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Your search keyword '"Ogura, Kazuo"' showing total 24 results
Start Over Author "Ogura, Kazuo" Journal plasma and fusion research
24 results on '"Ogura, Kazuo"'

17. Experimental Study on Performance of Slow Cyclotron Maser in Weakly Relativistic Region

Author

Bansho, Kiyoshi, Ogura, Kazuo, Oe, Hiroaki, Kazahari, Yusuke, Iizuka, Hiroshi, Sugawara, Akira, Shimozuma, Takashi, Kobayashi, Sakuji, and Okada, Kohji

Subjects
slow cyclotron maser, Cherenkov interaction, weakly relativistic beam, periodic corrugation, slowwave device
Abstract

Studies of slow cyclotron maser operation of a slow-wave device are presented. The beam voltage is weakly relativistic, less than 100 kV. The slow-wave structure is a periodically corrugated oversized waveguide for K-band operation. When using rectangular corrugation having a relatively small ratio of corrugation width to periodic length of about 20 %, the dispersion curve near the upper cut-off becomes flat and second harmonic slow cyclotron maser operation is observed in the low-energy region near 30 kV. Another type of combined resonance of Cherenkov and slow cyclotron interaction is also demonstrated in which an absolute instability is driven by the slow cyclotron interaction. By using sinusoidal corrugation and rectangular corrugation having a 50 % ratio of corrugation width to periodic length, amplification effects due to the fundamental and second harmonic slow cyclotron interactions are observed.

Published
2010

18. Numerical Analysis of Slow-Wave Instabilities in Oversized Sinusoidaly Corrugated Waveguide Driven by Finitely Thick Annular Electron Beam

Author

Otubo, Kosuke, Ogura, Kazuo, Yamakawa, Mitsuhisa, and Takashima, Yusuke

Subjects
slow cyclotron instability, Physics::Accelerator Physics, Cherenkov instability, annular beam, oversized sinusoidaly corrugated waveguide, boundary condition
Abstract

Three kinds of models are used for beam instability analyses: those based on a solid beam, an infinitesimally thin annular beam, and a finitely thick annular beam. In high-power experiments, the electron beam is an annulus of finite thickness. In this paper, a numerical code for a sinusoidally corrugated waveguide with a finitely thick annular beam is presented and compared with other models. Our analysis is based on a new version of the self-consistent linear theory that takes into account three-dimensional beam perturbations. Slow-wave instabilities in a K-band oversized sinusoidally corrugated waveguide are analyzed. The dependence of the Cherenkov and slow cyclotron instabilities on the annular thickness and guiding magnetic field are examined.

Published
2010

21. Effects of Radially Sheared Electric Field on Turbulence Reduction Analyzed with End-Loss Analysing Systems

Author

HIRATA, Mafumi, primary, CHO, Teruji, additional, KOHAGURA, Junko, additional, NUMAKURA, Tomoharu, additional, KIMINAMI, Serina, additional, ITO, Marie, additional, MORIMOTO, Naoyuki, additional, HIRAI, Katsuaki, additional, YAMAGISHI, Tooru, additional, IKUNO, Toshinori, additional, NAMIKI, Shohei, additional, MIYATA, Yoshiaki, additional, MINAMI, Ryutaro, additional, OGURA, Kazuo, additional, KONDOH, Takashi, additional, KARIYA, Tsuyoshi, additional, IMAI, Tsuyoshi, additional, and MIYOSHI, Syoichi, additional

Published
2007
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23. Instability of Annular Beam with Finite Thickness in Dielectric-Loaded Cylindrical Waveguide

Author

Tamura, Shusuke, Yamakawa, Mitsuhisa, Takashima, Yusuke, and Ogura, Kazuo

Subjects
slow cyclotron instability, low-frequency surface wave mode, Physics::Accelerator Physics, Cherenkov instability, finite thickness, high-frequency surface wave mode, Nonlinear Sciences::Pattern Formation and Solitons, annular beam
Abstract

The cherenkov and slow cyclotron instabilities driven by an axially injected electron beam in a cylindrical waveguide are studied using a new version of the self-consistent linear theory considering three-dimensional beam perturbations. There are three kinds of models for beam instability analysis, which are based on a cylindrical solid beam, an infinitesimally thin annular beam, and a finitely thick annular beam. Among these models, the beam shape properly representing the often used actual annular electron beams is the finitely thick annulus. We develop a numerical code for a cylindrical waveguide with a finitely thick annular beam. Our theory is valid for any beam velocity. We present eigen-modes of the cylindrical system with the plasma and beam. Instabilities driven by the annular beam in a dielectric-loaded waveguide are also examined.

Published
2008

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