Kyushu University Academic Staff Educational and Research Activities Database
List of Papers
Makoto Sasaki Last modified date:2019.06.28

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


Papers
1. T. Kobayashi, U. Losada, B. Liu, T. Estrada, B.Ph. van Milligen, R. Gerrú, M. Sasaki C. Hidalgo, Frequency and plasma condition dependent spatial structure of low frequency global potential oscillations in the TJ-II stellarator, Nuclear Fusion Letter, 10.1088/1741-4326/ab0122, 59, 044006, 2019.05.
2. A. Fujisawa, Y. Nagashima, K. Yamasaki, S. Inagaki, T. Yamada, M. Sasaki, Combined methods of moment vectors and Stokes parameters to analyze tomographic image of plasma turbulence, Physics of Plasmas , 10.1063/1.5048970, 26, 012305, 2019.01.
3. Z. Shi, J. Cheng, Y. Xu, T. Tokuzawa, Z. Qiu, M. Sasaki, W. Zhong, K. Ida, Z. Wang, T. Zhang, J. Kim, J. M. Kwon, T. Kobayashi, W. Lee, Summary of the 8th Asia-Pacific Transport Working Group (APTWG) Meeting, Nuclear Fusion, 10.1088/1741-4326/aaf74c, 59, 047001, 2019.01.
4. M. Lesur, J. Mediana, M. Sasaki, A. Shimizu, Subcritical instabilities in neutral fluids and plasmas, Fluids, https://doi.org/10.3390/fluids3040089, 3, 89, 2018.11.
5. Y. Kawachi,S. Inagaki, K. Tomita, K. Yamasaki, F. Kin, Y. Kosuga, M. Sasaki, Y. Nagashima, N. Kasuya, K. Hasamada, B. Zhang, A. Fujisawa, Determination of spatiotemporal structure of fluctuations by statistical averaging method, Plasma Fusion Research, 10.1585/pfr.13.3401105, 13, 3401105, 2018.08.
6. F. Kin, K. Itoh, A. Fujisawa, Y. Kosuga, M. Sasaki, T. Yamada, S. Inagaki, S.-I. Itoh, T. Kobayashi, Y. Nagashima, N. Kasuya, H. Arakawa, K. Yamasaki, K. Hasamada, Extraction of nonlinear waveform in turbulent plasma, Physics of Plasmas, https://doi.org/10.1063/1.5093218, 25, 062304, 2018.05.
7. M. Sasaki, Y. Camenen, A. Escarguel, S. Inagaki, N. Kasuya, K. Itoh, T. Kobayashi, Formation of spiral structures of turbulence driven by a strong rotation in magnetically cylindrical plasmas, Phys. Plasmas, 10.1063/1.5085372, 26, 042305, 2019.03.
8. M. Sasaki, K. Itoh, Y. Kosuga, J. Dong, S. Inagaki, T. Kobayashi, J. Cheng, K. Zhao, S.-I. Itoh, Parallel flow driven instability due to toroidal return flow in H-mode plasmas, Nuclear Fusion, https://doi.org/10.1088/1741-4326/ab1292, 59, 066039, 2019.03.
9. M. Sasaki, K. Itoh, T. Kobayashi, N. Kasuya, A. Fujisawa, S.-I. Itoh, Propagation direction of geodesic acoustic modes driven by drift wave turbulence, Nuclear Fusion, 10.1088/1741-4326/aad251, 58, 112005, 2018.10, 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..
10. M. Sasaki, Trapping of turbulence clumps by geodesic acoustic modes, AIP Proc, https://doi.org/10.1063/1.5048717, 1993, 20007, 2018.08.
11. M. Sasaki, K. Itoh, T. Ido, A. Shimizu, T. Kobayashi, H. Arakawa, N. Kasuya, A. Fujisawa, S.-I. Itoh, Evaluation of measurement signal of Heavy Ion Beam Probe of energetic-particle driven geodesic acoustic modes, Plasma Fusion Research, https://doi.org/10.1585/pfr.13.3403040, 13, 3403040, 2018.05.
12. Naohiro Kasuya, Makoto Sasaki, Satoshi Abe, Masatoshi Yagi, On the radial eigenmode structure of drift wave instability with inhomogeneous damping in cylindrical plasmas, Journal of the Physical Society of Japan, 10.7566/JPSJ.87.024501, 87, 2, 2018.01, Plasma flows can be driven by turbulent stresses from excited modes in magnetized plasmas. Our recent numerical simulation of resistive drift wave turbulence in a linear device has shown that the radial inhomogeneity of the neutral density affects azimuthal flow generation by changing the phase structure of the most unstable eigenmodes. Eigenmode analyses show that the mode structure has a complex Bessel-type function shape in the central region of the plasma, and the imaginary part arises from the radial inhomogeneity of the damping term caused by ion-neutral collisions. The amplitude of turbulent stress is proportional to the inhomogeneity under a marginally stable condition. Global structural formation is an important factor for determining the plasma turbulent state, and this result clearly shows that several kinds of radial background distributions, the plasma and neutral densities in this case, can influence the global structures..
13. T. Kobayashi, Makoto Sasaki, T. Ido, K. Kamiya, Y. Miura, Yoshihiko Nagashima, K. Ida, Inagaki Shigeru, akihide fujisawa, Sanae Itoh, K. Itoh, Quantification of Turbulent Driving Forces for the Geodesic Acoustic Mode in the JFT-2M Tokamak, Physical Review Letters, 10.1103/PhysRevLett.120.045002, 120, 4, 2018.01, We investigate spatial structures of turbulence and turbulent transport modulated by the geodesic acoustic mode (GAM), from which the excitation mechanism of the GAM is discussed. The GAM is found to be predominantly excited through a localized Reynolds stress force, rather than the dynamic shearing force. The evaluated growth rate is larger than the linear damping coefficients and is on the same order of magnitude as the effective growth rate evaluated from time evolution in the GAM kinetic energy..
14. Makoto Sasaki, T. Kobayashi, K. Itoh, Naohiro Kasuya, Yusuke Kosuga, akihide fujisawa, Sanae Itoh, Spatio-temporal dynamics of turbulence trapped in geodesic acoustic modes, Physics of Plasmas, 10.1063/1.5008541, 25, 1, 2018.01, The spatio-temporal dynamics of turbulence with the interaction of geodesic acoustic modes (GAMs) are investigated, focusing on the phase-space structure of turbulence, where the phase-space consists of real-space and wavenumber-space. Based on the wave-kinetic framework, the coupling equation between the GAM and the turbulence is numerically solved. The turbulence trapped by the GAM velocity field is obtained. Due to the trapping effect, the turbulence intensity increases where the second derivative of the GAM velocity (curvature of the GAM) is negative. While, in the positive-curvature region, the turbulence is suppressed. Since the trapped turbulence propagates with the GAMs, this relationship is sustained spatially and temporally. The dynamics of the turbulence in the wavenumber spectrum are converted in the evolution of the frequency spectrum, and the simulation result is compared with the experimental observation in JFT-2M tokamak, where the similar patterns are obtained. The turbulence trapping effect is a key to understand the spatial structure of the turbulence in the presence of sheared flows..
15. Takuma Yamada, Inagaki Shigeru, Makoto Sasaki, Yoshihiko Nagashima, Fumiyoshi Kin, Hiroyuki Arakawa, Tatsuya Kobayashi, Kotaro Yamasaki, Naohiro Kasuya, Yusuke Kosuga, akihide fujisawa, Kimitaka Itoh, Sanae Itoh, Three-dimensional structure of the streamer in linear plasmas, Journal of the Physical Society of Japan, 10.7566/JPSJ.87.034501, 87, 3, 2018.01, The three-dimensional structures of the streamer and its carrier waves and mediator were observed in a linear plasma device for the first time. Not only the cross-sectional structure but also the axial structure was observed. While carrier drift waves, which form the streamer structure by nonlinear interaction, had an axial mode number of 1, the streamer and mediator had an axial mode number of 0. The relationship of these axial mode numbers is well explained by the matching condition of the nonlinear interaction between the carrier waves and the mediator..
16. Naohiro Kasuya, S. Abe, Makoto Sasaki, Inagaki Shigeru, T. Kobayashi, M. Yagi, Turbulence simulation taking account of inhomogeneity of neutral density in linear devices, Physics of Plasmas, 10.1063/1.5009803, 25, 1, 2018.01, It is important to consider a combination of inhomogeneities, which drive and/or damp instabilities in magnetized plasmas. The inhomogeneity of neutral particle density is taken into account for analyzing turbulent states in linear devices by combining two kinds of simulations in this research. One is a simulation for 2D profiles of neutral particles and the other is that for resistive drift wave turbulence. Radial and axial profiles of neutral particles are calculated by the Monte Carlo method with a configuration of linear device PANTA. The ratio for ionization of neutral particles depends on the electron temperature, and the higher temperature in the operation range makes the neutral density smaller near the center of the plasma. Then, the radial profile of the ion-neutral collision frequency is set by introducing these neutral density profiles into resistive drift wave turbulence simulations. Smaller ion-neutral collision frequency makes the instabilities more unstable, and its inhomogeneity enhances mean electrostatic potential formation. The eigenmode structure is changed with the inhomogeneous ion-neutral collision frequency, and convective derivative nonlinearity generates the azimuthal flow near the center of the plasma. Two roles of the neutral particles on the turbulence, the direct change in linear instabilities and formation of background flows, become clear..
17. Makoto Sasaki, K. Itoh, K. Hallatschek, Naohiro Kasuya, M. Lesur, Yusuke Kosuga, Sanae Itoh, Enhancement and suppression of turbulence by energetic-particle-driven geodesic acoustic modes, Scientific Reports, 10.1038/s41598-017-17011-y, 7, 1, 2017.12, We propose a novel mechanism of enhancement of turbulence by energetic-particle-driven geodesic acoustic modes (EGAMs). The dynamics of drift-wave-type turbulence in the phase space is investigated by wave-kinetic equation. Spatially inhomogeneous turbulence in the presence of a transport barrier is considered. We discovered that trapping of turbulence clumps by the EGAMs is the key parameter that determines either suppress or enhance turbulence. In regions where turbulence is unstable, EGAM suppresses the turbulence. In contrast, in the stable region, EGAM traps clumps of turbulence and carries them across the transport barrier, so that the turbulence can be enhanced. The turbulence trapped by EGAMs can propagate independent of the gradients of density and temperature, which leads to non-Fickian transport. Hence, there appear a new global characteristic velocity, the phase velocity of GAMs, for turbulence dynamics, in addition to the local group velocity and that of the turbulence spreading. With these effect, EGAMs can deteriorate transport barriers and affect turbulence substantially. This manuscript provides a basis to consider whether a coherent wave breaks or strengthen transport barriers..
18. Makoto Sasaki, Naohiro Kasuya, K. Itoh, S. Toda, Takuma Yamada, Yusuke Kosuga, Yoshihiko Nagashima, T. Kobayashi, H. Arakawa, K. Yamasaki, akihide fujisawa, Inagaki Shigeru, Sanae Itoh, Topological bifurcation of helical flows in magnetized plasmas with density gradient and parallel flow shear, Physics of Plasmas, 10.1063/1.5000343, 24, 11, 2017.11, The topological bifurcation of the flow in non-equilibrium magnetized plasmas is demonstrated by a turbulence simulation. A system with two generic sources of turbulence, the gradients of density and parallel flow, is considered. Topological index of the flow is introduced, in order to indicate the chirality of flow pattern. We here report that the turbulence-driven flow forms the structure of co-axial helixes with opposite chirality. By changing the source of plasma particles, which modifies the density gradient, the transition between three turbulent states is obtained. In addition to the two turbulent states, which are dominated by the drift wave and the D'Angelo mode, respectively, the new state is found. In this third state, fluctuations are driven by both of the free energy sources simultaneously, and compete with the others. The result illustrates the generic feature of turbulence flow generation in non-equilibrium magnetized plasmas..
19. M. Sasaki, N. Kasuya, K. Itoh, S. Toda, T. Yamada, Y. Kosuga, Y. Nagashima, T. Kobayashi, H. Arakawa, K. Yamasaki, A. Fujisawa, S. Inagaki, S.-I. Itoh, Bifurcation of turbulence and flow topology in plasmas with density gradient and parallel flow shear, Plasma Conference (2017), 21aDp-04, 2017.11.
20. M. Sasaki, Enhancement and suppression of turbulence by energetic particle driven geodesic acoustic modes, 15th Burning Plasma Simulation Initiative (BPSI) Meeting (2017) , 2017.11.
21. M. Sasaki, N. Kasuya, S. Toda, T. Yamada, Y. Kosuga, H. Arakawa, T. Kobayashi, S. Inagaki, A. Fujisawa, Y. Nagashima, K. Itoh, S.-I. Itoh, Multiple-instabilities in magnetized plasmas with density gradient and velocity shears, Plasma and Fusion Research, https://doi.org/10.1585/pfr.12.1401042, 12, 1401042-1-1401042-7, 2017.10.
22. K. J. Zhao, Yoshihiko Nagashima, F. M. Li, Yuejiang Shi, P. H. Diamond, J. Q. Dong, K. Itoh, Sanae Itoh, G. Zhuang, H. Liu, Z. P. Chen, J. Cheng, L. Nie, Y. H. Ding, Q. M. Hu, Z. Y. Chen, B. Rao, Z. F. Cheng, L. Gao, X. Q. Zhang, Z. J. Yang, N. C. Wang, L. Wang, W. Jin, W. Yan, J. Q. Xu, Y. F. Wu, L. W. Yan, akihide fujisawa, Inagaki Shigeru, Yusuke Kosuga, Makoto Sasaki, Temporal-spatial structures of plasmas flows and turbulence around tearing mode islands in the edge tokamak plasmas, Nuclear Fusion, 10.1088/1741-4326/aa8341, 57, 12, 2017.09, The temporal-spatial structures of plasma flows and turbulence around tearing mode islands are presented. The experiments were performed using Langmuir probe arrays in the edge plasmas of J-TEXT tokamak. The correlation analyses clearly show that the flows have similar structures of m/n = 3/1 as the magnetic island does (m and n are the poloidal and toroidal mode numbers, respectively). The sign of the potential fluctuations for the flows inverses and the powers significantly reduce at q = 3 surface. Approaching to the last closed flux surface for the magnetic islands, the radially elongated flow structure forms. The flows are concentrated near separatrix and show quadrupole structures. The turbulence is concentrated near X-point and partly trapped inside the magnetic islands..
23. K. Itoh, Sanae Itoh, K. Ida, Inagaki Shigeru, Y. Kamada, K. Kamiya, J. Q. Dong, C. Hidalgo, T. Evans, W. H. Ko, H. Park, T. Tokuzawa, S. Kubo, T. Kobayashi, Yusuke Kosuga, Makoto Sasaki, G. S. Yun, S. D. Song, Naohiro Kasuya, Yoshihiko Nagashima, C. Moon, M. Yoshinuma, R. Makino, T. Tsujimura, H. Tsuchiya, U. Stroth, Hysteresis and fast timescales in transport relations of toroidal plasmas, Nuclear Fusion, 10.1088/1741-4326/aa796a, 57, 10, 2017.07, This article assesses current understanding of hysteresis in transport relations, and its impact on the field. The rapid changes of fluxes compared to slow changes of plasma parameters are overviewed for both core and edge plasmas. The modulation ECH experiment is explained, in which the heating power cycles on-and-off periodically, revealing hysteresis and fast changes in the gradientflux relation. The key finding is that hystereses were observed simultaneously in both the the gradientflux and gradientfluctuation relations. Hysteresis with rapid timescale exists in the channels of energy, electron and impurity densities, and plausibly in momentum. Advanced methods of data analysis are explained. Transport hysteresis can be studied by observing the higher harmonics of temperature perturbation δTm in heating modulation experiments. The hysteresis introduces the term δTm, which depends on the harmonic number m in an algebraic manner (not exponential decay). Next, the causes of hysteresis and its fast timescale are discussed. The nonlocal-in-space coupling works here, but does not suffice. One mechanism for the heating heats turbulence is that the external source S in phase space for heating has its fluctuation in turbulent plasma. This coupling can induce the direct input of heating power into fluctuations. The height of the jump in transport hysteresis is smaller for heavier hydrogen isotopes, and could be one of the origins of isotope effects on confinement. Finally, the impacts of transport hysteresis on the control system are assessed. Control systems must be designed so as to protect the system from sudden plasma loss..
24. , K. J. Zhao, Y. Nagashima, Yoshihiko Nagashima, J. Q. Dong, K. Itoh, S. I. Itoh, Sanae Itoh, J. Cheng, A. Fujisawa, akihide fujisawa, Inagaki Shigeru, Yusuke Kosuga, Makoto Sasaki, D. L. Yu, Q. Li, X. Q. Ji, X. M. Song, Y. Huang, Yi Liu, Q. W. Yang, X. T. Ding, X. R. Duan, Mesoscale electric fluctuations interacting with zonal flows, magnetic fluctuations and turbulence, Nuclear Fusion, 10.1088/1741-4326/aa6f35, 57, 7, 2017.06, New mesoscale electric fluctuations (MSEFs) are identified in the edge plasmas of the HL-2A tokamak using multiple Langmuir probe arrays. The MSEFs, resulting from the synchronization and having components of dominant geodesic acoustic mode (GAM) and m/n = 6/2 potential fluctuations, are found at the same frequency as that of the magnetic fluctuations of m/n = 6/2 (m and n are poloidal and toroidal mode numbers, respectively). The temporal evolutions of the MSEFs and the magnetic fluctuations clearly show the frequency entrainment and the phase lock between the GAM and the m/n = 6/2 magnetic fluctuations. The results indicate that GAMs and magnetic fluctuations can transfer energy through nonlinear synchronization. The nonlinear coupling analyses show that the MSEFs couple to turbulence and low frequency zonal flows (LFZFs). This suggests that the MSEFs may contribute to the LFZF formation, reduction of turbulence level, and thus confinement regime transitions. The analysis of the envelope modulation demonstrates that both the MSEFs and the LFZFs modulate the turbulence while the MSEFs are modulated by the LFZFs..
25. T. Kobayashi, S. Inagaki, M. Sasaki, Y. Kosuga, H. Arakawa, F. Kin, T. Yamada, Y. Nagashima, N. Kasuya, A. Fujisawa, S.-I. Itoh, K. Itoh, Phenomenological classification of turbulence states in linear magnetized plasma PANTA, Plasma and Fusion Research, https://doi.org/10.1585/pfr.12.1401019, 12, 1401019-1-1401019-8, 2017.05.
26. T. Ido, K. Itoh, M. Lesur, M. Osakabe, A. Shimizu, K. Ogawa, M. Nishiura, I. Yamada, R. Yasuhara, Yusuke Kosuga, Makoto Sasaki, K. Ida, Inagaki Shigeru, Sanae Itoh, Observation of subcritical geodesic acoustic mode excitation in the large helical device, Nuclear Fusion, 10.1088/1741-4326/aa665a, 57, 7, 2017.04, The abrupt and strong excitation of the geodesic acoustic mode (GAM) has been found in the large helical device (LHD), when the frequency of a chirping energetic particle-driven GAM (EGAM) approaches twice that of the GAM frequency. The temporal evolution of the phase relation between the abrupt GAM and the chirping EGAM is common in all events. The result indicates a coupling between the GAM and the EGAM. In addition, the nonlinear evolution of the growth rate of the GAM is observed, and there is a threshold in the amplitude of the GAM for the appearance of nonlinear behavior. A threshold in the amplitude of the EGAM for the abrupt excitation of the GAM is also observed. According to one theory (Lesur et al 2016 Phys. Rev. Lett. 116 015003, Itoh et al 2016 Plasma Phys. Rep. 42 418) the observed abrupt phenomenon can be interpreted as the excitation of the subcritical instability of the GAM. The excitation of a subcritical instability requires a trigger and a seed with sufficient amplitude. The observed threshold in the amplitude of the GAM seems to correspond with the threshold in the seed, and the threshold in the amplitude of the EGAM seems to correspond with the threshold in the magnitude of the trigger. Thus, the observed threshold supports the interpretation that the abrupt phenomenon is the excitation of a subcritical instability of the GAM..
27. K. Itoh, Sanae Itoh, Makoto Sasaki, Yusuke Kosuga, Effects of hydrogen isotope in coupling between confinement, wall material and SoL turbulence, Nuclear Fusion, 10.1088/1741-4326/aa65eb, 57, 5, 2017.03, The hydrogen isotope effect on confinement is discussed by investigating the coupling between confinement, wall material and scrape-off-layer (SoL) turbulence. An emphasis is placed upon the dependence of the neutral density on the hydrogen mass number. The momentum loss via CX process in the barrier is studied, and its influence on the radial electric field in the barrier (so as to modify the suppression of transport) is discussed. The penetration of slow neutrals and the reflection of fast neutrals on the wall are considered. Combining these processes, the influence of hydrogen mass number on the atomic, molecular, material and plasma interactions is investigated. The penetration of strong fluctuations in the SoL plasma into the confined plasma via the fuelling of neutral particles (i.e. fuelling fuels turbulence) is also discussed. The hydrogen isotope effect on this source of edge turbulence, which can affect the core-confinement, is discussed..
28. Yasuhiro Nariyuki, Makoto Sasaki, Naohiro Kasuya, Tohru Hada, Masatoshi Yagi, Phase coherence among the Fourier modes and non-Gaussian characteristics in the Alfven chaos system, Progress of Theoretical and Experimental Physics, 10.1093/ptep/ptx016, 2017, 3, 2017.03, Non-Gaussian characteristics in time series of the Alfven chaos system are discussed. The phase coherence index, a measure defined by using the surrogate data method and the structure function, is used to evaluate the phase coherence among the Fourier modes. Through Monte Carlo significance testing, it is found that the phase coherence decays monotonically with increasing dissipative parameter and time scale. By applying the Mori projection operator method assuming the Markov process, a model equation for the time correlation function is derived from the generalized Langevin equation. As opposed to the result of the phase coherence analysis, it is concluded that the difference between the direct numerical simulation and the model equation becomes pronounced as the dissipative parameters are increased. This suggests that, even when the phase coherence index is not significant, the underlying physical system may be a non-Gaussian process..
29. Makoto Sasaki, Naohiro Kasuya, K. Itoh, Yusuke Kosuga, M. Lesur, K. Hallatschek, Sanae Itoh, Toroidal momentum channeling of geodesic acoustic modes driven by fast ions, Nuclear Fusion, 10.1088/1741-4326/aa4eb4, 57, 3, 2017.03, Toroidal momentum channeling by fast ion-driven geodesic acoustic mode (EGAM) is proposed based on a quasi-linear analysis. We focus on a branch due to the magnetic drift resonance. Without the magnetic drift resonance, the eigenfunction of the EGAM has up-down anti-symmetric property in the poloidal direction, and the toroidal momentum flux by the EGAM is zero. If the magnetic drift resonance is considered, the up-down anti-symmetry in the poloidal eigenfunction is violated, and, as a result, the toroidal momentum flux becomes finite. Comparing its magnitude to the other processes such as external momentum input, and the turbulent residual stress, the momentum flux induced by the EGAM is found to be significant in the total momentum balance. This suggests that EGAMs can be used as a control knob for the toroidal rotation..
30. N. Dupertuis, S. Inagaki, Y. Nagashima, Y. Kosuga, F. Kin, T. Kobayashi, N. Kasuya, M. Sasaki, A. Fujisawa, M.Q. Tran, S.-I. Itoh and K. Itoh , Coexistence of drift waves and D'Angelo modes at different position and frequency in linear plasma device, Plasma and Fusion Research, 12, 1201008-1-1201008-3 , 2017.03.
31. M. Sasaki, Status and future plans of turbulence simulation on linear plasmas, 14th Burning Plasma Simulation Initiative (BPSI) Meeting (2016), 2016.12.
32. Makoto Sasaki, Naohiro Kasuya, K. Itoh, K. Hallatschek, M. Lesur, Yusuke Kosuga, Sanae Itoh, A branch of energetic-particle driven geodesic acoustic modes due to magnetic drift resonance, Physics of Plasmas, 10.1063/1.4963397, 23, 10, 2016.10, Eigenmode analysis of geodesic acoustic modes (GAMs) driven by fast ions is performed, based on a set of gyrokinetic equations. Resonance to the magnetic drift of the fast ions can destabilize GAMs. A new branch is found in the family of GAMs, whose frequency is close to the magnetic drift frequency of the fast ions. The poloidal eigenfunction of this branch has bump structures in the poloidal direction where the resonance of the magnetic drift with the mode is strong. The ion heating rate by the GAMs is evaluated in the framework of quasi-linear theory. The heating is localized poloidally around the resonance locations. Owing to the bumps in the eigenfunction, the magnitude of the heating is much larger than that estimated without the magnetic drift resonance..
33. T. Kobayashi, Inagaki Shigeru, Yusuke Kosuga, Makoto Sasaki, Yoshihiko Nagashima, Takuma Yamada, H. Arakawa, Naohiro Kasuya, akihide fujisawa, Sanae Itoh, K. Itoh, Structure formation in parallel ion flow and density profiles by cross-ferroic turbulent transport in linear magnetized plasma, Physics of Plasmas, 10.1063/1.4965915, 23, 10, 2016.10, In this paper, we show the direct observation of the parallel flow structure and the parallel Reynolds stress in a linear magnetized plasma, in which a cross-ferroic turbulence system is formed [Inagaki et al., Sci. Rep. 6, 22189 (2016)]. It is shown that the parallel Reynolds stress induced by the density gradient driven drift wave is the source of the parallel flow structure. Moreover, the generated parallel flow shear by the parallel Reynolds stress is found to drive the parallel flow shear driven instability D'Angelo mode, which coexists with the original drift wave. The excited D'Angelo mode induces the inward particle flux, which seems to help in maintaining the peaked density profile..
34. M. Sasaki, N. Kasuya, Y. Kosuga, K. Itoh, K. Hallatschek, M. Lesur, S.-I. Itoh, A new branch of geodesic acoustic modes driven by fast ions, 26th IAEA Fusion Energy Conference (FEC 2016), TH/P4-12, 2016.10.
35. Fumiyoshi Kin, Takuma Yamada, Inagaki Shigeru, Yoshihiko Nagashima, Hiroyuki Arakawa, Tatsuya Kobayashi, Yudai Miwa, Naohiro Kasuya, Makoto Sasaki, Yusuke Kosuga, akihide fujisawa, Kimitaka Itoh, Sanae Itoh, Changes of particle flux during end-plate biasing experiment in PANTA, Journal of the Physical Society of Japan, 10.7566/JPSJ.85.093501, 85, 9, 2016.09, Here we report changes in the turbulence spectrum and turbulence-driven particle flux during end-plate biasing experiments in a linear plasma. Outward radial flux driven by drift waves is decreased as the amplitude of the drift waves is reduced. During biasing, the cross-phase between potential and density fluctuations of mediator, which plays a key role in nonlinear interactions of turbulence, changed from negative to positive. Then the radial flux is induced reversal from inward to outward..
36. H. Arakawa, Inagaki Shigeru, Makoto Sasaki, Yusuke Kosuga, T. Kobayashi, Naohiro Kasuya, Yoshihiko Nagashima, Takuma Yamada, M. Lesur, akihide fujisawa, K. Itoh, Sanae Itoh, Eddy, drift wave and zonal flow dynamics in a linear magnetized plasma, Scientific Reports, 10.1038/srep33371, 6, 2016.09, Turbulence and its structure formation are universal in neutral fluids and in plasmas. Turbulence annihilates global structures but can organize flows and eddies. The mutual-interactions between flow and the eddy give basic insights into the understanding of non-equilibrium and nonlinear interaction by turbulence. In fusion plasma, clarifying structure formation by Drift-wave turbulence, driven by density gradients in magnetized plasma, is an important issue. Here, a new mutual-interaction among eddy, drift wave and flow in magnetized plasma is discovered. A two-dimensional solitary eddy, which is a perturbation with circumnavigating motion localized radially and azimuthally, is transiently organized in a drift wave-zonal flow (azimuthally symmetric band-like shear flows) system. The excitation of the eddy is synchronized with zonal perturbation. The organization of the eddy has substantial impact on the acceleration of zonal flow..
37. K. J. Zhao, Yoshihiko Nagashima, P. H. Diamond, J. Q. Dong, K. Itoh, Sanae Itoh, L. W. Yan, J. Cheng, akihide fujisawa, Inagaki Shigeru, Yusuke Kosuga, Makoto Sasaki, Z. X. Wang, L. Wei, Z. H. Huang, D. L. Yu, W. Y. Hong, Q. Li, X. Q. Ji, X. M. Song, Y. Huang, Yi Liu, Q. W. Yang, X. T. Ding, X. R. Duan, Synchronization of Geodesic Acoustic Modes and Magnetic Fluctuations in Toroidal Plasmas, Physical Review Letters, 10.1103/PhysRevLett.117.145002, 117, 14, 2016.09, The synchronization of geodesic acoustic modes (GAMs) and magnetic fluctuations is identified in the edge plasmas of the HL-2A tokamak. Mesoscale electric fluctuations (MSEFs) having components of a dominant GAM, and m/n=6/2 potential fluctuations are found at the same frequency as that of the magnetic fluctuations of m/n=6/2 (m and n are poloidal and toroidal mode numbers, respectively). The temporal evolutions of the MSEFs and the magnetic fluctuations clearly show the frequency entrainment and the phase lock between the GAM and the m/n=6/2 magnetic fluctuations. The results indicate that GAMs and magnetic fluctuations can transfer energy through nonlinear synchronization. Such nonlinear synchronization may also contribute to low-frequency zonal flow formation, reduction of turbulence level, and thus confinement regime transitions..
38. T. Kanzaki, Y. Nagashima, S. Inagaki, F. Kin, Y. Miwa, M. Sasaki, T. Yamada, A. Fujisawa, T. Kobayashi, N. Kasuya, Y. Kosuga, S.-I. Itoh, K. Itoh, Improvement of the Reynolds stress probe for end-plate biasing experiment in a cylindrical laboratory plasma, Plasma and Fusion Research: Rapid Communications, in press, 2016.05.
39. M. Lesur, K. Itoh, T. Ido, S.-I. Itoh, Y. Kosuga, M. Sasaki, S. Inagaki, M. Osakabe, K. Ogawa, A. Shimizu, K. Ida, Nonlinear excitation of subcritical fast ion-driven modes, Nuclear Fusion, 56, 056009-1-056009-14, 2016.04.
40. M. Lesur, K. Itoh, T. Ido, Sanae Itoh, Yusuke Kosuga, Makoto Sasaki, Inagaki Shigeru, M. Osakabe, K. Ogawa, A. Shimizu, K. Ida, Nonlinear excitation of subcritical fast ion-driven modes, Nuclear Fusion, 10.1088/0029-5515/56/5/056009, 56, 5, 2016.04, In collisionless plasma, it is known that linearly stable modes can be destabilized (subcritically) by the presence of structures in phase-space. The growth of such structures is a nonlinear, kinetic mechanism, which provides a channel for free-energy extraction, different from conventional inverse Landau damping. However, such nonlinear growth requires the presence of a seed structure with a relatively large threshold in amplitude. We demonstrate that, in the presence of another, linearly unstable (supercritical) mode, wave-wave coupling can provide a seed, which can lead to subcritical instability by either one of two mechanisms. Both mechanisms hinge on a collaboration between fluid nonlinearity and kinetic nonlinearity. If collisional velocity diffusion is low enough, the seed provided by the supercritical mode overcomes the threshold for nonlinear growth of phase-space structure. Then, the supercritical mode triggers the conventional subcritical instability. If collisional velocity diffusion is too large, the seed is significantly below the threshold, but can still grow by a sustained collaboration between fluid and kinetic nonlinearities. Both of these subcritical instabilities can be triggered, even when the frequency of the supercritical mode is rapidly sweeping. These results were obtained by modeling the subcritical mode kinetically, and the impact of the supercritical mode by simple wave-wave coupling equations. This model is applied to bursty onset of geodesic acoustic modes in an LHD experiment. The model recovers several key features such as relative amplitude, timescales, and phase relations. It suggests that the strongest bursts are subcritical instabilities, with sustained collaboration between fluid and kinetic nonlinearities..
41. S. Inagaki, T. Kobayahi, Y. Kosuga, T. Mitsuzono, Y. Nagashima, H. Arakawa, T. Yamada, Y. Miwa, N. Kasuya, M. Sasaki, M. Lesur, A. Fujisawa, K. Itoh, A Concept of Cross-Ferroic Plasma Turbulence, Scientific Reports, 6, 22189-1-22189-6, 2016.02.
42. K. Itoh, K. Zhao, J. Dong, S.-I. Itoh, A. Fujisawa, S. Inagaki, M. Sasaki, Y. Nagashima, Yusuke Kosuga, J. Cheng, T. Kobayashi, A Calibration of Setting of Mach Probes by Observing GAM Oscillations, Plasma and Fusion Research, 11, 1402002-1-1402002-4, 2016.02.
43. Inagaki Shigeru, T. Kobayashi, Yusuke Kosuga, Sanae Itoh, T. Mitsuzono, Yoshihiko Nagashima, H. Arakawa, Takuma Yamada, Y. Miwa, Naohiro Kasuya, Makoto Sasaki, M. Lesur, akihide fujisawa, K. Itoh, A Concept of Cross-Ferroic Plasma Turbulence, Scientific Reports, 10.1038/srep22189, 6, 2016.02, The variety of scalar and vector fields in laboratory and nature plasmas is formed by plasma turbulence. Drift-wave fluctuations, driven by density gradients in magnetized plasmas, are known to relax the density gradient while they can generate flows. On the other hand, the sheared flow in the direction of magnetic fields causes Kelvin-Helmholtz type instabilities, which mix particle and momentum. These different types of fluctuations coexist in laboratory and nature, so that the multiple mechanisms for structural formation exist in extremely non-equilibrium plasmas. Here we report the discovery of a new order in plasma turbulence, in which chained structure formation is realized by cross-interaction between inhomogeneities of scalar and vector fields. The concept of cross-ferroic turbulence is developed, and the causal relation in the multiple mechanisms behind structural formation is identified, by measuring the relaxation rate and dissipation power caused by the complex turbulence-driven flux..
44. T. Ido, K. Itoh, M. Osakabe, M. Lesur, A. Shimizu, K. Ogawa, K. Toi, M. Nishiura, S. Kato, M. Sasaki, K. Ida, S. Inagaki, S.-I. Itoh, Observation of strong destabilization of stable modes with a half frequency associated with chirping EGAMs in the LHD, Physical Review Letters, 116, 015002-1-015002-5, 2016.01.
45. M. Lesur, K. Itoh, T. Ido, M. Osakabe, K. Ogawa, A. Shimizu, M. Sasaki, K. Ida, S. Inagaki, S.-I. Itoh, Nonlinear excitation of subcritical instabilities in a toroidal plasma, Physical Review Letters, 116, 015003-1-015003-5, 2016.01.
46. Kimitaka Itoh, Kaijun Zhao, Jiaqi Dong, Sanae Itoh, akihide fujisawa, Inagaki Shigeru, Makoto Sasaki, Yoshihiko Nagashima, Yusuke Kosuga, Jun Cheng, Tatsuya Kobayashi, A calibration of setting of mach probes by observing GAM oscillations, Plasma and Fusion Research, 10.1585/pfr.11.1402002, 11, 2016.01, The influence of relative displacement of Mach probe (which is placed near the top of magnetic surface) on the interference of signals is discussed. An error can arise in measured value of poloidal electric field. The Mach number perturbation at the GAM frequency has an interference from the density perturbation. The interference from the density perturbation can propagate to all of Mach number measurement. By observing the signals associated with GAM oscillations, the error in setting the probe arrays can be detected. This result can be applied to correct the positioning of probes..
47. Tomotsugu Kanzaki, Yoshihiko Nagashima, Inagaki Shigeru, Fumiyoshi Kin, Yudai Miwa, Makoto Sasaki, Takuma Yamada, akihide fujisawa, Tatsuya Kobayashi, Naohiro Kasuya, Yusuke Kosuga, Sanae Itoh, Kimitaka Itoh, Improvement of the reynolds stress probe for end-plate biasing experiments in a cylindrical laboratory plasma, Plasma and Fusion Research, 10.1585/pfr.11.1201091, 11, 2016.01, We improved the signal-to-noise ratio of a Reynolds stress (RS) probe in order to measure the Reynolds stress more accurately. By introducing a shield pipe in the probe, the power spectral density of the noise was suppressed to approximately one tenth in an electric biasing experiment. It was also confirmed that the leak current in the RS probe, which had been used in previous experiments, was small enough for the study of drift waves in our linear device..
48. M. Lesur, K. Itoh, T. Ido, M. Osakabe, K. Ogawa, A. Shimizu, Makoto Sasaki, K. Ida, Inagaki Shigeru, Sanae Itoh, Nonlinear Excitation of Subcritical Instabilities in a Toroidal Plasma, Physical Review Letters, 10.1103/PhysRevLett.116.015003, 116, 1, 2016.01, In a collisionless plasma, it is known that linearly stable modes can be destabilized (subcritically) by the presence of structures in phase space. However, nonlinear growth requires the presence of a seed structure with a relatively large threshold in amplitude. We demonstrate that, in the presence of another, linearly unstable (supercritical) mode, wave-wave coupling can provide a seed, which is significantly below the threshold, but can still grow by (and only by) the collaboration of fluid and kinetic nonlinearities. By modeling the subcritical mode kinetically, and the impact of the supercritical mode by simple wave-wave coupling equations, it is shown that this new kind of subcritical instability can be triggered, even when the frequency of the supercritical mode is rapidly sweeping. The model is applied to the bursty onset of geodesic acoustic modes in a LHD experiment. The model recovers several key features such as relative amplitude, time scales, and phase relations. It suggests that the strongest bursts are subcritical instabilities, driven by this mechanism of combined fluid and kinetic nonlinearities..
49. T. Ido, K. Itoh, M. Osakabe, M. Lesur, A. Shimizu, K. Ogawa, K. Toi, M. Nishiura, S. Kato, Makoto Sasaki, K. Ida, Inagaki Shigeru, Sanae Itoh, Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device, Physical Review Letters, 10.1103/PhysRevLett.116.015002, 116, 1, 2016.01, Abrupt and strong excitation of a mode has been observed when the frequency of a chirping energetic-particle driven geodesic acoustic mode (EGAM) reaches twice the geodesic acoustic mode (GAM) frequency. The frequency of the secondary mode is the GAM frequency, which is a half-frequency of the primary EGAM. Based on the analysis of spatial structures, the secondary mode is identified as a GAM. The phase relation between the secondary mode and the primary EGAM is locked, and the evolution of the growth rate of the secondary mode indicates nonlinear excitation. The results suggest that the primary mode (EGAM) contributes to nonlinear destabilization of a subcritical mode..
50. T. Kobayashi, S. Inagaki, M. Sasaki, Y. Kosuga, H. Arakawa, T. Yamada, Y. Nagashima, Y. Miwa, N. Kasuya, A. Fujisawa, S.-I. Itoh, K. Itoh, Azimuthal inhomogeneity of turbulence structure and its impact on intermittent particle transport in linear magnetized plasmas, Physics of Plasmas, 22, 112301-1-112301-8, 2015.11.
51. H. Arakawa, S. Inagaki, M. Sasaki, K. Itoh, Sanae-I. Itoh, An application of Hadamard transform for plasma laser-induced fluorescence spectroscopy, Plasma and Fusion Research: Rapid Communications, 10, 1201085-1-1201085-3, Plasma and Fusion Research: Rapid Communications, 10, 1201085-1, 1201085-3 (2015), 2015.09.
52. 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, 10.1063/1.4916490, 22, 032315-1-032315-10, 22, 032315-1, 032315-10 (2015), 2015.03.
53. Fumiyoshi Kin, Takuma Yamada, Shigeru Inagaki, Hiroyuki Arakawa, Yoshihiko Nagashima, Naohiro Kasuya, Akihide Fujisawa, Kousuke Nakanishi, Hikaru Kono, Takaaki Mizokami, Makoto Sasaki, Maxime Lesur, Yusuke Kosuga, Kimitaka Itoh, Sanae-I. Itoh, Evaluation of Non-Linear Mode Coupling During End-Plate Biasing Experiment in PANTA, Plasma and Fusion Research, 10, 3401043-1-3401043-4, 10 3401043-1, 3401043-4 (2015), 2015.03.
54. Makoto Sasaki, Naohiro Kasuya, Kimitaka Itoh, Takuma Yamada, Masatoshi Yagi, Sanae-I. Itoh, Steep wave front of drift waves in linear magnetized plasmas, 12th Burning Plasma Simulation Initiative (BPSI) Meeting, 2-4, 2014.12.
55. 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, 114009, 2014.11.
56. Makoto Sasaki, Naohiro Kasuya, Kimitaka Itoh, Maxime Lesur, Sanae-I. Itoh, Non-equilibrium and extreme state -Heating effect on bulk ions by energetic particle driven GAMs-, Plasma Conference, 21aC1-5-1-21aC1-5-2, 2014.11.
57. Makoto Sasaki, Naohiro Kasuya, Kimitaka Itoh, Masatoshi Yagi, Sanae-I. Itoh, Dynamical response of turbulent structures in cylindrical magnetized plasmas, JPS Conference Proceedings, 1, 015011 (2014) , 2014.03.
58. Takuma Yamada, Inagaki Shigeru, Tatsuya Kobayashi, Yoshihiko Nagashima, Tomohiro Mitsuzono, Yudai Miwa, Hiromitsu Fujino, Makoto Sasaki, Naohiro Kasuya, Maxime Lesur, Yusuke Kosuga, Akihide Fujisawa, SANAE INOUE ITOH, Kimitaka Itoh, End plate biasing experiments in linear magnetized plasmas, Nuclear Fusion, in press, 2014.02.
59. Inagaki Shigeru, Miwa Yudai, Kobayashi Tatsuya, Takuma Yamada, Yoshihiko Nagashima, Hiromitsu Fujino, Makoto Sasaki, Naohiro Kasuya, Maxime Lesur, Yusuke Kosuga, Akihide Fujisawa, SANAE INOUE ITOH, Kimitaka Itoh, Identification of Quasi-Periodic Nonlinear Waveforms in Turbulent Plasmas, Plasma and Fusion Research: Rapid Communications, 9, 1201016 (2014), 2014.01.
60. 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], A nonlinear simulation of resistive drift wave turbulence in a cylindrical plasma is carried out. Long time evolution of turbulence with formation of a zonal flow is obtained for more than 1000 times of the typical drift wave period, which is sufficient for statistical analyses. Dynamical particle and momentum balance for the formation of the mean reveals that the radial turbulent fluxes are dominant contributors for the evolution of fluctuations. The particle flux is found to precede the momentum flux for 0.4 times of the typical drift wave period with large temporal variance. The analyses of the time series data of 3-D fields give the understanding of the dynamical structural formation mechanism..
61. Yudai Miwa, Naohiro Kasuya, Makoto Sasaki, Inagaki Shigeru, Kimitaka Itoh, MASATOSHI YAGI, Akihide Fujisawa, Yoshihiko Nagashima, Maxime Lesur, Tatsuya Kobayashi, Soutaro Yamada, Tetsuo Yamashita, Satoshi Ootsubo, Shinsuke Kakigawa, Tomohiro Mitsuzono, Hirofumi Fujino, SANAE INOUE ITOH, Evaluation of Excitation Conditions of ITG Modes in the PANTA, Plasma and Fusion Research, 8, 2403133 (2013), 2013.09, To study the nonlinear saturation mechanism in turbulent plasmas, we plan to obseve ion temperature gra- dient (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..
62. Inagaki Shigeru, Kimitaka Itoh, Takuma Yamada, SANAE INOUE ITOH, Tokihiko Tokuzawa, Akihide Fujisawa, Naohiro Kasuya, Makoto Sasaki, Yoshihiko Nagashima, Hiroyuki Arakawa, Measurement of Dynamical Density Profiles Using a Microwave Frequency Comb Reflectometer, Plasma and Fusion Research: Rapid Communication, 8, 1201171 (2013), 2013.09.
63. Naohiro Kasuya, Satoru Sugita, Makoto Sasaki, Inagaki Shigeru, Masatoshi Yagi, Kimitaka Itoh, SANAE INOUE(論文のみ) ITOH, Evaluation of Spatial Variation of Nonlinear Energy Transfer by Use of Turbulence Diagnostic Simulator, Plasma and Fusion Research, 8, 2403070-1-2403070-5, 8, 2403070 (2013), 2013.05.
64. T. Yamada, M. Sasaki, N. Kasuya, Y. Nagashima, S. Inagaki, T. Kobayashi, M. Yagi, A. Fujisawa, A. Fujisawa, S.-I. Itoh and K. Itoh, Streamer Structures in Experiment and Modeling, Plasma Fusion Research, 8, 2401022-1-2401022-5, 8, 2401022 (2013), 2013.03.
65. 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.
66. N. Teplova, K. Itoh, S.- I. ITOH, E. Gusakov, S. Heuraux, Inagaki Shigeru, M. Sasaki, T. Kobayashi, Yoshihiko Nagashima, STELLA OLDENBURGER, Akihide Fujisawa, On turbulence-correlation analysis based on correlation reflectometry, Physica Scripta, 87, 045502 (2013) , 2013.02, [URL], 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..
67. T. Kobayashi, S. Inagaki, S. Oldenbürger, K. Kawashima, N. Ohyama, Y. Tobimatsu, H. Arakawa, M. Sasaki, Y. Nagashima, T. Yamada, S. Sugita, M. YAgi, N. Kasuya, A. Fujisawa, S.-I. Itoh, K. Itoh, Time Evolution of Power Spectrum Density in Spontaneous Transition in Cylindrical Magnetized Plasma, Plasma Fusion Research, 7, 2401054, (2012) 7, 2401054, 2012.06.
68. 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, Observations of intermittent structures in the periphery of cylindrical linear plasma in PANTA, Plasma and Fusion Research, 7, 1201025, 2012.02.
69. M. Sasaki, K. Itoh, S.-I. Itoh and N. Kasuya, Zonal flows induced by symmetry breaking with existence of geodesic acoustic modes, Nuclear Fusion, 10.1088/0029-5515/52/2/023009, 52, 023009, 2012.01, [URL], The nonlinear dynamics of zonal flows (ZFs) is investigated when geodesic acoustic modes (GAMs) have substantial influence on plasma states. Simultaneous existence of multiple GAMs with different radial phase velocities gives additional nonlinear mode couplings, and asymmetry of the turbulence spectrum induces energy exchanges between GAMs and a ZF. A set of model equations is derived to describe the nonlinear dynamics of a ZF, GAMs and ambient turbulence. The model includes the mechanism of ZF generation by a pair of GAMs, and the back interaction from the turbulence is solved self-consistently. Two stationary solutions are obtained; one is the known solution that the GAM propagates as a travelling wave with no ZF excitation, and the other is a new solution that a pair of GAMs forms a standing wave, which induces a ZF. The accessibility to the steady states, and the threshold for the transition between them are obtained. The GAM and ZF formation in the new state affects the background plasmas. The effects on the turbulent heat diffusivity and the ion heating rate are discussed..
70. Sasaki Makoto, Nonlinear processes of zonal flows near a plasma edge, Plasma Conference 2011, 24D07, 2011.11.
71. Katsuyuki KAWASHIMA, Yasuhiro MIYOSHI, STELLA OLDENBURGER, Inagaki Shigeru, Hiroyuki ARAKAWA, Yoshihiko Nagashima, Takuma YAMADA, Makoto Sasaki, Tatsuya KOBAYASHI, Kazuya URIU, Satoru SUGITA, MASATOSHI YAGI, Naohiro KASUYA, Akihide Fujisawa, SANAE INOUE ITOH, Kimitaka ITOH, Evaluation of Electron Temperature Fluctuations Using Two Different Probe Techniques in Plasma Assembly for Nonlinear Turbulence Analysis (PANTA), Plasma Fusion Research, 6, 2406118, 2011.06.
72. 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, 10.1088/0741-3335/53/8/085017, 53, 085017-1-085017-11, 2011.06, [URL].
73. T. Kobayashi, Y. Nagashima, Inagaki Shigeru, H. Arakawa, Makoto Sasaki, T. Yamada, MASATOSHI YAGI, N. Kasuya, Akihide Fujisawa, SANAE INOUE(論文のみ) ITOH, K. Itoh, Method for Estimating the Wavenumber of Standing Waves Using Three Langmuir Probes, Plasma and Fusion Research, 6, 1401050-1-1401050-5, 6, 1401050 (2011), 2011.05.
74. 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, Observation of Nonlinear Coupling between Low Frequency Coherent Modes and Background Turbulence in LMD-U, Plasma Fusion Res, 6, 2401082, 2011.05.
75. T Kobayashi, S Inagaki, S-I Itoh, K Ida, S Oldenbürger, H Tsuchiya, Y Nagayama, K Kawahata, H Yamada, M Sasaki, A Fujisawa, K Itoh and the LHD Experiment Group, Verification of wavelet analysis for a heat pulse propagation experiment, Plasma Phys. Control. Fusion, 53, 095012, 2011.04.
76. J.Sugiyama, A.Ejiri, Y.Takase, O.Watanabe, Y.Adachi, H.Tojo, M.Sasaki, T.Masuda, T.Oosako, S.Kainaga, Electron Cyclotron Heating Start-Up Experiments on TST-2, Plasma and Fusion Research, 3, 026, 2011.04.
77. T. Kobayashi, Y. Nagashima, S. Inagaki, H. Arakawa, M. Sasaki, T. Yamada, M. Yagi, N. Kasuya, A. Fujisawa, S-I. Itoh, K. Itoh, A method to estimate a wave number for standing waves using three Langmuir probes, Plasma Fusion Research, 2011.04.
78. Makoto Sasaki, Kimitaka Itoh, SANAE INOUE(論文のみ) ITOH, Masatoshi Yagi, Akihide Fujisawa, Dynamics of low frequency zonal flow driven by geodesic acoustic modes, 23rd IAEA Fusion Energy Conference, THC/6-2Rb, 2010.10, [URL].
79. 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.
80. T. Oosako, Y. Takase, A. Ejiri, Y. Nagashima, Y. Adachi, H. Kasahara, T. Yamada, O. Watanabe, H. Tojo, S. Kainaga, J. Sugiyama, T. Yamaguchi, B. An, H. Hayashi, H. Kobayashi, H. Kurashina, H. Matsuzawa, K. Yamada, R. Kumazawa, F. Shimpo, Y. Ono, T. Masuda, M. Sasaki, Parametric decay instability during high harmonic fast wave heating experiments on the TST-2 spherical tokamak, NUCLEAR FUSION, 10.1088/0029-5515/49/6/065020, 49, 6, 065020-1-065020-6, 49, 065020 (2009) , 2009.06.
81. A. Ejiri, Y. Takase, T. Oosako, T. Yamaguchi, Y. Adachi, O. Watanabe, Y. Nagashima, B. I. An, H. Kobayashi, H. Kurashina, H. Hayashi, H. Matsuzawa, K. Yamada, H. Tojo, T. Masuda, M. Sasaki, R. Kumazawa, H. Kasahara, F. Shimpo, Non-inductive plasma current start-up by EC and RF power in the TST-2 spherical tokamak, Nucl. Fusion, 49, 065010-1-065010-12, 49, 065010 (2009), 2009.05.
82. H. Tojo, A. Ejiri, Y. Takase, Y. Nagashima, O. Watanabe, Y. Adachi, T. Oosako, T. Yamaguchi, B. I. An, H. Kobayashi, H. Kurashina, H. Matsuzawa, K. Yamada, M. Sasaki, T. Masuda, Phase Alignments between MHD Modes Followed by Minor Collapses on TST-2, Plasma and Fusion Research: Rapid Communications, 4, 015-1-015-3, 4, 015 (2009), 2009.02.
83. 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.
84. 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.
85. Osamu WATANABE, Akira EJIRI, Takashi YAMAGUCHI, Junichi SUGIYAMA, Takuya OOSAKO, Yuuki ADACHI, Kotaro YAMADA, Hiroshi TOJO, Soichiro KAINAGA, Yuichi TAKASE, Yoshihiko NAGASHIMA, Makoto SASAKI and Tetsuya MASUDA, Plasma Current Sustainment by RF Power in ECH Start-up Plasma in the TST-2 Spherical Tokamak, Plasma and Fusion Research, 3, 049, 2008.06.
86. Y. Adachi, A. Ejiri, Y. Takase, O. Watanabe, T. Oosako, H. Tojo, S. Kainaga, T. Masuda, M. Sasaki, J. Sugiyama, and T. Yamaguchi, Detection of a New PDI Branch in TST-2 during High Harmonic Fast WaveHeating, Review of Scientific Instruments, 79, 10F507, 2008.06.
87. M. Sasaki, K. Itoh, A. Ejiri, Y. Takase, Modification of Symmetry of Poloidal Eigenmode of Geodesic Acoustic Modes, Plasma Fusion Research Volume, 3, 009, 009-1,009-8 (2008), 2008.05.
88. S.Kainaga, A.Ejiri, Y.Takase, O.Watanabe, Y.Adachi, T.Oosako, M.Sasaki, H.Tojo, T.Masuda, J.Sugiyama, T.Yamaguchi, Development of a compact Thomson scattering system for the TST-2 spherical tokamak, Plasma and Fusion Research, 3, 027, 2008.04.
89. M. Sasaki, K. Itoh, A. Ejiri, Y. Takase, Geodesic acoustic modes in multi-ion system, Plasma and Fusion Research, 3 , S1017, 3 S1017-1,S1017-4 (2008), 2008.02.
90. S-I. Itoh, K. Itoh, M. Sasaki, A. Fujisawa, T. Ido, Y. Nagashima, Geodesic Acoustic Mode Spectroscopy, Plasma Phys. Control. Fusion, 49, L7-L10, 2007.07, [URL].
91. H. TOJO, A. EJIRI, Y. TAKASE, Y. TORII, T. OSAKO, M. SASAKI, T. MASUDA, Y. SHIMADA, N. SUMITOMO, J. TSUJIMURA, H. NUGA, S. KAINAGA, Soft X-ray Emission Profile and Mode Structure During MHD Events in the TST-2 Spherical Tokamak, Plasma and Fusion Research, 2, S1065, 2007.04.
92. Yuki TORII, Akira EJIRI, Tetsuya MASUDA , Takuya OOSAKO, Makoto SASAKI , Hiroshi TOJO , Hideo NUGA, Yoshiyuki SHIMADA, Nobuyuki SUMITOMO, Jiro TSUJIMURA, Soichiro KAINAGA, Junichi SUGIYAMA and Yuichi TAKASE, First Observation of RF-Induced Visible Light Fluctuations, Plasma and Fusion Research, 2, 023, 2007.04.
93. T.YAMADA, A.EJIRI, Y.SHIMADA, T.OOSAKO, J.TSUJIMURA, Y.TAKASE, Y.TORII, M.SASAKI, H.TOJO, T.MASUDA, H.NUGA, N.SUMITOMO, S.KAINAGA, J.SUGIYAMA, Reflectometry for Density Fluctuation and Profile Measurements in TST-2, Plasma and Fusion Research, 2, S1037, 2007.03.
94. A. Ejiri, T. Oosako, J. Tsujimura, Y. Takase, Y. Torii, M. Sasaki, H. Tojo, T. Masuda, H. Nuga, N. Sumitomo, S. Kainaga, J. Sugiyama, N. Tsujii, ECH and HHFW start-up experiments on the TST-2 spherical tokamak, Fusion science and technology, 168-170, 51 , 2007.02.
95. Takase, Y.; Ejiri, A.; Shiraiwa, S.; Adachi, Y.; Ishii, N.; Kasahara, H.; Nuga, H.; Ono, Y.; Oosako, T.; Sasaki, M.; Shimada, Y.; Sumitomo, N.; Taguchi, I.; Tojo, H.; Tsujimura, J.; Ushigome, M.; Yamada, T.; Hanada, K.; Hasegawa, M.; Idei, H.; Nakamura, K.; Sakamoto, M.; Sasaki, K.; Sato, K. N.; Zushi, H.; Nishino, N.; Mitarai, O., Plasma current start-up experiments without the central solenoid in the TST-2 spherical tokamak, Nuclear Fusion, 10.1088/0029-5515/46/8/S05, 46, 8, S598-S602, 2006.08.