR FUSION   47.0 ( 10.0 )   S718 - S726   2007年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The present status of experiments on zonal flows in magnetic confinement experiments is examined. The innovative use of traditional and modem diagnostics has revealed unambiguously the existence of zonal flows, their spatio-temporal characteristics, their relationship to turbulence and their effects on confinement. In particular, a number of observations have been accumulated on the oscillatory branch of zonal flows, named geodesic acoustic modes, suggesting the necessity for theories to give their proper description. In addition to these basic properties of zonal flows, several new methods have elucidated the processes of zonal flow generation from turbulence. Further investigation of the relationship between zonal flows and confinement is strongly encouraged as cross-device activity including low temperature, toroidal and linear devices.

    DOI: 10.1088/0029-5515/47/10/S19

  • In search of zonal flows by using direct density fluctuation measurements 査読 国際誌

    Nagashima, Y.; Itoh, K.; Itoh, S-I; Fujisawa, A.; Yagi, M.; Hoshino, K.; Shinohara, K.; Ejiri, A.; Takase, Y.; Ido, T.; Uehara, K.; Miura, Y.

    PLASMA PHYSICS AND CONTROLLED FUSION   49.0 ( 10.0 )   1611.0 - 1625.0   2007年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A method for zonal flow study by using direct density fluctuation measurements is proposed. When ambient drift-wave turbulence is modulated by zonal flows (i.e. in the drift-wave-zonal flow systems), an envelope of the ambient density fluctuations has spectral peaks around zonal flow frequencies. A spectral peak at the geodesic acoustic mode (GAM) frequency is observed in the envelope of the ambient density fluctuations measured in edge plasma of the JFT-2M tokamak. The significant cross-bicoherence is also found between the ambient density fluctuations and its envelope in the GAM frequency. This result demonstrates that we can measure the GAM only by using density fluctuation data. This method provides a possibility of zonal flow research in burning core plasma by density fluctuation diagnostics such as microwave reflectometry.

    DOI: 10.1088/0741-3335/49/10/002

  • Geodesic acoustic mode spectroscopy 査読 国際誌

    Itoh, S-I; Itoh, K.; Sasaki, M.; Fujisawa, A.; Id, T.; Nagashima, Y.

    PLASMA PHYSICS AND CONTROLLED FUSION   49.0 ( 8.0 )   2007年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A new kind of plasma diagnostics, geodesic acoustic mode (GAM) spectroscopy, is proposed. Radial eigenmodes of GAMs with discrete eigenfrequencies in toroidal plasmas are analysed. The eigenmode has a wavelength of the order of p(T)(2/3) L-T(1/3) (p(i) the ion gyroradius, L-T the temperature PT T I gradient scale length) and has the highest peak near the radius where the eigenfrequency coincides with the local GAM,frequency. Therefore, observing the radial position of the highest peak of the eigenmode provides a method to measure the local ion sound velocity. A novel method to measure the ion composition is given, combined with densities and temperatures.

    DOI: 10.1088/0741-3335/49/8/L01

  • Turbulent transport of poloidal momentum in toroidal Plasmas 査読 国際誌

    Itoh, Kimitaka; Toda, Shinichiro; Fujisawa, Akibide; Itoh, Sanae-I.; Yagi, Masatoshi; Fukuyama, Atsushi

    JOURNAL OF NUCLEAR MATERIALS   76.0 ( 8.0 )   0.0 - 0.0   2007年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In this article, we discuss the turbulent transport of the momentum (component perpendicular to main magnetic field) in toroidal plasmas. The fluctuations in the quasi-linear response tend to induce the shear of mean poloidal flow, as in the case of driving the zonal flows. The case in which the shear of mean poloidal flow and the mesoscale zonal flows coexist is studied. Zonal flows, which have a more rapid growth rate than the shear of mean flow, reaches the nonlinear saturation state, and modify the interaction between microscopic fluctuations and the shear of mean flow. Taking into account the screening effect of zonal flows, the shear of mean poloidal flow is subject to diffusive damping. Responses to the external force are also studied. A new bifurcation (from the state where mesoscale zonal flows are dominant to the one where zonal flows are suppressed) is found.

    DOI: 10.1143/JPSJ.76.084502

  • Transport analysis of the effect of zonal flows on electron internal transport barriers in toroidal helical plasmas 査読 国際誌

    Toda, S.; Itoh, K.; Fujisawa, A.; Itoh, S.-I.; Yagi, M.; Fukuyama, A.; Diamond, P. H.; Ida, K.

    NUCLEAR FUSION   47.0 ( 8.0 )   914.0 - 919.0   2007年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The role of zonal flows in the formation of transport barrier in helical plasmas is analysed using the transport code. A set of one-dimensional transport equations is analysed, including the effect of zonal flows. The turbulent transport coefficient is shown to be suppressed when the plasma state takes the strong positive radial electric field. This bifurcation of the turbulent transport is newly caused by the change of the damping rate of zonal flows. It is theoretically demonstrated that the damping rate of zonal flows plays an important role in global confinement in toroidal plasmas.

    DOI: 10.1088/0029-5515/47/8/024

  • Geodesic acoustic mode spectroscopy 査読 国際誌

    S-I. Itoh, K. Itoh, M. Sasaki, A. Fujisawa, T. Ido, Y. Nagashima

    PLASMA PHYSICS AND CONTROLLED FUSION   49.0 ( 8.0 )   L7   2007年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Evaluation of local magnetic field fluctuation in a toroidal plasma with heavy ion beam probe 査読 国際誌

    A. Fujisawa, A. Shimizu, H. Nakano, S. Ohshima

    PLASMA PHYSICS AND CONTROLLED FUSION   49.0 ( 6.0 )   845.0   2007年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Experimental evidence of a zonal magnetic field in a toroidal plasma 査読 国際誌

    Fujisawa, A.; Itoh, K.; Shimizu, A.; Nakano, H.; Ohshima, S.; Iguchi, H.; Matsuoka, K.; Okamura, S.; Minami, T.; Yoshimura, Y.; Nagaoka, K.; Ida, K.; Toi, K.; Takahashi, C.; Kojima, M.; Nishimura, S.; Isobe, M.; Suzuki, C.; Akiyama, T.; Nagashima, Y.; Itoh, S.-I.; Diamond, P. H.

    PHYSICAL REVIEW LETTERS   98.0 ( 16.0 )   2007年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A zonal magnetic field is found in a toroidal plasma. The magnetic field has a symmetric bandlike structure, which is uniform in the toroidal and poloidal directions and varies radially with a finite wavelength of mesoscale, which is analogous to zonal flows. A time-dependent bicoherence analysis reveals that the magnetic field should be generated by the background plasma turbulence. The discovery is classified as a new kind of phenomenon of structured magnetic field generation, giving insight into phenomena such as dipole field generation in rotational planets.

    DOI: 10.1103/PhysRevLett.98.165001

  • Causal relationship between zonal flow and turbulence in a toroidal plasma 査読 国際誌

    Fujisawa, Akihide; Shimizu, Akihiro; Nakano, Haruhisa; Ohshima, Shinsuke; Itoh, Kimitaka; Nagashima, Yoshihiko; Itoh, Sanae-I.; Iguchi, Harukazu; Yoshimura, Yasuo; Minami, Takashi; Nagaoka, Keiichi; Takahashi, Chihiro; Kojima, Mamoru; Nishimura, Shin; Isobe, Mitsutaka; Suzuki, Chihiro; Akiyama, Tsuyoshi; Ido, Takeshi; Matsuoka, Keisuke; Okamura, Shoichi; Diamond, Patrick H.

    JOURNAL OF NUCLEAR MATERIALS   76.0 ( 3.0 )   2007年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Electric field fluctuations are directly measured using twin heavy-ion-beam probes in Compact Helical System. The spectrum of the electric field fluctuation reveals the existence of a zonal flow at a frequency of less than 1 kHz, coherent modes with a long correlation length (conjectured as geodesic acoustic modes), and background turbulence. Analyses using a wavelet elucidate nonlinear interactions between these fluctuation components in disparate scales. The highlighted findings are that the turbulent fluctuations should be modulated in response to the direction of zonal flow, and should be suppressed, on average, by the zonal flow. This is the first observation that demonstrates the causal linkage between zonal flow and turbulence in toroidal plasmas at a high temperature.

    DOI: 10.1143/JPSJ.76.033501

  • Intermittent characteristics in coupling between turbulence and zonal flows 査読 国際誌

    Fujisawa, A.; Shimizu, A.; Nakano, H.; Ohshima, S.; Itoh, K.; Nagashima, Y.; Itoh, S. -I; Iguchi, H.; Yoshimura, Y.; Minami, T.; Nagaoka, K.; Takahashi, C.; Kojima, M.; Nishimura, S.; Isobe, M.; Suzuki, C.; Akiyama, T.; Ido, T.; Matsuoka, K.; Okamura, S.; Diamond, P. H.

    PLASMA PHYSICS AND CONTROLLED FUSION   49.0 ( 3.0 )   211.0 - 217.0   2007年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    An extended application of Gabour's wavelet to bicoherence analysis succeeds in resolving the instantaneous structure of three wave couplings between disparate scale electric field fluctuations in the high temperature core in a toroidal plasma device named the compact helical system. The obtained results quantify an intermittent linkage between turbulence and zonal flows - a highlighted issue in the present plasma research. This is the first demonstration that the intermittent nature of the three wave coupling should underlie the turbulence power modulation due to zonal flows.

    DOI: 10.1088/0741-3335/49/3/002

  • Physics of internal transport barrier of toroidal helical plasmas 査読 国際誌

    Itoh, K.; Toda, S.; Fujisawa, A.; Itoh, S. -I.; Yagi, M.; Fukuyama, A.; Diamond, P. H.; Ida, K.

    PHYSICS OF PLASMAS   14.0 ( 2.0 )   0.0 - 0.0   2007年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The role of zonal flows (ZFs) in the formation of an internal transport barrier in a toroidal helical plasma is analyzed. The turbulent transport coefficient is shown to be suppressed when the plasma state changes from the branch of a weak negative radial electric field to the strong positive one. This new transition of turbulent transport is caused by the change of the damping rate of the ZFs. It is clearly demonstrated, theoretically and experimentally, that the damping rate of the ZFs governs the global confinement of toroidal plasmas.(c) 2007 American Institute of Physics.

    DOI: 10.1063/1.2435310

  • Recipe for Fabricating Zeolite Ion Source for Plasma Probing 査読 国際誌

    A. Fujisawa, A. Shimizu, H. Nakano, S. Ohshima, H. Iguchi

    JAPANESE JOURNAL OF APPLIED PHYSICS   2007年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Reconstruction Method of Local Density Fluctuation for Heavy Ion Beam Probe Measurements 査読 国際誌

    H. Nakano, A. Fujisawa, A. Shimizu, S. Ohshima, H. Iguchi, Y. Yoshimura, and T. Minami

    REVIEW OF SCIENTIFIC INSTRUMENTS   78.0   2007年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Scaling of Power Threshold for Edge Transport Barrier Formation in CHS with Density, Magnetic Field and Magnetic Configuration 査読 国際誌

    T Akiyama, S Okamura, T Minami, A Fujisawa, T Oishi, S Kado, M Takeuchi, K Toi, K Ida, M Yoshinuma, K Matsuoka, M Isobe, S Nishimura, C Suzuki, Y Yoshimura, K Nagaoka, C Takahashi and the CHS Experimental Group

    PLASMA PHYSICS AND CONTROLLED FUSION   48.0 ( 11.0 )   1683.0   2006年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • First Observation of High Density Edge Transport Barrier Formation during Reheat Mode of Helical Plasma in CHS 査読 国際誌

    Takashi MINAMI, Shoichi OKAMURA , Tsuyoshi AKIYAMA, Mitsutaka ISOBE, Tetsutarou OISHI, Shinichiro KADO, Katsumi IDA , Akihide FUJISAWA, Haruhisa NAKANO, Kiichiro NAKAMURA, KenichiNAGAOKA, Mikiro YOSHINUMA, Chihiro SUZUKI, Yasuo YOSHIMURA, Masaki TAKEUCHI, Kazuo TOI, Shinsuke OHSHIMA, Harukazu IGUCHI, Shin NISHIMURA, Akihiro SHIMIZU, Keisuke MATSUOKA, Chihiro TAKAHASHI and CHS group

    Plasma and Fusion Research   1.0 ( RC )   2006年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    An improved confinement mode with reheat and edge transport barrier is observed in the Compact Helical System (CHS). This mode provides enhanced confinement in high density region (ne ˜ 1.2 × 1020 m-3) due to the increase in temperature while high density is maintained in the peripheral region.

  • Experimental study of nonlinear processes in edge turbulence of toroidal plasmas 査読 国際誌

    Yoshihiko NAGASHIMA, Katsumichi HOSHINO, Kenichi NAGAOKA, Kouji SHINOHARA, Akihide FUJISAWA, Kazuya UEHARA, Yoshinori KUSAMA, Katsumi IDA, Yasuo YOSHIMURA, Shoichi OKAMURA, Keisuke MATSUOKA, Akira EJIRI, Yuichi TAKASE, Kimitaka ITOH, Masatoshi YAGI, Sanae-I. ITOH, JFT-2M group and CHS group

    Plasma and Fusion Research   1.0 ( RA )   2006年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This paper presents experimental studies of nonlinear processes between meso-scale structures and turbulent fluctuations, by use of bispectral analysis, in the edge region of toroidal plasmas. In ohmically heated plasmas of the JFT-2M tokamak, the drift wave-zonal flow system is investigated by observation of the potential fluctuations. The total bicoherence is composed of two components, i.e., the peak at the geodesic acoustic mode (GAM) frequency and broadband distribution. The biphase is also obtained, which indicates the phase angle of coherent interaction between GAM oscillations and broadband fluctuations. Bispectral functions (e.g., magnitude and phase) give an order-of-estimate agreement for the drift wave-zonal flow systems. Bicoherence analysis is also applied to the edge plasmas of the high-confinement mode (H-mode) of the Compact Helical System (CHS). In the case of CHS plasmas, nonlinear couplings in a system composed of coherent global magneto-hydrodynamic (MHD) oscillations and broadband fluctuations (up to hundreds kHz range) have been observed. Bispectral analysis enhances our understanding of the self-regulation systems of various toroidal plasmas in which strong turbulence and meso-scale structures coexist.

  • Geodesic Acoustic Eigenmodes 査読 国際誌

    Kimitaka ITOH, Sanae-I. ITOH, Patrick H. DIAMOND, Akihide FUJISAWA, Masatoshi YAGI, Tetsuo WATARI, Yoshihiko NAGASHIMA and Atsushi FUKUYAMA

    Plasma and Fusion Research   1.0 ( RC )   2006年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The eigenmode of a geodesic acoustic mode in the presence of a temperature gradient is discussed. Eigenmodes are obtained and the characteristic wavelength scales as ρi2/3LT1/3 (ρi: ion gyroradius, LT: temperature gradient scale length). The direction of propagation is discussed.

  • Study of Edge Transport Barrier Formation on CHS Plasma 査読 国際誌

    Takashi MINAMI, Shoichi OKAMURA, Tsuyoshi AKIYAMA, Mitsutaka ISOBE, Tetsutaro OHISHI, Haruhisa NAKANO, Katsumi IDA, Akihide FUJISAWA, Kiichiro NAKAMURA, Kenichi NAGAOKA, Mikiro YOSHINUMA, Chihiro SUZUKI, Yasuo YOSHIMURA, Kazuo TOI, Masaki NISHIURA, Shinsuke OHSHIMA, Zenzo NARUHIRO, Harukazu IGUCHI, Shin NISHIMURA, Akihiro SHIMIZU, Keisuke MATSUOKA and Chihiro TAKAHASHI

    Plasma and Fusion Research   1.0 ( RA )   2006年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    An edge transport barrier (ETB) similar to the tokamak H-mode has been observed for beam-heated plasma with two co-injected Neutral Beam Injectors (NBIs) in CHS. The Hα emission showed a clear spontaneous drop followed by an increase of line-averaged electron density at the L-H transition. Stored energy increased by ˜ 40% with H-factor improvement up to ˜ 30% compared to the international stellarator scaling (ISS04v03). A rapid density increase in the edge region to two-times level of the L-mode was observed to accompany a ˜ 15% increase in the density gradient. An ETB was formed when the plasma density exceeded the lower density limit by ˜ 1.5 × 1013 cm-3 and the total NBI power exceeds the threshold level (Pdeposit / ne ˜ 200 × 10-13 kW/cm-3 at BT = 0.95 T, Rax = 92.1 cm, where Pdeposit is the deposited NBI power, ne is electron density, BT is troidal magnetic field strength and Rax is location of magnetic axis). The power threshold increased with the magnetic field strength, as in tokamak scaling, and depends on the magnetic field configuration of the helical plasma.

  • Observation of coherent bicoherence and biphase in potential fluctuations around geodesic acoustic mode frequency on JFT-2M 査読 国際誌

    Nagashima, Y; Itoh, K; Itoh, SI; Hoshino, K; Fujisawa, A; Ejiri, A; Takase, Y; Yagi, M; Shinohara, K; Uehara, K; Kusama, Y

    PLASMA PHYSICS AND CONTROLLED FUSION   48.0 ( 0.0 )   #<Spreadsheet::Excel::Error:0xb8aedb8> - #<Spreadsheet::Excel::Error:0xb8aecc8>   2006年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Two types of small-poloidal wavelength low frequency floating potential fluctuations (similar to 1 kHz, and 10-15 kHz) are observed in the edge region of ohmically heated plasmas in the JFT-2M tokamak. The higher frequency fluctuations are inferred as geodesic acoustic modes (GAMs). Significant bicoherences between both modes and the broad-band fluctuations are observed simultaneously; however, frequency ranges are different. A significant bicoherence range is from 70 to 125 kHz at the lower frequency modes (LFM) and is from 20 to 125 kHz at the GAM. Phase angles at the significant bicoherences are coherent around pi. These results indicate that both modes are nonlinearly coupled to the broad-band fluctuations. Two spectral peaks are observed around the GAM frequency and the difference in peak frequencies is around the LFM frequency, suggesting nonlinear couplings between the LFM and the GAM. However, the modulation of the GAM by the LFM is not conclusive. In this paper, the results of the letter (Nagashima et al 2005 Phys. Rev. Lett. 95 095002) are presented in detail.

    DOI: 10.1088/0741-3335/48/5A/S38

  • Properties of turbulence and stationary zonal flow on transport barrier in CHS 査読 国際誌

    Fujisawa, A; Shimizu, A; Nakano, H; Ohsima, S; Itoh, K; Iguchi, H; Matsuoka, S; Okamura, S; Itoh, SI; Diamond, PH

    PLASMA PHYSICS AND CONTROLLED FUSION   48.0   A365   2006年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Spectral changes in electric field fluctuation are measured using twin heavy ion beam probes in compact helical system (CHS) before and after an internal transport barrier is broken down. Wavelet analysis reveals intermittent behaviour of the fluctuations and a significant correlation between fluctuation powers of the low (2.5 < f < 10 kHz) and high (30 < f < 250 kHz) ranges. The high frequency (turbulence) fluctuation increases with a decrease in the low frequency fluctuation after the back-transition. The change in the power distribution between these two frequency ranges may contribute to the improved transport on the barrier.

    DOI: 10.1088/0741-3335/48/5A/S36

  • Physics of zonal flows 査読 国際誌

    Itoh, K; Itoh, SI; Diamond, PH; Hahm, TS; Fujisawa, A; Tynan, GR; Yagi, M; Nagashima, Y

    PHYSICS OF PLASMAS   13.0 ( 5.0 )   0.0 - 0.0   2006年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Zonal flows, which means azimuthally symmetric band-like shear flows, are ubiquitous phenomena in nature and the laboratory. It is now widely recognized that zonal flows are a key constituent in virtually all cases and regimes of drift wave turbulence, indeed, so much so that this classic problem is now frequently referred to as "drift wave-zonal flow turbulence." In this review, new viewpoints and unifying concepts are presented, which facilitate understanding of zonal flow physics, via theory, computation and their confrontation with the results of laboratory experiment. Special emphasis is placed on identifying avenues for further progress. (c) 2006 American Institute of Physics.

    DOI: 10.1063/1.2178779

  • Bispectral analysis applied to coherent floating potential fluctuations obtained in the edge plasmas on JFT-2M 査読 国際誌

    Nagashima, Y; Itoh, K; Itoh, SI; Fujisawa, A; Hoshino, K; Takase, Y; Yagi, M; Ejiri, A; Ida, K; Shinohara, K; Uehara, K; Kusama, Y

    PLASMA PHYSICS AND CONTROLLED FUSION   48.0 ( 4.0 )   S1 - S15   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This paper presents results of bispectral analysis applied to floating potential fluctuations in the edge region of ohmically heated plasmas in the JAERI Fusion Torus-2 Modified (JFT-2M) tokamak. Inside the outermost surface of plasmas, coherent mode fluctuations, (CMs) in floating potential were observed around the frequency of the geodesic acoustic mode. The squared bicoherence shows significant nonlinear couplings between the CMs and background fluctuations. The biphase at the frequency of the CMs is localized around pi, while that at frequencies of background fluctuations distributes in a wide range. The total bicoherence at the frequency of the CMs is proportional to the squared amplitude of the CMs. These observations are consistent with the theoretical prediction on the drift wave-zonal flow systems. Interpretation of the absolute value of the total bicoherence is also discussed.

    DOI: 10.1088/0741-3335/48/4/S01

  • Turbulence and transport characteristics of a barrier in a toroidal plasma 査読 国際誌

    Fujisawa, A; Shimizu, A; Nakano, H; Ohsima, S; Itoh, K; Iguchi, H; Yoshimura, Y; Minami, T; Nagaoka, K; Takahashi, C; Kojima, M; Nishimura, S; Isobe, M; Suzuki, C; Akiyama, T; Nagashima, Y; Ida, K; Toi, K; Ido, T; Itoh, SI; Matsuoka, K; Okamura, S; Diamond, PH

    PLASMA PHYSICS AND CONTROLLED FUSION   48.0 ( 4.0 )   #<Spreadsheet::Excel::Error:0xc914eb4> - #<Spreadsheet::Excel::Error:0xc914d24>   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Turbulence and zonal flow at, a transport barrier are studied with twin heavy ion beam probes in a toroidal helical plasma. A wavelet analysis is used to extract turbulence properties, e.g. spectra of both density and potential fluctuations, the coherence and the phase between them and the dispersion relation. Particle transport estimated from the fundamental characteristics is found to clearly rise with their intermittent activities after the barrier is broken down. Time-dependent analysis reveals that the intermittency of turbulence is correlated with the evolution of the stationary zonal flow.

    DOI: 10.1088/0741-3335/48/4/S15

  • Spectrograph of electric field fluctuation in toroidal helical plasma 査読 国際誌

    Fujisawa, A; Itoh, K; Shimizu, A; Nakano, H; Ohsima, S; Iguchi, H; Matsuoka, K; Okamura, S; Itoh, SI; Diamond, PH

    PLASMA PHYSICS AND CONTROLLED FUSION   48.0 ( 4.0 )   #<Spreadsheet::Excel::Error:0xa07e018> - #<Spreadsheet::Excel::Error:0xa07dc08>   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This is a report on fluctuation measurements using twin heavy ion beam probes in CHS. The observation shows that dozens of coherent modes with intermittent nature co-exist in an electron cyclotron heated plasma. The modes are found to have a long-distance correlation in the toroidal direction. The radial structure of the modes is evaluated in potential fluctuation. The characteristics are consistent with those of the geodesic acoustic modes.

    DOI: 10.1088/0741-3335/48/4/S03

  • Geodesic-acoustic-mode in JFT-2M tokamak plasmas 査読 国際誌

    Ido, T; Miura, Y; Kamiya, K; Hamada, Y; Hoshino, K; Fujisawa, A; Itoh, K; Itoh, SI; Nishizawa, A; Ogawa, H; Kusama, Y

    PLASMA PHYSICS AND CONTROLLED FUSION   48.0 ( 4.0 )   S41   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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,,GAM) and the amplitude of the density fluctuation indicates that the modulation of the ambient density fluctuation delays the (E) over tilde (r,GAM). The causality between the GAM and the modulation of the density fluctuation is revealed.

    DOI: 10.1088/0741-3335/48/4/S04

  • Convergence study of bispectral analysis in experiments of high temperature plasmas 査読 国際誌

    Nagashima, Y; Itoh, SI; Yagi, M; Itoh, K; Fujisawa, A; Hoshino, K; Shinohara, K; Uehara, K; Kusama, Y; Ejiri, A; Takase, Y

    REVIEW OF SCIENTIFIC INSTRUMENTS   77.0 ( 4.0 )   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A convergence study of bispectral analysis on toroidal plasma turbulence is presented with a theoretical estimate of bicoherence for the system of the drift wave and zonal flow. Examples are chosen from the analysis of floating potential fluctuation in the edge region of the JFT-2M tokamak. The convergence properties of the bispectral functions are clarified for an oscillatory branch of zonal flow (or geodesic acoustic mode) and drift waves. The total squared bicoherence or the biphase converges inversely proportional to the realization number or to the square root of the realization number, respectively. The numbers of realizations to qualitatively converge and obtain a quantitatively significant value of bicoherence are discussed for the drift wave fluctuations and for the zonal flow. (c) 2006 American Institute of Physics.

    DOI: 10.1063/1.2194016

  • Development of Zeolite Ion Source for Beam Probe Measurements of High Temperature Plasma 査読 国際誌

    Ohshima, Shinsuke ; Fujisawa, Akihide ; Shimizu, Akihiro ; Nakano, Haruhisa

    REVIEW OF SCIENTIFIC INSTRUMENTS   77.0 ( 3.0 )   2006年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • 4. 1 Formation Conditions of Electron Internal Transport Barriers in JT-60 U Plasmas[1]

    Fujita, T; Fukuda, T; Sakamoto, Y; Ide, S; Suzuki, T; Takenaga, H; Ida, K; Idei, H; Shimozuma, T; Fujisawa, A;

    JAEA-Review   2005.0   20.0   2006年1月

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    記述言語:英語   掲載種別:研究論文(大学,研究機関等紀要)  

  • Turbulence and transport characteristics on a barrier in a toroidal plasma 査読 国際誌

    A. Fujisawa, A. Shimizu, H. Nakano et al.

    PLASMA PHYSICS AND CONTROLLED FUSION   2006年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Transport in core plasmas. Formation conditions of electron internal transport barriers in JT-60U plasmas

    Takaaki Fujita, Yoshiteru Sakamoto, Shunsuke Ide, Takahiro Suzuki, Hidenobu Takenaga, T Fukuda, K Ida, T Shimozuma, A Fujisawa, S Ohdachi, K Toi, H Idei

    Review of JT-60U experimental results in 2003 and 2004   2006年1月

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    記述言語:英語   掲載種別:研究論文(大学,研究機関等紀要)  

  • Observation of Internal Coherent Mode Structure using Heavy Ion Beam Probe 査読 国際誌

    S. Ohshima, A. Fujisawa, A. Shimizu, H. Nakano

    REVIEW OF SCIENTIFIC INSTRUMENTS   77.0   2006年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Common Features of Core Electron Root Confinement in Helical Device 査読 国際誌

    M. Yokoyama, H. Maassberg, C. D. Beidler, V. Tribaldos, K. Ida, F. Castej?n, T. Estrada, A. Fujisawa, T. Minami, T. Shimozuma, Y. Takeiri, J. Herranz, S. Murakami, H. Yamada

    FUSION SCIENCE AND TECHNOLOGY   50.0 ( 3.0 )   327.0 - 342.0   2006年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Influence of magnetic topology on transport and stability in stellarators 査読 国際誌

    F. Castejon, A. Fujisawa, K. Ida, J. N. Talmadge, T. Estrada, D. Lopez-Bruna, C. Hidalgo, L. Krupnik and A. Melnikov

    PLASMA PHYSICS AND CONTROLLED FUSION   47.0 ( 12B )   B53   2005年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Internal Transport Barrier Physics in Helical Systems 査読 国際誌

    M. Yokoyama, H. Maassberg, K. Ida, T. Estrada, F. Castejon, T. Minami, A. Fujisawa, O. Yamagishi, M. G. Shats, A. Dinklage, V. Tribaldos, C. D. Beidler, T. Shimozuma, Y. Takeiri, J. Herranz, S. Murakami, H. Yamada

    15th International Stellarator Workshop, Madrid,3-7 Octobar 200   2005年10月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • On the bicoherence analysis of plasma turbulence 査読 国際誌

    Itoh, K; Nagashima, Y; Itoh, SI; Diamond, PH; Fujisawa, A; Yagi, M; Fukuyama, A

    PHYSICS OF PLASMAS   12.0 ( 10.0 )   0.0 - 0.0   2005年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The bicoherence of fluctuations in a system of drift waves and zonal flows is discussed. In strong drift-wave turbulence, where broadband fluctuations are excited, the bicoherence is examined. A Langevin equation formalism of turbulent interactions allows us to relate the bicoherence coefficient to the projection of nonlinear force onto the test mode. The dependence of the summed bicoherence on the amplitude of zonal flows is clarified. The importance of observing biphase is also stressed. The results provide a basis for measurement of nonlinear interaction in a system of drift waves and zonal flow.

    DOI: 10.1063/1.2062627

  • Consideration of Magnetic Field Fluctuation Measurements in Torus Plasma with a Heavy Ion Beam Probe 査読 国際誌

    Shimizu, A. Fujisawa, S. Ohshima, H. Nakano

    REVIEW OF SCIENTIFIC INSTRUMENTS   76.0   2005年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Extension of geodesic acoustic mode theory to helical systems 査読 国際誌

    T. Watari, H. Hamada, A. Fujisawa, K. Toi, K. Itoh

    PHYSICS OF PLASMAS   12.0 ( 6.0 )   2005年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The present paper extends the theory of geodesic acoustic mode (GAM) oscillation, which so far has been applied to tokamaks, to helical systems. By using drift kinetic equations for three-dimensional equilibriums, a generalized dispersion relation is obtained including Landau damping. The oscillation frequency is obtained in terms of the squared sum of Fourier components of the magnetic field intensity expressed by means of magnetic flux coordinates. An analytic form of the collisionless damping rate of GAM is obtained by solving the dispersion relation perturbatively. It is found that the GAM frequency is higher in helical systems than in tokamaks and that damping rate is enhanced in multi-helicity magnetic configurations. However, damping rates are predicted to be small if the temperature of electrons is higher than that of ions.

  • Effects of Sheared Flow on Microinstabilities and Transport in Plasmas 査読 国際誌

    H Sanuki, K Itoh, A Fujisawa and J Q Dong

    PLASMA SCIENCE & TECHNOLOGY   7.0 ( 1.0 )   2005年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Theoretical and experimental studies associated with electric field effects on the stability and transport are briefly surveyed. The effects of radial electric field on the suppression and/or enhancement of various microinstabilities such as drift waves, flute mode and temperature gradient modes are discussed. The suppression of flow shear on the electron temperature gradient mode in plasmas with slightly hollow density profiles is investigated by solving the gyrokinetic integral eigenvalue equation. Comparison between theoretical predictions and experimental observations based on the HIBP measurements with high temporal and spatial resolutions is made in bumpy tori and heliotron (CHS) devices.

  • Edge and internal transport barrier formation in CHS 査読 国際誌

    S. Okamura, T. Minami, T. Akiyama, T. Oishi, A. Fujisawa, K. Ida, H. Iguchi, M. Isobe, S. Kado, K. Nagaoka, K. Nakamura, S. Nishimura, K. Matsuoka, H. Matsushita, H. Nakano, M. Nishimura, S. Ohshima, A. Shimizu, C. Suzuki, C. Takahashi, K. Toi, Y. Yoshimura, M. Yoshinuma, CHS Group

    NUCLEAR FUSION   45.0   863.0   2005年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Identification of zonal flows in a toroidal plasma 査読 国際誌

    Fujisawa, A; Itoh, K; Iguchi, H; Matsuoka, K; Okamura, S; Shimizu, A; Minami, T; Yoshimura, Y; Nagaoka, K; Takahashi, C; Kojima, M; Nakano, H; Ohsima, S; Nishimura, S; Isobe, M; Suzuki, C; Akiyama, T; Ida, K; Toi, K; Itoh, SI; Diamond, PH

    PHYSICAL REVIEW LETTERS   93.0 ( 16.0 )   0.0 - 0.0   2004年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    This Letter presents experimental confirmation of the presence of zonal flows in magnetically confined toroidal plasma using an advanced diagnostic system-dual heavy ion beam probes. The simultaneous observation of an electric field at two distant toroidal locations (similar to1.5 m apart) in the high temperature (similar to1 keV) plasma provides a fluctuation spectrum of electric field (or flow), a spatiotemporal structure of the zonal flows (characteristic radial length of similar to1.5 cm and lifetime of similar to1.5 ms), their long-range correlation with toroidal symmetry (n=0), and the difference in the zonal flow amplitude with and without a transport barrier. These constitute essential elements of turbulence-zonal flow systems, and illustrate one of the fundamental processes of structure formation in nature.

    DOI: 10.1103/PhysRevLett.93.165002

  • Internal Transport Barrier and Bifurcation Phenomena in Stellarators 査読 国際誌

    Akihide Fujisawa

    Fusion Science and Technology   46.0 ( 1.0 )   91.0 - 100.0   2004年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Comparison of electron internal transport barriers in the large helical device and JT-60U plasmas 査読 国際誌

    Ida, K; Fujita, T; Fukuda, T; Sakamoto, Y; Ide, S; Toi, K; Inagaki, S; Shimozuma, T; Kubo, S; Idei, H; Fujisawa, A; Ohdachi, S; Yoshinuma, M; Funaba, H; Narihara, K; Murakami, S; Wakasa, A; Yokoyama, M; Takeiri, Y; Watanabe, KY; Tanaka, K; Liang, Y; Ohyabu, N

    PLASMA PHYSICS AND CONTROLLED FUSION   46.0 ( 5A )   A45 - A50   2004年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Plasmas with an electron internal transport barrier (ITB), which is characterized by peaked electron temperature profiles, are obtained in the JT-60U tokamak and in the large helical device (LHD) when the electron cyclotron heating (ECH) is focused on the magnetic axis. The maximum values of R/L-Te, where R is the major radius and LT. is the scale length of the electron temperature gradient, are similar for the LHD and JT-60U ITB plasmas. However, there is a clear jump of R/L-Te observed in LHD but not in JT-60U in the ECH power scan. This result is consistent with the fact that the trigger mechanism of the electron ITB is the fast transition of the radial electric field from a small negative E, to a large positive E, in LHD and a change of the magnetic shear from positive to negative is required for the formation of the electron ITB in JT-60U. There are also differences in the electron temperature profiles inside the ITB. The flattening of the electron temperature profile inside the strong ITB could be explained by the sharp increase of q values observed in JT-60U, while no flattening of the electron temperature profile is observed in LHD, where the central q values stay low.

    DOI: 10.1088/0741-3335/46/5A/004

  • Formation conditions for electron internal transport barriers in JT-60U plasmas 査読 国際誌

    Fujita, T; Fukuda, T; Sakamoto, Y; Ide, S; Suzuki, T; Takenaga, H; Ida, K; Idei, H; Shimozuma, T; Fujisawa, A; Ohdachi, S; Toi, K

    PLASMA PHYSICS AND CONTROLLED FUSION   46.0 ( 10A )   A35 - A43   2004年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The formation of electron internal transport barriers (ITBs) was studied using electron cyclotron (EC) heating in JT-60U positive shear (PS) and reversed shear (RS) plasmas with scan of neutral beam (NB) power. With no or low values of NB power and with a small radial electric field (Er) gradient, a strong, box-type electron ITB was formed in RS plasmas while a peaked profile with no strong electron ITBs was observed in PS plasmas within the available EC power. When the NB power and the Er gradient were increased, the electron transport in strong electron ITBs with EC heating in RS plasmas was not affected, while electron thermal diffusivity was reduced in conjunction with the reduction of ion thermal diffusivity, and strong electron and ion ITBs were formed in PS plasmas.

    DOI: 10.1088/0741-3335/46/5A/003

  • Observation of bifurcation properties of radial electric fields using a heavy ion beam probe 査読 国際誌

    Fujisawa, A; Iguchi, H; Minami, T; Yoshimura, Y; Sanuki, H; Itoh, K; Isobe, M; Nishimura, S; Suzuki, C; Tanaka, K; Osakabe, M; Nomura, I; Ida, K; Okamura, S; Toi, K; Kado, S; Akiyama, R; Shimizu, A; Takahashi, C; Kojima, M; Itoh, SI; Matsuoka, K; Hamada, Y; Fujiwara, M

    NUCLEAR FUSION   41.0 ( 5.0 )   575.0 - 584.0   2001年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The bifurcated nature of the potential profile of a toroidal helical plasma is investigated in CHS using a heavy ion beam probe. The measurements reveal that three main branches of potential profile exist in ECR heated plasmas with a low density of (n) over tilde (e) approximate to 0.5 x 10(19) m(-3). The branches with higher central potential exhibit a rather strong radial electric field shear that should result in fluctuation reduction and formation of a transport barrier. An analysis of the pulsating behaviour in the potential suggests the existence of a fine structure in the potential profiles between the main branches. Lissajous and histogram expressions are useful in extracting the bifurcation characteristics of the potential structure.

    DOI: 10.1088/0029-5515/41/5/310

  • Multilayer mirror based soft x-ray spectrometer as a high temperature plasma diagnostic 査読 国際誌

    Duorah, S; Ejiri, A; Lee, S; Iguchi, H; Fujisawa, A; Kojima, M; Matsuoka, K; Ishiyama, E; Hanada, K; Shiraiwa, S; Toyama, H; Takase, Y

    REVIEW OF SCIENTIFIC INSTRUMENTS   72.0 ( 1.0 )   1183.0 - 1187.0   2001年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A fully calibrated multilayer mirror (MLM) based soft x-ray spectrometer has been developed and installed on the Compact Helical System (CHS). This MLM based spectrometer is a new approach to devising a soft x-ray spectrometer with medium time and energy resolutions. The spectrometer mainly consists of a MLM as the dispersive element and a 20-channel (p-i-n) pin diode array for the detection of the soft x-rays. Both the MLM and the pin diodes have been calibrated at the KEK (High Energy Accelerator Research Organization) Photon Factory for an energy range of 300-1200 eV. The reflectivity of the mirror was found to increase from 3% (photon energy of 335 eV) to 25% (photon energy of 1050 eV). The pin diodes were found to have almost 100% efficiency for creating electron-hole pairs in the calibrated energy range. The spectrometer was installed on the CHS with the aim of fast electron temperature measurement and study of fast magneto-hydrodynamic (MHD) events occurring in plasmas. The experiments show that in the energy range of measurement, the electron "temperature" determined from the slope of the soft x-ray spectrum is much lower than that measured by the Thomson scattering diagnostic. Analysis showed that the soft x-ray spectrum is highly contaminated by impurity emission. Therefore it may be possible to measure electron temperature with this diagnostic if we choose another energy range where we can measure the continuous spectrum. The present time resolution of the system is of the order similar to0.1 ms, which made it possible to study the behavior of the plasma during fast MHD events. Modulations in the soft x-ray intensity were observed during MHD events in CHS plasmas. Analysis of these shows that these may be due to modulations in the temperature or the impurity concentration. (C) 2001 American Institute of Physics.

    DOI: 10.1063/1.1324745

  • Experimental study of the bifurcation nature of the electrostatic potential of a toroidal helical plasma 査読 国際誌

    Fujisawa, A; Iguchi, H; Minami, T; Yoshimura, Y; Tanaka, K; Itoh, K; Sanuki, H; Lee, S; Kojima, M; Itoh, SI; Yokoyama, M; Kado, S; Okamura, S; Akiyama, R; Ida, K; Isobe, M; Nishimura, S; Osakabe, M; Nomura, I; Shimizu, A; Takahashi, C; Toi, K; Matsuoka, K; Hamada, Y; Fujiwara, M

    PHYSICS OF PLASMAS   7.0 ( 10.0 )   4152.0 - 4183.0   2000年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The bifurcation nature of the electrostatic structure is studied in the toroidal helical plasma of the Compact Helical System (CHS) [K. Matsuoka , Proceedings of the 12th International Conference on Plasma Physics and Controlled Nuclear Fusion Research, Nice, 1988 (International Atomic Energy Agency, Vienna, 1989), Vol. 2, p. 411]. Observation of bifurcation-related phenomena is introduced, such as characteristic patterns of discrete potential profiles, and various patterns of self-sustained oscillations termed electric pulsation. Some patterns of the electrostatic structure are found to be quite important for fusion application owing to their association with transport barrier formation. It is confirmed, as is shown in several tokamak experiments, that the thermal transport barrier is linked with electrostatic structure through the radial electric field shear that can reduce the fluctuation resulting in anomalous transport. This article describes in detail spatio-temporal evolution during self-sustained oscillation, together with correlation between the radial electric field and other plasma parameters. An experimental survey to find dependence of the temporal and spatial patterns on plasma parameters is performed in order to understand systematically the bifurcation property of the toroidal helical plasma. The experimental results are compared with the neoclassical bifurcation property that is believed to explain the observed bifurcation property of the CHS plasmas. The present results show that the electrostatic property plays an essential role in the structural formation of toroidal helical plasmas, and demonstrate that toroidal plasma is an open system with a strong nonlinearity to provide a new attractive problem to be studied. (C) 2000 American Institute of Physics. [S1070-664X(00)04310-X].

    DOI: 10.1063/1.1290483

  • Energetic ion driven MHD instabilities observed in the heliotron/torsatron devices Compact Helical System and Large Helical Device 査読 国際誌

    K Toi, M Takechi, M Isobe, N Nakajima, M Osakabe, S Takagi, T Kondo, G Matsunaga, K Ohkuni, M Sasao, S Yamamoto, S Ohdachi, S Sakakibara, H Yamada, KY Watanabe, DS Darrow, A Fujisawa, M Goto, K Ida, H Idei, H Iguchi, S Lee, S Kado, S Kubo, O Kaneko, K Kawahata, K Matsuoka, T Minami, S Morita, O Motojima, K Narihara, S Nishimura, N Ohyabu, Y Oka, S Okamura, T Ozaki, K Sato, M Sato, A Shimizu, T Shimozuma, Y Takeiri, K Tanaka, T Tokuzawa, K Tsumori, I Yamada, Y Yoshimura

    NUCLEAR FUSION   40.0 ( 7.0 )   1349.0   2000年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Thermal transport barrier in heliotron-type devices (Large Helical Device and Compact Helical System) 査読 国際誌

    N Ohyabu, A Fujisawa, N Ashikawa, M Emoto, H Funaba, M Goto, Y Hamada, H Iguchi, K Ida, K Itoh, M Isobe, H Idei, S Inagaki, N Inoue, K Ikeda, S Kado, S Kubo, R Kumazawa, K Khlopenkov, O Kaneko, K Kawahata, A Komori, T Kobuchi, S Lee, Y Liang, T Minami, J Miyazawa, S Masuzaki, K Matsuoka, T Morisaki, S Morita, S Murakami, T Mutoh, S Muto, K Narihara, Y Nagayama, Y Nakamura, H Nakanishi, K Nishimura, S Nishimura, N Noda, I Nomura, T Notake, S Okamura, S Ohdachi, K Ohkubo, Y Oka, M Osakabe, T Ozaki, BJ Peterson, RO Pavlichenko, A Sagara, S Sakakibara, R Sakamoto, M Sasao, K Sato, H Sanuki, K Saito, M Sato, T Seki, A Shimizu, T Shimozuma, M Shoji, H Suzuki, S Sudo, H Sasao, Y Takeiri, K Tanaka, K Toi, T Tokuzawa, K Tsumori, K Tsuzuki, M Takechi, N Tamura, Y Torii, I Yamada, H Yamada, S Yamaguchi, K Yamazaki, M Yokoyama, Y Yoshimura, S Yamamoto, KY Watanabe, T Watanabe, T Watari, O Motojima, M Fujiwara

    PHYSICS OF PLASMAS   7.0 ( 5.0 )   1802.0 - 1808.0   2000年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Transport barrier formation and bifurcation patterns of potential profiles in the compact helical system heliotron/torsatron 査読 国際誌

    Fujisawa, A; Iguchi, H; Minami, T; Yoshimura, Y; Tanaka, K; Itoh, K; Sanuki, H; Itoh, SI; Isobe, M; Nishimura, S; Okamura, S; Matsuoka, K; Fujiwara, M

    PLASMA PHYSICS AND CONTROLLED FUSION   42.0 ( 0.0 )   #<Spreadsheet::Excel::Error:0xc97e6e8> - #<Spreadsheet::Excel::Error:0xc97e4f4>   2000年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In the compact helical system, several bifurcation patterns have been observed in potential profiles of electron-cyclotron-heated plasmas. In a bifurcation pattern with a strong shear of radial electric field, an internal transport barrier is confirmed to be established for electron thermal energy. Probabilistic treatment with realization of the pattern or internal transport barrier is discussed.

    DOI: 10.1088/0741-3335/42/5A/309

  • Possibility of electric field bifurcation and internal transport barrier formation in LHD plasma 査読 国際誌

    Sanuki, H; Itoh, K; Yokoyama, M; Fujisawa, A; Ida, K; Toda, S; Itoh, I; Yagi, M; Fukuyama, A

    JOURNAL OF NUCLEAR MATERIALS   69.0 ( 2.0 )   445.0 - 450.0   2000年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Theoretical analysis of the electric field bifurcation is made for the LHD plasma. For given shapes of plasma profiles; a region of bifurcation is obtained in a space of the plasma parameters. In this region of plasma parameters, the electric field domain interface is predicted to appear in the plasma column. The reduction of turbulent transport is expected to occur in the vicinity of the interface; inducing internal transport barrier. Within the present simple model, the electric field bifurcation associated with the internal transport barrier is predicted to be realized for the parameter of T-e(0) similar or equal to 2 keV and n(0) similar or equal to 10(18)(m(-3)). The boundary of the region of multiple solution is characterized by a scaling T-e(0) similar to [n(0)](0.4).

    DOI: 10.1143/JPSJ.69.445

  • Global MHD modes excited by energetic ions in heliotron/torsatron plasmas 査読 国際誌

    K Toi, M Takechi, S Takagi, G Matsunaga, M Isobe, T Kondo, M Sasao, DS Darrow, K Ohkuni, S Ohdachi, R Akiyama, A Fujisawa, M Gotoh, K Ida, H Idei, H Iguchi, S Kado, M Kojima, S Kubo, S Lee, K Matsuoka, T Minami, S Morita, N Nikai, S Nishimura, S Okamura, M Osakabe, A Shimizu, Y Shirai, C Takahashi, K Tanaka, T Watari, Y Yoshimura

    NUCLEAR FUSION   39.0 ( 11Y )   1929.0   1999年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Confinement physics study in a small low aspect ratio helical device: CHS 査読 国際誌

    S Okamura, K Matsuoka, R Akiyama, DS Darrow, A Ejiri, A Fujisawa, M Fujiwara, M Goto, K Ida, H Idei, H Iguchi, N Inoue, M Isobe, K Itoh, S Kado, K Khlopenkov, T Kondo, S Kubo, A Lazaros, S Lee, G Matsunaga, T Minami, S Morita, S Murakami, N Nakajima, N Nikai, S Nishimura, I Nomura, S Ohdachi, K Ohkuni, M Osakabe, R Pavlichenko, BJ Peterson, R Sakamoto, H Sanuki, M Sasao, A Shimizu, Y Shirai, S Sudo, S Takagi, C Takahashi, S Takayama, M Takechi, K Tanaka, K Toi, T Watari, K Yamazaki, M Yokoyama, Y Yoshimura

    NUCLEAR FUSION   39.0 ( 9Y )   1337.0   1999年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Energetic-Ion-Driven Toroidal Alfvacute en Eigenmodes Observed in a Heliotron/Torsatron Plasma 査読 国際誌

    Takechi, M; Takagi, S; Matsunaga, G; Ohkuni, K; Shimizu, M; Toi, K; Ohdachi, S; Akiyama, R; Fujisawa, A; Gotoh, M;

    Physical review letters   83.0 ( 2.0 )   312.0   1999年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Transition from L mode to high ion temperature mode in CHS heliotron/torsatron plasmas 査読 国際誌

    K Ida, M Osakabe, K Tanaka, T Minami, S Nishimura, S Okamura, A Fujisawa, K Yamazaki, Y Yoshimura, S Kubo, R Akiyama, DS Darrow, H Idei, H Iguchi, M Isobe, S Kado, T Kondo, S Lee, K Matsuoka, S Morita, I Nomura, S Ohdachi, M Sasao, A Shimizu, S Takagi, C Takahashi, S Takayama, M Takechi, K Toi, K Tsumori, T Watari

    NUCLEAR FUSION   39.0 ( 11Y )   1649.0   1999年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Electric pulsation and profile quantization in CHS heliotron/torsatron 査読 国際誌

    Fujisawa, A; Iguchi, H; Idei, H; Kubo, S; Matsuoka, K; Okamura, S; Tanaka, K; Minami, T; Ohdachi, S; Morita, S; Zushi, H; Lee, S; Osakabe, M; Akiyama, R; Yoshimura, Y; Toit, K; Sanuki, H; Itoh, K; Shimizu, A; Takagi, S; Ejiri, A; Takahashi, C; Kojima, M; Hidekuma, S; Ida, K; Nishimura, S; Isobe, M; Inoue, N; Sakamoto, R; Itoh, SI; Hamada, Y; Fujiwara, M

    PLASMA PHYSICS AND CONTROLLED FUSION   41.0 ( 3A )   A561   1999年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Radial electric field is a key physical quantity in determining the structure of toroidal helical plasmas, owing to the nonlinear dependence of transport on the, radial electric field. It has been observed that the potential profiles show various interesting patterns in space and time in the compact helical system (CHS) plasmas. In particular, the phenomenon of electric pulsation, clearly demonstrates the nature of bifurcation of radial electric field in toroidal helical plasmas.

    DOI: 10.1088/0741-3335/41/3A/049

  • Electron thermal transport barrier and density fluctuation reduction in a toroidal helical plasma 査読 国際誌

    Fujisawa, A; Iguchi, H; Minami, T; Yoshimura, Y; Sanuki, H; Itoh, K; Lee, S; Tanaka, K; Yokoyama, M; Kojima, M; Itoh, SI; Okamura, S; Akiyama, R; Ida, K; Isobe, M; Morita, S; Nishimura, S; Osakabe, M; Shimizu, A; Takahashi, C; Toi, K; Hamada, Y; Matsuoka, K; Fujiwara, M

    PHYSICAL REVIEW LETTERS   82.0 ( 13.0 )   2669.0 - 2672.0   1999年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A thermal transport barrier resulting in a high central electron temperature of similar to 2 keV is established in the core of electron-cyclotron-resonance heated plasmas of the Compact Helical System Heliotron/Torsatron. The formation of the barrier is correlated with the reduction in the density fluctuations and with a structural change of the radial electric field profile at the barrier location. The results suggest that the decrease in fluctuation should contribute to a reduction of anomalous transport and a drastic increase in electron temperature at the barrier. [S0031-9007(99)08825-0].

    DOI: 10.1103/PhysRevLett.82.2669

  • Electric field bifurcation and transition in CHS heliotron/torsatron 査読 国際誌

    FUJISAWA Akihide, IGUCHI Harukazu, IDEI Hiroshi, KUBO Shin, LEE Seishu, MATSUOKA Keisuke, OKAMURA Shoichi, TANAKA Kenji, MINAMI Takashi, MORITA Shigeru, OHDACHI Satoshi, OSAKABE Masaki, AKIYAMA Ryuichi, YOSHIMURA Yasuo, TOI Kazuo, SANUKI Heiji, ITOH Kimitaka, TAKAHASHI Chihiro, KOJIMA Mamoru, HIDEKUMA Shigeru, IDA Katsumi, NISHIMURA Shin, EIIRI Akira, HAMADA Yasushi, ITOH Sanae-L1, INOUE Noriyuki, SAKAMOTO Ryuichi and FUJMARA Masami

    JOURNAL OF NUCLEAR MATERIALS   1.0   84.0 - 87.0   1998年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Transition in radial electric field has been observed in CHS plasmas during a combined heating phase of ECH+NBI, using a heavy ion beam probe. The transition occurs in a timescale of a few dozen or a hundred microseconds. Radial current to induce the transition is evaluated by high temporal resolution of the heavy ion beam probe. Neoclassical dependence of radial electric field on a plasma parameter will be discussed to clarify the nonlinearity to allow the transition.

  • Discovery of electric pulsation in a toroidal helical plasma 査読 国際誌

    Fujisawa, A; Iguchi, H; Idei, H; Kubo, S; Matsuoka, K; Okamura, S; Tanaka, K; Minami, T; Ohdachi, S; Morita, S; Zushi, H; Lee, S; Osakabe, M; Akiyama, R; Yoshimura, Y; Toi, K; Sanuki, H; Itoh, K; Shimizu, A; Takagi, S; Ejiri, A; Takahashi, C; Kojima, M; Hidekuma, S; Ida, K; Nishimura, S; Isobe, M; Inoue, N; Sakamoto, R; Itoh, SI; Hamada, Y; Fujiwara, M

    PHYSICAL REVIEW LETTERS   81.0 ( 11.0 )   2256.0 - 2259.0   1998年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A pulsating behavior of the electrostatic potential has been discovered in a low-density, high-electron-temperature plasma of the CHS heliotron/torsatron. The potential profiles were observed to swing repeatedly between two distinctive states in a constant external magnetic field under a continuous supply of particles and energy. The change of the potential profile, which occurs on a much faster time scale (microseconds) than the diffusive time scale (milliseconds), is accompanied by changes in density and temperature. This discovery clearly demonstrates that even in a low beta regime a toroidal helical plasma can produce a self-sustaining dynamic steady state, like the sawtooth oscillation in tokamaks.

    DOI: 10.1103/PhysRevLett.81.2256

  • Electric field bifurcation and transition in the core plasma of CHS 査読 国際誌

    Fujisawa, A; Iguchi, H; Sanuki, H; Itoh, K; Itoh, SI; Okamura, S; Matsuoka, K; Hamada, Y

    PLASMA PHYSICS AND CONTROLLED FUSION   40.0 ( 5.0 )   627.0 - 630.0   1998年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    In the CHS heliotron/torsatron, dynamic phenomena associated with transitions in radial electric field were observed during combined ECH+NBI heated plasmas. The observations with high temporal resolution confirmed a nonlinear relationship between radial electric field and radial current as the cause of these phenomena associated with electric field bifurcation.

    DOI: 10.1088/0741-3335/40/5/011

  • Plasma and Beam Physics-Discovery of Electric Pulsation in a Toroidal Helical Plasma 査読 国際誌

    Fujisawa, A; Iguchi, H; Idei, H; Kubo, S; Matsuoka, K; Okamura, S; Tanaka, K; Minami, T; Ohdachi, S; Morita, S;

    Physical Review Letters   1998年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • Dynamic behavior of potential in the plasma core of the CHS heliotron/torsatron 査読 国際誌

    Fujisawa, A; Iguchi, H; Sanuki, H; Itoh, K; Lee, S; Hamada, Y; Kubo, S; Idei, H; Crowley, TP; Akiyama, R; Tanaka, K; Minami, T; Ida, K; Nishimura, S; Morita, S; Kojima, M; Hidekuma, S; Itoh, SI; Takahashi, C; Inoue, N; Suzuki, H; Okamura, S; Matsuoka, K

    PHYSICAL REVIEW LETTERS   79.0 ( 6.0 )   1054.0 - 1057.0   1997年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    During combined electron cyclotron and neutral beam heating, an abrupt drop and rise in potential by about one half of the central electron temperature (similar to 400 V) was observed in the core of the compact helical system heliotron/torsatron plasma. Drastic changes of radial electric field between positive and negative states occur over periods as short as 60 mu s, which is much shorter than the energy confinement time scale of about a few milliseconds. A nonlinear relation between the radial electric field and radial current is obtained. This is the first experimental observation of a microsecond time scale spontaneous transition based on an electric field bifurcation in toroidal helical plasmas.

    DOI: 10.1103/PhysRevLett.79.1054

  • Direct observation of potential profiles with a 200 keV heavy ion beam probe on the Compact Helical System 査読 国際誌

    A Fujisawa, H Iguchi, S Lee, TP Crowley, Y Hamada, S Kubo, H Idei, H Sanuki, K Itoh, T Minami, K Tanaka, S Nishimura, K Ida, S Hidekuma, M Kojima, C Takahashi, S Okamura, K Matsuoka

    PHYSICS OF PLASMAS   4.0 ( 5.0 )   1357.0 - 1361.0   1997年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • RF heating experiments in CHS and RF development for LHD 国際誌

    T. Watari, R. Kumazawa, K. Nishimura, T. Mutoh, T. Seki, S. Masuda, T. Shoji, F. Simbo, T. Ido, R. Akiyama, A. Ando, A. Ejiri, A. Fujisawa, H. Idei, K. Ida, H. Iguchi, M. Isobe, M. Iwase, S. Kubo, T. Minami, K. Matsuoka, T. Morisaki, S. Morita, S. Mutoh, S. Murakami, K. Narihara, S. Okamura, T. Ozaki, M. Sasao, C. Takahashi, T. Kawamoto, K. Tanaka, J. Xu, J. M. Noterdaeme, D. A. Rasmussen, J. F. Lyon, J. B. Wilgen, D. E. Greenwood, D. J. Hoffman, E. F. Jaeger and M. Murakami

    The twelfth topical conference on radio frequency power in plasmas   403.0 ( 1.0 )   57.0 - 64.0   1997年4月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Measurement of ablation cloud parameters and plasma potential with on/off-axis pellet injection in the JIPP T-IIU tokamak 査読 国際誌

    Sakakita, H; Sato, KN; Nomura, I; Hamada, Y; Nishizawa, A; Kawasumi, Y; Ida, K; Xu, J; Narihara, K; Toi, K; Ejiri, A; Seki, T; Adachi, K; Iguchi, H; Fujisawa, A; Liang, R; Sakamoto, M; Kano, Y; Hirokura, S; Hidekuma, S; Kojima, M

    FUSION ENGINEERING AND DESIGN   34.0   329.0 - 332.0   1997年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A pellet injection system with controllability of the injection angle has been developed and installed in the JIPP T-IIU tokamak. A long helical ablation cloud ('tail') has been observed when an ice pellet is injected into the tokamak plasma using the controllable injection angle system. The 'tail' does not flow along the direction of the total magnetic field lines of the torus. In order to understand the details of the ice pellet ablation structure in the 'tail mode', the local parameters of electron density and temperature within the ablation cloud are obtained by a spectroscopic method. The electron density determined from Stark broadening of the Balmer beta line is in the range 1.0 x 10(16) - 1.0 x 10(17) cm(-3), while the temperature obtained from the line-to-continuum intensity ratios is in the range 1-4 eV. It has also been observed by a heavy ion beam probe (HIBP) measurement that the potential at the plasma centre becomes more negative and the potential profile becomes deeper negatively after pellet injection. (C) 1997 Elsevier Science S.A.

    DOI: 10.1016/S0920-3796(96)00655-2

  • Potential profile measurements on compact helical system (CHS) using a 200 keV heavy ion beam probe 査読 国際誌

    Fujisawa, A; Iguchi, H; Lee, S; Crowley, TP; Hamada, Y; Hidekuma, S; Kojima, M; Kubo, S; Idei, H; Nishimura, K;

    FUSION ENGINEERING AND DESIGN   34.0   649.0 - 651.0   1997年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

  • PROBE IN THE COMPACT HELICAL SYSTEM 国際誌

    FUJISAWA, A; KUBO, S; IGUCHI, H; IDEI, H; MINAMI, T; SANUKI, H; ITOH, K; OKAMURA, S; MATSUOKA, K; TANAKA, K;

    Fusion energy 1996: proceedings of the Sixteenth International Conference on Fusion Energy   1997年1月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Studies of Perturbative Plasma Transport, Ice Pellet Ablation and Sawtooth Phenomena in the JIPP T-IIU Tokamak 国際誌

    K. TOI, K. N. SATO, Y. HAMADA, S. OHDACHI, H. SAKAKITA, A. NISHIZAWA, A. EJIRI, K. NARIHARA, H. KURAMOTO, Y. KAWASUMI, S. KUBO, T. SEKI, K. KITACHI, J. XU, K. IDA, K. KAWAHATA, I. NOMURA, K. ADACHI, R. AKIYAMA, A. FUJISAWA, J. FUJITA, S. HIDEKUMA, N. HIRAKI, S. HIROKURA, H. IDEI, T. IDO, H. IGUCHI, M. ISOBE, K. IWASAKI, O. KANEKO, Y. KANO, M. KOJIMA, J. KOOG, R. KUMAZAWA, T. KURODA, J. LI, R. LIANG, T. MINAMI, S. MORITA, K. OHKUBO, Y. OKA, S. OKAJIMA, M. OSAKABE, Y. SAKAWA, M. SASAO, K. SATO, T. SHIMPO, T. SHOJI, H. SUGAI, T. WATARI, I. YAMADA, K. YAMAUTI

    16th Conference Proceedings of Fusion Energy   1.0   559.0   1996年10月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Experimental study of plasma confinement and heating efficiency through potential profile measurements with a heavy ion beam probe in the compact helical system 国際誌

    A Fujisawa, S Kubo, H Iguchi, H IDEI, T MINAMI, H SANUKI, K ITOH, S OKAMURA, K MATSUOKA, K TANAKA, S LEE, M KOJIMA, TP CROWLEY, Y HAMADA, M IWASE, H NAGASAKI, H SUZUKI, N INOUE, R AKIYAMA, M OSAKABE, S MORITA, C TAKAHASHI, S MUTO, A EJIRI, K IDA, S NISHIMURA, K NARIHARA, I YAMADA, K TOI, S OHDACHI, T OZAKI, A KOMORI, K NISHIMURA, S HIDEKUMA, K OHKUBO, DA RASMUSSEN, JB WILGEN, M MURAKAMI, T WATARI, M FUJIWARA

    Proc. 16th IAEA Fusion Energy Conference, Montreal, Canada 1996   2.0   41.0 - 54.0   1996年1月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

  • Impact of rotational transform profile control on plasma confinement and stability in CHS 国際誌

    K. TOI, T. MORISAKI, S. SAKAKIBARA, A. EJIRI, H. YAMADA, S. MORITA, K. TANAKA, N. NAKAJIMA, S. OKAMURA, H. IGUCHI, K. IDA, K. TSUMORI, S. OHDACHI, K. NISHIMURA, K. MATSUOKA, J. XU, I. YAMADA, T. MINAMI, K. NARIHARA, R. AKIYAMA, A. ANDO, H. ARIMOTO, A. FUJISAWA, M. FUJIWARA, H. IDEI, O. KANEKO, K. KAWAHATA, A. KOMORI, S. KUBO, R. KUMAZAWA, T. OZAKI, A. SAGARA, C. TAKAHASHI, Y. TAKITA, T. WATARI

    Plasma Physics and Controlled Nuclear Fusion Research 1994: Fifteenth Conference Proceedings, Seville, Spain, 26 September-1 October 1994, Vol. 2   2.0   331.0   1994年9月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

▼全件表示

書籍等出版物

  • Experimental Achievements on Plasma Confinement and Turbulence

    A. Fujisawa(担当:単著)

    2009年7月 

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    担当ページ:in 2nd ITER Summer School, 2009, p146-170 (Melville, New York, American Institute of Physics)   記述言語:英語   著書種別:一般書・啓蒙書

  • Structural bifurcation in a toroidal plasma: A brief review of bifurcation phenomena in CHS stellarator

    A. Fujisawa(担当:単著)

    2004年5月 

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    担当ページ:in Recent Research Developments in Physics, Vol. 5 Par-III 2004, p1147-1164 (Karala, India, Transworld Research Network)   記述言語:英語   著書種別:一般書・啓蒙書

  • Bifurcation phenomena associated with radial electric field in a toroidal helical plasma, in Bifurcation phenomena in Plasmas

    A. Fujisawa(担当:単著)

    2002年1月 

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    担当ページ:in Bifurcation Phenomena in Plasmas, 2002, p255-278 (Fukuoka, Japan, Kyushu University)   記述言語:英語   著書種別:一般書・啓蒙書

講演・口頭発表等

  • Tomography as a Diagnostic Tool for Plasma Turbule 国際会議

    Akihide Fujisawa, 永島 芳彦, 稲垣 滋

    European Physical Society, Conference on plasma physics  2016年7月 

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    開催年月日: 2016年7月

    記述言語:英語   会議種別:口頭発表(一般)  

    開催地:Leuven   国名:ベルギー王国  

    Plasma turbulence consists of micro-scale fluctuations (such as drift waves), meso-scale structures, such as zonal flows and streamers and macroscale fluctuations generated from the background micro-scale fluctuations. The modern view shows that these elemental fluctuations and structure should interact nonlinearly with each other to maintain the dynamics structure of the turbulent plasma (Nucl. Fusion 49 (2009) 013001). Therefore, further systematic understanding of turbulent plasma requires superior experimental observations that can cover the whole plasma with fine resolution to identify the fluctuations from micro- to macroscale. One of such diagnostics able to realize such requirements is computed tomography (CT) for plasma emission. For measuring the turbulence structure with CT, a large number of spatial channels are necessary to resolve such fine structure in space and time, comparable to ion Lamor radius and drift wave frequency, respectively. Therefore, the proposed tomography system should need to have a sufficient number of the detectors to identify plasma local turbulence with a sufficient spatial resolution. A prototype of such diagnostics has been made in a linear plasma device, PANTA. The system is equipped with four sets of 132 detectors that can catch the different energy photons in visible, infra-red regimes for observing all plasma regions different in temperature and density. Recently, the tomography system has succeeded in providing the first results of local turbulence for the whole regions of the plasma [1]. The paper reports the obtained results of the two dimensional global measurement of the local turbulence with tomography and discusses the future application. This work is supported by the Grant-in-Aids for Scientific Research (No. 23246162) and the Grant-in-Aids for Scientific Research (No. 21224014).

  • Experimental studies of mesoscale structure and its interactions with microscale waves in plasma turbulence 招待 国際会議

    Akihide Fujisawa

    European Physical Society 38th COnference on Plasma Physics  2011年6月 

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    開催年月日: 2011年6月 - 2011年7月

    会議種別:口頭発表(招待・特別)  

    国名:フランス共和国  

    プラズマ乱流はプラズマ・核融合分野において、磁場閉じこめに関わる重要な学術テーマである。この分野において、従来プラズマ乱流はドリフト波の集合体として扱われていたの対して、ドリフト波と帯状流として捉える新しい考え方が主流となっている。この新しいパラダイムの実現に寄与した実験研究を帯状流や帯状磁場の発見を中心として概説する基調講演をヨーロッパ物理学会プラズマ分科会にておこなった。

  • IUPAPとその100周年について

    藤澤彰英

    RIAMフォーラム2023  2023年6月 

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    開催年月日: 2023年6月

    記述言語:日本語   会議種別:口頭発表(一般)  

    国名:日本国  

  • Introduction of IUPAP and its Centenary 招待 国際会議

    Akihide Fujisawa

    The 31st International Toki Conference on Plasma and Fusion Research (IUPAP Session)  2022年11月 

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    開催年月日: 2022年11月

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    開催地:online   国名:日本国  

  • PANTA、PLATO、QUESTが拓く核融合の未来 招待

    藤澤 彰英

    核融合エネルギーフォーラム 第14回全体会合  2022年3月 

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    開催年月日: 2022年3月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:オンライン   国名:日本国  

  • プラズマ乱流統合観測装置(PLATO)による乱流と構造の大域性の研究 招待

    藤澤 彰英

    プラズマ核融合学会  2019年12月 

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    開催年月日: 2019年11月 - 2019年12月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:中部大学   国名:日本国  

  • プラズマ乱流トモグラフィーと Stokes 偏光解析の応用

    藤澤 彰英

    画像計測研究会2019  2019年9月 

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    開催年月日: 2019年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:核融合科学研究所   国名:日本国  

  • PLATO計画の概要と進捗状況

    藤澤 彰英

    日本物理学会  2019年9月 

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    開催年月日: 2019年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:岐阜大学   国名:日本国  

  • PLATO (PLAsma Turbulence Observatory)プロジェクトと現状について

    藤澤 彰英

    先進トカマク研究会  2019年9月 

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    開催年月日: 2019年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:核融合科学研究所   国名:日本国  

  • Turbulence in fusion and laboratory plasmas - An experimentalist view of past and future for turbulence studies with a history of PLATO project

    藤澤 彰英

    9th East-Asia School and Workshop on Laboratory, Space, and Astrophysical Plasmas (Nagoya University, Japan, 2019.7.29-8.2)  2019年7月 

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    開催年月日: 2019年7月 - 2019年8月

    記述言語:英語   会議種別:公開講演,セミナー,チュートリアル,講習,講義等  

    開催地:名古屋大学   国名:日本国  

  • プラズマ乱流研究の進展と今後の展望 招待

    藤澤 彰英

    Plasma Conference 2017  2017年11月 

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    開催年月日: 2017年11月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:姫路商工会議所   国名:日本国  

  • 非平衡極限プラズマ全国共同連携ネットワーク研究計画

    Akihide Fujisawa

    日本学術会議  2016年3月 

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    開催年月日: 2016年3月

    記述言語:日本語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:日本学術会議   国名:日本国  

  • プラズマ乱流のトモグラフィーを用いた全体精密計測の開発について

    Akihide Fujisawa

    日本物理学会  2015年9月 

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    開催年月日: 2015年9月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:関西大学千里山キャンパス   国名:日本国  

  • トモグラフィーによる直線プラズマの局所乱流観測

    藤澤 彰英, 永島 芳彦, 稲垣 滋, 松岡啓介, 伊藤公孝, 伊藤 早苗

    日本物理学会 2015年年次大会  2015年3月 

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    開催年月日: 2015年3月 - 2015年9月

    記述言語:日本語  

    開催地:早稲田大学   国名:日本国  

  • プラズマ乱流研究の新方向 招待

    Akihide Fujisawa

    プラズマ・核融合学会 第31回年会  2014年11月 

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    開催年月日: 2014年11月

    記述言語:日本語   会議種別:口頭発表(一般)  

    開催地:新潟市 朱鷺メッセ   国名:日本国  

    The research of plasma turbulence enters into a new era after establishing a modern view of plasma turbulence. Further understanding based on the modern view requires development of a new diagnostics that can measure the whole plasma with fine resolution up to micro-scale. A candidate of such diagnostics is tomography, and a prototype is constructed in linear cylindrical plasma to provide successful and promising results. Therefore, in order to advance the plasma turbulence suffering from topological effects of confinement magnetic field, it is necessary to construct a special toroidal that allows such tomography measurement to cover the whole plasma with fine resolution from micro-scale to macro-scale fluctuations.

  • Present status and future of plasma turbulence experiments 招待

    Akihide Fujisawa

    エネルギー理工学研究所国際シンポジウム  2014年10月 

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    開催年月日: 2014年10月

    記述言語:英語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:Uji Kyoto   国名:日本国  

  • HIBP Measurements for Electric Field and Plasma Turbulence 招待 国際会議

    Akihide Fujisawa

    日韓セミナー  2014年8月 

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    開催年月日: 2014年8月

    記述言語:日本語   会議種別:公開講演,セミナー,チュートリアル,講習,講義等  

    国名:日本国  

  • What can we learn from basic experiments ? 招待 国際会議

    Akihide Fujisawa

    Asian and Pacific Transport Working Group  2014年6月 

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    開催年月日: 2014年6月

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    開催地:Fukuoka   国名:日本国  

    It is well-known that meso-scale and macro-scale structures generated by drift-waves, such as zonal flows [1], streamers [2] and large-scale fluctuating structure [3], exist in turbulent plasmas, and their interaction govern the structural formation and dynamics of turbulent plasmas [4]. This paradigm gives us a guiding principle for basic experiments to investigate the plasma turbulence experimentally. Nowadays, analysis tools have been developed to elucidate steady and dynamic characteristics of plasma turbulence, and to quantify elementary processes, e.g., the nonlinear couplings and energy transfer direction between the elementary waves in turbulence. Accordingly, basic experiments to clarify these fluctuating structures and their interaction are possible to advance fundamental understanding of structural formation and transport in turbulent plasma in presence of suitable experimental environments [5]. Plasma devices of low temperature, such as linear cylindrical and torus devices, provide excellent environment to perform the basic experiments, with these analysis tools, to identify the fundamental structures and their interactions. The devices own high accessibility and flexibility, easy controllability of plasma, moreover, advantages to use traditional probes and to develop new diagnostics. In fact, up to date, a huge number of experiments, e.g., CASTOR, CSDX, HYPER-I, MIRABELLE, PANTA, QT-Upgrade, TJ-K, TORPEX, VINETA, etc., have been done in plasma devices of low temperature.The paper introduces what can we learn from such experiments done in linear cylindrical and toroidal devices with brief description of advanced analyses and diagnostics on turbulence; e.g, quantification of nonlinear couplings in wavenumber in k-ω space, energy transfer analysis in wavenumber space, discovery of streamers, investigation of blob generation, detailed studies on EXB shearing effects, and so on. Finally, future direction of such basic experiments is indicated with their contribution to understanding the magnetically confined plasmas oriented for nuclear fusion. [1] S. Inagaki et al., Phys. Rev. Lett. 107 115001 (2011) [2] T. Yamada et al. Nature Phys. 4 721 (01 Sep. 2008). [3] A. Fujisawa et al., Phys. Rev. Lett. 93 165002 (2004) [4] G. R. Tynan et al., Plasma Phys. Control. Fusion 51 (2009) 113001. A. Fujisawa, Nucl. Fusion 49 013001 (2009). [5] A. Fujisawa, Plasma Fusion Res. 5 046 (2010).

  • プラズマ乱流全域マルチスケール観測と装置設計

    藤澤 彰英

    プラズマ・核融合学会 第30回年会  2013年12月 

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    開催年月日: 2013年12月

    記述言語:日本語  

    開催地:東京工業大学大岡山キャンパス   国名:日本国  

  • PANTAにおけるトモグラフィを目指した多チャンネル分光計測

    藤野博充

    プラズマ・核融合学会 第30回年会  2013年12月 

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    開催年月日: 2013年12月

    記述言語:日本語  

    開催地:東京工業大学大岡山キャンパス   国名:日本国  

  • Extended paradigm of and diagnostics for plasma turbulence 国際会議

    Akihide Fujisawa

    14th International Workshop on H-mode Physics and Transport Barriers  2013年10月 

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    開催年月日: 2013年10月

    記述言語:英語  

    開催地:Kyushu University, Fukuoka, Japan   国名:日本国  

  • プラズマ乱流の描像と全域マルチスケール観測の必要について

    藤澤 彰英, 永島 芳彦, 稲垣 滋, 松岡啓介, 伊藤公孝, 伊藤 早苗

    日本物理学会 2013年秋季大会  2013年9月 

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    開催年月日: 2013年9月

    記述言語:日本語  

    開催地:徳島大学常三島キャンパス   国名:日本国  

  • 乱雑さの中から生まれる構造

    藤澤 彰英

    平成25年度九州大学(大学院総合理工学府)公開講座 最先端・次世代プラズマ科学 -万物流転の法則から医療滅菌まで  2013年8月 

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    開催年月日: 2013年8月

    記述言語:日本語  

    開催地:九州大学筑紫キャンパス 総合研究棟3階 講義室   国名:日本国  

  • Turbulence in toroidal plasma 招待 国際会議

    Akihide Fujisawa

    APPC12  The 12th Asia Pacific Physics Conference  2013年7月 

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    開催年月日: 2013年7月

    記述言語:英語  

    開催地:International Conference Hall, Makuhari Messe, Chiba, JAPAN   国名:日本国  

  • Investigation of Essential Nonlinear Processes in Plasma Turbulence 国際会議

    Yoshihiko Nagashima, SANAE INOUE(論文のみ) ITOH, Inagaki Shigeru, K. Kamataki, H. Arakawa, T. Yamada, Naohiro Kasuya, M. Yagi, Akihide Fujisawa, K. Itoh

    40th European Physical Society Conference on Plasma Physics  2013年7月 

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    開催年月日: 2013年7月

    記述言語:英語  

    開催地:Espoo, Finland   国名:フィンランド共和国  

  • プラズマ乱流と帯状電磁場構造

    藤澤 彰英

    RIAMフォーラム2013  2013年6月 

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    開催年月日: 2013年6月

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    開催地:九州大学筑紫地区   国名:日本国  

  • 乱流プラズマの輸送と界面のダイナミクス 招待

    藤澤 彰英

    日本物理学会  2013年3月 

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    開催年月日: 2013年3月

    記述言語:日本語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:広島大学 東広島キャンパス   国名:日本国  

    磁場閉じこめプラズマ、レーザープラズマ、大気圧プラズマ、重相プラズマ、宇宙プラズマなど、現在プラズマ物理学は様々な対象へと展開し、著しい発展を見せている。その応用は脱CO2社会へと貢献する核融合発電等の先進エネルギー、カーボンナノチューブやスーパーダイアモンドなど新機能性物質創成による産業応用、大気圧プラズマによる止血、滅菌等の医療応用の他、多方面への応用が期待されている。このように多彩な発展を遂げているプラズマを「非平衡極限プラズマ」という共通学理から統一的に理解しようとする動きがある。夫々のプラズマ独自の特徴および共通する普遍的な問題や機構を抽出し、そして固有のプラズマに対し用いられる様々な方法を互いに適用することで、プラズマ物理の学術としての更なる進展、新領域の開拓を狙った試みである。このシンポジウムは、乱流磁化プラズマ、気液界面プラズマ、ナノ・バイオプラズマ、レーザー高密度プラズマの領域からそれぞれ最新のトピックスについて講演が準備されている。 今回「界面」を一つのキーワードとなっているが、磁場閉じ込めプラズマで「界面」に関連する代表的現象は輸送障である。核融合を目指したプラズマは乱流状態にあり乱流によってその閉じこめ特性が決定されている。1980代に、プラズマの周辺のごく狭い(メソスケール)領域で突然乱流輸送が低減する現象(Hモードあるいは輸送障壁)が発見され[1]、高性能プラズマの実現とその物理機構の解明のため盛んに研究が行われてきた。その結果、磁場閉じ込めプラズマに内在する自発電場の分岐性の存在が明らかになり、その分岐界面によって生じるシアー流(メソスケール)が乱流を低減する機構が同定されている。最近の実験では、ガスパフ・イメージング等の2次元計測の進歩により輸送障壁—すなわち分岐界面の領域で乱流のパターンが可視化され、その変化の詳細が明らかになってきている。 一方で、より基礎的な部分で、プラズマ乱流と輸送の研究は更なる展開を見せている。これまで、プラズマ乱流状態はドリフト波の集合体と考えられてきたが、最近の研究においてドリフト波は帯状流やストリーマなどのメソスケール構造を作ることが分かってきている。ここでいうメソスケールとは、プラズマ半径とイオンラーマー半径の相乗平均程度の長さ(~ )に当たる。帯状流は磁気軸の廻りの対称な流れであり、磁場を横切る輸送に寄与しない。そのためドリフト波から帯状流にエネルギーが移行することで乱流は抑制され輸送は低減する。すなわち、ドリフト波乱流自身の自己組織化によって輸送が規定される機構が明らかになってきており、プラズマの閉じ込めの根源的理解に結びつく知見をもたらした [2,3]。最近の実験で、乱流が駆動するよりプラズマ副半径に及ぶ巨視的な揺らぎの構造も見つかり上記の乱流の描像はメソスケールからさらにマクロスケール(プラズマ半径程度)の揺らぎを含むまでに至っている[4]。すなわち、プラズマ乱流とは、ドリフト波(ミクロスケール)とドリフト波が創る出すメソスケールからマクロスケール構造が非線形に絡み合う系として認識されるに至っている。 最近の興味深い問題として、リミットサイクルを示す輸送障壁領域での揺動と電場シアーのダイナミクス、「補食—被捕食者モデル」を示唆するような観測が見つかるほか、HモードとLモードの中間状態の存在など輸送障壁についても新しい観測が得られ、測地線音波モードを含む帯状流が輸送障壁の形成にどのように関与しているか、などの問題を提示している。また、プラズマに追加熱を行うと瞬時に乱流状態が変化し輸送が変ることが実験的に示され、加熱—分布関数を変形させようとする力が乱流に影響を及ぼすこと、すなわち位相空間と乱流の重要な関連が示されており、これまで謎であった非局所輸送などの現象にも解明の糸口が与えられる等、乱流と乱流輸送の研究は新しい局面を迎えている。以上、磁場閉じこめプラズマの領域ではプラズマ乱流や輸送障壁—すなわち乱流プラズマの構造形成について重要な知見が得られている。この進展には、先に述べたガスパフ・イメージングを含む計測器(マイクロ波散乱、重イオンビームプローブ、BES, Doppler Reflectometor, ECE Array, etc)や解析法(Bicoherence, Wavelet, Wavelet-Bicoherence, etc)の進歩が不可欠であった [5]。本講演では、輸送障壁に関連し最近のトピックス、および近年得られたプラズマ乱流に関する新しいパラダイム、乱流と構造形成の現代的描像について紹介する。さらに今後研究を進展させるために必要な研究について議論する。

  • プラズマ物理学の未来 招待

    藤澤 彰英

    日本学術会議  2013年1月 

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    開催年月日: 2013年1月

    記述言語:日本語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:日本学術会議   国名:日本国  

  • 磁化プラズマ乱流研究の進展 招待

    藤澤 彰英

    プラズマ核融合学会  2012年12月 

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    開催年月日: 2012年12月

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    開催地:九州大学 筑紫キャンパス   国名:日本国  

    プラズマ乱流の理解が著しく進展している。乱流と平均流の相互作用に始まりドリフト波の集合と考えられてきたプラズマ乱流がドリフト波とドリフト波が生成する構造の系として認識されるに至っている。講演ではこれまでの研究成果を振返り現在得られているプラズマ乱流の描像を解説する

  • PANTAにおける分光による揺動スペクトル観測

    大坪聡, 藤澤 彰英

    プラズマ核融合学会  2012年11月 

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    開催年月日: 2012年11月

    記述言語:日本語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:春日市 クローバープラザ   国名:日本国  

    Turbulence plays an important role on structure formation of magnetically confined plasmas by enhancing the transport. Thus the understanding of plasma turbulence is strongly required for realization of fusion reactors. In PANTA in Kyushu University [1], a multi-sight spectroscopic system is made to aim at two-dimensional measurement of turbulence, and the system will be extended for tomographic reconstruction of turbulence images. This poster presents preliminary results from a test of the system on spectral analysis of the line-integrated light emission. PANTA is a cylindrical linear plasma device with the diameter of ~0.1 m and axial length of 4 m. Plasma is generated by helicon wave (7 MHz, 3 kW). The magnetic field is fixed at 0.09 T. The spectroscopic system consists of 132 (33 rows x 4 columns) channels and can measure different light bands in wavelength using four kinds of optical filters ; infrared (900±20 nm), red (696.5±30 nm), blue (476.5±30 nm), and UV (294±20 nm). The 33 channels in a set are aligned in the vertical direction with the intervals of 5 mm. The filtered light signals, integrated along the horizontal line-of-sight across the plasma, are transferred to photo-diode detectors through optical fibers. The present measurement is performed for selected 16 channels with weighted on different radial positions. The significant fluctuation signals in blue light are obtained in an argon plasma, and red light in a neon plasma. Fast Fourier Transform (FFT) was applied to the observed signals to obtain fluctuation spectra with the frequency resolution of ~50 Hz. Figure 1 (a) and (b) shows an example of power spectrum of emission intensity fluctuation along the central chord (including r = 0 mm) and deviated chord from the center (including r = 20 mm) in the blue range of wavelength in a argon plasma, respectively. As is shown in Fig. 1, we can find several spectral peaks in low frequencies, for example at ~5 kHz, significantly above the noise level, suggesting a possibility to infer the radial position where such coherent modes are located using the 1D multi-channel measurement.

  • 直線プラズマ装置PANTAにおける分光計測とアーベル変換による画像再構成

    柿川伸介, 藤澤 彰英

    プラズマ核融合学会  2012年11月 

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    開催年月日: 2012年11月

    記述言語:日本語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:春日市 クローバープラザ   国名:日本国  

    Understanding of plasma turbulence is an essential issue to realize and control fusion plasmas since turbulence-driven transport affects significantly plasma confinement. Turbulence state consists of various spatio-temporal scale fluctuations, therefore, the plasma turbulence needs to be observed multi-dimensionally with covering a wide range of spatial scales. In a cylindrical plasma device PANTA in Kyushu University[1], a spectroscopic system surrounding the plasma for tomography is being constructed to measure two-dimensional structure of turbulence with a fine resolution, and as its first trial, the reconstruction of local emission profile in steady states is being made from one dimensional measurement in argon plasmas of PANTA. PANTA produces a linear cylindrical plasma device with the diameter of ~0.1 m and axial length of 4 m by helicon wave (7 MHz, 3 KW). The line-integrated measurements were carried out for four different ranges of wavelength by optical filters; blue (480 nm), red (700 nm), infrared (900 nm), and UV (300 nm) light. The system for each wavelength range consists of 33 channels aligned in the vertical direction. In this experiment, the magnetic field was fixed at 0.9 kG with argon gas pressue of 1 mTorr. The measurement was performed with selecting 16 channels that covered the plasma region from the center to an edge on one side. Assuming azimuthal symmetry of the cylindrical plasmas, radial profile of local emission is reconstructed by different procedures, i.e., using the Abel inversion after fitting functions to the measured profile of line integrated profile, and solving a linear matrix equation to connect the local emission to the line integrated profile. Figure 1 shows an example of the measured line-integrated profle and the inferred profile of local emission obtained the method of solving the matrix equation for the case of the blue light (ArII emission) for an argon plasma, suggesting a sharply peaked profile around the plasma center of r less than 2cm. The poster presents the initial results obtained with the devloping system for tomography and details of the reconstruciton methods, with the progress and future in the construction of a two-dimensional observation system in PANTA.

  • 乱流と構造研究の新しい展開 はじめに、おわりに 招待

    藤澤 彰英

    プラズマ核融合学会  2012年11月 

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    開催年月日: 2012年11月

    記述言語:日本語   会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:春日市 クローバープラザ   国名:日本国  

    プラズマ乱流はプラズマの閉じ込めに関わる極めて重要な課題で、磁場閉じこめ核融合分野では半世紀以上に渡り国際的に研究されてきたが、近年の研究で著しい進展が見られている。70年代にプラズマ乱流の原因としてドリフト波が同定され、21世紀にはドリフト波が創るメソスケール構造として帯状流やストリーマが見つかり、プラズマ乱流はドリフト波と帯状流などメソスケール構造から成り立つ系として捉えられるに至っている。また、最近の大型ヘリカル装置でのドリフト波が創る巨視的揺らぎ構造の発見により、このプラズマ乱流の見方はマクロスケールを含む系として拡張されている。本シンポジウムではプラズマ乱流の実験、理論、シミュレーションの夫々についての最新のトピックスを紹介し、プラズマ乱流の研究を今後更に発展させるため、その方向を議論するために企画された。  シンポジウム最初は最近発見された巨視的揺らぎ構造に関する講演(九州大学の稲垣氏)で加熱パワーモジュレーション時に見られる輸送の瞬間的変化(閉じこめ時間に比べ圧倒的に短い)が揺らぎの変化によることを実験的に検証したことが紹介された。次の講演(伊藤公孝氏 核融合研)では、加熱パワーの変化が直接プラズマに位相(速度)空間上の影響を与え、特に波長の長い不安定性を変化させることで瞬間的揺らぎと輸送の変化が説明できることが理論的に示唆された。またプラズマの特徴である位相空間乱流という概念が紹介された。3番目の講演(矢木雅敏氏 原子力研究所)では、核融合プラズマでは原子レベルの現象から装置サイズにおよぶマルチスケールの現象の解明を目指した統合シミュレーションコードの他に、乱流診断シミュレータが紹介された。乱流シミュレータとはプラズマ乱流を特定の計測器でどのよう観測されるかをシミュレーションしその実体を推測し実験を効率的に推進するためのツールである。最後の講演(Prof. H.PARK、POSTECH 韓国)では、電子サイクロトロン輻射イメージングによる三次元計測が紹介され、KSTARトカマクでのELM時の電子温度観測による時空間(3次元)発展の詳細が示された。イメージング与える力が余すことなく示され、今後の乱流研究にも果たすべき重要な役割が示唆された。  最後に、これまで計測器の発展とともに、プラズマ乱流研究の研究は進展してきた。マイクロ波散乱によるドリフト波の同定、重イオンビームプローブによる帯状流の発見、ECEの径方向分布計測による巨視的揺動の発見などによって、現在のプラズマ乱流は、ミクロ、メソ、マクロの揺らぎの非線形相互作用によって成り立つ系とする描像に至っている。今後その描像に基づいてプラズマ乱流の理解を本質的に進めるためには、プラズマ乱流は一点のみ観測しているだけでは困難である。最初に掲げた問いへの回答として―プラズマ全域およびすべてのスケールに渡る観測が必要であり、それを支持するシミュレーション・理論との密接な三位一体の研究方法の推進が必要である。

  • 磁化プラズマにおける乱流と構造形成 招待

    藤澤彰英(代理 伊藤公孝)

    天文学会  2012年4月 

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    開催年月日: 2012年4月

    会議種別:口頭発表(招待・特別)  

    開催地:京都 龍谷大学   国名:日本国  

  • 磁場閉じ込めプラズマ中の乱流とメソスケール構造の生成について 招待

    藤澤彰英

    日本物理学会  2012年4月 

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    開催年月日: 2012年4月

    会議種別:口頭発表(招待・特別)  

    開催地:関西学院大学 西宮   国名:日本国  

  • 乱流プラズマにおける構造形成の実験観測 招待

    藤澤彰英

    2012年2月 

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    開催年月日: 2012年2月

    会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:生産技術研究所   国名:日本国  

  • Modern View of Turbulence and Transport in Magnetized Plasmas 招待

    藤澤彰英

    プラズマ核融合学会  2011年11月 

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    開催年月日: 2011年11月

    会議種別:口頭発表(招待・特別)  

    開催地:金沢 石川県立音楽堂   国名:日本国  

    The modern view of turbulence has been established due to the discovery of structures drift-waves generate, such as zonal flows and streamers, providing a new framework for understanding turbulence-driven transport and structural formation in magnetized plasmas. This paper presents recent development of laboratory experiments to have advanced the understanding of plasma turbulence and transport, focusing on discoveries of mesoscale structures, such as zonal flows and streamers, the analyzing techniques to quantify the couplings between different scale structures, and physics of turbulence transport and barrier formation.

  • Physics of zonal flows and transport bifurcations 招待 国際会議

    Akihide Fujisawa

    3rd EFDA Transport Topical Group Meeting &15th EU-US transport task force workshop  2010年9月 

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    開催年月日: 2010年9月

    会議種別:シンポジウム・ワークショップ パネル(公募)  

    開催地:岡山大学津島キャンパス   国名:スペイン  

    EFDA(Europe Fusion Development Agreement) transport topical group meeting(第3回目)とEU-US transport Task Force Meeting(第15回)の合同コンファレンスが2009年の9月7日から10日にスペイン、コルトバにて開催された。その会議に招待されReview講演を行った。合衆国とEUの合同による会議であり、その目的は磁場閉じ込め核融合における乱流輸送の物理理解および制御であり、後者は毎年開催され当該分野では歴史のある会議である。

  • QUESTにおける高周波入射を用いた電流立ち上げ実験

    石黒正貴,花田和明,図子秀樹,中村一男,藤澤彰英,出射浩,坂本瑞樹,長谷川真,東園雄太,磯部光考,田島西夜,江尻晶,高瀬雄一,前川孝,御手洗修,岸本泰明,川崎昌二,中島寿年,東島亜紀

    日本物理学会第65回年次大会  2010年3月 

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    開催年月日: 2010年3月

    会議種別:口頭発表(一般)  

    開催地:岡山大学津島キャンパス   国名:日本国  

  • LMD-Uにおける密度およびポテンシャル揺動の非線形結合の解析

    小林達哉,稲垣滋,荒川弘之,鎌滝晋礼,永島芳彦,山田琢磨,矢木雅敏,糟谷直宏,藤澤彰英,伊藤早苗,伊藤公孝

    日本物理学会第65回年次大会  2010年3月 

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    開催年月日: 2010年3月

    開催地:岡山大学津島キャンパス   国名:日本国  

  • LMD-Uにおける揺動位相速度遷移のダイナミクス

    荒川弘之,稲垣滋,永島芳彦,山田琢磨,鎌滝晋礼,小林達哉,杉田暁,矢木雅敏,糟谷直宏,藤澤彰英,伊藤公孝,伊藤早苗

    日本物理学会第65回年次大会  2010年3月 

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    開催年月日: 2010年3月

    開催地:岡山大学津島キャンパス   国名:日本国  

  • LMD-Uにおける揺動駆動輸送の統計的性質

    稲垣滋,下田雅人,荒川弘之,鎌滝晋礼,永島芳彦,山田琢磨,藤澤彰英,糟谷直宏,矢木雅敏,伊藤公孝,伊藤早苗

    日本物理学会第65回年次大会  2010年3月 

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    開催年月日: 2010年3月

    開催地:岡山大学津島キャンパス   国名:日本国  

  • EBWH/CD Experiments using Phased-array Antenna System in QUEST 国際会議

    H. Idei, H. Zushi, H. Hanada, K. Nakamura, A. Fujisawa, O. Mitarai, M. Sakaguchi, K.N. Sato, M. Sakamoto, M. Hasegawa, Y. Higashizono, K. Ishiguro, H. Liu, S. Sharma, T. Ryokai, S. Tashima, Y.Hisano, N. Yoshida, H. Watanabe, T. Tokunaga, S. Kawasaki, H. Nakashima, A. Higashijima, T. Fujiwara, H. Igami, S. Kubo, M. Isobe, N. Nishino, Y. Nakashima, T. Maekawa, Y. Kishimoto, and Y. Takase

    US-Japan Workshop on RF Physics  2010年3月 

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    開催年月日: 2010年3月

    開催地:General Atomics, San Diego   国名:アメリカ合衆国  

  • 赤外線カメラを使用した壁面温度計測による熱負荷の測定

    岡本 篤知,横峯 健彦,石黒 正貴(九大応力研) 花田 和明,中村 一男,図子 秀樹,藤澤 彰英,出射 浩,坂本 瑞樹,長谷川 真,川崎 昌二,中島 寿年,東島 亜紀(東大新領域) 高瀬 雄一(京大エネ) 前川 孝,岸本 泰明(東海大) 御手洗 修(兵庫県立大) 福本 直之,永田 正義

    プラズマ・核融合学会 九州・沖縄・山口支部(於 平成21 年12 月22 日(火)-23 日(水))  2009年12月 

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    開催年月日: 2009年12月 - 2010年12月

    会議種別:口頭発表(一般)  

    開催地:山口大学常盤キャンパス   国名:日本国  

  • QUEST における赤外線観測用真空窓の熱設計

    立川 博章,横峯 健彦,石黒 正貴(九大応力研) 花田 和明,中村 一男,図子 秀樹,藤澤 彰英,出射 浩,坂本 瑞樹,長谷川 真,川崎 昌二,中島 寿年,東島 亜紀(東大新領域) 江尻 晶,高瀬 雄一(京大エネ) 前川 孝,岸本 泰明(兵庫県立大) 福本 直之(東海大) 御手洗

    プラズマ・核融合学会 九州・沖縄・山口支部大会  2009年12月 

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    開催年月日: 2009年12月

    開催地:山口大学常盤キャンパス   国名:日本国  

  • QUEST におけるECR 放電時のラングミュアプローブ計測

    郷田 到,小川 和真,尾崎 和基,大山 亮平,靏昭 太朗,A. Rusinov (九大応力研) 坂本 瑞樹,東園 雄太,図子 秀樹,中村 一男,藤澤 彰英,花田 和明,出射 浩,長谷川 真,川崎 昌二,中島 寿年,東島 亜紀(横浜国立大) 津嶋 晴(東大新領域) 高瀬 雄一(京大エネ) 前川 孝,岸本 泰明(東海大) 御手洗 修

    プラズマ・核融合学会 九州・沖縄・山口支部大会  2009年12月 

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    開催年月日: 2009年12月

    会議種別:口頭発表(一般)  

    開催地:山口大学常盤キャンパス   国名:日本国  

  • QUEST における真空磁気面再構成法の検討

    池田 旭彰,石黒 正貴(九大応力研) 花田 和明,図子 秀樹,藤澤 彰英,中村 一男,出射 浩,坂本 瑞樹,長谷川 真,川崎 昌二,中島 寿年,東島 亜紀,東園 雄太(アイテル) 新谷 吉郎(東大新領域) 高瀬 雄一(京大エネ) 前川 孝,岸本 泰明(東海大) 御手洗 修

    プラズマ・核融合学会 九州・沖縄・山口支部大会  2009年12月 

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    開催年月日: 2009年12月

    開催地:山口大学常盤キャンパス   国名:日本国  

  • トーラスプラズマ乱流実験研究

    藤澤彰英

    プラズマ・核融合学会第26回年会 シンポジウムⅣ「乱流プラズマの構造形成と選択則の総合的研究」  2009年12月 

     詳細を見る

    開催年月日: 2009年12月

    会議種別:口頭発表(一般)  

    開催地:京都市国際交流会館   国名:日本国  

  • Comparative Studies for Future Device Beyond ITER (Invited Talk) 招待

    Akihide Fujisawa

    18th International Toki Conference  2008年12月 

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    開催年月日: 2008年12月

    会議種別:口頭発表(一般)  

    開催地:Toki Japan   国名:日本国  

  • Oscillatory Zonal Flows Driven by Interaction between Energetic Ions and CHS Fishbone-like Instability 国際会議

    A. Fujisawa, S. Ohshima A. Shimizu, H. Nakano, H. Iguchi, K. Itoh, S. Okamura, K. Matsuoka, T. Minami, Y. Yoshimura, K. Nagaoka, C. Takahashi, S. Nishimura, M. Isobe, C. Suzuki, T Akiyama, CHS group

    22nd IAEA Conference on Fusion Energy 2008  2008年10月 

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    開催年月日: 2008年10月

    会議種別:口頭発表(一般)  

    開催地:Geneve, Switzerland   国名:スイス連邦  

  • Turbulence Measurements and Discovery of Zonal Magnetic Field using HIBPs in CHS 国際会議

    Akihide Fujisawa, Kimitaka Itoh, Akihiro Shimizu, Haruhisa Nakano, Shinsuke Ohshima, Harukazu Iguchi, Shoichi Okamura, Keisuke Matsuoka, CHS group

    International Congress on Plasma Physics  2008年9月 

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    開催年月日: 2008年9月

    会議種別:口頭発表(一般)  

    開催地:Fukuoka, Japan   国名:日本国  

  • Experimental Studies of Zonal Flow and Field in CHS Plasma 招待 国際会議

    A. Fujisawa, K. Itoh, A. Shimizu, H. Nakano, S. Ohshima, H. Iguchi, K. Matsuoka, S. Okamura, T. Minami, Y. Yoshimura, K. Nagaoka,K. Ida, K. Toi, C. Takahashi, M. Kojima, S. Nishimura, M. Isobe, C. Suzuki, T Akiyama, T. Ido, Y. Nagashima, S.-I. Itoh, and P. H. Diamond

    49th Annual Meeting of the Division of Plasma Physics  2007年11月 

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    開催年月日: 2007年11月

    会議種別:口頭発表(一般)  

    開催地:Orlando, Florida   国名:アメリカ合衆国  

  • Zonal Flows and Fields Generated by Turbulence in CHS 招待 国際会議

    A. Fujisawa, K. Itoh, A. Shimizu, H. Nakano, S. Ohshima, K. Matsuoka, S. Okamuara, CHS-group

    17th International Toki Conference  2007年10月 

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    開催年月日: 2007年10月

    会議種別:口頭発表(一般)  

    開催地:Toki, Japan   国名:日本国  

  • Experimental Progress on Zonal Flow Physics in Toroidal Plasmas 国際会議

    A. Fujisawa, T. Ido, A. Shimizu, S. Okamura, K. Matsuoka, H. Iguchi, Y. Hamada, H. Nakano, S. Ohshima, K. Itoh, K. Hoshino, K. Shinohara, Y. Miura, Y. Nagashima, S.-I. Itoh, M. Shats, H. Xia, J.Q. Dong, L.W. Yan, K.J. Zhao, G.D. Conway, U. Stroth, A.V. Melnikov, L.G. Eliseev, S.E. Lysenko, S.V. Perfilov, C. Hidalgo, G.R. Tynan, C. Holland, P.H. Diamond, G.R. McKee, R.J. Fonck and D.K. Gupta

    21st IAEA Conference on Fusion Energy 2006  2006年10月 

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    開催年月日: 2006年10月

    会議種別:口頭発表(一般)  

    開催地:Chengdu, China   国名:中華人民共和国  

  • Experiments on turbulence and zonal flow in toroidal plasmas 招待 国際会議

    A. Fujisawa

    International Congress on Plasma Physics  2006年5月 

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    開催年月日: 2006年5月

    会議種別:口頭発表(一般)  

    開催地:Kiev,Ukraine   国名:ウクライナ  

  • Zonal flow experiments in CHS 国際会議

    A. Fujisawa

    8th Meeting of the ITPA CDBM Topical Group  2005年4月 

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    開催年月日: 2005年4月

    会議種別:口頭発表(一般)  

    開催地:Kyoto Univ.   国名:日本国  

  • Zonal flow experiments in CHS 国際会議

    A. Fujisawa

    8th Meeting of the ITPA CDBM Topical Group  2005年4月 

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    開催年月日: 2005年4月

    会議種別:口頭発表(一般)  

    開催地:Kyoto Univ.   国名:日本国  

  • Zonal flow experiments in CHS 国際会議

    A. Fujisawa

    8th Meeting of the ITPA CDBM Topical Group  2005年4月 

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    開催年月日: 2005年4月

    会議種別:口頭発表(一般)  

    開催地:Kyoto Univ.   国名:日本国  

  • Experiments on electric field dynamics and zonal flows in a toroidal plasma 国際会議

    A. Fujisawa

    Lecture at SWIP China  2004年12月 

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    開催年月日: 2004年12月

    会議種別:口頭発表(一般)  

    開催地:Southwestern Institute of Physics, Chengdu   国名:中華人民共和国  

  • Experiments on electric field dynamics and zonal flows in a toroidal plasma 国際会議

    A. Fujisawa

    Lecture at ASIPP China  2004年12月 

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    開催年月日: 2004年12月

    会議種別:口頭発表(一般)  

    開催地:Academy of Sciences, Institute of Plasma Physics Hehei   国名:中華人民共和国  

  • Experiments on electric field dynamics and zonal flows in a toroidal plasma 国際会議

    A. Fujisawa

    Lecture at Tsinghua University  2004年12月 

     詳細を見る

    開催年月日: 2004年12月

    会議種別:口頭発表(一般)  

    開催地:Tsinghua University, Beijng   国名:中華人民共和国  

  • Experimental Studies of Zonal Flows in CHS and JIPPT-IIU (Oral ,combined) 国際会議

    A. Fujisawa, K. Itoh, H. Iguchi, K. Matsuoka, S. Okamura, A. Shimizu, T. Minami, Y. Yoshimura, K. Nagaoka, C. Takahashi, M. Kojima, H. Nakano, S. Ohshia, S. Nishimura, M. Isobe, C. Suzuki, T. Akiyama, K. Ida, K. Toi, S.-I. Itoh, P.H. Diamond, Y. Hamada, A. Nishizawa, T. Ido, T. Watari and Y. Kawasumi

    20th IAEA Conference on Fusion Energy 2004  2004年11月 

     詳細を見る

    開催年月日: 2004年11月

    会議種別:口頭発表(一般)  

    開催地:Vilamoura, Portugal(IAEA-EX/8-5RB)   国名:ポルトガル共和国  

  • Experimental Identification of Zonal Flows in CHS 招待 国際会議

    A. Fujisawa, K. Itoh, H. Iguchi, K. Matsuoka, S. Okamura, A. Shimizu, T. Minami, Y. Yoshimura, K. Nagaoka, C. Takahashi, M. Kojima, H. Nakano, S. Ohshima, S. Nishimura, M. Isobe, C. Suzuki, T. Akiyama, K. Ida, K. Toi, S.-I. Itoh and P. H. Diamond

    31st European Physical Society Conference on Plasma Physics  2004年6月 

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    開催年月日: 2004年6月 - 2004年7月

    会議種別:口頭発表(一般)  

    開催地:Imperial College, London   国名:グレートブリテン・北アイルランド連合王国(英国)  

▼全件表示

MISC

  • メゾスケールダイナモの発見と基礎過程

    藤澤彰英

    パリティ Vol. 24 p16   2009年1月

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • はじめに (小特集 ゾーナルフローの研究の現状と展望)

    藤澤彰英

    プラズマ核融合学会誌   2005年12月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • おわりに (小特集 ゾーナルフローの研究の現状と展望)

    藤澤彰英

    プラズマ核融合学会誌   2005年12月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • 重イオンビームプローブによるゾーナルフロー研究I (小特集 ゾーナルフローの研究の現状と展望)

    藤澤彰英、清水昭博

    プラズマ核融合学会誌   2005年12月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • プラズマを操る(科学啓発教育とプラズマの世界)

    藤澤彰英

    プラズマ核融合学会誌   2003年6月

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    掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • トロイダルプラズマの径電場分岐性と時空間パターンの形成について

    藤澤彰英

    プラズマ核融合学会誌   2000年4月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • 特別推進研究 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

    Akihide Fujisawa

    Journal of Plasma and Fusion Research   2019年8月

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • 乱流局在ープラズマ乱流研究の最前線

    Akihide Fujisawa

    パリティ vol. 342019 20p   2019年1月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • 非平衡極限プラズマネットワーク構想

    Akihide Fujisawa

    プラズマ核融合学会   2014年3月

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    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

    プラズマ物理科学の分野で、乱流、光、機能性プラズマの各分野を、全国の拠点のネットワークを構築し融合した研究領域と新しい学術分野の創成が進んでいる。本論文ではその概要を説明する。

  • プラズマ乱流研究の新展開ー巨視的揺らぎ構造の発見と新パラダイム

    Akihide Fujisawa

    パリティ vol. 29 2014 20p   2014年1月

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • 球状トカマクをべースとする核融合発電炉

    Akihide Fujisawa

    電気学会   2013年12月

     詳細を見る

    記述言語:日本語   掲載種別:記事・総説・解説・論説等(学術雑誌)  

  • ヘリカルプラズマにおける電場の非線形性と自励振動(最近の研究から)

    藤澤彰英

    日本物理学会誌   1999年4月

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    掲載種別:記事・総説・解説・論説等(学術雑誌)  

▼全件表示

所属学協会

  • プラズマ核融合学会

  • 日本物理学会

委員歴

  • 日本物理学会   日本物理学会論文賞選考委員長   国内

    2022年4月 - 2023年3月   

  • 日本物理学会   日本物理学会論文賞選考委員長   国内

    2022年4月 - 2023年3月   

  • 日本物理学会   日本物理学会論文賞選考委員   国内

    2021年4月 - 2022年3月   

  • 日本物理学会   代議員   国内

    2018年4月 - 2021年3月   

  • プラズマ核融合学会九州山口沖縄支部会   監査   国内

    2018年4月 - 2020年3月   

  • 日本物理学会   領域2 若手賞審査委員委員長   国内

    2017年4月 - 2018年3月   

  • プラズマ核融合学会   九州沖縄山口支部会 支部長   国内

    2016年6月 - 2018年5月   

  • 日本物理学会   領域2 代表   国内

    2015年4月 - 2016年3月   

  • プラズマ核融合学会   九州沖縄山口支部会 庶務幹事   国内

    2014年6月 - 2016年5月   

  • 日本物理学会   領域2 副代表   国内

    2014年4月 - 2015年3月   

▼全件表示

学術貢献活動

  • 核融合科学研究所運営会議運営委員

    役割:審査・評価

    核融合科学研究所  2023年4月 - 2025年3月

     詳細を見る

    種別:審査・学術的助言 

  • 核融合科学研究所運営会議運営委員

    役割:審査・評価

    核融合科学研究所  2021年4月 - 2023年3月

     詳細を見る

    種別:審査・学術的助言 

  • IAEA FEC2020国内選考委員

    役割:審査・評価

    文部科学省  2020年1月 - 2020年10月

     詳細を見る

    種別:審査・学術的助言 

  • 核融合科学研究所運営会議共同研究委員会

    役割:審査・評価

    核融合科学研究所  2019年9月 - 2021年4月

     詳細を見る

    種別:審査・学術的助言 

  • 学術論文等の審査

    役割:査読

    2019年

     詳細を見る

    種別:査読等 

    外国語雑誌 査読論文数:5

  • 座長(Chairmanship)

    日本学術会議 公開シンポジウム 「新しい国際単位系 (SI) 重さ、電気、温度、 そして時間の計測と私たちの暮らし」  ( 日本学術会議講堂 ) 2018年12月

     詳細を見る

    種別:大会・シンポジウム等 

  • IAEA FEC2018国内選考委員

    役割:審査・評価

    文部科学省  2018年1月 - 2018年10月

     詳細を見る

    種別:審査・学術的助言 

  • 学術論文等の審査

    役割:査読

    2018年

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    種別:査読等 

    外国語雑誌 査読論文数:2

  • 学術論文等の審査

    役割:査読

    2017年

     詳細を見る

    種別:査読等 

    外国語雑誌 査読論文数:4

  • 座長(Chairmanship)

    プラズマ核融合学会  ( 名古屋大学 ) 2016年11月

     詳細を見る

    種別:大会・シンポジウム等 

  • 座長(Chairmanship)

    日本物理学会  ( 東北学院大学 ) 2016年3月

     詳細を見る

    種別:大会・シンポジウム等 

  • IAEA FEC2016国内選考委員

    役割:審査・評価

    文部科学省  2016年1月 - 2016年2月

     詳細を見る

    種別:審査・学術的助言 

  • 学術論文等の審査

    役割:査読

    2016年

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    種別:査読等 

    外国語雑誌 査読論文数:3

  • 第11回核融合エネルギー連合講演会プログラム委員会委員

    第11回核融合エネルギー連合講演会プログラム委員会  ( 九大 伊都キャンパス ) 2015年7月 - 2016年7月

     詳細を見る

    種別:大会・シンポジウム等 

  • 日本学術振興会  学術システム研究センター/プログラムオフィサー

    役割:審査・評価

    日本学術振興会  2015年4月 - 2018年3月

     詳細を見る

    種別:審査・学術的助言 

  • 座長(Chairmanship)

    プラズマカンファレンス2014  ( 新潟市 朱鷺メッセ ) 2014年11月

     詳細を見る

    種別:大会・シンポジウム等 

  • 座長(Chairmanship) 国際学術貢献

    APTWG  ( Kyushu University, Kasuga Fukuoka Japan Japan ) 2014年6月

     詳細を見る

    種別:大会・シンポジウム等 

  • 座長(Chairmanship)

    日本物理学会  ( 東海大学  湘南キャンパス ) 2014年3月

     詳細を見る

    種別:大会・シンポジウム等 

  • 座長(Chairmanship) 国際学術貢献

    Hモードワークショップ  ( 九州大学 筑紫キャンパス ) 2013年10月

     詳細を見る

    種別:大会・シンポジウム等 

  • シンポジウム座長

    物理学会  ( 徳島大学 ) 2013年9月 - 2013年10月

     詳細を見る

    種別:大会・シンポジウム等 

    参加者数:100

  • 座長(Chairmanship)

    日本物理学会  ( 徳島大学 ) 2013年9月

     詳細を見る

    種別:大会・シンポジウム等 

  • 座長

    物理学会  ( 徳島大学 ) 2013年9月

     詳細を見る

    種別:大会・シンポジウム等 

    参加者数:100

  • 座長(Chairmanship)

    日本物理学会  ( 広島大学 東広島キャンパス ) 2013年3月

     詳細を見る

    種別:大会・シンポジウム等 

  • Plasma and Fusion Research 国際学術貢献

    2012年12月 - 2020年12月

     詳細を見る

    種別:学会・研究会等 

  • 司会(Moderator)

    プラズマ核融合学会  ( 春日市 クローバプラザ ) 2012年11月

     詳細を見る

    種別:大会・シンポジウム等 

  • 座長(Chairmanship) 国際学術貢献

    Plasma Conference 2011  ( 金沢市 ) 2011年11月 - 2012年11月

     詳細を見る

    種別:大会・シンポジウム等 

  • Plasma Physics and Controlled Fusion 国際学術貢献

    2011年8月 - 2015年12月

     詳細を見る

    種別:学会・研究会等 

  • International Advisory Board 国際学術貢献

    Workshop on electric Fields, turbulence and self-organization in magnetized plasmas  ( Strasbourg France ) 2011年7月

     詳細を見る

    種別:大会・シンポジウム等 

    参加者数:26

  • 不明

    QUEST研究会  ( 九州大学 総合研究棟C-CUBE ) 2010年8月

     詳細を見る

    種別:大会・シンポジウム等 

▼全件表示

その他

  • 非平衡極限プラズマ全国共同連携ネットワーク研究計画のマスタープラン2017重要課題28に採択される。

    2017年2月

     詳細を見る

    「非平衡極限プラズマ全国共同連携ネットワーク研究計画」は、ネットワークによって、最先端プラズマ物理研究を非平衡極限プラズマの共通学理に基づいて学問的に体系化し新学術分野を創成するとともに、核融合や新エネルギーの実現と新機能物質創成を加速するものであり、久保総長を代表として日本のプラズマ研究の各拠点が九州大学を中心として連携しプラズマ物理科学の新領域を開拓するプロジェクトである。日本学術会議が公募に基づき作成するマスタープラン2017における重要大型計画28に採択され、さらに文部科学省の大型プロジェクとに関するロードマップ2014の重点10課題に採用される。

  • 非平衡極限プラズマ全国共同連携ネットワーク研究計画のマスタープラン2014重要課題27に採択される。

    2014年2月

     詳細を見る

    「非平衡極限プラズマ全国共同連携ネットワーク研究計画」は、ネットワークによって、最先端プラズマ物理研究を非平衡極限プラズマの共通学理に基づいて学問的に体系化し新学術分野を創成するとともに、核融合や新エネルギーの実現と新機能物質創成を加速するものであり、有川総長を代表として日本のプラズマ研究の各拠点が九州大学を中心として連携しプラズマ物理科学の新領域を開拓するプロジェクトである。日本学術会議が公募に基づき作成するマスタープラン2014における重要大型計画27に採択され、さらに文部科学省の大型プロジェクとに関するロードマップ2014の重点10課題に採用される。

共同研究・競争的資金等の研究課題

  • 非接触式プラズマ計測技術に関する研究開発コンサルティング

    2023年2月 - 2024年1月

    個人研究

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    担当区分:研究代表者  資金種別:その他産学連携による資金

  • トモグラフィーによるトーラスプラズマ乱流場の大域観測とアイソトープ効果の解明

    2022年4月 - 2025年3月

    九州大学応用力学研究所および極限プラズマ研究連携センター 

      詳細を見る

    担当区分:研究代表者 

  • トモグラフィーによるトーラスプラズマ乱流場の大域観測とアイソトープ効果の解明

    研究課題/領域番号:22H00120  2022年 - 2024年

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    藤澤 彰英

      詳細を見る

    担当区分:研究代表者  資金種別:科研費

    本課題では、PLATO (主半径 0.7 m 副半径0.3 m 磁場 0.25 T プラズマ定常時間 100ms以上)の運転領域の拡大およびトモグラフィーなど一部計測器の拡張を実施し、多様な閉じ込め磁場形状対して軽水素および重水素プラズマにおいて乱流場の偏在(対称性の破れ)と結合(大域性)をトモグラフィー(2断面)およびHIBP(1断面)によって大域局所精密観測する。両者の乱流場の構造と機能の関係を、異なる閉じ込め磁場形状の下で捉えアイソトープ効果の物理機構を明らかにする。アイソトープ効果の起源の探究を通して、閉じ込め性能などにおいて高機能な乱流状態を実現する原理を探し出す。

    CiNii Research

  • 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

    2017年4月 - 2022年3月

    九州大学応用力学研究所および極限プラズマ研究連携センター 

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    担当区分:研究代表者 

    プラズマは自然界の至る所に存在し、核融合などこれからの革新的技術の基盤となっています。そのプラズマの構造やダイナミクスを決定しているのが乱流です。特に、核融合を目指したプラズマの磁場閉じ込めの研究では乱流は特性を決めるものとして半世紀以上にわたって国際的に研究されてきました。その結果、今、プラズマ乱流の新しい見方が提案され革新的な時代を迎えています。それは、乱流プラズマ中に存在するスケールの違った揺らぎの結合が大域相関を生み局所的な揺らぎを同調させ、プラズマの特性を決めているとするものです。本研究の目的は、この仮説に基づいて、乱流プラズマの本質に迫り、その構造形成や機能発現の原理を解明することです。

  • 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

    研究課題/領域番号:17H06089  2017年 - 2021年

    日本学術振興会  科学研究費助成事業  特別推進研究

    藤澤 彰英, 井戸 毅, 稲垣 滋, 飯尾 俊二

      詳細を見る

    担当区分:研究代表者  資金種別:科研費

    変容する自然の理解および核融合炉実現のための磁場閉じ込めプラズマの学術体系化を目指した乱流プラズマの統合大域精密観測装置PLATOが完成し運転を開始している。その建設過程において装置電源としての誘導型フライホイールほか1000チャンネルを超えるトモグラフィーデータ記録装置などの経済的技術も生まれている。PLATOプロジェクトを支援する研究としての直線プラズマ装置PANTAにおいては準3次元トモグラフィーが完成しそのための画像解析法(Fourier-Rectangular級数展開法など)も開発された。理論シミュレーショ研究では、広く乱流プラズマに関連した成果が多数上がっている。

    CiNii Research

  • 磁場閉じ込めのための先進乱流計測および解析法の開拓

    2017年 - 2019年

    LHD計画共同研究

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    担当区分:研究代表者  資金種別:受託研究

  • 乱流プラズマ研究のためのプラズマ回転を利用した高解像度トモグラフィーの開発

    研究課題/領域番号:16K13921  2016年 - 2017年

    科学研究費助成事業  挑戦的萌芽研究

      詳細を見る

    担当区分:研究代表者  資金種別:科研費

  • 非平衡極限プラズマ全国共同連携ネットワーク計画 国際共著

    2013年4月 - 2023年3月

    九州大学 

      詳細を見る

    担当区分:研究分担者 

    プラズマの主要研究領域、乱流、光、機能の領域を融合し、基礎から応用までの新しい学問領域を開拓する九大を中心とした学術機関連携によるネットワーク研究計画。マスタープラン2014重点27課題に採択されている。

  • 2次元乱流ダイナミクス観測のための多波長超多点観測法の開発

    研究課題/領域番号:23246162  2011年 - 2013年

    日本学術振興会  科学研究費助成事業  基盤研究(A)

      詳細を見る

    担当区分:研究代表者  資金種別:科研費

  • 国際キャリアパス拠点とe-Scienceを基軸とした国際研究教育の先進化

    2011年

    P&P(Cタイプ)

      詳細を見る

    担当区分:研究代表者  資金種別:学内資金・基金等

  • 乱流プラズマの動的応答と動的輸送の統合研究

    研究課題/領域番号:21224014  2010年

    日本学術振興会  科学研究費助成事業  基盤研究(S)

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    担当区分:研究分担者  資金種別:科研費

  • 乱流プラズマの動的応答と動的輸送の総合研究

    2009年4月 - 2014年3月

    九州大学 

      詳細を見る

    担当区分:研究分担者 

    国際熱核融合実験炉(ITER)における核燃焼プラズマの実現に向けて、プラズマの高性能化と制御を目指しプラズマ乱流と構造の詳細研究が世界中で活発に行われている。近年の研究により、帯状流やストリーマーといったメゾスケールの揺動が微視的揺動と共存し、乱流輸送を規定する、という描像が確立しつつある。この描像により、磁場閉じ込めプラズマで広く観察される、拡散的輸送より圧倒的に速いプラズマの構造あるいは輸送の変化を説明できる可能性がある。プラズマ燃焼の制御のためには輸送のダイナミックな変動を制御する必要があり、そのために動的輸送応答の理解が強く求められている。本研究では、従来の「線形・局所的・決定論的」描像を「非線型揺動・大域的・確率的」描像へと拡張すべく、乱流と乱流輸送研究の枠組みを改革する事を目標とする。「プラズマ乱流物理学」を一段と深く進展させ、動的・大域的な輸送現象のモデルを形成し、磁場閉じ込めプラズマの動的輸送現象を解明し、ITER等の燃焼制御法の確固たる基盤を提供する。

  • パーソナルコンピュータクラスターを用いたトロイダルプラズマの乱流と構造の解析

    研究課題/領域番号:18360447  2006年 - 2008年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

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    担当区分:研究代表者  資金種別:科研費

  • 2台の重イオンビームプローブによるトロイダルプラズマの構造とダイナミクスの研究 平成15年度—平成17年度 基盤B

    研究課題/領域番号:15360497  2003年 - 2005年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

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    担当区分:研究代表者  資金種別:科研費

  • 重イオンビームを用いた多点同時観測による電位構造変化の研究

    研究課題/領域番号:12480129  2000年 - 2002年

    日本学術振興会  科学研究費助成事業  基盤研究(B)

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    担当区分:研究代表者  資金種別:科研費

▼全件表示

担当授業科目

  • プラズマ概論

    2023年4月 - 2023年6月   春学期

  • プラズマ概論

    2022年4月 - 2022年6月   春学期

  • プラズマ概論

    2021年4月 - 2021年6月   春学期

  • エネルギー輸送概論

    2020年4月 - 2020年9月   前期

  • エネルギー輸送概論

    2019年4月 - 2019年9月   前期

  • エネルギー輸送概論

    2018年4月 - 2018年9月   前期

  • エネルギー輸送概論

    2017年4月 - 2017年9月   前期

  • エネルギー輸送概論

    2016年4月 - 2016年9月   前期

  • エネルギー輸送概論

    2015年4月 - 2015年9月   前期

  • 核融合プラズマ特論

    2014年10月 - 2015年3月   後期

  • エネルギー輸送概論

    2014年4月 - 2014年9月   前期

  • 核融合プラズマ特論

    2013年10月 - 2014年3月   後期

  • エネルギー輸送概論

    2013年4月 - 2013年9月   前期

  • プラズマ輸送特論

    2012年10月 - 2013年3月   後期

  • 核融合プラズマ計測特論(プラズマ基礎物理学)

    2012年4月 - 2012年9月   前期

  • プラズマ輸送特論

    2011年10月 - 2012年3月   後期

  • 核融合プラズマ計測特論(プラズマ基礎物理学)

    2011年4月 - 2011年9月   前期

  • プラズマ輸送特論

    2010年10月 - 2011年3月   後期

  • 核融合プラズマ計測特論(プラズマ基礎物理学)

    2010年4月 - 2010年9月   前期

▼全件表示

他大学・他機関等の客員・兼任・非常勤講師等

  • 2006年  京都大学  区分:客員教員  国内外の区分:国内 

  • 2005年  京都大学  区分:客員教員  国内外の区分:国内 

国際教育イベント等への参加状況等

  • 2023年7月

    EU

    EPS2023においてIoPと共同で九州大学伊藤賞の審査委員長を務める。

      詳細を見る

    開催国・都市名:フランス ボルドー

  • 2022年7月

    Institute of Physics UK

    EPS2022においてIoPと共同で九州大学伊藤賞の審査委員長を務める。

      詳細を見る

    開催国・都市名:オンライン

  • 2022年3月

    Max-Planck Institute, Greifswald University

    MAx=Planck研究所博士論文審査

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    開催国・都市名:ドイツ(オンライン)

  • 2021年7月

    Institute of Physics UK

    EPS2020-21においてIoPと共同で九州大学伊藤賞の審査委員長を務める。

      詳細を見る

    開催国・都市名:オンライン

  • 2019年7月

    Institute of Physics UK

    EPS2019においてIoPと共同で九州大学伊藤賞の審査委員長を務める。

      詳細を見る

    開催国・都市名:イタリア ミラノ

  • 2019年7月

    文部科学省、九州大学、核融合科学研究所、プロバンス大学、日本原子力研究機構、ITER機構、フランス大使館、プラズマ・核融合学会

    9th East-Asia School and Workshop on Laboratory, Space, and Astrophysical Plasmas (Nagoya University, Japan, 2019.7.29-8.2)

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    開催国・都市名:日本・名古屋

    参加者数:50

  • 2018年6月

    Institute of Physics UK

    EPS2018においてIoPと共同で九州大学伊藤賞の審査委員長を務める。

      詳細を見る

    開催国・都市名:チェコプラハ

  • 2017年6月

    Insititute of Physics UK

    EPS2017においてIoPと共同で 九州大学伊藤賞の審査委員長を務める

      詳細を見る

    開催国・都市名:Bellfast UK

    参加者数:600

  • 2016年8月

    A3フォーサイト 東京大学 九州大学

    A3 Foresight Summer School and Workshop on Spherical Torus

      詳細を見る

    開催国・都市名:日本 福岡

    参加者数:100

  • 2016年8月

    韓国 NFRI 日本 NIFS

    8th Korea-Japan Seminar on Advanced Diagnostics for Steady-State Fusion Plasmas, Aug. 24-27, 2016 Busan Korea。

      詳細を見る

    開催国・都市名:韓国 釜山

    参加者数:50

  • 2008年7月

    文部科学省、九州大学、核融合科学研究所、プロバンス大学、日本原子力研究機構、ITER機構、フランス大使館、プラズマ・核融合学会

    2nd International ITER Summer School

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    開催国・都市名:日本・福岡

    参加者数:200

▼全件表示

社会貢献・国際連携活動概要

  • Hモードワークショップ開催

社会貢献活動

  • 仁科記念財団諮問委員を務める

    2023年

     詳細を見る

    仁科記念財団諮問委員を務める

  • 公開講座講演 「乱雑さの中から生まれる構造」

    総理工  九大筑紫キャンパス   2013年8月

     詳細を見る

    対象:社会人・一般, 学術団体, 企業, 市民団体, 行政機関

    種別:講演会

メディア報道

  • プラズマに関する子供向け解説 新聞・雑誌

    西日本新聞  2010年4月

     詳細を見る

    プラズマに関する子供向け解説

  • 磁場閉じ込めプラズマ中の帯状流の発見の核融合へのインパクトと木星の縞について 新聞・雑誌

    科学新聞  2007年3月

     詳細を見る

    磁場閉じ込めプラズマ中の帯状流の発見の核融合へのインパクトと木星の縞について

政策形成、学術振興等への寄与活動

  • 2023年6月 - 2025年6月   仁科記念財団

    運営諮問委員として財団の活動に携わる

  • 2020年10月 - 2023年9月   日本学術会議

    日本学術会議連携会員
    物理学委員会物性一般分科会幹事、IUPAP分科会委員長

  • 2019年7月   欧州物理学会プラズマ分科会および英国物理学会出版(IoPP)

    九州大学伊藤プロジェクト賞の継続と審査活動

  • 2019年1月 - 2022年12月  

    プラズマ核融合研究所に関する日仏連携研究所の設立と日本側所長に就任

  • 2017年10月 - 2023年9月   日本学術会議

    日本学術会議連携会員およびIUPAP委員会副委員長
    科学に関する重要事項を審議し、その実現を図ること。科学に関する研究の連絡を図り、その能率を向上させること。

  • 2017年10月 - 2020年9月   International Union of Pure and Applied Physics (IUPAP)

    International Union of Pure and Applied Physics (IUPAP) C16(プラズマ物理)のsecretaryを務める

  • 2014年10月 - 2017年9月   International Union of Pure and Applied Physics (IUPAP)

    International Union of Pure and Applied Physics (IUPAP) C16(プラズマ物理)のメンバーを務める

▼全件表示

外国人研究者等の受け入れ状況

  • EuroFusion

    受入れ期間: 2018年4月  

    国籍:オランダ王国

  • University of Science and Technology of China

    受入れ期間: 2009年11月 - 2009年12月   (期間):2週間以上1ヶ月未満

    国籍:中華人民共和国

    専業主体:日本学術振興会

海外渡航歴

  • 2010年9月

    滞在国名1:スペイン   滞在機関名1:Congress Palace

学内運営に関わる各種委員・役職等

  • 2020年4月 - 2022年3月   全学 シニアアドバイザー

  • 2017年4月 - 2021年3月   センター 極限プラズマ研究連携センター長

  • 2015年4月 - 2017年3月   研究所 高温プラズマ力学研究センター運営委員会 センター次長

  • 2014年4月 - 2015年3月   専攻 先端エネルギー理工学専攻 連携活動委員(正)

  • 2013年4月 - 2015年3月   研究所 公開研究発表会等実行委員会 委員

  • 2012年4月 - 2013年3月   専攻 先端エネルギー理工専攻主任

  • 2011年4月 - 2015年3月   研究所 高温プラズマ力学研究センター運営委員会委員

  • 2011年4月 - 2013年3月   その他 学務委員会委員

  • 2011年4月 - 2013年3月   その他 安全委員会委員

  • 2011年4月 - 2012年3月   全学 附属図書館商議委員会委員

  • 2011年4月 - 2012年3月   研究所 「九州大学百年史」部局史編集委員会委員

  • 2011年4月 - 2012年3月   研究所 出版広報委員会委員 委員長

  • 2011年4月 - 2012年3月   研究所 自己点検評価報告書WG

  • 2011年4月 - 2012年3月   地区 附属図書館筑紫図書館運営委員会委員

  • 2010年4月 - 現在   地区 筑紫地区図書館運営委員会委員

  • 2010年4月 - 2012年3月   全学 宙空環境研究センター委員会委員

  • 2010年4月 - 2011年3月   研究所 出版広報委員会委員 副委員長

  • 2010年4月 - 2011年3月   研究所 「九州大学百年史」部局史編集委員会委員

  • 2010年4月 - 2011年3月   研究所 三層会世話人

  • 2010年4月 - 2011年3月   地区 附属図書館筑紫図書館運営委員会

  • 2010年4月 - 2011年3月   全学 広報委員会部局等広報担当者

  • 2010年4月 - 2011年3月   全学 広報専門委員会委員

  • 2009年10月 - 2011年3月   研究所 高温プラズマ力学研究センター運営委員会委員

  • 極限プラズマ研究連携センター長

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