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249 results on '"Kiwamoto, Y."'

5. X-ray tomography of hot electrons in the barrier region of the tandem mirror GAMMA 10.

Author

Kondoh, T., Cho, T., Hirata, M., Yamaguchi, N., Saito, T., Kiwamoto, Y., and Miyoshi, S.

Subjects
TOMOGRAPHY, PROTON-induced X-ray emission, ELECTRONS, PLASMA gases
Abstract

Studies the tomographic reconstruction of x-ray emission from hot electrons in the barrier region of the tandem mirror GAMMA 10 plasmas. Reason for the increase importance of x-ray tomographic reconstruction techniques; Description of the experimental apparatus; Experimental results.

Published
1990
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14. Electron Vortex Dynamics and Two-Dimensional Field Analysis

Author

KYOTO UNIV (JAPAN), Ito, K., Sanpei, A., Kiwamoto, Y., KYOTO UNIV (JAPAN), Ito, K., Sanpei, A., and Kiwamoto, Y.

Abstract

In recent paper (K. Ito, el al., Jpn. J. Appl. Phys. 40, 2558 (2001), we present a fast and sufficiently accurate procedure to construct the potential and the electric field distribution from the observed electron density distribution in two-dimensional plane. Using this procedure, we obtain quantitative agreement between the observed velocity of the clump motion and the calculated velocity of that determined by the field analysis. in addition, the strong deformation of the clump is observed when that moves in the shear of the background Vortex., This article is from CP606, Non-Neutral Plasma Physics IV, p474-479, 2001. Pub. in AIP Conference Proceedings: volume 606. Prepared in cooperation with Ernst-Moritz-Arndt-Universitaet, Greifswald, Germany. This article is from ADA404831 Non-Neutral Plasma Physics 4. Workshop on Non-Neutral Plasmas (2001) Held in San Diego, California on 30 July-2 August 2001

Published
2002

15. Interaction of Electron Vortices under the Influence of Background Vorticity Distribution

Author

KYOTO UNIV (JAPAN), Kiwamoto, Y., Ito, K., Sanpei, A., Soga, Y., Yuyama, T., KYOTO UNIV (JAPAN), Kiwamoto, Y., Ito, K., Sanpei, A., Soga, Y., and Yuyama, T.

Abstract

We report experimental studies on vortex dynamics carried out recently in Kyoto University by using electron plasmas that are trapped in the Malmberg configuration with variety of initial configurations. This report includes (I) relaxation of many-clump dynamic states to "crystallization", (2) single clump dynamics in a background vorticity distribution. (3) two-clump interaction in a low-level background vorticity distribution, and (4) accelerated crystallization" of three clumps in a background vorticity distribution. Details are provided in companion papers reported in this workshop., This article is from CP606, Non-Neutral Plasma Physics IV, p464-473, 2001. Pub. in AIP Conference Proceedings: volume 606. Prepared in cooperation with Ernst-Moritz-Arndt-Universitaet, Greifswald, Germany. This article is from ADA404831 Non-Neutral Plasma Physics 4. Workshop on Non-Neutral Plasmas (2001) Held in San Diego, California on 30 July-2 August 2001

Published
2002

16. Nonlinear Landau damping in the ionosphere

Author

Kiwamoto, Y and Benson, R. F

Subjects
Geophysics
Abstract

A model which explains the nonresonant waves which produce the diffuse resonance observed near 3/2 f(H) by the Alouette and Isis topside sounders, where f(H) is the ambient electron cyclotron frequency, is presented. These waves are the result of plasma wave instabilities driven by anisotropic electron velocity distributions initiated by the high-power short-duration sounder pulse. Calculations of the nonlinear wave-particle coupling coefficients show that the diffuse resonance wave can be maintained by nonlinear Landau damping of the sounder-stimulated 2f(H) wave which is observed with a time duration longer than that of the diffuse resonance wave. The time duration of the diffuse resonance is determined by the transit time of the instability-generated and nonlinearly maintained diffuse resonance wave from the remote short-lived hot region back to the antenna. The model is consistent with the Alouette/Isis observations and it demonstrates the existence of nonlinear wave-particle interactions in the ionosphere.

Published
1979

17. Nonlinear Landau damping in the ionosphere

Author

Kiwamoto, Y and Benson, R. F

Subjects
Geophysics
Abstract

A model is presented to explain the non-resonant waves which give rise to the diffuse resonance observed near 3/2 f sub H by the Alouette and ISIS topside sounders, where f sub H is the ambient electron cyclotron frequency. In a strictly linear analysis, these instability driven waves will decay due to Landau damping on a time scale much shorter than the observed time duration of the diffuse resonance. Calculations of the nonlinear wave particle coupling coefficients, however, indicate that the diffuse resonance wave can be maintained by the nonlinear Landau damping of the sounder stimulated 2f sub H wave. The time duration of the diffuse resonance is determined by the transit time of the instability generated and nonlinearly maintained diffuse resonance wave from the remote short lived hot region back to the antenna. The model is consistent with the Alouette/ISIS observations, and clearly demonstrates the existence of nonlinear wave-particle interactions in the ionosphere.

Published
1978

31. Mechanisms of Merger and Binary Structure Formation of Two Discrete Vortices in a Non-Neutral Plasma.

Author

Soga, Y., Kiwamoto, Y., Sanpei, A., and Aoki, J.

Subjects
*NONNEUTRAL plasma, *ELECTRONS, *RELAXATION phenomena
Abstract

Observations have shown that two discrete vortices (clumps) immersed in a broad profile of background vorticity merge quickly or form a binary state that lasts for a long period. The different paths of the vortical evolution critically depend on slight differences in the initial background vorticity distribution (BGVD). By a fine control of the BGVD the asymptotic inter-clump distance is found to be a two-valued function of ∇ζ[sub b]/ζ[sub b][sup 2], where ζb is the BGV at the initial location of the clumps, corresponding to the merger and the binary state. The degeneracy is removed by considering the degree of depletion of BGVD between two clumps at the time of their proximity in the initial phase. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2003
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32. Formation of a Triangle Vortex Configuration Assisted by a Background Vorticity Distribution.

Author

Sanpei, A., Kiwamoto, Y., Soga, Y., and Aoki, J.

Subjects
*NONNEUTRAL plasma, *SCALING laws (Nuclear physics), *CRYSTALLIZATION
Abstract

A vortex crystal is a quasi-stationary, symmetric array of intense vortices (clumps). A low-level of background vorticity is experimentally observed to assist three clumps in forming an equilateral triangle starting from initial positions on a linear array. The triangle constitutes a unit cell of a crystal in a many-vortex system. The background vortex curbs the orbital motion of the clumps with unequal strengths to arrest them at the vertices of an equilateral triangle by wrapping them with different sized belts of depleted vorticity (ring holes). We characterize the contributions of a low-level background vorticity distribution on the formation of ordered states of clumps. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2003
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36. Interaction of electron vortices under the influence of background vorticity distribution.

Author

Kiwamoto, Y., Ito, K., Sanpei, A., Soga, Y., Yuyama, T., and Michishita, T.

Subjects
*PLASMA gases, *ELECTRONS
Abstract

We report experimental studies on vortex dynamics carried out recently in Kyoto University by using electron plasmas that are trapped in the Malmberg configuration with variety of initial configurations. This report includes (1) relaxation of many-clump dynamic states to "crystallization", (2) single clump dynamics in a background vorticity distribution, (3) two-clump interaction in a low-level background vorticity distribution, and (4) accelerated "crystallization" of three clumps in a background vorticity distribution. Details are provided in companion papers reported in this workshop. [ABSTRACT FROM AUTHOR]

Published
2002

37. Electron vortex dynamics and two-dimensional field analysis.

Author

Ito, K., Sanpei, A., and Kiwamoto, Y.

Subjects
ELECTRONS, ELECTRIC fields
Abstract

In recent paper [K. Ito, et al., Jpn. J. Appl. Phys. 40, 2558 (2001)], we present a fast and sufficiently accurate procedure to construct the potential and the electric field distribution from the observed electron density distribution in two-dimensional plane. Using this procedure, we obtain quantitative agreement between the observed velocity of the clump motion and the calculated velocity of that determined by the field analysis. In addition, the strong deformation of the clump is observed when that moves in the shear of the background vortex. [ABSTRACT FROM AUTHOR]

Published
2002

40. Plasma confinement in the GAMMA 10 tandem mirror

Author

Yatsu, K, primary, Bruskin, L.G, additional, Cho, T, additional, Hamada, M, additional, Hirata, M, additional, Hojo, H, additional, Ichimura, M, additional, Ishii, K, additional, Itakura, A, additional, Katanuma, I, additional, Kiwamoto, Y, additional, Kohagura, J, additional, Kubota, S, additional, Mase, A, additional, Nakashima, Y, additional, Saito, T, additional, Sakamoto, Y, additional, Tamano, T, additional, Tatematsu, Y, additional, Tokuzawa, T, additional, and Yoshikawa, M, additional

Published
1999
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43. Measurement and Control of End Loss Electrons from the GAMMA 10 Tandem Mirror

Author

Saito, T., primary, Tatematsu, Y., additional, Kiwamoto, Y., additional, Kajiwara, K., additional, Yoshimura, Y., additional, Abe, H., additional, Ito, K., additional, Suzuki, A., additional, Yamazaki, A., additional, Koyama, H., additional, Umehara, S., additional, Ishii, K., additional, Ichimura, M., additional, Mase, A., additional, Tamano, T., additional, and Yatsu, K., additional

Published
1999
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44. Charge-exchange neutral particle measurements on electron cyclotron resonance heating experiments in hot-ion-mode plasmas of the GAMMA 10 tandem mirror

Author

Nakashima, Y., primary, Hasegawa, Y., additional, Shoji, M., additional, Kobayashi, S., additional, Saito, T., additional, Kiwamoto, Y., additional, Cho, T., additional, Mase, A., additional, Ichimura, M., additional, Itakura, A., additional, Hirata, M., additional, Kohagura, J., additional, Islam, K. Md., additional, Oishi, M., additional, Yoshikawa, M., additional, Tamano, T., additional, and Yatsu, K., additional

Published
1999
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