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Makoto Sasaki Last modified date:2016.05.12



Graduate School
Other Organization


E-Mail
Homepage
http://tokusui.riam.kyushu-u.ac.jp/Itoh_Lab_en/home.html
Theoretical and experimental research for plasma turbulence is done. The basic physics research in thermonuclear fusion plasmas, the confinement physics (e.g. the self-organization mechanisms in nonlinear and non-equilibrium systems) is the current topic. Research on nonlinear dynamics of waves and fluctuations is also made, which includes the topics on solitons and chaos as well as on turbulence. .
Phone
092-583-7724
Fax
092-583-7723
Academic Degree
PhD (Science)
Field of Specialization
Plasma Physics, Fluid Physics
Outline Activities
Theory and simulation on turbulence in magnetized plasmas, and education
Theoretical study: Importance of zonal flows, which suppress turbulent transport, has been widely recognized. In the presence of magnetic curvature such as toroidal plasmas, oscillatory components (GAMs) exist in combination with the stationary zonal flows (ZFs). We study nonlinear theory of GAMs and ZFs. The theoretical understandings of the nonlinear saturation mechanism of GAMs and of the energy partition between ZFs and GAMs have developed. Recently, We focus on the properties of GAMs driven by energetic particles.
Simulation study: We study nonlinear fundamental processes of drift waves, using a three-dimensional turbulence simulation in linear magnetized plasma devices (such as PANTA), and collaborate with experiments. Recently, we obtain nonlinear competition among zonal flows, streamer and flute structure, which are linearly stable and driven by nonlinear coupling of the drift waves. The formation mechanism of a solitary drift wave has been theoretically understood, whose results are consistent with the simulation and the experiments.
Research
Research Interests
  • Numerical Simulation on turbulence in linear magnetized plasma
    keyword : plasma turbulence, nonlinear process, zonal flow, streamer, meso-scale structure
    2011.11.
  • Theoretical study of nonlinear processes in plasma turbulence
    keyword : plasma turbulence, zonal flow, geodesic acoustic mode, structural formation, meso-scale structure
    2007.04.
Current and Past Project
  • The purpose of this study is to elucidate the kinetic effects of energetic particles on the turbulence transport and particle heating. Recently, it has been pointed out that oscillatory zonal flows (geodesic acoustic modes, GAMs) driven by energetic particles heat bulk ions via ion Landau damping. In addition to this, nonlinear coupling between Alfven eigenmodes (AEs) driven by energetic particles and stationary zonal flows (ZFs) has been observed. Previous studies on zonal flow-turbulence theory do not include such effects. This study will extend the zonal flow-turbulence theory to include the particle heating and turbulence suppression effects of energetic driven modes self-consistently, and will discuss the controllability of heating and transport.
  • The purpose of this study is to evaluate the effect of zonal flow (including low-frequency zonal flows (ZFs), geodesic acoustic modes (GAMs)) on the energy confinement time in turbulent toroidal plasmas. In previous studies, the assumption has been used that the wavelength of zonal flows is much shorter than the scale length of density or temperature profile. Therefore, although the energy density of zonal flows and turbulence has been reported, the energies of them, which are the volume integrals of the energy densities, have not been understood. In this study, first, we elucidate the nonlocal spatial structures of ZFs and GAMs and energy partition between them, considering the nonlinear coupling among turbulence, ZFs and GAMs. Second, the effect of ZFs and GAMs on the energy confinement time is investigated. Finally, we will present the minimum model that can describe the turbulent transport in toroidal plasmas.
Academic Activities
Papers
1. Makoto Sasaki, Naohiro Kasuya, Tatsuya Kobayashi, Hiroyuki Arakawa, Kimitaka Itoh, Kouhei Fukunaga, Takuma Yamada, Masatoshi Yagi, Sanae-I. Itoh, Formation mechanism of steep wave front in magnetized plasmas, Physics of Plasmas, 22, 22, 032315-1, 032315-10 (2015), 2015.03.
2. Makoto Sasaki, Naohiro Kasuya, Kimitaka Itoh, Masatoshi Yagi, Sanae-I. Itoh, Nonlinear competition of turbulent structures and improved confinement in magnetized cylindrical plasmas, Nuclear Fusion, 54, 2014.11.
3. Makoto Sasaki, Naohiro Kasuya, Masatoshi Yagi, Kimitaka Itoh, Yoshihiko Nagashima, Inagaki Shigeru, SANAE INOUE(論文のみ) ITOH, Statistical analyses of turbulent particle and momentum fluxes in a cylindrical magnetized plasmas, Plasma and Fusion Research, 8, 2401113 (2013) , 2013.09, [URL].
4. Makoto Sasaki, Kimitaka Itoh, Klaus Hallatschek, SANAE INOUE(論文のみ) ITOH, On a nonlinear dispersion effect of geodesic acoustic modes, Plasma Fusion Research, 8, 1403010 (2013), 2013.02.
5. M. Sasaki, K. Itoh, S.-I. Itoh and N. Kasuya, Zonal flows induced by symmetry breaking with existence of geodesic acoustic modes, Nuclear Fusion, 52, 023009, 2012.01, [URL].
6. Makoto Sasaki, Kimitaka Itoh, SANAE INOUE ITOH, Energy channeling from energetic particles to bulk ions via beam driven geodesic acoustic mode - GAM channeling, Plasma Physics and Controlled Fusion, 53, 085017, 2011.06, [URL].
7. M. Sasaki, K. Itoh, A. Ejiri, Y. Takase, Transient excitation of Zonal Flows by Geodesic Acoustic Modes, Plasma Phys. Control. Fusion, 51, 085002, 51 085002 (2009)., 2009.07.
8. M. Sasaki, K. Itoh, Y.Nagashima, A. Ejiri, Y. Takase , Nonlinear self-interaction of Geodesic Acoustic Modes in toroidal plasmas, Phys. Plasmas, 16, 022306, 16, 022306-1, 022306-8 (2009), 2009.01.
9. M. Sasaki, K. Itoh, A. Ejiri, Y. Takase , Poloidal Eigenmode of Geodesic Acoustic Mode in the limit of high safety factor, Journal of Plasma Phys., 75, No.6, 721, 75 No.6 721 (2009)., 2009.01.
Presentations
1. M. Sasaki, N. Kasuya, S. Toda, T. Yamada, M. Yagi, K. Itoh, S.-I. Itoh, Bifurcation between flow driven instability and drift wave in cylindrical plasmas, 5th Asia Pacific Transport Working Group International Conference, 2015.06.11.
2. Makoto Sasaki, Naohiro Kasuya, Tatsuya Kobayashi, Hiroyuki Arakawa, Takuma Yamada, Kouhei Fukunaga, Masatoshi Yagi, Kimitaka Itoh, Sanae-I. Itoh, Formation mechanism of steep wave front in drift wave turbulence, 24th International Toki Conference, 2014.11.06.
3. Makoto Sasaki, Naohiro Kasuya, Kimitaka Itoh, Maxime Lesur, Sanae-I. Itoh, Eigenmode analysis of geodesic acoustic modes induced by energetic particles, 4th Asia Pacific Transport Working Group International Conference, 2014.06.12.
4. Makoto Sasaki, Naohiro Kasuya, Kimitaka Itoh, MASATOSHI YAGI, SANAE INOUE ITOH, Dynamical response of a poloidal flow with particle source modulation, H mode workshop, 2013.10.02.
5. Makoto Sasaki, Naohiro Kasuya, Kimitaka Itoh, MASATOSHI YAGI, SANAE INOUE(論文のみ) ITOH, Nonlinear competition of zonal flow, flute structure and streamer in resistive drift wave turbulence in cylindrical plasmas, 12th Asia Pacific Physics Conference , 2013.07.17.
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Membership in Academic Society
  • The Japan Society of Plasma Science and Nuclear Fusion Research
  • The Physical Society of Japan
Awards
  • Theoretical study on spatio-temporal structures and energy transfer processes of oscillatory zonal flows
  • Theoretical study on nonlinear dispersion relation and dynamics of oscillatory zonal flows
  • Plasma Conference 2011 was held, which was co-sponsored by the Physical Society of Japan and the Japan Society of Plasma Science and Nuclear Fusion Research. I had a oral presentation, whose title was ''Nonlinear process of geodesic acoustic modes near a plasma edge'', and the presentation was highly evaluated.
  • Encouraging prize on doctor thesis in Tokyo University
Educational
Other Educational Activities
  • 2014.06.
  • 2013.10, We hold the international conference, 14th H mode workshop 2013, as a local organizer..
  • 2007.08.