| 山田 琢磨（やまだ たくま） | データ更新日：2023.11.28 |
教授 ／
基幹教育院
自然科学実験系部門
| 1. | A. Fujisawa, N. Kasuya, Y. Kosuga, Y. Nagashima, M. Sasaki, T. Yamada, Sanae‑Inoue Itoh 1952–2019: a memorial note for a pioneer researcher of plasma bifurcation, Reviews of Modern Plasma Physics, 7, 21, 2023.05. |
| 2. | 藤原なつみ, 山田琢磨, 古屋謙治, 巣山慶太郎, 山崎博史, 山中隆志, 「実験で学ぶ自然科学」の授業実践 リベラルサイエンス講義に向けた検討, 基幹教育紀要, 9, 125-140, 2023.02. |
| 3. | Y. Nagashima, A. Fujisawa, K. Yamasaki, S. Inagaki, C. Moon, F. Kin, Y. Kawachi, H. Arakawa, T. Yamada, T. Kobayashi, N. Kasuya, M. Sasaki, T. Ido, A Proposal to Evaluate Electron Temperature and Electron Density Fluctuations Using Dual Wavelength Emission Intensity Tomography in a Linear Plasma, Journal of the Physical Society of Japan, 10.7566/JPSJ.92.033501, 92, 033501-033501, 2023.02. |
| 4. | Y. Kawachi, M. Sasaki, Y. Kosuga, K. Terasaka, T. Nishizawa, T. Yamada, N. Kasuya, C. Moon, S. Inagaki, Spatiotemporal dynamics of high-wavenumber turbulence in a basic laboratory plasma, Scientific Reports, 10.1038/s41598-022-23559-1, 12, 19799-19799, 2022.12. |
| 5. | H. Arakawa, M. Sasaki, S. Inagaki, M. Lesur, Y. Kosuga, T. Kobayashi, F. Kin, T. Yamada, Y. Nagashima, A. Fujisawa, K. Itoh, Formation Process of a Solitary Vortex in a Zonal Flow - Drift-Wave Dynamics, Plasma and Fusion Research, 10.1585/pfr.17.1301106, 17, 1301106-1301106, 2022.05. |
| 6. | Y. Kawachi, S. Inagaki, M. Sasaki, Y. Kosuga, K. Yamasaki, T. Kobayashi, F. Kin, T. Yamada, H. Arakawa, Y. Nagashima, C. Moon, N. Kasuya, A. Fujisawa, Dynamic interaction between fluctuations with different origins in a linear magnetized plasma, Physics of Plasmas, doi: 10.1063/5.0065887, 28, 11, 112302, 2021.11. |
| 7. | M. Sasaki, H. Arakawa, T. Kobayashi, F. Kin, Y. Kawachi, T. Yamada, K. Itoh, Interactions of drift wave turbulence with streamer flows in wave-kinetic formalism, PHYSICS OF PLASMAS, 10.1063/5.0059839, 28, 10, 102304, 2021.10. |
| 8. | T. Ido, A. Fujisawa, K. Takemura, T.-K. Kobayashi, D. Nishimura, N. Kasuya, A. Fukuyama, C. Moon, K. Yamasaki, S. Inagaki, Y. Nagashima, and T. Yamada, Conceptual design of heavy ion beam probes on the PLATO tokamak, Review of Scientific Instruments , 10.1063/5.0041814, 92, 053553, 2021.05. |
| 9. | 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, Modal polarization analysis using Fourier-rectangular function transform in a cylindrical plasma, JOURNAL OF APPLIED PHYSICS, 10.1063/5.0037352, 129, 9, 093301, 2021.03. |
| 10. | T.-K. Kobayashi, A. Fujisawa, Y. Nagashima, C. Moon, K. Yamasaki, D. Nishimura, S. Inagaki, T. Yamada, N. Kasuya, Y. Kosuga, M. Sasaki and Y Kawachi, Correlation-estimated conditional average method and its application on solitary oscillation in PANTA, PLASMA PHYSICS AND CONTROLLED FUSION, 10.1088/1361-6587/abd980, 63, 3, 032001, 2021.03. |
| 11. | C. Moon, K. Yamasaki, Y. Nagashima, S. Inagaki, T. Ido, T. Yamada, N. Kasuya, Y. Kosuga, M. Sasaki, Y. Kawachi, D. Nishimura, T. Kobayashi, and A. Fujisawa, The first observation of 4D tomography measurement of plasma structures and fluctuations, SCIENTIFIC REPORTS, 10.1038/s41598-021-83191-3, 11, 1, 3720, 2021.02. |
| 12. | Y. Nagashima, A. Fujisawa, K. Yamasaki, S. Inagaki, C. Moon, F. Kin, Y. Kawachi, H. Arakawa, T. Yamada, T. Kobayashi, N. Kasuya, Y. Kosuga, M. Sasaki and T. Ido, Comparison between Tomography and Langmuir Probe Data in PANTA, JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN, 10.7566/JPSJ.89.093501, 89, 9, 093501, 2020.09. |
| 13. | Y. Kawachi, S. Inagaki, F. Kin, K. Yamasaki, Y. Kosuga, M. Sasaki, Y. Nagashima, T. Yamada, H. Arakawa, N. Kasuya, C. Moon, K. Hasamada and A. Fujisawa, Observation of spatiotemporal structures of temperature fluctuations by using of a statistical phase detection method in a linear magnetized plasma, PLASMA PHYSICS AND CONTROLLED FUSION, 10.1088/1361-6587/ab8132, 62, 5, 055011, 2020.05. |
| 14. | K. Yamasaki, A. Fujisawa, Y. Nagashima, C. Moon, S. Inagaki, T. Yamada, Tomography system for two-dimensional observation of fluctuation in magnetized plasma, Review of Scientific Instruments, 10.1063/1.5144480, 91, 3, 033502, 2020.03, [URL], A tomography system is developed for observing local fluctuations, pursuing higher spatial resolution, over the entire plasma of a linear cylindrical plasma. The system is equipped with totally 126 lines-of-sight that are distributed equally to six sets of light guide arrays placed around the plasma. The system has succeeded in measuring the two-dimensional structure of plasma emission and resolving coherent fluctuation structures, with spatial resolution comparable to the ion Larmor radius.. |
| 15. | Makoto Sasaki, Naohiro Kasuya, Yusuke Kosuga, Tatsuya Kobayashi, Takuma Yamada, Hiroyuki Arakawa, Shigeru Inagaki and Kimitaka Itoh, Turbulence Simulation on Zonal Flow Formations in the Presence of Parallel Flows, Plasma and Fusion Research, 10.1585/pfr.14.1401161, 14, 1401161, 2019.10. |
| 16. | Boyu Zhang, Shigeru Inagaki, Kazunobu Hasamada, Kotaro Yamasaki, Fumiyoshi Kin, Yoshihiko Nagashima, Takuma Yamada, Akihide Fujisawa, Study of turbulence intermittency in linear magnetized plasma, Plasma Physics and Controlled Fusion, 10.1088/1361-6587/ab434f, 61, 11, 115010, 2019.10, [URL], The intermittent behavior of a quasi-coherent density fluctuation is observed in a laboratory plasma. The quasi-coherent fluctuation is localized but intermittent events are observed in the whole region of plasma. Conditional averaging shows the intermittent events propagate from the central region of the magnetized plasma column to the peripheral region. Auto-correlation function of fluctuations and Hurst analysis reveal the intermittency is highly auto-correlated and the Hurst parameter reaches to 0.8, indicating the existence of self-similar behavior and long-range time correlation, and self-organized criticality dynamics might be the mechanism. Cross-bicoherence between different radii shows the nonlinear coupling between the quasi-coherent fluctuation and ambient turbulence, which will contribute to the generation of intermittency of turbulence.. |
| 17. | K. Yamasaki, A. Fujisawa, Y. Nagashima, C. Moon, S. Inagaki, N. Kasuya, Y. Kosuga, M. Sasaki, T. Yamada, Fourier-rectangular function analysis for cylindrical plasma images, Journal of Applied Physics, 10.1063/1.5108717, 126, 4, 043304, 2019.07, [URL], An analysis method is developed for imaging measurement systems, such as the tomography system or fast camera imaging, in order to extract the spatial structure properties of fluctuation. In this analysis method, rectangular functions and Fourier series are adopted for the basis functions of the radial and azimuthal coordinates, respectively. The examples of this analysis method show that this method is useful for quantifying the spatial structure of the 2D image such as the radial profile of the power and the rotation angle of each azimuthal mode. The method proposed in this article allows us to elucidate the features of the 2D spatial structure of phenomena in magnetized plasma.. |
| 18. | Hirotyuki Arakawa, Shigeru Inagaki, Yusuke Kosuga, Makoto Sasaki, Fumiyoshi Kin, Kazunobu Hasamada, Kotaro Yamasaki, Tatsuya Kobayashi, Takuma Yamada, Yoshihiko Nagashima, Akihide Fujisawa, Naohiro Kasuya, Kimitaka Itoh, Sanae I. Itoh, Ion temperature measurement by laser-induced fluorescence spectroscopy in panta, IEEJ Transactions on Electrical and Electronic Engineering, 10.1002/tee.22962, 14, 10, 1450-1454, 2019.07, [URL], A laser-induced fluorescence spectroscopy system was developed in a linear magnetized helicon plasma at Kyushu University. The thermal Doppler broadening on velocity distribution function follows the Maxwell distribution, and the averaged central ion temperature was evaluated to be ∼0.36 eV. The effect of Zeeman splitting was observed for a more accurate assessment of the measurement and is consistent with the calculation. The temperature ratio of electrons and ions, Ti/Te, was evaluated to be ∼0.1. The result is valuable for evaluating the nonlinear processes of the plasma turbulence.. |
| 19. | H. Arakawa, M. Sasaki, S. Inagaki, Y. Kosuga, T. Kobayashi, N. Kasuya, T. Yamada, Y. Nagashima, F. Kin, A. Fujisawa, K. Itoh, S. I. Itoh, Roles of solitary eddy and splash in drift wave-zonal flow system in a linear magnetized plasma, Physics of Plasmas, 10.1063/1.5094577, 26, 5, 052305, 2019.05, [URL], 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.. |
| 20. | Yuichi Kawachi, Sigeru Inagaki, Kazunobu Hasamada, Kotaro Yamasaki, Fumiyoshi Kin, Yusuke Kosuga, Makoto Sasaki, Yoshihiko Nagashima, Naohiro Kasuya, Takuma Yamada, Boyu Zhang, Akihide Fujisawa, Estimation of particle flux driven by coherent mode using of statistical conditional averaging, Plasma and Fusion Research, 10.1585/PFR.14.1402090, 14, 1402090, 2019.05, [URL], We proposed a new method to evaluate particle flux in magnetized turbulent plasma. To extract fundamental fluctuation pattern, we used template method which is a kind of statistical conditional averaging technique. The method allows as not only to extract coherent patterns of density and potential fluctuations but also to evaluate time delay between them. We succeeded to calculate particle flux driven by fluctuation pattern and observed this pattern drives inward particle flux. Result obtained by the method is in good agreement with that obtained by a conventional method.. |
| 21. | 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, Observations of radially elongated particle flux induced by streamer in a linear magnetized plasma, Physics of Plasmas, 10.1063/1.5093218, 26, 4, 2019.04, [URL], 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.. |
| 22. | akihide fujisawa, Yoshihiko Nagashima, K. Yamasaki, Inagaki Shigeru, Takuma Yamada, Makoto Sasaki, Combined methods of moment vectors and Stokes parameters to analyze tomographic image of plasma turbulence, Physics of Plasmas, 10.1063/1.5048970, 26, 1, 2019.01, [URL], 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.. |
| 23. | Kimitaka Itoh, Sanae I. Itoh, Yoshihiko Nagashima, Takuma Yamada, Yusuke Kosuga, Akihide Fujisawa, Symmetry-breaking of turbulence structure and position identification in toroidal plasmas, Plasma and Fusion Research, 10.1585/PFR.13.1102113, 13, 1102113, 2018.10, [URL], As a result of the progresses in the study of plasma turbulence, the picture of 'multiple-scale turbulence' is widely accepted, and the 'nonlinear excitation, nonlocal interaction, probabilistic transition' views have been developed. Along the paths of these progresses, importance of new problem, i.e., the symmetry-breaking of turbulence structure (such as up-down asymmetry, excitation of streamer, etc.) is gradually recognized. In this topical review article, we revisit these issues, and illuminate the possibilities that the new progresses (which will be brought about by studying the symmetry-breaking of turbulence) are expected. Examining theoretical predictions and preceding experimental achievements, new advancements, which will be realized, are explained. The experimental study of symmetry-breaking of turbulence structure ultimately requires to measure fluctuations (at all scales) over the whole plasma cross-section simultaneously. In addition, new type of demands can be imposed in measuring of fluctuations over the whole plasma cross-section simultaneously. One of such demands is the accuracy of the measurement position. Problems in this aspect are also discussed. This concise review is used to identify what will be discovered and how it will be reached in future experiments, in the subject of the symmetry-breaking of turbulence structure.. |
| 24. | 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, Extraction of nonlinear waveform in turbulent plasma, Physics of Plasmas, 10.1063/1.5027124, 25, 6, 2018.06, [URL], 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.. |
| 25. | 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, 034501, 2018.02, [URL], 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.. |
| 26. | S. Kamio, M. Inomoto, K. Yamasaki, Takuma Yamada, C. Z. Cheng, Y. Ono, Magnetic island dynamics in magnetic reconnection in UTST experiments, Physics of Plasmas, 10.1063/1.5006092, 25, 1, 012126, 2018.01, [URL], The dynamics of the magnetic island formed inside the reconnection current layer was investigated under the strong guide field in the UTST spherical tokamak merging experiment. A pair of proximately located O- and X-points was generated at ∼5 cm away from the other X-point. The formed O- and X-points immediately started to move toward the downstream region inside the current layer, but the O-point had larger velocity and caught up the preceding X-point within 0.5 μs. The results from Doppler spectroscopy indicated that the ion flow velocity had the intermediate value between the O- and X-point velocities, suggesting that the ions flowed with approximately the same velocity with the magnetic island.. |
| 27. | Kimitaka Itoh, Sanae Itoh, Yoshihiko Nagashima, Takuma Yamada, akihide fujisawa, Position identification of measurement for the study of symmetry-breaking of turbulence structure in toroidal plasmas, Journal of the Physical Society of Japan, 10.7566/JPSJ.87.025002, 87, 2, 025002, 2018.01, [URL], In order to understand the plasma turbulence, experimental studies on the subject of “symmetry-breaking of turbulence structure” has been designed recently. The accuracy of the position identification, which is required for such experimental studies, is analyzed. Possible approach to fulfill the demands is discussed.. |
| 28. | 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, 112103, 2017.11, [URL], 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.. |
| 29. | Makoto Sasaki, Naohiro Kasuya, Shinichiro Toda, Takuma Yamada, Yusuke Kosuga, Hiroyuki Arakawa, Tatsuya Kobayashi, Shigeru Inagaki, Akihide Fujisawa, Yoshihiko Nagashima, Kimitaka Itoh and Sanae-I. Itoh, Multiple-Instabilities in Magnetized Plasmas with Density Gradient and Velocity Shears, Plasma and Fusion Research, 10.1585/pfr.12.1401042, 12, 1401042, 2017.10. |
| 30. | A. Kirk, J. Adamek, R. J. Akers, S. Allan, L. Appel, F. Arese Lucini, M. Barnes, T. Barrett, N. Ben Ayed, W. Boeglin, J. Bradley, P. K. Browning, J. Brunner, P. Cahyna, S. Cardnell, M. Carr, F. Casson, M. Cecconello, C. Challis, I. T. Chapman, S. Chapman, J. Chorley, S. Conroy, N. Conway, W. A. Cooper, M. Cox, N. Crocker, B. Crowley, G. Cunningham, A. Danilov, D. Darrow, R. Dendy, D. Dickinson, W. Dorland, B. Dudson, D. Dunai, L. Easy, S. Elmore, M. Evans, T. Farley, N. Fedorczak, A. Field, G. Fishpool, I. Fitzgerald, M. Fox, S. Freethy, L. Garzotti, Y. C. Ghim, K. Gi, Takuma Yamada, Overview of recent physics results from MAST, Nuclear Fusion, 10.1088/1741-4326/aa65e0, 57, 10, 102007, 2017.06, [URL], New results from MAST are presented that focus on validating models in order to extrapolate to future devices. Measurements during start-up experiments have shown how the bulk ion temperature rise scales with the square of the reconnecting field. During the current ramp-up, models are not able to correctly predict the current diffusion. Experiments have been performed looking at edge and core turbulence. At the edge, detailed studies have revealed how filament characteristics are responsible for determining the near and far scrape off layer density profiles. In the core the intrinsic rotation and electron scale turbulence have been measured. The role that the fast ion gradient has on redistributing fast ions through fishbone modes has led to a redesign of the neutral beam injector on MAST Upgrade. In H-mode the turbulence at the pedestal top has been shown to be consistent with being due to electron temperature gradient modes. A reconnection process appears to occur during edge localized modes (ELMs) and the number of filaments released determines the power profile at the divertor. Resonant magnetic perturbations can mitigate ELMs provided the edge peeling response is maximised and the core kink response minimised. The mitigation of intrinsic error fields with toroidal mode number n > 1 has been shown to be important for plasma performance.. |
| 31. | Tatsuya Kobayashi, Inagaki Shigeru, Yusuke Kosuga, Makoto Sasaki, Yoshihiko Nagashima, Takuma Yamada, Hiroyuki Arakawa, Naohiro Kasuya, Akihide Fujisawa, SANAE INOUE（論文のみ） ITOH, Kimitaka Itoh, Phenomenological Classification of Turbulence States in Linear Magnetized Plasma PANTA, Plasma and Fusion Research, 10.1585/pfr.12.1401019, 12, 1401019, 2017.05. |
| 32. | H. Tanabe, Takuma Yamada, T. Watanabe, K. Gi, M. Inomoto, R. Imazawa, M. Gryaznevich, R. Scannell, N. J. Conway, C. Michael, B. Crowley, I. Fitzgerald, A. Meakins, N. Hawkes, K. G. McClements, J. Harrison, T. O'Gorman, C. Z. Cheng, Y. Ono, Investigation of merging/reconnection heating during solenoid-free startup of plasmas in the MAST Spherical Tokamak, Nuclear Fusion, 10.1088/1741-4326/aa6608, 57, 5, 056037, 2017.05, [URL], We present results of recent studies of merging/reconnection heating during central solenoid (CS)-free plasma startup in the Mega Amp Spherical Tokamak (MAST). During this process, ions are heated globally in the downstream region of an outflow jet, and electrons locally around the X-point produced by the magnetic field of two internal P3 coils and of two plasma rings formed around these coils, the final temperature being proportional to the reconnecting field energy. There is an effective confinement of the downstream thermal energy, due to a thick layer of reconnected flux. The characteristic structure is sustained for longer than an ion-electron energy relaxation time, and the energy exchange between ions and electrons contributes to the bulk electron heating in the downstream region. The peak electron temperature around the X-point increases with toroidal field, but the downstream electron and ion temperatures do not change.. |
| 33. | H. Tanabe, Takuma Yamada, T. Watanabe, K. Gi, M. Inomoto, R. Imazawa, M. Gryaznevich, C. Michael, B. Crowley, N. J. Conway, R. Scannell, J. Harrison, I. Fitzgerald, A. Meakins, N. Hawkes, K. G. McClements, T. O'Gorman, C. Z. Cheng, Y. Ono, Recent progress of magnetic reconnection research in the MAST spherical tokamak, Physics of Plasmas, 10.1063/1.4977922, 24, 5, 056108, 2017.05, [URL], In the last three years, magnetic reconnection research in the MAST spherical tokamak achieved major progress by the use of new 32 chord ion Doppler tomography and 130 channel YAG and 300 channel Ruby Thomson scattering diagnostics. In addition to the previously achieved high power plasma heating during merging, detailed full temperature profile measurements including the diffusion region have been achieved for the first time. 2D imaging measurements of ion and electron temperature profiles have revealed that magnetic reconnection mostly heats ions globally in the downstream region of outflow jet and electrons locally around the X-point. The toroidal field in MAST "over 0.3T" strongly inhibits cross-field thermal transport, and the characteristic peaked electron temperature profile around the X-point is sustained on a millisecond time scale. In contrast, ions are mostly heated in the downstream region of outflow acceleration and around the stagnation point formed by reconnected flux mostly by viscosity dissipation and shock-like compressional damping of the outflow jet. Toroidal confinement also contributes to the characteristic ion temperature profile, forming a ring structure aligned with the closed flux surface. There is an effective confinement of the downstream thermal energy due to a thick layer of reconnected flux. The characteristic structure is sustained for longer than an ion-electron energy relaxation time (∼4 ms), and the energy exchange between ions and electrons contributes to the bulk electron heating in the downstream region. The toroidal guide field mostly contributes to the formation of a localized electron heating structure around the X-point but not to bulk ion heating downstream.. |
| 34. | Tatsuya Kobayashi, Inagaki Shigeru, Yusuke Kosuga, Makoto Sasaki, Yoshihiko Nagashima, Takuma Yamada, Hiroyuki Arakawa, Naohiro Kasuya, Akihide Fujisawa, SANAE INOUE（論文のみ） ITOH, Kimitaka 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, 102311, 2016.10. |
| 35. | Hiroyuki Arakawa, Inagaki Shigeru, Makoto Sasaki, Yusuke Kosuga, Tatsuya Kobayashi, Naohiro Kasuya, Yoshihiko Nagashima, Takuma Yamada, Maxime Lesur, Akihide Fujisawa, Kimitaka Itoh, SANAE INOUE（論文のみ） ITOH, Eddy, drift wave and zonal flow dynamics in a linear magnetized plasma, SCIENTIFIC REPORTS, 10.1038/srep33371, 6, 33371, 2016.09. |
| 36. | Takuma Yamada, H. Tanabe, T. G. Watanabe, Y. Hayashi, R. Imazawa, M. Inomoto, Y. Ono, M. Gryaznevich, R. Scannell, C. Michael, Localized electron heating during magnetic reconnection in MAST, NUCLEAR FUSION, 10.1088/0029-5515/56/10/106019, 56, 10, 106019, 2016.10. |
| 37. | 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 INOUE（論文のみ） 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, 093501, 2016.09. |
| 38. | Tomohiko Ushiki, Michiaki Inomoto, Kotaro Yamasaki, Xuehan Guo, Takumichi Sugawara, Keita Matsuyama, Haruhisa Koguchi, Takuma Yamada, Generation of Energetic Electrons during Spherical Tokamak Merging in UTST, Plasma and Fusion Research, 10.1585/pfr.11.2402100, 11, 2402100, 2016.07. |
| 39. | H. Tanabe, Takuma Yamada, T. Watanabe, K. Gi, K. Kadowaki, M. Inomoto, R. Imazawa, M. Gryaznevich, R. Scannell, N. Conway, B. Crowley, K. G. McClements, I. Fitzgerald, C. Michael, J. Harrison, A. Meakins, N. Hawkes, T. O'Gorman, C. Z. Cheng, Application of Tomographic Ion Doppler Spectroscopy to Merging Plasma Startup in the MAST Spherical Tokamak, Plasma and Fusion Research, 10.1585/pfr.11.1302093, 11, 1302093, 2016.06. |
| 40. | Tomotsugu Kanzaki, Yoshihiko Nagashima, Inagaki Shigeru, Fumiyoshi Kin, Yudai Miwa, Makoto Sasaki, Takuma Yamada, Akihide Fujisawa, Tatsuya Kobayashi, Naohiro Kasuya, Yusuke Kosuga, SANAE INOUE（論文のみ） ITOH, Kimitaka Itoh, Improvement of the Reynolds Stress Probe for End-Plate Biasing Experiment in a Cylindrical Laboratory Plasma, Plasma and Fusion Research, 10.1585/pfr.11.1201091, 11, 1201092, 2016.06. |
| 41. | Inagaki Shigeru, Tatsuya Kobayashi, Yusuke Kosuga, SANAE INOUE（論文のみ） ITOH, Tomohiro Mitsuzono, Yoshihiko Nagashima, Hiroyuki Arakawa, Takuma Yamada, Yudai Miwa, Naohiro Kasuya, Makoto Sasaki, Maxime Lesur, Akihide Fujisawa, Kimitaka Itoh, A Concept of Cross-Ferroic Plasma Turbulence, SCIENTIFIC REPORTS, 10.1038/srep22189, 6, 22189, 2016.02. |
| 42. | H. Tanabe, Takuma Yamada, T. Watanabe, K. Gi, K. Kadowaki, M. Inomoto, R. Imazawa, M. Gryaznevich, C. Michael, B. Crowley, N. J. Conway, R. Scannell, J. Harrison, I. Fitzgerald, A. Meakins, N. Hawkes, K. G. McClements, T. O'Gorman, C. Z. Cheng, Y. Ono, Electron and Ion Heating Characteristics during Magnetic Reconnection in the MAST Spherical Tokamak, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.115.215004, 115, 21, 112301, 2015.11. |
| 43. | Tatsuya Kobayashi, Inagaki Shigeru, Makoto Sasaki, Yusuke Kosuga, Takuma Yamada, Hiroyuki Arakawa, Yoshihiko Nagashima, Yudai Miwa, Naohiro Kasuya, Akihide Fujisawa, SANAE INOUE（論文のみ） ITOH, Kimitaka Itoh, Azimuthal inhomogeneity of turbulence structure and its impact on intermittent particle transport in linear magnetized plasmas, PHYSICS OF PLASMAS, 10.1063/1.4934537, 22, 11, 112301, 2015.11. |
| 44. | K. Yamasaki, S. Inoue, S. Kamio, T. G. Watanabe, T. Ushiki, X. Guo, T. Sugawara, K. Matsuyama, N. Kawakami, Takuma Yamada, M. Inomoto, Y. Ono, Laboratory study of diffusion region with electron energization during high guide field reconnection, PHYSICS OF PLASMAS, 10.1063/1.4932345, 22, 10, 101202, 2015.10. |
| 45. | I. T. Chapman, J. Adamek, R. J. Akers, S. Allan, L. Appel, O. Asunta, M. Barnes, N. Ben Ayed, T. Bigelow, W. Boeglin, J. Bradley, J. Brünner, P. Cahyna, M. Carr, J. Caughman, M. Cecconello, C. Challis, S. Chapman, J. Chorley, G. Colyer, N. Conway, W. A. Cooper, M. Cox, N. Crocker, B. Crowley, G. Cunningham, A. Danilov, D. Darrow, R. Dendy, A. Diallo, D. Dickinson, S. Diem, W. Dorland, B. Dudson, D. Dunai, L. Easy, S. Elmore, A. Field, G. Fishpool, M. Fox, E. Fredrickson, S. Freethy, L. Garzotti, Y. C. Ghim, K. Gibson, J. Graves, C. Gurl, W. Guttenfelder, C. Ham, Takuma Yamada, Overview of MAST results, Nuclear Fusion, 10.1088/0029-5515/55/10/104008, 55, 10, 104008, 2015.06, [URL], The Mega Ampere Spherical Tokamak (MAST) programme is strongly focused on addressing key physics issues in preparation for operation of ITER as well as providing solutions for DEMO design choices. In this regard, MAST has provided key results in understanding and optimizing H-mode confinement, operating with smaller edge localized modes (ELMs), predicting and handling plasma exhaust and tailoring auxiliary current drive. In all cases, the high-resolution diagnostic capability on MAST is complemented by sophisticated numerical modelling to facilitate a deeper understanding. Mitigation of ELMs with resonant magnetic perturbations (RMPs) with toroidal mode number nRMP = 2, 3, 4, 6 has been demonstrated: at high and low collisionality; for the first ELM following the transition to high confinement operation; during the current ramp-up; and with rotating nRMP = 3 RMPs. nRMP = 4, 6 fields cause less rotation braking whilst the power to access H-mode is less with nRMP = 4 than nRMP = 3, 6. Refuelling with gas or pellets gives plasmas with mitigated ELMs and reduced peak heat flux at the same time as achieving good confinement. A synergy exists between pellet fuelling and RMPs, since mitigated ELMs remove fewer particles. Inter-ELM instabilities observed with Doppler backscattering are consistent with gyrokinetic simulations of micro-tearing modes in the pedestal. Meanwhile, ELM precursors have been strikingly observed with beam emission spectroscopy (BES) measurements. A scan in beta at the L-H transition shows that pedestal height scales strongly with core pressure. Gyro-Bohm normalized turbulent ion heat flux (as estimated from the BES data) is observed to decrease with increasing tilt of the turbulent eddies. Fast ion redistribution by energetic particle modes depends on density, and access to a quiescent domain with 'classical' fast ion transport is found above a critical density. Highly efficient electron Bernstein wave current drive (1 A W-1) has been achieved in solenoid-free start-up. A new proton detector has characterized escaping fusion products. Langmuir probes and a high-speed camera suggest filaments play a role in particle transport in the private flux region whilst coherence imaging has measured scrape-off layer (SOL) flows. BOUT++ simulations show that fluxes due to filaments are strongly dependent on resistivity and magnetic geometry of the SOL, with higher radial fluxes at higher resistivity. Finally, MAST Upgrade is due to begin operation in 2016 to support ITER preparation and importantly to operate with a Super-X divertor to test extended leg concepts for particle and power exhaust.. |
| 46. | Yoshihiko Nagashima, Inagaki Shigeru, Akihide Fujisawa, Hiroyuki Arakawa, Takuma Yamada, Yudai Miwa, Tatsuya Kobayashi, SANAE INOUE（論文のみ） ITOH, Kimitaka Itoh, Observation of Parallel Force Balance for Drift Wave Fluctuation by a Fast Voltage Sweeping Method in a Linear Plasma, Journal of Physics Society of Japan, 10.7566/JPSJ.84.063501, 84, 6, 063501, 2015.06. |
| 47. | Yasushi Ono, Hiroshi Tanabe, Takuma Yamada, Keii Gi, Takenori G. Watanabe, Toru Ii, Mikhail Gryaznevich, Roly Scannell, Neil Conway, Basil Crowley, Clive Michael, High power heating of magnetic reconnection in merging tokamak experiments, PHYSICS OF PLASMAS, 10.1063/1.4920944, 22, 5, 055708, 2015.05. |
| 48. | Fumiyoshi Kin, Takuma Yamada, Inagaki Shigeru, Hiroyuki Arakawa, Yoshihiko Nagashima, Naohiro Kasuya, Akihide Fujisawa, Kousuke Nakanishi, Hikaru Kono, Takaaki Mizokami, Makoto Sasaki, Maxime Lesur, Yusuke Kosuga, Kimitaka Itoh, SANAE INOUE（論文のみ） ITOH, Evaluation of Non-Linear Mode Coupling During End-Plate Biasing Experiment in PANTA, Plasma and Fusion Research, 10.1585/pfr.10.3401043, 10, 3401043, 2015.04. |
| 49. | Makoto Sasaki, Naohiro Kasuya, Tatsuya Kobayashi, Hiroyuki Arakawa, Kimitaka Itoh, Kouhei Fukunaga, Takuma Yamada, Masatoshi Yagi, SANAE INOUE（論文のみ） ITOH, Formation mechanism of steep wave front in magnetized plasmas, PHYSICS OF PLASMAS, 10.1063/1.4916490, 22, 3, 032315, 2015.03. |
| 50. | Michiaki Inomoto, Takenori G. Watanabe, Keii Gi, Kotaro Yamasaki, Shuji Kamio, Ryota Imazawa, Takuma Yamada, Xuehan Guo, Tomohiko Ushiki, Hiroki Ishikawa, Hiroki Nakamata, N Kawakami, T Sugawara, K Matsuyama, K Noma, Akihiro Kuwahata, Hiroshi Tanabe, Centre-solenoid-free merging start-up of spherical tokamak plasmas in UTST, NUCLEAR FUSION, 10.1088/0029-5515/55/3/033013, 55, 3, 2401112, 2015.03. |
| 51. | Takuma Yamada, Inagaki Shigeru, Tatsuya Kobayashi, Yoshihiko Nagashima, Tomohiro Mitsuzono, Yudai Miwa, Kousuke Nakanishi, Hiromitsu Fujino, Makoto Sasaki, Naohiro Kasuya, Maxime Lesur, Yusuke Kosuga, Akihide Fujisawa, SANAE INOUE（論文のみ） ITOH, Kimitaka Itoh, End plate biasing experiments in linear magnetized plasmas, Nuclear Fusion, 10.1088/0029-5515/54/11/114010, 54, 11, 114010, 2014.11, Meso-scale streamer has a radially elongated structure and is believed to enhance the radial transport. In order to study the control of the streamer, we demonstrated an end plate biasing to the streamer state in the PANTA linear plasma. During the end plate biasing, the electron density profile became more peaked, fluctuation was suppressed, the streamer structure was deconstructed, and the waveform became a periodic solitary state. The radial electric field only induced at around the end plate was found to play an important role for the streamer suppression.. |
| 52. | Takahiro Shinya, Akira Ejiri, Yuichi Takase, Takuma Wakatsuki, Takuya Oosako, Naoto Tsujui, Hidetoshi Kakuda, Hirokazu Furuji, Junichi Hiratsuka, Takuma Inada, Kazuhiro Imamura, Keishun Nakamura, Ayaka Nakanishi, Masateru Sonehara, Hiro Togashi, Shintaro Tsuda, Takashi Yamaguchi, Hiroshi Kasahara, Yoshihiko Nagashima, Takuma Yamada, Identification of Waves by RF Magnetic Probes during Lower Hybrid Wave Injection Experiments on the TST-2 Spherical Tokamak, Plasma Fusion Res., 10.1585/pfr.9.3402040, 9, 3402040, 2014.05. |
| 53. | Shuji Kamio, Takenori G. Watanabe, Kotaro Yamasaki, Qinghong Cao, Takuma Yamada, Michiaki Inomoto, Yasushi Ono, Experimental Results of Ion Heating by Magnetic Reconnection Using External Coils, Plasma Fusion Res., 10.1585/pfr.9.3402038, 9, 3402038, 2014.05. |
| 54. | Inagaki Shigeru, Yudai Miwa, Tatsuya Kobayashi, Takuma Yamada, Yoshihiko Nagashima, Tomohiro Mitsuzono, Hiromitsu Fujino, Makoto Sasaki, Naohiro Kasuya, Maxime Lesur, Yusuke Kosuga, Akihide Fujisawa, SANAE INOUE（論文のみ） ITOH, Kimitaka Itoh, Identification of Quasi-Periodic Nonlinear Waveforms in Turbulent Plasmas, Plasma Fusion Res., 10.1585/pfr.9.1201016, 9, 1201016, 2014.03. |
| 55. | Takenori G. Watanabe, Yasushi Ono, Takuma Yamada, Shuji Kamio, Qinghong Cao, Hirotomo Itagaki, Koichiro Takemura, Kotaro Yamasaki, Koji Ishiguchi, Michiaki Inomoto, Plasmoid-Induced Pull Reconnection Experiments in University of Tokyo Spherical Tokamak, Plasma Fusion Res., 10.1585/pfr.8.2401148, 8, 2401148, 2013.11. |
| 56. | Michiaki Inomoto, Shuji Kamio, Akihiro Kuwahata, Takenori G. Watanabe, Kotaro Yamasaki, Kazutake Kadowaki, Taichi Ito, Yasuhiro Kaminou, Takuma Yamada, Yasushi Ono, Initiation of Impulsively Fast Magnetic Reconnection Induced by Current Sheet Ejection, Plasma Fusion Res., 10.1585/pfr.8.2401112, 8, 2401112, 2013.09. |
| 57. | Kotaro Yamasaki, Shuji Kamio, Koichiro Takemura, Qinghong Cao, Takenori G. Watanabe, Hirotomo Itagaki, Takuma Yamada, Michiaki Inomoto, Yasushi Ono, Experimental Study of Two-Fluid Effect during Magnetic Reconnection in the UTST Merging Experiment, Plasma Fusion Res., 10.1585/pfr.8.2401130, 8, 2401130, 2013.09. |
| 58. | Takuma Yamada, Makoto Sasaki, Naohiro Kasuya, Yoshihiko Nagashima, Inagaki Shigeru, Tatsuya Kobayashi, MASATOSHI YAGI, Akihide Fujisawa, SANAE INOUE（論文のみ） ITOH, Kimitaka Itoh, Streamer Structures in Experiment and Modeling, Plasma Fusion Res., 10.1585/pfr.8.2401022, 8, 2401022, 2013.04, 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.. |
| 59. | Shuji Kamio, Kotaro Yamasaki, Koichiro Takemura, Qinghong Cao, Takenori G. Watanabe, Hirotomo Itagaki, Toshiki Tsutsui, Koji Ishiguchi, Ryota Imazawa, Takuma Yamada, Chio-Zong Cheng, Michiaki Inomoto, Yasushi Ono, Electron Acceleration by Magnetic Reconnection During Spherical Tokamak Merging Experiment, IEEJ Transactions on Fundamentals and Materials, 10.1541/ieejfms.133.166, 133, 4, 166-172, 2013.04, Meso-scale streamer has a radially elongated structure and is believed to enhance the radial transport. In order to study the control of the streamer, we demonstrated an end plate biasing to the streamer state in the PANTA linear plasma. During the end plate biasing, the electron density profile became more peaked, fluctuation was suppressed, the streamer structure was deconstructed, and the waveform became a periodic solitary state. The radial electric field only induced at around the end plate was found to play an important role for the streamer suppression.. |
| 60. | Takuma Yamada, Merging Startup Experiments on the UTST Spherical Tokamak, Plasma Fusion Res., 10.1585/pfr.5.S2100, 5, S2100, 2010.12. |
| 61. | Takuma Yamada, Nonlinear Mode Couplings in a Cylindrical Magnetized Plasma, 19th International Toki Conf. (ITC19) on Advanced Phys. in Plasma and Fus. Res., 10.1585/pfr.5.S2016, 5, S2016, 2010.12. |
| 62. | Takuma Yamada, SANAE INOUE（論文のみ） ITOH, Inagaki Shigeru, Yoshihiko Nagashima, Naohiro Kasuya, KAMATAKI KUNIHIRO, Hiroyuki Arakawa, Tatsuya Kobayashi, MASATOSHI YAGI, Akihide Fujisawa, Kimitaka Itoh, Observation of Quasi-Two-Dimensional Nonlinear Interactions in a Drift-Wave Streamer, PHYSICAL REVIEW LETTERS, 10.1103/PhysRevLett.105.225002, 105, 22, 225002, 2010.11. |
| 63. | Takuma Yamada, Study of Amplitude Correlation Technique in a Cylindrical Magnetized Plasma, Journal of Physics Society of Japan, 10.1143/JPSJ.79.085001, 79, 8, 085001, 2010.08. |
| 64. | Takuma Yamada, SANAE INOUE（論文のみ） ITOH, Inagaki Shigeru, Yoshihiko Nagashima, Shunjiro Shinohara, Naohiro Kasuya, Kenichiro Terasaka, KAMATAKI KUNIHIRO, Hiroyuki Arakawa, MASATOSHI YAGI, Akihide Fujisawa, Kimitaka Itoh, Two-dimensional bispectral analysis of drift wave turbulence in a cylindrical plasma, PHYSICS OF PLASMAS, 10.1063/1.3429674, 17, 5, 052313, 2010.05. |
| 65. | Takuma Yamada, Measurement of Nonlinear Mode Couplings in the Large Mirror Device-Upgrade, J. Plasma and Fusion Res., 8, 87-90, 2009.09. |
| 66. | Takuma Yamada, Spatiotemporal Behavior of Drift Waves in LMD-U, Plasma Fusion Res., 10.1585/pfr.3.S1021, 3, S1021, 2008.08. |
| 67. | Takuma Yamada, SANAE INOUE（論文のみ） ITOH, Takashi Maruta, Naohiro Kasuya, Yoshihiko Nagashima, Shunjiro Shinohara, Kenichiro Terasaka, MASATOSHI YAGI, Inagaki Shigeru, Yoshinobu Kawai, Akihide Fujisawa, Kimitaka Itoh, Anatomy of plasma turbulence, NATURE PHYSICS, 10.1038/nphys1029, 4, 9, 721-725, 2008.07. |
| 68. | Takuma Yamada, Experimental Study of Drift Wave Turbulence on Linear Plasma, Plasma Fusion Res. , 10.1585/pfr.3.044, 3, 044, 2008.07. |
| 69. | Takuma Yamada, Fine positioning of a poloidal probe array, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.2818796, 78, 12, 123501, 2007.12. |
| 70. | Takuma Yamada, Detection of Cascading Process in Drift Wave Turbulence in LMD-U Detected by a Probe Array, Plasma Fusion Res., 10.1585/pfr.2.051, 2, 051, 2007.12. |
| 71. | Takuma Yamada, Direct measurement of density oscillation induced by a radio-frequency wave, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.2769351, 78, 8, 083502, 2007.08. |
| 72. | Takuma Yamada, Reflectometry for Density Fluctuation and Profile Measurements in TST-2, Plasma and Fusion Research, 10.1585/pfr.2.S1037, 2, S1037, 2007.11. |
| 73. | Takuma Yamada, Application of differential phase method to interferometry, REVIEW OF SCIENTIFIC INSTRUMENTS, 10.1063/1.2405394, 77, 12, 124701, 2006.12. |
| 74. | Takuma Yamada, Akira Ejiri, Syu N.Ichi Shiraiwa, Yuichi Takase, Two-chord interferometry using a pin switch for plasma density measurement, Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers, 10.1143/JJAP.40.7083, 40, 12, 7083-7084, 2001.12, Microwave interferometry is a useful diagnostic for measuring the line-integrated density of plasmas. To obtain a detailed profile of the electron density, multi chord interferometry is indispensable. Using a pin switch, we have successfully measured the density along two chords by alternating the beam with a time interval of 2 μs for each chord. This method is very cost advantageous, because it requires only one set of sources and detection components. The system has been applied to Tokyo Spherical Tokamak-2 (TST-2) to measure two vertical chords at different major radii. It is shown that from the densities measured along the two chords, profile changes can be deduced.. |
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