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Your search keyword '"Saito, T"' showing total 19 results
Start Over Author "Saito, T" Journal physics of plasmas
19 results on '"Saito, T"'

4. Influence of the electron velocity spread and the beam width on the efficiency and mode competition in the high-power pulsed gyrotron for 300GHz band collective Thomson scattering diagnostics in the large helical device.

Author

Dumbrajs, O., Saito, T., Tatematsu, Y., and Yamaguchi, Y.

Subjects
*GYROTRONS, *THOMSON scattering, *ELECTRIC potential, *COMPUTER simulation, *OSCILLATIONS
Abstract

We present results of a theoretical study of influence of the electron velocity spread and the radial width on the efficiency and mode competition in a 300-kW, 300-GHz gyrotron operating in the TE22,2 mode. This gyrotron was developed for application to collective Thomson scattering diagnostics in the large helical device and 300-kW level high power single TE22,2 mode oscillation has been demonstrated [Yamaguchi et al., J. Instrum. 10, c10002 (2015)]. Effects of a finite voltage rise time corresponding to the real power supply of this gyrotron are also considered. Simulations tracking eight competing modes show that the electron velocity spread and the finite beam width influence not only the efficiency of the gyrotron operation but also the mode competition scenario during the startup phase. A combination of the finite rise time with the electron velocity spread or the finite beam width affects the mode competition scenario. The simulation calculation reproduces the experimental observation of high power single mode oscillation of the TE22,2 mode as the design mode. This gives a theoretical basis of the experimentally obtained high power oscillation with the design mode in a real gyrotron and moreover shows a high power oscillation regime of the design mode. [ABSTRACT FROM AUTHOR]

Published
2016
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5. Start-up scenario of a high-power pulsed gyrotron for 300GHz band collective Thomson scattering diagnostics in the large helical device.

Author

Dumbrajs, O., Saito, T., and Tatematsu, Y.

Subjects
*THOMSON scattering, *ELECTROMAGNETIC wave scattering, *GYROTRONS, *MAGNETIC fields, *OSCILLATIONS
Abstract

We present results of theoretical study of mode competition during the voltage rise of a 300-kW, 300-GHz gyrotron operating in the TE22,2,1 mode. Simulations tracking eight competing modes show that, with a proper choice of the magnetic field, stable excitation of the operating mode can be realized, despite the presence of parasitic modes in the resonator spectrum. A finite voltage rise time, 1 kV/4 ns referred to as the slow voltage rise case, is taken into account to simulate realistically the experimental condition. Simulation results with the finite voltage rise time are in good agreement with the experimental test, in which the gyrotron demonstrated reliable operation at power levels up to 300 kW. Moreover, interesting phenomena are observed. Along with voltage rise, the oscillation manner changes from backward wave oscillation to gyrotron oscillation. In the range of the magnetic field lower than the magnetic field strength at which the TE22,2 mode attains to the maximum power, mode competition with the TE21,2 mode takes place although many other competing modes exist in between the two modes. In addition to the slow voltage rise case, the fast voltage rise case, 10 kV/ 4 ns, and the instant voltage rise case are considered. For these cases, simulations also predict stable oscillation of the TE22,2 mode with the same power level with the slow voltage rise case. This indicates that stable oscillations of the TE22,2 mode can be obtained in a wide range of the voltage rise time. [ABSTRACT FROM AUTHOR]

Published
2016
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8. High-density plasma production with potential confinement in the GAMMA 10 tandem mirror

Author

Ichimura, M., primary, Cho, T., additional, Hirata, M., additional, Hojo, H., additional, Ishii, K., additional, Itakura, A., additional, Katanuma, I., additional, Kohagura, J., additional, Nakashima, Y., additional, Saito, T., additional, Tamano, T., additional, Tanaka, S., additional, Tatematsu, Y., additional, Yatsu, K., additional, and Yoshikawa, M., additional

Published
2001
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16. Detection of fusion neutrons from a deuterium‐proton mixed plasma in the GAMMA 10 Tandem Mirror

Author

Kiwamoto, Y., primary, Tatematsu, Y., additional, Saito, T., additional, Abe, H., additional, Ichimura, M., additional, Inutake, M., additional, Yamaguchi, N., additional, Tamano, T., additional, Nakashima, Y., additional, Shoji, M., additional, Cho, T., additional, Hirata, M., additional, Hojo, H., additional, Ikeda, K., additional, Ishii, K., additional, Itakura, A., additional, Katanuma, I., additional, Mase, A., additional, Nagayama, Y., additional, and Yatsu, K., additional

Published
1996
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