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Start Over Author "Yusuke Kosuga" Journal journal of the physical society of japan
9 results on '"Yusuke Kosuga"'

2. An Evaluation of Localized Heat Flux Associated with the Streamer at the Onset of Type-III ELMs on HL-2A Tokamak

Author

S. I. Itoh, Kimitaka Itoh, Kaijun Zhao, Yusuke Kosuga, Jiaqi Dong, and Jun Cheng

Subjects
Physics, Tokamak, Heat flux, Physics::Plasma Physics, law, General Physics and Astronomy, Perturbation (astronomy), Mechanics, law.invention
Abstract

A method is discussed to evaluate the localized radial heat flux, which is associated with the streamer, based on the observed temperature perturbation at the onset of Type-III ELMs in HL-2A tokama...

Published
2021
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3. Comparison between Tomography and Langmuir Probe Data in PANTA

Author

Makoto Sasaki, Yoshihiko Nagashima, Yuichi Kawachi, H. Arakawa, Takeshi Ido, Takuma Yamada, Akihide Fujisawa, Naohiro Kasuya, Fumiyoshi Kin, Shigeru Inagaki, T. Kobayashi, Yusuke Kosuga, Chanho Moon, and Kotaro Yamasaki

Subjects
symbols.namesake, Electron density, Materials science, Physics::Plasma Physics, symbols, General Physics and Astronomy, Langmuir probe, Electron temperature, Plasma, Tomography, Atomic physics, Emission intensity
Abstract

Emission intensity \(\epsilon \) from plasmas is a complicated function of electron temperature Te and electron density ne. To understand the dependence of \(\epsilon \) on Te and ne, an experiment...

Published
2020
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4. Possible Break-down of Up–Down Symmetry for Propagation of Parallel Velocity Gradient Driven Mode near Edge Transport Barrier

Author

Kimitaka Itoh, Yusuke Kosuga, and Sanae I. Itoh

Subjects
Physics, Velocity gradient, Mode (statistics), General Physics and Astronomy, Plasma, Transport barrier, Edge (geometry), Symmetry (physics), Computational physics
Abstract

The propagation direction of parallel velocity gradient driven mode in the edge of H-mode plasmas is investigated. We study the possibility to observe a preferential propagation (either up-ward or ...

Published
2020
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5. Comparison between Tomography and Langmuir Probe Data in PANTA.

Author

Yoshihiko Nagashima, Akihide Fujisawa, Kotaro Yamasaki, Shigeru Inagaki, Chanho Moon, Fumiyoshi Kin, Yuichi Kawachi, Hiroyuki Arakawa, Takuma Yamada, Tatsuya Kobayashi, Naohiro Kasuya, Yusuke Kosuga, Makoto Sasaki, and Takeshi Ido

Abstract

Emission intensity ε from plasmas is a complicated function of electron temperature Te and electron density ne. To understand the dependence of ε on Te and ne, an experimental comparison between tomography data (local ε of ArII) and Langmuir probe data (Te and ne) in a linear plasma device PANTA is presented in this paper. In the comparison, the local emission intensity is modeled as εmodel ∝ Teα ne², and the model is validated by calculating both cross-correlation function and least squares of residuals between the fluctuations of ε and εmodel. The comparison reveals that the both methods provide α = 2.3-2.7, higher than 2 that of the exponent of ne. This result confirms that dependence of Te on ε is larger than that of ne when Te is low, as in PANTA. [ABSTRACT FROM AUTHOR]

Published
2020
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6. Three-Dimensional Structure of the Streamer in Linear Plasmas

Author

Kotaro Yamasaki, Yusuke Kosuga, Sanae I. Itoh, Takuma Yamada, Yoshihiko Nagashima, Akihide Fujisawa, Naohiro Kasuya, Hiroyuki Arakawa, T. Kobayashi, Fumiyoshi Kin, Shigeru Inagaki, Makoto Sasaki, and Kimitaka Itoh

Subjects
Physics, Carrier signal, Physics::Plasma Physics, 0103 physical sciences, Structure (category theory), General Physics and Astronomy, Plasma, Atomic physics, 010306 general physics, 01 natural sciences, 010305 fluids & plasmas
Abstract

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 a...

Published
2018
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7. An Evaluation of Localized Heat Flux Associated with the Streamer at the Onset of Type-III ELMs on HL-2A Tokamak.

Author

Kimitaka Itoh, Yusuke Kosuga, Jun Cheng, Jiaqi Dong, Kaijun Zhao, and Sanae-Inoue Itoh

Abstract

A method is discussed to evaluate the localized radial heat flux, which is associated with the streamer, based on the observed temperature perturbation at the onset of Type-III ELMs in HL-2A tokamak. Treating the observed temperature perturbation of the streamer as a given parameter, its impact on energy flux in the core plasma is discussed. It is found that the observed streamer can have an important role in the immediate crash of the core temperature at the onset of the Type-III ELM. [ABSTRACT FROM AUTHOR]

Published
2021
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8. Changes of Particle Flux during End-Plate Biasing Experiment in PANTA

Author

Takuma Yamada, Yudai Miwa, Naohiro Kasuya, Yoshihiko Nagashima, Fumiyoshi Kin, Shigeru Inagaki, Akihide Fujisawa, Makoto Sasaki, Sanae I. Itoh, Hiroyuki Arakawa, T. Kobayashi, Yusuke Kosuga, and Kimitaka Itoh

Subjects
Physics, Turbulence, General Physics and Astronomy, Flux, Biasing, Plasma, Mechanics, 01 natural sciences, 010305 fluids & plasmas, Physics::Fluid Dynamics, Nonlinear system, Amplitude, 0103 physical sciences, Astrophysics::Earth and Planetary Astrophysics, 010306 general physics, Particle flux
Abstract

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.

Published
2016
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9. On Magnetic Signals of a Large-Scale Quasi-electrostatic Perturbation

Author

Katsumi Ida, Yusuke Kosuga, Kimitaka Itoh, and Sanae I. Itoh

Subjects
Physics, Toroid, General Physics and Astronomy, Perturbation (astronomy), Plasma, 01 natural sciences, 010305 fluids & plasmas, Magnetic field, symbols.namesake, Classical mechanics, Maxwell's equations, Physics::Plasma Physics, Quantum electrodynamics, Physics::Space Physics, 0103 physical sciences, symbols, Plasma diagnostics, Magnetohydrodynamics, 010306 general physics, Excitation
Abstract

In this article, we discuss a method to identify whether the observed perturbation in toroidal plasmas is a quasi-electrostatic perturbation or not. A criterion is derived based on the observed data of plasma deformation and external magnetic perturbations. This result can be applied to the study of properties of quasi-modes, which have been observed in toroidal plasmas.

Published
2016
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