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Your search keyword '"Tokunaga, Kazutoshi"' showing total 38 results
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38 results on '"Tokunaga, Kazutoshi"'

10. Quaternion Analysis of Transient Phenomena of Motor-Generator

Author

NAKAMURA, Kazuo, primary, ZHANG, Yifan, additional, ONCHI, Takumi, additional, IDEI, Hiroshi, additional, HASEGAWA, Makoto, additional, TOKUNAGA, Kazutoshi, additional, HANADA, Kazuaki, additional, IDO, Takeshi, additional, IKEZOE, Ryuya, additional, CHIKARAISHI, Hirotaka, additional, MITARAI, Osamu, additional, KAWASAKI, Shoji, additional, HIGASHIJIMA, Aki, additional, NAGATA, Takahiro, additional, and SHIMABUKURO, Shun, additional

Published
2023
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14. Quaternion Analysis of Transient Phenomena in Matrix Converter Based on Space-Vector Modulation

Author

NAKAMURA, Kazuo, primary, ZHANG, Yifan, additional, ONCHI, Takumi, additional, IDEI, Hiroshi, additional, HASEGAWA, Makoto, additional, TOKUNAGA, Kazutoshi, additional, HANADA, Kazuaki, additional, CHIKARAISHI, Hirotaka, additional, MITARAI, Osamu, additional, KAWASAKI, Shoji, additional, HIGASHIJIMA, Aki, additional, NAGATA, Takahiro, additional, and SHIMABUKURO, Shun, additional

Published
2022
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21. Matrix Converter in Power Electronics as a Power Supply for Plasma Control : A Short Review and a Foresight

Author

Jamil, Irfan, Jamil, Rehan, Nakamura, Kazuo, Tokunaga, Kazutoshi, Hasegawa, Makoto, Araki, Kuniaki, Zushi, Hideki, Hanada, Kazuaki, Fujisawa, Akihide, Idei, Hiroshi, Nagashima, Yoshihiko, Kawasaki, Shouji, Nakashima, Hisatoshi, and Higashijima, Aki

Subjects
Milestones, Matrix Converter, Plasma Control, Review R & D, Topologies
Abstract

In recent years, with the state advancement of R&D strategies in matrix converter and the increasing demand of high efficient power supply in power electronics, matrix converter has raised wide attention among the research scientists. In order to cope with these demands, various converters with different rate of power are being developed and related research is realized to accomplish the new matrix converters. Thus, matrix converter as a power supply for plasma control is an important case in this paper. Survey of matrix converter topologies with low cost, small volume and high efficiency are discussed as a power supply for the plasma control. And a short review and a foresight of milestones, significant research and development of a matrix converter from 1950 till present are appended in this paper. In addition, the major contributions which review includes primary, secondary and significant historical research milestones in matrix converters with thematical and chronological order respectively are demonstrated.

Published
2015

22. Quaternion Analysis of Power Supply for Tokamak Plasma Control

Author

Nakamura, Kazuo, Jamil, Irfan, Liu, Xiaolong, Mitarai, Osamu, Hasegawa, Makoto, Tokunaga, Kazutoshi, Araki, Kuniaki, Zushi, Hideki, Hanada, Kazuaki, Fujisawa, Akihide, Idei, Hiroshi, Nagashima, Yoshihiko, Kawasaki, Shouji, Nakashima, Hisatoshi, and Higashijima, Aki

Subjects
Quaternion, Generator equation, Three-phase power electronic circuit, Conjugation, Tokamak plasma control, Biquaternion, Quaternion power, Ohm's law, Matrix converter
Abstract

Power supply for plasma control has been developed from condenser bank with ignitron for pulse tokamak plasma to PWM inverter with IGBT for steady tokamak plasma. Quaternion, four-dimensional hypercomplex number is good at describing three-dimensional rotation. Utilizing the performance of the quaternion rotation,we analyze three-phase power electronic circuit for the tokamak plasma control of equilibrium and stability. By further introduction of biquaternion concept, we can deal with phasor of each phase of three-phase AC similarly. But, we have to multiply the rotation operator from the left-hand side and from the right-hand side by using the conjugation. We try to verify the merits beyond the multiplication inconvenience from both sides. Not only symmetrical three-phase AC (positive sequence) but also negative sequence and zero sequence can be dealt with. Concerning quaternion power of three-phase AC, we can obtain the similar result as the one in pq theory. Quaternion can divide three-dimensional vector. The capability is utilized to develop matrix converter strategy based not only on Venturini method but also on space vector method in more detail.

Published
2015

31. Guiding Center Orbit Calculation for Evaluating the Current Density Distributions of the Electrons in Electron Cyclotron Heating on QUEST

Author

Alam, Md Mahbub, primary, Nakamura, Kazuo, additional, Idei, Hiroshi, additional, Hasegawa, Makoto, additional, Tokunaga, Kazutoshi, additional, Araki, Kuniaki, additional, Hanada, Kazuaki, additional, Fujisawa, Akihide, additional, Nagashima, Yoshihiko, additional, Kawasaki, Shoji, additional, Nakashima, Hisatoshi, additional, Higashijima, Aki, additional, Xia, Fan, additional, and Mitarai, Osamu, additional

Published
2016
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32. A 6 MW/m2High Heat Flux Testing Facility of Irradiated Materials Using Infrared Plasma-Arc Lamps

Author

Sabau, Adrian S., Tokunaga, Kazutoshi, Littleton, Michael G., Kiggans, James O., Schaich, Charles R., Dinwiddie, Ralph B., Moore, Daniel T., Ueda, Yoshio, and Katoh, Yutai

Abstract

AbstractAssessing the effect of neutron irradiation of plasma-facing materials has been challenging due to both the technical and radiological challenges involved. In an effort to address the radiological challenges, a facility was developed to conduct high heat flux testing (HHFT) of inherently small samples of neutron-irradiated materials. A new line-focus reflector was designed and fabricated at Oak Ridge National Laboratory for a plasma-arc lamp (PAL) to attain a source heat flux of 12 MW/m2. The new reflector was fabricated with two ports for monitoring specimen condition during HHFT. At the same operational conditions for PAL, the absorbed heat flux in tungsten was increased from 1.39 MW/m2with the uniform irradiance reflector to 5.12 MW/m2for the line-focus reflector. This fourfold increase in the heat flux, at the same PAL electrode lifetimes, enabled cost-effective facility operation for a high number of cyclic high heat flux tests. Specifically, the test section is confined to a hemispherical dome, and specimens are bolted directly to a water-cooled copper alloy rod. Temperature measurement in the PAL facility was a main challenge due to a limited line of sight. For the first time in a PAL facility operating at high heat fluxes, the specimen surface temperature was directly measured during HHFT with a pyrometer. The HHFT data, which were obtained in this upgraded PAL facility, demonstrated the facility readiness for irradiated materials.

Published
2019
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33. Development of a high-performance control system by decentralization with reflective memory on QUEST

Author

Hasegawa, Makoto, primary, Nakamura, Kazuo, additional, Zushi, Hideki, additional, Hanada, Kazuaki, additional, Fujisawa, Akihide, additional, Mitarai, Osamu, additional, Tokunaga, Kazutoshi, additional, Idei, Hiroshi, additional, Nagashima, Yoshihiko, additional, Kawasaki, Shoji, additional, Nakashima, Hisatoshi, additional, and Higashijima, Aki, additional

Published
2015
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35. Shape Reconstruction of RF-Driven Divertor Plasma on QUEST

Author

Nakamura, Kazuo, primary, Fujita, H., additional, Liu, X. L., additional, Xue, E. B., additional, Xia, Fan, additional, Mitarai, Osamu, additional, Kurihara, Kenichi, additional, Kawamata, Y., additional, Sueoka, M., additional, Hasegawa, Makoto, additional, Tokunaga, Kazutoshi, additional, Zushi, H., additional, Hanada, K., additional, Fujisawa, A., additional, Matsuoka, K., additional, Idei, H., additional, Nagashima, Y., additional, Kawasaki, S., additional, Nakashima, H., additional, Higashijima, A., additional, Araki, Kuniaki, additional, and Fukuyama, A., additional

Published
2014
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37. Effect of surface quality on hydrogen/helium irradiation behavior in tungsten

Author

Chen, Hongyu, Xu, Qiu, Wang, Jiahuan, Li, Peng, Yuan, Julong, Lyu, Binghai, Wang, Jinhu, Tokunaga, Kazutoshi, Yao, Gang, Luo, Laima, and Wu, Yucheng

Abstract

As the plasma facing material in the nuclear fusion reactor, tungsten has to bear the irradiation impact of high energy particles. The surface quality of tungsten may affect its irradiation resistance, and even affect the service life of fusion reactor. In this paper, tungsten samples with different surface quality were polished by mechanical processing, subsequently conducted by D2+implantation and thermal desorption. D2+implantation was performed at room temperature (RT) with the irradiation dose of 1 × 1021D2+/m2by 5 keV D2+ions, and thermal desorption spectroscopy measurements were done from RT to 900 K. In addition, He irradiation was also performed by 50 eV He+ions energy with the fluxes of 5.5 × 1021 m−2s−1and 1.5 × 1022 m−2s−1, respectively. Results reveal that the hydrogen/helium irradiation behavior are both related to surface quality. Samples with high surface quality has superior D2+retention behavior with less D2retained after implantation. However, such samples are more likely to generate fuzzes on the surface after helium irradiation. Different morphologies (smooth, wavy, pyramids) after helium irradiation also demonstrates that the surface morphology is related to tungsten crystallographic orientation.

Published
2021
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