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Akihide Fujisawa Last modified date:2018.06.28



Graduate School
Other Organization
Administration Post
Director of the Research Center for Plasma Turbulence


E-Mail
Phone
092-583-7709
Fax
092-573-6899
Academic Degree
Ph. D
Field of Specialization
Plasma Physics
Outline Activities
Major activities are the experimental research of plasma turbulence.
Now I am taking charge in the conduction of the experiments in a linear cylindrical device, PANTA, development of analyzing methods of turbulence data
in Itoh research center for plasma turbulence and advance fusion research center of RIAM.
Now I am doing the design of the magnetically plasma confinement device of torus shape for plasma turbulence studies.
Research
Research Interests
  • Research Network on ‘Non-equilibrium and Extreme State Plasma
    keyword : Extreme state of plasma
    2014.04~2023.03.
  • Experimental study of plasma turbulence and bifurcation
    keyword : plasma turbulence, bifurcation, transport, nuclear fusion
    2014.04~2023.03.
  • Research Network on ‘Non-equilibrium and Extreme State Plasma
    keyword : Extreme state of plasma
    2010.10~2016.09.
Current and Past Project
  • Plasma is ubiquitous, and it provides understanding nature, and modern and bases for future technologies It is turbulence that determines the structure and dynamics of plasma. Particularly, the turbulence has been extensively studied in the research of magnetically confined plasmas aiming at nuclear fusion, since it is a key to determine the plasma properties. Thanks to these efforts, a new paradigm has been proposed recently, that is, the couplings between disparate scale fluctuations and structure produces a global scale correlation to determine plasma properties. The purpose of the project is, being based on the paradigm, to clarify the structural formation and function expression of turbulent plasmas.
  • To control and predict the properties of the magnetically confined plasmas the worldwide researches have been vitally carried out toward realizing a burning plasma in International Tokamak Experimental Reactor (ITER). According to the recent achievement, the new concept is being established that the mesoscale fluctuating structure such as zonal flows and streamers coexist with microscale fluctuations, to regulate the turbulent transport. The new concept makes it enable to explain the changes in structure and transport occurring in much faster time scale than diffusive one. It is necessary to manage the dynamics changes in transport for control the burning plasma state, thus, the understanding of dynamics transport response should be mandatory. The purposes of this projects are i) to complete the paradigm shift from linear, local, deterministic view to nonlinear, non-local, probabilistic one, ii) to develop and advance the physics of turbulent plasma to accomplish the mode dynamics and nonlocal transport phenomena, and iv) to clarify the dynamic transport phenomena in the magnetically confined plasmas for provide a concrete base to control the burning plasma in ITER.
Academic Activities
Papers
1. Akihide Fujisawa, Turbulence in Toroidal Plasma, Proceedings of the 12th Asia Pacific Physics Conference, Article No. 015005, 2014.04, 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..
2. Fujisawa, Akihide, Experimental studies of mesoscale structure and its interactions with microscale waves in plasma turbulence, PLASMA PHYSICS AND CONTROLLED FUSION, 10.1088/0741-3335/53/12/124015, 53.0, 12.0, Article No. 124015, 2011.12, 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..
3. 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., Observation of Long-Distance Radial Correlation in Toroidal Plasma Turbulence, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.107.115001, 107.0, 11.0, 0.0-0.0, Article No. 115001, 2011.09, 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..
Presentations
1. 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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Membership in Academic Society
  • Japanese Physic Society
  • The Japanese Society of Plasma Science and Nuclear Fusion Research
Educational
Educational Activities
Giving lectures and instruction of graduate students in department of advanced energy engineering science, interdisciplinary graduate school of engineering sciences. The names of lectures are 'physics for plasma' and 'special lecture on plasma transport'.