Kyushu University Academic Staff Educational and Research Activities Database
List of Presentations
Akihide Fujisawa Last modified date:2020.06.22

Professor / Division of Nuclear Fusion Dynamics / Research Institute for Applied Mechanics


Presentations
1. 藤澤 彰英, Turbulence in fusion and laboratory plasmas - An experimentalist view of past and future for turbulence studies with a history of PLATO project, 9th East-Asia School and Workshop on Laboratory, Space, and Astrophysical Plasmas (Nagoya University, Japan, 2019.7.29-8.2), 2019.07.
2. Akihide Fujisawa, 永島 芳彦, 稲垣 滋, Tomography as a Diagnostic Tool for Plasma Turbule, European Physical Society, Conference on plasma physics, 2016.07, 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).
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3. Akihide Fujisawa, Present status and future of plasma turbulence experiments, エネルギー理工学研究所国際シンポジウム, 2014.10.
4. Akihide Fujisawa, What can we learn from basic experiments ?
, Asian and Pacific Transport Working Group, 2014.06, 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).
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5. Akihide Fujisawa, Extended paradigm of and diagnostics for plasma turbulence, 14th International Workshop on H-mode Physics and Transport Barriers, 2013.10.
6. Akihide Fujisawa, Turbulence in toroidal plasma, APPC12  The 12th Asia Pacific Physics Conference, 2013.07.
7. 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, Investigation of Essential Nonlinear Processes in Plasma Turbulence, 40th European Physical Society Conference on Plasma Physics, 2013.07.
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