Updated on 2023/02/05

写真a

 
OGURA Kazuo
 
Organization
Academic Assembly Institute of Science and Technology JOUHOU DENSHI KOUGAKU KEIRETU Professor
Graduate School of Science and Technology Electrical and Information Engineering Professor
Faculty of Engineering Department of Engineering Professor
Title
Professor
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Degree

  • 理学博士 ( 1989.5   京都大学 )

Research Areas

  • Manufacturing Technology (Mechanical Engineering, Electrical and Electronic Engineering, Chemical Engineering) / Electron device and electronic equipment

  • Energy Engineering / Fundamental plasma

  • Energy Engineering / Nuclear fusion

Research History (researchmap)

  • Niigata University   Faculty of Engineering Department of Engineering   Professor

    2017.4

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  • Niigata University   Graduate School of Science and Technology Electrical and Information Engineering   Professor

    2010.4

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  • Niigata University   Graduate School of Science and Technology Electrical and Information Engineering   Professor

    2010.4

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  • Niigata University   Faculty of Engineering Department of Electrical and Electronic Engineering   Professor

    1999.4 - 2017.3

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  • Niigata University   Faculty of Engineering   Associate Professor (as old post name)

    1993.4 - 1999.3

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  • Niigata University   Graduate School of Science and Technology   Research Assistant

    1989.3 - 1993.3

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Research History

  • Niigata University   Faculty of Engineering Department of Engineering   Professor

    2017.4

  • Niigata University   Graduate School of Science and Technology Electrical and Information Engineering   Professor

    2010.4

  • Niigata University   Graduate School of Science and Technology Electrical and Information Engineering   Professor

    2010.4

  • Niigata University   Faculty of Engineering Department of Electrical and Electronic Engineering   Professor

    1999.4 - 2017.3

  • Niigata University   Faculty of Engineering   Associate Professor (as old post name)

    1993.4 - 1999.3

  • Niigata University   Graduate School of Science and Technology   Research Assistant

    1989.3 - 1993.3

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Professional Memberships

  • The Institute of Electrical Engineers of Japan

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  • The Japan Society of Plasma Science and Nuclear Fusion Research

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  • The Physical Society of Japan

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  • IEEE

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Papers

  • Dispersion relation of spoof surface plasmon resonant mode on concentric annular metal corrugation

    Yuta Annaka, Kazuo Ogura, Masaya Ito

    AIP Advances   12 ( 11 )   115005 - 115005   2022.11

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    Publishing type:Research paper (scientific journal)   Publisher:AIP Publishing  

    In this study, we demonstrate near-field measurement of a spoof surface plasmon (SSP) on a corrugated metal disk with concentric annular corrugation. The SSP is excited at the center of the disk and is probed by a needle antenna on the corrugated surface. In the measurement, SSP resonant modes are observed around the upper cut-off frequency. The dispersion relation and group velocity are extracted from the measured parameters and correspond well to the calculated dispersion relation. Our results help in designing SSP resonators to improve the device performance of an intense terahertz wave source.

    DOI: 10.1063/5.0123732

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  • Effect of Oversized Factor on 0.1 THz Surface Wave Oscillator

    Yuta ANNAKA, Kazuo OGURA, Mao AOKI, Shingo HAMADA, Tsubasa KATO, Masaya ITO

    Plasma and Fusion Research   17   2406036 - 2406036   2022.4

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    Authorship:Last author   Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Plasma Science and Nuclear Fusion Research  

    DOI: 10.1585/pfr.17.2406036

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  • Experimental study on performance change in F-band surface-wave oscillator due to slow-wave structure length

    M. Aoki, Y. Annaka, K. Ogura, M. Ito

    Japanese Journal of Applied Physics   60 ( 9 )   096004 - 096004   2021.9

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    Authorship:Last author   Publishing type:Research paper (scientific journal)   Publisher:IOP Publishing  

    DOI: 10.35848/1347-4065/ac1de9

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    Other Link: https://iopscience.iop.org/article/10.35848/1347-4065/ac1de9/pdf

  • Experimental Study on Microwave Generation due to Merged Instability in F-Band Surface Wave Oscillator

    Keiichiro RACHI, Kazuo OGURA, Yuta ANNAKA, Mao AOKI, Tsubasa KATO

    Plasma and Fusion Research   16   2401028 - 2401028   2021.3

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    Authorship:Last author   Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Plasma Science and Nuclear Fusion Research  

    DOI: 10.1585/pfr.16.2401028

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  • Design and Fabrication of 200-GHz Oversized Surface-Wave Oscillator

    Yuta Annaka, Kazuo Ogura, Keiichiro Rachi, Yukihisa Hoshi, Shin Kubo, Takashi Shimozuma, Sakuji Kobayashi, Kohji Okada

    IEEE Transactions on Plasma Science   49 ( 1 )   33 - 39   2021.1

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    Publishing type:Research paper (scientific journal)   Publisher:Institute of Electrical and Electronics Engineers (IEEE)  

    DOI: 10.1109/tps.2020.2998119

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  • Spoof-Plasmon Instability in Terahertz Region Excited by Magnetized Electron Beam Reviewed

    Kazuo Ogura, Yuta Annaka, Yukihisa Hoshi, Toru Takahashi

    IEEE Transactions on Plasma Science   49 ( 1 )   40 - 47   2021.1

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    Publishing type:Research paper (scientific journal)   Publisher:Institute of Electrical and Electronics Engineers (IEEE)  

    DOI: 10.1109/tps.2020.3011469

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  • Experimental study of surface-wave oscillator with different electron beam forms Reviewed

    Yuta Annaka, Kazuo Ogura, Yuki Sato, Makoto Nakasone

    Japanese Journal of Applied Physics   59 ( SH )   2020.3

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  • Enhancement-limit of Smith-Purcell radiation with self-bunched keV-order electron beam Reviewed International journal

    Yuta Annaka, Kazuo Ogura, Yuki Sato, Makoto Nakasone, Keiichiro Rachi, Toru Takahashi, Yukihisa Hoshi

    Physics of Plasmas   27 ( 023102 )   2020.2

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  • Study of Spoof Plasmon Formed on Periodically Corrugated Metal Surface Based on Cavity Resonance Method Reviewed

    Kazuo OGURA, Kei SEKINE, Yuta ANNAKA, Min Thu SAN

    Plasma and Fusion Research   14 ( 2406008 )   2019.1

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    Language:English   Publishing type:Research paper (international conference proceedings)  

    DOI: 10.1585/pfr.14.2406008

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  • Non-axisymmetric Radiation from Surface-Wave Oscillator Driven by Weakly Relativistic Electron Beam Reviewed

    Yuta Annaka, Kazuo OGURA, Kosuke OZAWA, Makoto NAKASONE, Yuki SATO

    Plasma and Fusion Research   14 ( 2406015 )   2019.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1585/pfr.14.2406015

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  • Experimental Study on Backward Wave Oscillators Using Dielectric Discharge Cold Cathodes Reviewed

    M. Sakagami, A. Sugawara, T. Otsuki, Y. Annaka, Min Thu San, K. Yambe, K. Ogura, W. Kim

    Plasma and Fusion Research   13 ( 2 )   3406107_1 - 4   2018.9

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1585/pfr.13.3406107

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  • Enhancement of Smith-Purcell radiation with temporal harmonics of surface wave on cylindrical corrugated waveguide Reviewed

    Y. Annaka, K. Ogura, K. Ozawa, K. Sekine, Min Thu San

    Physics of Plasmas   25 ( 6 )   063115-1 - 063115-6   2018.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:American Institute of Physics Inc.  

    We experimentally studied an intense Smith-Purcell (SP) radiation based on a cylindrical corrugated waveguide driven by a weakly relativistic electron beam. The corrugated waveguide has a rectangular periodic structure, and an annular electron beam with energy less than 100 keV and current of the order of 100 A is injected. We observe both intense surface-wave radiation at 25 GHz and intense SP radiations up to 150 GHz. The observed SP radiations are enhanced by the sixth and fourth temporal harmonics of the surface wave. The characteristics of the enhanced SP radiation depend on the periodic number of the structure. In the experiment with the use of the 60-period structure, the observed power of the SP radiation at the fourth harmonic is higher than that of the radiation at the sixth harmonic. In the case of the 30 period-structure, the power level of the radiation at the sixth harmonic is comparable to that at the fourth harmonic.

    DOI: 10.1063/1.5035139

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  • Study on Operation of Oversized Backward Wave Oscillator for Broadband Terahertz Radiation Reviewed

    Min Thu San, Kazuo Ogura, Kazuki Kubota, Yuta Annaka, Kiyoyuki Yambe, Akira Sugawara

    IEEE Transactions on Plasma Science   46 ( 3 )   530 - 538   2018.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Institute of Electrical and Electronics Engineers Inc.  

    We studied the operation of an oversized backward wave oscillator driven by an electron beam with energy less than 100 keV for terahertz radiation. Cylindrical slow wave structures (SWSs) with rectangular corrugations and annular electron beam are used to generate broadband terahertz radiation. The starting conditions for intense terahertz radiation are examined by varying the beam parameter and the SWS length. Operation frequencies in the range of 0.26-0.34 THz and 0.31-0.39 THz are obtained using two types of SWSs with different corrugation amplitudes. The obtained maximum output power is at the kilowatt level. Characteristics of the beam instabilities in the terahertz-SWSs are examined by comparison between the experimental and numerical results.

    DOI: 10.1109/TPS.2018.2796559

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  • Study on Operation of a Surface-Wave Oscillator Around the pi-Point Region Reviewed

    Min Thu San, Kazuo Ogura, Kiyoyuki Yambe, Yuta Annaka, Junpei Fujita

    IEEE TRANSACTIONS ON PLASMA SCIENCE   45 ( 1 )   30 - 38   2017.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    We numerically and experimentally studied the operation of a W-band (75-110 GHz) surface-wave oscillator driven by the electron beam energy of less than 100 keV. Two numerical methods of the real wavenumber analysis and the saddle point analysis are studied to examine the operation of the oscillator. We analyzed the Cherenkov instability for the interaction of the space charge modes and the structure modes EH01. We showed that the instabilities are of absolute instabilities when the oscillator operates around the p-point region. In the experiment, radiations due to the absolute instability are detected around the pi-point region when the length of the slow-wave structure (SWS) is short enough. On the other hand, the absolute instability generates no meaningful radiation in the p-point region for the long length of SWS.

    DOI: 10.1109/TPS.2016.2633550

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  • Characteristic of generation of intense microwave in oversized w-band surface wave oscillator driven by weakly relativistic electron beam Reviewed

    Yuta Annaka, Kiyoyuki Yambe, Kazuo Ogura

    IEEJ Transactions on Fundamentals and Materials   137 ( 3 )   165 - 170   2017

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Institute of Electrical Engineers of Japan  

    We studied an oversized W-band (75-110 GHz) surface wave oscillator driven by a weakly relativistic electron beam. Surface wave is formed on slow wave structure (SWS) with rectangular corrugations and has an upper-cutoff frequency of about 100 GHz. To excite the surface wave, an annular electron beam is generated by a disc type cold cathode with beam energy between about 10 and 80 keV. The oscillator is driven in the backward wave oscillator (BWO) region for beam energy less than 30 keV and in the traveling wave tube (TWT) region for beam energy more than 30 keV. In the BWO region, microwaves are generated due to Cherenkov interaction between electron beam and surface wave in the W-band. In the TWT region, two types of microwaves are generated. One is due to the W-band surface wave as in the case of the BWO region. The other is due to higher order modes above 140 GHz.

    DOI: 10.1541/ieejfms.137.165

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  • Beam Interactions With Surface Waves and Higher Order Modes in Oversized G-band Slow-Wave Structure Reviewed

    Kazuo Ogura, Akihiro Shirai, Masahiko Ogata, Shaoyan Gong, Kiyoyuki Yambe

    IEEE TRANSACTIONS ON PLASMA SCIENCE   44 ( 2 )   201 - 210   2016.2

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    Beam interactions with surface waves and higher order modes in oversized G-band slow-wave structures (SWSs) are studied in a coaxial SWS. The coaxial SWS reduces the number of higher order mode and eases the mode competition problem. The SWS is excited by an annular electron beam. The slow cyclotron (SC) interaction as well as the Cherenkov interaction occurs due to 3-D beam perturbations of the electron beam. Growth rates for the surface waves are larger than those for the higher order modes and increase with increasing beam current. The SC interaction merges with the Cherenkov interaction for a sufficiently high beam current and a relatively low magnetic field. And the merged growth rate also increases with the beam current.

    DOI: 10.1109/TPS.2016.2514380

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  • Dependence of Plasma Plume Formation on Applied Voltage Waveform in Atmospheric-Pressure Plasma Reviewed

    Kiyoyuki Yambe, Kohmei Konda, Kazuo Ogura, Hajime Sakakita

    IEEE TRANSACTIONS ON PLASMA SCIENCE   44 ( 1 )   107 - 112   2016.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    We have studied an atmospheric-pressure plasma generated using a quartz tube, helium gas, and a copper foil electrode by the application of a radio-frequency high voltage. The atmospheric-pressure plasma, which is generated in the form of a bullet, is released as a plume into the atmosphere. To study the properties of plasma plume formation, we examine the relationships among the plasma plume length and charge and the applied voltage waveform. The dependences of the waveform on the plasma plume length and charge are not clear. However, the plasma plume length increases with increasing plasma plume charge in laminar flow. Consequently, we find that the plasma plume length depends on the plasma plume charge becoming an energy source so that electric charge travels the plasma.

    DOI: 10.1109/TPS.2015.2506784

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  • Experimental study on W-band (75 - 110 GHz) oversized surface wave oscillator driven byweakly relativistic electron beams Reviewed

    Min Thu San, Kazuo Ogura, Kiyoyuki Yambe, Yuta Annaka, Shaoyan Gong, Jun Kawamura, Takuro Miura, Shin Kubo, Takashi Shimozuma, Sakuji Kobayashi, Kohji Okada

    Plasma and Fusion Research   11 ( 1 )   2406085   2016

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Plasma Science and Nuclear Fusion Research  

    A W-band (75 - 110 GHz) oversized surface wave oscillator driven by weakly relativistic electron beams with energy in the range of 10 - 80 keV is studied. Rectangular corrugations are used as slow-wave structures (SWS) having surface waves with an upper cutoff frequency of approximately 100 GHz (W-band). Uniformly distributed annular electron beams are generated by a disk-type cold cathode and then are injected into theW-band oscillator. A longer SWS length causes the oscillator to function in both backward wave oscillator (BWO) and travelling wave tube (TWT) operations, and no meaningful oscillation occurs at the π-point or the Bragg condition. When the SWS length is short enough, oscillation occurs in all regions: BWO, π-point and TWT. The operations of the oscillator are strongly affected by the structure length. The maximum radiation power is estimated to be approximately 20kW with the figure of merit of about 2 � 102MW.GHz2.

    DOI: 10.1585/pfr.11.2406085

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  • Measurement Method of Plasma Current and Density in Atmospheric Pressure Plasma Jet Reviewed

    Kiyoyuki Yambe, Hiroki Saito, Kazuo Ogura

    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING   10 ( 6 )   614 - 618   2015.11

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:WILEY-BLACKWELL  

    We present a measurement method of the plasma current and density in an atmospheric-pressure plasma generated using a quartz tube, helium gas, and copper foil electrode by applying a high RF voltage. The plasma in the form of a bullet is released as a plume or jet into the atmosphere. To study the characteristics of the atmospheric-pressure plasma, the plasma current is measured using a current probe, and the drift velocity of plasma plume is measured using a photodetector. The current of the plasma plume is estimated by subtracting the ground line current from the power line current in the circuit. The density of plasma plume n is estimated from the plasma plume current I and the drift velocity v as I = envS, where S is the cross section of plasma plume. The density of the released plasma into the atmosphere is estimated as similar to 10(18) m(-3) by the method. (C) 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

    DOI: 10.1002/tee.22127

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  • Oscillation-Starting Conditions for Oversized G-Band (140-220 GHz) Backward Wave Oscillator Driven by Weakly Relativistic Electron Beam Reviewed

    Shaoyan Gong, Kazuo Ogura, Shintaro Nomizu, Akihiro Shirai, Kosuke Yamazaki, Kiyoyuki Yambe, Shin Kubo, Takashi Shimozuma, Sakuji Kobayashi, Kohji Okada

    IEEE TRANSACTIONS ON PLASMA SCIENCE   43 ( 10 )   3530 - 3536   2015.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    An oversized G-band backward wave oscillator (BWO) driven by a weakly relativistic electron beam less than 100 kV is studied. Rectangular corrugations are used as the slow-wave structure (SWS), which have surface waves with upper cutoff frequencies of above 150 GHz [G-band (140-220 GHz)]. In this paper, we examine the starting conditions for intense G-band BWO operation by varying the beam parameters and SWS lengths. It is shown that a starting energy exists for the G-band BWO and that the starting energy is more critical than the starting current in the oversized BWO. Above the starting energy, very intense output powers on the order of 10 kW are obtained. The oscillation-starting condition for such intense operation may play an important role in high-intensity terahertz wave sources.

    DOI: 10.1109/TPS.2015.2424993

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  • Experimental study of intense radiation in terahertz region based on cylindrical surface wave resonator Reviewed

    Shaoyan Gong, Kazuo Ogura, Kiyoyuki Yambe, Shintaro Nomizu, Akihiro Shirai, Kosuke Yamazaki, Jun Kawamura, Takuro Miura, Sho Takanashi, Min Thu San

    JOURNAL OF APPLIED PHYSICS   118 ( 12 )   2015.9

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    Periodical corrugations structured on a cylindrical conductor have cylindrical surface waves (CSWs), which are reflected at the corrugation ends and form a CSW-resonator. In this paper, intense radiations in terahertz region based on the CSW-resonator are reported. The CSW-resonators with upper cut off frequencies in the modern IEEE G-band (110-300 GHz) are excited by a coaxially injected annular beam in a weakly relativistic region less than 100 kV. It is shown that there exists an oscillation starting energy for the CSW-resonator. Above the starting energy, very intense terahertz radiations on the order of kW are obtained. The operation frequencies in the range of 166-173 GHz and 182-200 GHz are obtained using two types of CSW-resonator with the different corrugation amplitude. Electromagnetic properties of the CSW-resonator can be controlled by the artificial structure and may play an important role in high-intensity terahertz generations and applications. (C) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4931371

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  • Influence of flowing helium gas on plasma plume formation in atmospheric pressure plasma Reviewed

    Kiyoyuki Yambe, Kohmei Konda, Kazuo Ogura

    PHYSICS OF PLASMAS   22 ( 5 )   2015.5

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    We have studied atmospheric pressure plasma generated using a quartz tube, helium gas, and a foil electrode by applying RF high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. The helium gas flowing out of quartz tube mixes with air, and the flow channel is composed of the regions of flowing helium gas and air. The plasma plume length is equivalent to the reachable distance of flowing helium gas. Although the amount of helium gas on the flow channel increases by increasing the inner diameter of quartz tube at the same gas flow velocity, the plasma plume length peaks at around 8m/s of gas flow velocity, which is the result that a flow of helium gas is balanced with the amount of gas. The plasma plume is formed at the boundary region where the flow of helium gas is kept to the wall of the air. (C) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4921657

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  • Enhancement of smith-purcell radiations by selfbunched electron beams in oversized backward wave oscillators

    K. Ogura, K. Yambe, T. Iwasaki, S. Magori, J. Kojima

    ICOPS/BEAMS 2014 - 41st IEEE International Conference on Plasma Science and the 20th International Conference on High-Power Particle Beams   2015.1

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    Language:English   Publishing type:Research paper (international conference proceedings)   Publisher:Institute of Electrical and Electronics Engineers Inc.  

    Smith-Purcell (SP) radiations of weakly relativistic oversized backward wave oscillator (BWO) are examined experimentally. Our oversized BWOs are driven by weakly relativistic electron beams less than 100 keV. New element of this work is an enhancement of SP radiation in the oversized BWO using the bunching section. An annular beam is self-bunched in the K-band bunching section and then is injected into the oversized K-band BWO. SP radiations in the BWO are strongly enhanced in the U-band, which is about twice of the bunching frequency. Moreover, the oversized BWO is developed to G-band. By using the G-band bunching, the SP radiations are enhanced in the H-band. The enhancement of SP-radiation in the oversized BWO by the self-bunched electron beam is attractive to develop THz wave sources.

    DOI: 10.1109/PLASMA.2014.7012770

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  • Relation between plasma plume charge and length in atmospheric pressure plasma Reviewed

    Kiyoyuki Yambe, Shogo Taka, Kazuo Ogura

    IEEJ Transactions on Electrical and Electronic Engineering   9 ( 1 )   S13 - S16   2014.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:John Wiley and Sons Inc.  

    We present atmospheric pressure plasma generated using a quartz tube, helium gas, and copper foil electrode by applying a radio frequency high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. To study the formation of the plasma plume, the dependences of the plasma plume charge and the plasma plume length on the gas flow rate are examined. In a quartz tube with inner diameter 1.5 mm, which has more helium than air in the cross section of the flow channel, the distributions of the length and charge on the gas flow rate show similar tendencies. Consequently, when more helium gas is present than air, the travel length of the plasma plume correlates with the plasma plume charge.

    DOI: 10.1002/tee.22039

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  • Experimental study on Smith-Purcell radiations of weakly relativistic oversized backward wave oscillators Reviewed

    Takayuki Iwasaki, Kazuo Ogura, Shota Magori, Junpei Kojima, Kiyoyuki Yambe

    JOURNAL OF THE KOREAN PHYSICAL SOCIETY   65 ( 8 )   1196 - 1200   2014.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:KOREAN PHYSICAL SOC  

    Smith-Purcell (SP) radiations of weakly relativistic oversized backward wave oscillator (BWO) are examined experimentally. A bunching section composed of a coaxial slow wave structure with inner K-band corrugation is placed upstream from the oversized BWO. An annular beam less than 100 kV is self-bunched in the bunching section and then excites the oversized BWO. SP radiations are examined by using 25.5- and 45.0-GHz oversized BWOs. The beam is too far away from the walls of the oversized BWO for SP radiation to occur without the self-bunching. When the corrugation parameters of the bunching section are the same as those of the oversized BWO, enhanced SP radiations in the frequency region above the surface wave are observed even when the beam propagates outside the interaction region of the surface wave.

    DOI: 10.3938/jkps.65.1196

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  • Electromagnetic Properties of a Trapezoidally Corrugated Slow Wave Structure for Backward Wave Oscillators Reviewed

    Md Ruhul Amin, Kazuo Ogura, Junpei Kojima, Rakibul Hasan Sagor

    IEEE TRANSACTIONS ON PLASMA SCIENCE   42 ( 6 )   1495 - 1501   2014.6

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC  

    In this paper, the electromagnetic properties of a beam free trapezoidally corrugated slow wave structure (TCSWS) are numerically and experimentally investigated. The dimensions of the TCSWS are selected so that it can be deployed in X-band backward wave oscillators (BWOs). The theoretical dispersion characteristics for the axisymmetric TM01-TM03 modes are obtained by solving the dispersion equation numerically. In order to verify the numerical calculation, a cold test is conducted using a 6-period TCSWS cavity and a vector network analyzer (VNA). The cavity is excited by a small needle-type antenna and frequency of the VNA is swept over the passbands. The dispersion characteristics are obtained from frequency values of the discrete resonant peaks of reflection measurement of each TM mode. Experimental results show an excellent agreement with numerical ones. The numerical and cold test results reveal that TCSWS can be used as an alternative to sinusoidally corrugated slow wave structure in BWO experiments with an advantage of ease of fabrication.

    DOI: 10.1109/TPS.2014.2308434

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  • Relation between plasma plume density and gas flow velocity in atmospheric pressure plasma Reviewed

    Kiyoyuki Yambe, Shogo Taka, Kazuo Ogura

    PHYSICS OF PLASMAS   21 ( 4 )   043511-1 - 043511-1   2014.4

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    We have studied atmospheric pressure plasma generated using a quartz tube, helium gas, and copper foil electrode by applying RF high voltage. The atmospheric pressure plasma in the form of a bullet is released as a plume into the atmosphere. To study the properties of the plasma plume, the plasma plume current is estimated from the difference in currents on the circuit, and the drift velocity is measured using a photodetector. The relation of the plasma plume density n(plu), which is estimated from the current and the drift velocity, and the gas flow velocity v(gas) is examined. It is found that the dependence of the density on the gas flow velocity has relations of n(plu) proportional to log(v(gas)). However, the plasma plume density in the laminar flow is higher than that in the turbulent flow. Consequently, in the laminar flow, the density increases with increasing the gas flow velocity. (C) 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4873384

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  • Influence of Gas Flow on Plasma Length in Atmospheric Pressure Plasma Jet Reviewed

    Kiyoyuki Yambe, Tsubasa Furuichi, Kazuo Ogura

    JPS Conference Proceedings   1   015084-1 - 015084-1   2014.3

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.7566/JPSCP.1.015084

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  • Beam interactions with surface waves and higher-order modes in oversized backward wave oscillators Reviewed

    Kazuo Ogura, Akihiko Kojima, Fumiaki Kawabe, Kiyoyuki Yambe, Md. Ruhul Amin

    Journal of the Korean Physical Society   65 ( 8 )   1209 - 1214   2014

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Korean Physical Society  

    Beam interactions with surface waves and higher-order modes in an oversized backward wave oscillator (BWO) are studied. In addition to the well-known Cherenkov interaction, the slow cyclotron interaction occurs due to transverse perturbations of the electron beam. The Cherenkov interaction dominates the slow cyclotron interaction. Growth rates of both the interactions for the higher order modes are small compared with those for the surface-wave modes in an oversized BWO. The coaxial slow-wave structure exhibits a reduced number of higher-order modes, which consequently reduces the mode competition problem and improves beam interactions with higher-order modes. For higher values of beam currents, the slow cyclotron wave grows at a faster rate than the Cherenkov waves.

    DOI: 10.3938/jkps.65.1209

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  • Experimental study on G-band oversized backward wave oscillator driven by weakly relativistic electron beam Reviewed

    Shota Magori, Kazuo Ogura, Takayuki Iwasaki, Junpei Kojima, Kiyoyuki Yambe, Shin Kubo, Takashi Shimozuma, Sakuji Kobayashi, Kohji Okada

    Plasma and Fusion Research   9 ( 2 )   3406032-1 - 3406032-4   2014

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:Japan Society of Plasma Science and Nuclear Fusion Research  

    We studied a G-band oversized backward wave oscillator (BWO) driven by a weakly relativistic electron beam of less than 100 kV. Rectangular corrugations are used as slow-wave structures having surface waves with upper cutoff frequencies above 150 GHz (G-band). We examine how dispersion characteristics of surface waves are affected by accuracy in machining the corrugation amplitude, width, and period length. Of these, accuracy in the amplitude has the largest effect. Uniformly distributed annular electron beams are generated by a disk-type cold cathode and injected into the G-band BWO. G-band BWO operations in 137-173 GHz and above 173 GHz are achieved by changing the corrugation amplitude. The radiation patterns are fairly broad, and the estimated radiation power is at kW level. © 2014 The Japan Society of Plasma Science and Nuclear Fusion Research.

    DOI: 10.1585/pfr.9.3406032

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  • Surface waves in oversized G-band slow-wave structures with rectangular corrugations Reviewed

    Kazuo Ogura, Akihiko Kojima, Fumiaki Kawabe, Kiyoyuki Yambe, Md. Ruhul Amin

    Plasma and Fusion Research   9 ( 2 )   340622-1 - 340622-4   2014

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    Surface waves in oversized G-band slow-wave structure with rectangularly corrugated wall are analyzed numerically. The inner corrugation generates cylindrical surface wave. The outer corrugation also generates transverse magnetic surface wave. The upper cut-offs of surface waves are controlled by corrugation amplitude. In excitation of the surface waves by an annular electron beam, the slow cyclotron interaction as well as the Cherenkov interaction occur due to there-dimensional beam perturbations. The slow cyclotron interaction merges with the Cherenkov interaction at lower magnetic field. The merged growth rate is enhanced by 13%as compared to the isolated Cherenkov growth rate. The surface waves on inner and outer corrugations can have different frequencies and can be excited selectively by adjusting the beam radius of the electron beam. © 2014 The Japan Society of Plasma Science and Nuclear Fusion Research.

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  • Normal Modes and Slow-Wave Instabilities in Oversized Coaxial Slow-Wave Structure With Rectangular Corrugations Reviewed

    Kazuo Ogura, Kiyoyuki Yambe, Kazumasa Yamamoto, Yoshihiro Kobari

    IEEE TRANSACTIONS ON PLASMA SCIENCE   41 ( 10 )   2729 - 2734   2013.10

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    Normal modes and slow-wave instabilities in an oversized coaxial slow-wave structure (SWS) are numerically analyzed for the case of a weakly relativistic annular beam. The coaxial SWS has outer and inner rectangular corrugations with K-band dimensions. The inner corrugations have a cylindrical surface wave, which is the fundamental mode and exists even if the outer conductor is removed. The outer corrugations generate higher-order waveguide modes. Both transverse and longitudinal beam perturbations are considered in the beam interactions, leading to slow cyclotron instabilities as well as Cherenkov instabilities. The instabilities of axisymmetric and nonaxisymmetric modes have almost the same growth rates. The relative position between the outer and inner corrugations affects the normal modes and may allow wide frequency tunability.

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  • Temporal Growth Study in Trapezoidally Corrugated Slow-Wave Structure for Backward-Wave Oscillator Reviewed

    Md. Ruhul Amin, Kazuo Ogura

    IEEE TRANSACTIONS ON PLASMA SCIENCE   41 ( 8 )   2257 - 2263   2013.8

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    The temporal growth rate (TGR) in a trapezoidally corrugated slow-wave structure for a backward-wave oscillator is theoretically studied. An intense relativistic annular electron is used as the energy source for the device. The annular electron beam is assumed to be infinitesimally thin in the radial extent and guided by an infinitely strong magnetic field. The trapezoidal profile of the structure is approximated by a sinusoidal function using Fourier approximation, and the dispersion relation of the system is derived using the Rayleigh-Fourier method. To study the TGR of the electromagnetic wave inside the system, the dispersion equation is solved for different values of the beam parameters. The dimensions of sinusoidally corrugated comparable trapezoidal structure are determined by comparing their dispersion characteristics. For the TM01 mode, TGR of instability that gives a qualitative measure of the microwave generation is calculated. The peak TGR of the proposed structure is found to be on average 1.5% higher than that of the sinusoidally corrugated slow-wave structure for the same set of beam parameters. Apart from its improved growth rate, the proposed structure has an added advantage of easy fabrication.

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  • Higher Order Mode Radiations of Weakly Relativistic Oversized Backward Wave Oscillator Reviewed

    Kazuo Ogura, Kiyoyuki Yambe, Shinji Hasegawa, Takayuki Iwasaki, Kazumasa Yamamoto, Yoshihiro Kobari

    Plasma and Fusion Research   8   2401085-1 - 2401085-5   2013.6

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    DOI: 10.1585/pfr.8.2401085

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  • CYLINDRICAL SURFACE WAVES AND SLOW-WAVE INSTABILITIES OF PERIODICALLY CORRUGATED CYLINDER Reviewed

    Kazuo Ogura, Kazumasa Yamamoto, Yoshihiro Kobari, Kiyoyuki Yambe

    FUSION SCIENCE AND TECHNOLOGY   63 ( 1T )   152 - 155   2013.5

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    Cylindrical surface waves (CSWs) and slow-wave instabilities of a rectangularly corrugated cylinder are numerically examined. CSWs are slow waves with upper cutoffs at the pi point. The upper cutoff frequency increases with increasing cylindrical radius R-0. There are two types of higher-order CSWs: one is due to azimuthal standing waves and the other is due to radial standing waves in the corrugation. Both higher-order types of SWSs have lower cutoffs as well as upper cutoffs leading to pass and stop bands. Slow space charge and slow cyclotron modes of an annular beam exist, which excite the Cherenkov and slow cyclotron instabilities of CSWs, respectively. The growth rates of the higher-order CSWs are comparable to those of the fundamental SWSs.

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  • SMITH-PURCELL RADIATION BASED ON CYLINDRICAL SURFACE WAVES Reviewed

    Shinji Hasegawa, Kazuo Ogura, Takayuki Iwasaki, Kiyoyuki Yambe

    FUSION SCIENCE AND TECHNOLOGY   63 ( 1T )   259 - 261   2013.5

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    Smith-Purcell (SP) radiations based on cylindrical surface wave are examined. Cylindrical surface waves are formed on metal cylinders having a periodically corrugated wall. Corrugation parameters are those used in K-band backward wave oscillators (BWOs). The corrugated metal cylinders are excited by an axially injected coaxial annular beam in a weakly relativistic region less than 100 kV. Cylindrical surface wave excitations due to BWO are observed at about 23 GHz. In addition, SP radiations are observed in the higher frequency regions up to about 90-100 GHz, which is about 4 times higher than the frequency of cylindrical surface wave.

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  • Experimental study on generation of electron beam utilizing cold cathode in the weakly relativistic energy region Reviewed

    Kiyoyuki Yambe, Kazuo Ogura, Shinji Hasegawa, Takaki Shinada, Takayuki Iwasaki, Tsubasa Furuichi

    IEEE Transactions on Plasma Science   41 ( 10 )   2781 - 2785   2013

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    Electron beam generation in a weakly relativistic region of less than 100 kV is investigated utilizing rectangular and disk cold cathodes made of copper. Electron emission areas are located on the edges of the cathodes. For uniform electron emission, some surface roughness is required on the emission surface, which is obtained by scratching the surface with sandpaper. A uniform sheet beam with a size of about 2×40 mm and an annular beam with a diameter of about 25 mm and a thickness of about 2 mm are demonstrated in the weakly relativistic region. Stable electron beams of sheet and annular shapes are experimentally demonstrated. © 1973-2012 IEEE.

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  • Mesurement on electron emission property of beam diode to wide-band pulse surface wave oscillator

    Record of Joint Conference of Electrical and Electronics Engineers in Kyushu   2013   397 - 397   2013

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    DOI: 10.11527/jceeek.2013.0_397

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  • Cylindrical surface wave on periodically corrugated metal Reviewed

    Kazuo Ogura, Hiroshi Iiduka, Kiyoyuki Yambe

    Plasma and Fusion Research   7 ( 1 )   2406022-1 - 2406022-4   2012

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    We present a numerical and experimental study of the dispersion characteristics of cylindrical surface waves on metallic cylinders with rectangular corrugations. In actual devices, reflections at both ends quantize the electromagnetic modes into resonant axial modes. A cavity method based on axial mode measurements is applied to study the properties of the cylindrical surface waves. The resonances are relatively sharp near the upper cutoff, but at low frequencies far from the cutoff, the resonances broaden to resemble those of a Sommerfeld wave. © 2012 The Japan Society of Plasma Science and Nuclear Fusion Research.

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  • Experimental Study on Weakly Relativistic Oversized Backward Wave Oscillator with Coaxial Rectangular Corrugations Reviewed

    Masatoh Takahashi, Kazuo Ogura, Hiroyuki Yoshimura, Hiroshi Iiduka, Akira Sugawara, Kiyoyuki Yambe, Won-Sop Kim

    JOURNAL OF THE KOREAN PHYSICAL SOCIETY   59 ( 6 )   3573 - 3577   2011.12

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    Experimental studies of coaxial oversized backward wave oscillators (BWOs) are presented. The beam voltage is weakly relativistic, less than 100 kV. The slow-wave structure (SWS) consists of a rectangularly corrugated oversized hollow waveguide and rectangularly corrugated inner conductor and has a target operating frequency due to Cherenkov interaction is in the K-band. The coaxial SINS can have two surface waves caused by the inner and the outer corrugations. The oversized BWO operations under the influences of two surface waves are examined. The oscillation start voltage is decreased by introducing a rectangularly corrugated inner conductor, The output. power is increased greatly as compared with those without; the corrugated inner conductor. The inner corrugation improves the oversized BWO operation.

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  • Numerical Study of Slow-wave Instabilities in an Oversized Coaxial Slow-wave Structure Reviewed

    Kazuo Ogura, Shingo Abe, Hiroki Kimura, Kazumasa Yamamoto, Kiyoyuki Yambe, Md Ruhul Amin

    JOURNAL OF THE KOREAN PHYSICAL SOCIETY   59 ( 6 )   3555 - 3559   2011.12

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    In this paper, slow-wave instabilities in oversized coaxial slow-wave structures (SWSs) are numerically analyzed. An infinitesimally thin annular beam with transverse perturbations and guided by a finite axial magnetic field is considered as an energy source for creating the instabilities. The coaxial SWSs consist of an outer oversized hollow waveguide and a central conductor and have sinusoidal corrugations. An electromagnetic slow-wave is generated by the inner corrugation and is called the inner surface wave (ISW). The ISW is a cylindrical surface wave and can exist even if the outer conductor is removed. The higher-order modes are produced by the outer waveguide. The annular beam interacts with the ISW and higher-order modes. A slow cyclotron instability occurs due to the transversely modulated beam boundary, in addition to the conventional Cherenkov instability. The slow-wave instabilities can be controlled by using the beam radius and the relative positions of inner and outer corrugations.

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  • Experimental study on backward wave oscillation based on cylindrical surfacewave of Smith-Purcell free electron laser Reviewed

    Kazuo Ogura, Kiyoyuki Yambe, Hiroyuki Yoshimura, Masatoh Takahashi

    Plasma and Fusion Research   6 ( 1 )   2401039_1 - 2401039_4   2011

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    Backward wave oscillation based on a cylindrical surface wave of Smith-Purcell free electron laser (SPFEL) is demonstrated. The SP-FEL is composed of a metal cylinder having a periodically corrugated wall and a surrounding hollow straight waveguide. Corrugation parameters are those used in K-band backward wave oscillators (BWOs). The metal cylinder has a surface wave due to the corrugation. The cylindrical surface wave is excited by an axially injected coaxial annular beam. Radiations due to the backward wave oscillation based on the cylindrical surface wave are examined in a weakly relativistic region less than 100 kV. An oscillation starting voltage exists for the backward wave oscillation as in the case of hollow oversized BWO. The frequencies are in K-band and are determined by the cylindrical corrugation. Radiations up to tens of kW are obtained. © 2011 The Japan Society of Plasma Science and Nuclear Fusion Research.

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  • Study on Electron Distribution Function and Spatial Structure of Weakly Relativistic Electrons in Microwave and Mirror Devices

    K., Ogura, K., Bansho, K., Otubo, H., Iizuka, A., Sugawara, T., Imai, M., Yoshikawa, R., Minami

    Annual Report of NIFS, April 2009-March 2010   490   2010.11

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  • Numerical Analysis of Slow-Wave Instabilities in an Oversized Sinusoidally Corrugated Waveguide Driven by a Finitely Thick Annular Electron Beam Reviewed

    K. Otubo, K. Ogura, M. Yamakawa, Y. Takashima

    Plasma and Fusion Research   5   S1047_1 - S1047_6   2010.1

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    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.

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  • Experimental Study of Oversized Backward Wave Oscillator with Coaxial Slow-Wave Structure Reviewed

    H. Yoshimura, K. Ogura, K. Bansho, H. Iiduka, M. Takahashi, A. Sugawara

    Plasma and Fusion Research   5   S2093_1 - S2093-4   2010.1

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    Studies of coaxial oversized backward wave oscillators (BWOs) are reported. The beam voltage is weakly relativistic (less than 100 kV). The slow-wave structure consists of a periodically corrugated oversized waveguide and periodically corrugated inner conductor, whose target operating frequency due to Cherenkov interaction is in the K-band. A starting energy exists for the coaxial oversized BWO as it does for a hollow oversized BWO. The coaxial slow-wave structure has two surface wave modes caused by the inner and outer corrugations. Operation based on these surface modes can be controlled by the beam diameter. The phase difference between the inner and outer corrugations has little effect on operation of the oversized BWO.

    DOI: 10.1585/pfr.5.S2093

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  • Experimental Study of Slow Cyclotron Maser Operation in Weakly Relativistic Region Reviewed

    K. Bansho, K. Ogura, H. Oe, Y. Kazahari, H. Iizuka, A. Sugawara, T. Shimozuma, S. Kobayashi, K. Okada

    Plasma and Fusion Research   5   S1049-1 - S1049-6   2010.1

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    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.

    DOI: 10.1585/pfr.5.S1049

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  • Numerical Analysis of Slow-Wave Instabilities in X-band Sinusoidally Corrugated Waveguide with Coaxial Slow-Wave Structure Reviewed

    S. Abe, K. Ogura, K. Otubo, H. Kimura

    Plasma and Fusion Research   5   S2091_1 - S2091_4   2010.1

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    The dispersion characteristics and slow-wave instabilities of a sinusoidally corrugated waveguide with coaxial slow-wave structure (SWS) are analyzed. In SWS, a central cylindrical conductor is surrounded by an outer cylindrical conductor. Sinusoidal corrugation is formed on either conductor or both conductors. The corrugation parameters are those used for an X-band SWS. The relative phase between the sinusoidal corrugations on the inner and outer conductors affects the dispersion characteristics. Instabilities due to beam interactions with the slow -waves are examined by considering three-dimensional beam perturbations. The slow cyclotron instability occurs in addition to the Cherenkov instability, since transverse as well as longitudinal perturbations are included.

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  • Experimental Study on Disk Type Cold Cathode in Weakly Relativistic Energy Region Reviewed

    H. Oe, K. Ogura, Y. Kazahari, K. Bansho, H. Iizuka, A. Sugawara, W.S.Kim

    Journal of Plasma and Fusion Research Series   8   1477 - 1482   2009.10

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  • Analysis of Slow-Wave Instability in Rectangularly Corrugated Cylindrical Waveguide Reviewed

    Y. Takashima, K. Ogura, M. Yamakawa, K. Otubo, M. R. Amin

    Journal of Plasma and Fusion Research Series   8   1512 - 1517   2009.10

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  • Instability of Annular Beam with Finite Thickness in Dielectric-Loaded Cylindrical Waveguide Reviewed

    S. Tamura, M. Yamakawa, Y. Takashima, K. Ogura

    Plasma and Fusion Research   3   S1020_1 - S1020_7   2008.5

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    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.

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  • Operation Characteristics of Microwave Sources Based on Slow-Wave Interaction in Rectangular Corrugation Reviewed

    Y. Takamura, Y. Kazahari, H. Oe, K. Ogura, A. Sugawara, M. Hirata

    Plasma and Fusion Research   3   S1078_1 - S1078_5   2008.5

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    Studies on slow-wave devices with a novel disk cathode and two types of rectangular corrugation are reported. The beam voltage is weakly relativistic, which is less than 100 kV. A disk cathode can generate a uniformly distributed annular beam in the weakly relative region. Rectangular corrugation having the ratio of the corrugation width to the periodic length of 50 or 20% is used. Using the former, output powers of about 200 kW are obtained at around 100 kV. For the latter, the effect of slow cyclotron resonance is observed in the low-energy region of around 30 kV. Output powers of slow cyclotron masers are in the range of a few hundred W. The operation mode of a slow cyclotron maser can be controlled between axisymmetric and nonaxisymmetric modes by changing the end condition of rectangular corrugation.

    DOI: 10.1585/pfr.3.S1078

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  • Studies of a Weakly Relativistic Oversized Backward Wave Oscillator with Disk Cathode and Rectangular Corrugation Reviewed

    K. Ogura, Y. Miyazawa, S. Aoyama, Y. Takamura, S. Tamura, A. Sugawara

    IEEJ Transactions on Fundamentals and Materials   127 ( 11 )   681 - 686   2007.11

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    Studies of an oversized BWO with a novel cathode and a rectangular corrugation are presented. The beam voltage is weakly relativistic, less than 100 kV. We propose to use a disk cathode made of metal only. The disk cathode can generate a uniformly distributed annular electron beam even in the weakly relativistic case. By using the annular electron beam, a weakly relativistic oversized BWO consisting of rectangularly corrugated cylindrical waveguide is demonstrated. The oscillation starting energy is about 60 kV for a 10-period rectangular corrugation. The maximum output power is estimated about 200 kW. The operation mode between axisymmetric and nonaxisymmetric modes can be controlled by changing the end condition of BWO.

    DOI: 10.1541/ieejfms.127.681

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  • Weakly Relativistic K-Band Oversized Backward Wave Oscillator with Bragg Reflector at Beam Entrance of Slow Wave Structure Reviewed

    K. Ogura, Y. Miyazawa, H. Tanaka, Y. Kiuchi, S. Aoyama, A. Sugawara

    Plasma and Fusion Research   2   S1041_1 - S1041_4   2007.10

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    We report an oversized K-band backward wave oscillator (BWO) operating above 20 GHz in the weakly relativistic region less than 100 kV. It is very important to prevent microwave from going into the beam diode, since intense microwaves will harmfully affect beam generation. A weakly relativistic oversized BWO is demonstrated using a Bragg reflector at the beam entrance of slow wave structure (SWS). The effect of the Bragg reflector on the BWO operation is examined, by changing the boundary condition at the beam entrance. The Bragg reflector improves the performance of the oversized BWO.

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  • Numerical study of instabilities induced by sheet electron beam on corrugated metal plate Reviewed

    Osamu Watanabe, Tsuguhiro Watanabe, Kazuo Ogura, Yoshinori Tatematsu, Yoriko Shima, Tsuyoshi Imai

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS BRIEF COMMUNICATIONS & REVIEW PAPERS   46 ( 9A )   6051 - 6056   2007.9

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    It has been confirmed that the normal mode of a surface wave on a corrugated metal plate can be excited by a sheet electron beam. Two types of instabilities are analyzed numerically. One is the Cherenkov instability between the surface normal mode and the slow-space-charge mode of the electron beam. This instability is possibly absolute instability. The oscillation frequency of this instability can be controlled by the amplitude of the corrugation depth. The electron beam energy for this instability is determined by the ratio of the period length and the amplitude of the corrugation. Another is the Smith-Purcell-type instability. This instability is always convective-type instability. The oscillation frequency is higher than that of the above-mentioned Cherenkov instability and is in a broad band. The temporal growth rate of this instability is strongly reduced as the beam energy is reduced.

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  • Dispersion characteristics of a rectangularly corrugated cylindrical slow-wave structure driven by a non-relativistic annular electron beam Reviewed

    M. R. Amin, K. Ogura

    IET MICROWAVES ANTENNAS & PROPAGATION   1 ( 3 )   575 - 579   2007.6

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    The dispersion relation of a rectangularly periodic cylindrical slow-wave structure (SWS) with an annular electron beam of energy < 100 keV and current around 200 A has been derived and solved numerically. This type of system is typically used in backward wave high-power microwave devices and linear accelerators. The dispersion relation is analysed for both the cold structure (for zero beam current) and structure with an annular beam. The cold structure dispersion relation is characterised by the real value of frequency and wavenumber. When an electron beam propagates through the structure and the beam energy and current are sufficient to produce instability, microwave radiation results. The strength of this radiation can be qualitatively approximated from the temporal growth rate of the instability, which is defined by the imaginary values of the frequency corresponding to the complex conjugate roots of the dispersion relation. The temporal growth rate for various beam parameters has been calculated. The proposed SWS is very easy to be fabricated and can be used in the real experiments for generating high-power microwaves.

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  • Overview of recent progress in the gamma 10 tandem mirror Reviewed

    T. Cho, H. Higaki, M. Hirata, H. Hojo, M. Ichimura, K. Ishii, K. Islam, A. Itakura, I. Katanuma, J. Kohagura, R. Minami, Y. Nakashima, T. Numakura, T. Saito, Y. Tatematsu, M. Yoshikawa, O. Watanabe, Y. Kubota, T. Kobayashi, Y. Yamaguchi, H. Saimaru, Y. Higashizono, Y. Miyata, S. Kiminami, K. Shimizu, M. Itou, T. Ikuno, A. Mase, Y. Yasaka, K. Sakamoto, M. Yoshida, A. Kojima, K. Ogura, N. Nishino, W. Horton, T. Kariya, T. Imai, V. P. Pastukhov, S. Miyoshi

    FUSION SCIENCE AND TECHNOLOGY   51 ( 2T )   11 - 16   2007.2

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    (1) Four-time progress in ion-confining potentials phi(c) to 3.0 kV in comparison to phi(c) attained 1992-2002 is achieved in the hot-ion mode (T-i=several keV). A scaling of phi(c), which favorably increases with plug electron-cyclotron heating (ECH) powers (P-PECH), is obtained. (2) The advance in phi(c) leads to a finding of remarkable effects of radially sheared electric fields (dE(r)/dr) on turbulence suppression and transverse-loss reduction. (3) A weak decrease in phi(c) with increasing n(c) to similar to 10(19) m(-3) with the recovery of phi(c) with increasing P-PECH is obtained. (4) The first achievement of active control and formation of an internal transport barrier (ITB) has been carried out with the improvement of transverse energy confinement. Off-axis ECH in an axisymmetric barrier mirror produces a cylindrical layer with energetic electrons, which flow through the central cell and into the end region. The layer, which produces a localized bumped ambipolar potential Phi(c), generates a strong E-r shear and peaked vorticity with the direction reversal of E(r)xB sheared flow near the Phi(c) peak. Intermittent vortex-like turbulent structures near the layer are suppressed in the central cell. This results in T-e and T-i rises surrounded by the layer. The phenomena are analogous to those in tokamaks with ITB. (5) Preliminary central ECH (170 kW 20 ms) in a standard tandem-mirror operation raises T-e0 from 70 to 300 eV together with T-i perpendicular to 0 from 4.5 to 6.1 keV, and T-i//0 from 0.5 to 1.2 keV with tau(p0)=95 ms for phi(c) (=1.4 kV) trapped ions. The on-axis particle to energy confining ratio of tau(p0)/tau(E0) is observed to be 1.7 for phi(c) trapped ions (consistent with Pastukhov's theory) and 2.4 for central mirror-trapped ions with 240-kW plug ECH and 90-kW ICH (eta(ICH)similar to 0.3; nl(c)=4.5X10(17)m(-2)). (6) Recently, a 200 kW central ECH with 430 kW plug ECH produces stable central-cell plasmas (T-e=600 eV and T-i=6.6 keV) with azimuthal E(r)xB sheared flow. However, in the absence of the shear flow, hot plasmas migrate unstably towards vacuum wall with plasma degradation.

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  • Improved performance of oversized backward wave oscillator driven by weakly relativistic electron beam Reviewed

    S. Aoyama, Y. Miyazawa, K. Ogura, A. Sugawara, M. Hirata

    FUSION SCIENCE AND TECHNOLOGY   51 ( 2T )   325 - 327   2007.2

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    We improve the performance of the K-band oversized backward wave oscillator. The beam is annular and weakly relativistic. The beam voltage is less than 100 kV and the beam current is less than 500 A. The operation frequencies are in the range of 23-27 GHz. The electromagnetic field of the K-band B WO concentrates in the vicinity of the SWS wall and the electron beam should be propagated within a few mm from the wall. The uniformity of annular beam is also very important for the efficient beam coupling. First, we modify the oversized SWS so that the beam interaction point is shifted to the pi point. Secondly, we improve uniformity of the annular electron beam and the output power increases up to about 500 kW level.

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  • Slow cyclotron and Cherenkov instabilities in weakly relativistic oversized backward wave oscillator Reviewed

    Y. Kiuchi, H. Tanaka, K. Ogura, O. Watanabe, T. Cho, Md. R. Amin

    FUSION SCIENCE AND TECHNOLOGY   51 ( 2T )   331 - 333   2007.2

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    We analyze instabilities of oversized backward wave oscillator (BWO) designed for K-band operations in a weakly relativistic region (less than 100 kV). For the oversized BWO, the electromagnetic field is a surface wave localized near the waveguide wall. Instabilities due to the beam interactions with the surface wave are examined by considering three-dimensional beam perturbations. There exist the slow cyclotron and Cherenkov instabilities as in the case of non-oversized BWO. Nonaxisymmetric as well as axisymmetric instabilities are excited, even in the completely axisymmetric system. The growth rates of both modes are in the same order. The growth rates decrease exponentially if the beam is apart from the SWS wall.

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  • Study of the effects of plasma-confining potentials using end-loss analysing systems Reviewed

    M. Hirata, T. Cho, J. Kohagura, T. Numakura, K. Shimizu, M. Ito, S. Kiminami, N. Morimoto, K. Hirai, T. Yamagishi, T. Ikuno, S. Namiki, Y. Miyata, R. Minami, K. Ogura, T. Kondoh, T. Kariya, T. Imai, S. Miyoshi

    FUSION SCIENCE AND TECHNOLOGY   51 ( 2T )   183 - 185   2007.2

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    An application of electron-cyclotron heating with an off-axis resonance location produces a cylindrical layer with energetic electrons and facilitates the formation for a profile of plasma rotation with a radially localized high-vorticity layer. These phenomena are detected by several types of end-loss ions- and electrons-analyser. Formation of radial transport barrier has been observed in the vicinity of the high-vorticity layer in GAMMA 10.

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  • Investigation of electron distribution functions in the plug region of the GAMMA 10 tandem mirror Reviewed

    J. Kohagura, T. Cho, M. Hirata, T. Numakura, Y. Tornii, S. Kiminami, N. Morimoto, K. Shimizu, M. Ito, T. Ikuno, S. Namiki, K. Hirai, T. Yamagishi, Y. Miyata, R. Minami, K. Ogura, T. Kariya, T. Imai, S. Miyoshi

    FUSION SCIENCE AND TECHNOLOGY   51 ( 2T )   204 - 207   2007.2

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    Generalized scaling laws for the formation of plasma confining potentials are investigated to find the physics essentials common to representative tandem-mirror operational modes in GAMMA 10. These modes are characterized in terms of (i) a high-potential mode and (ii) a hot-ion mode. The potential-formation scalings in these modes are consolidated and generalized on the basis of the consistency with finding of the wider validity of Cohen's strong electron-cyclotron heating (ECH) theory covering over both modes. A plateau-shaped electron distribution function is observed when a plug electron-confining potential is formed in the hot ion mode of GAMMA 10, as predicted in terms of the strong ECH theory.

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  • Effects of plasma confining potentials and the associated radially sheared electric fields on the plasma energy confinement Reviewed

    T. Numakura, T. Cho, J. Kohagura, M. Hirata, Y. Miyata, R. Minami, S. Kiminami, K. Shimizu, N. Morimoto, M. Itou, T. Ikuno, S. Namiki, T. Yamagishi, K. Hirai, K. Ogura, T. Kariya, T. Imai, S. Miyoshi

    FUSION SCIENCE AND TECHNOLOGY   51 ( 2T )   343 - 345   2007.2

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    The effects of the plasma-confining potentials and the associated radially sheared electric fields on the central-cell electron energy confinement are theoretically and experimentally investigated in the GAMMA 10 tandem mirror. In particular, the scaling of the central-cell electron temperatures with electron-confining potentials is studied on the basis of the local energy-balance equation. The obtained theoretical scaling of electron temperatures with electron-confining potentials is then compared with the experimentally observed relation between these two parameters.
    Recently, by the use of new 0.5-M'W level gyrotrons in the plug region, four-time progress in the formation of the ion-confining potential phi(c) including a new record of 3 W has been achieved in a hot-ion mode having bulk-ion temperature T-i = several keV In the hot-ion mode, intermittent vortex-like turbulent structures are observed in the case without the gyrotron injections; in this case, radially produced weak shear of electric fields dE(r)/dr and appreciable transverse losses are observed. However, during the application of electron-cyclotron heatings, the associated potential rise produces a stronger shear in the central cell (dE(r)/dr = several 10 kV/m2) resulting in the disappearance of such intermittent turbulent vortices with plasma confinement improvement.
    In order to investigate the effect of the radially sheared electric fields on the electron energy confinement, the radial profiles of the thermal diffusivity are derived from the local power-balance analysis by the use of the data from the following various diagnostics in the above-described hot-ion mode. The obtained radial profiles of radial electric field and thermal diffusivity imply that the reduction of the thermal diffusivity is associated with the radially produced strong shear of electric fields.

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

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

    Plasma and Fusion Research   2   S1077 - S1077   2007

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    Mirror devices, having open-ended regions, provide intrinsic important advantages in terms of the control of radial-potential or E<sub>r</sub> shear profiles on the basis of axial particle loss control for ambipolar potential formation. From the viewpoint of the mechanism investigation of radially localized transport-barrier formation, an idea of off-axis-resonant electron-cyclotron heating (ECH) is proposed and applied in the tandem mirror GAMMA 10, by the use of the aforementioned intrinsic advantage of mirror devices. The off-axis ECH produces a cylindrical layer with energetic electrons and facilitates the formation for a localized bumped ambipolar potential with a strong shear of radial electric fields E<sub>r</sub>. Remarkable effects of dE<sub>r</sub>/dr on the suppression of turbulent fluctuations with plasma confinement improvement are found by the use of signals of end-loss currents flowing from the central cell as well as the central-cell soft x ray. In association with the reduction of the fluctuations due to strong E<sub>r</sub> shear formation, increases in ion and electron temperatures are found.

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  • Slow cyclotron instability due to surface modulation of an annular beam Reviewed

    Kazuo Ogura, Hoshiyuki Yamazaki, Yutaka Kiuchi, Md. Ruhul Amin

    JOURNAL OF PLASMA PHYSICS   72 ( 6 )   905 - 908   2006.12

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    The Cherenkov instability used in slow-wave devices has been well studied in the literature. However, in previous analyses, the beam motion is restricted to the longitudinal direction assuming an infinitely strong magnetic field. For the finite strength magnetic field, the transverse beam perturbation cannot be ignored and leads to the slow cyclotron instability. Recently, a new version of self-consistent field theory considering three-dimensional perturbation has been developed based on a solid beam, in which the effect of the transverse perturbation appears as a surface charge at a fixed boundary. In the case of a thin annular beam, the boundary is modulated and is essentially different from the solid beam case. We propose a self-consistent field theory considering the moving modified boundary surface. The slow cyclotron instability due to the modulation of an infinitesimally thin annular electron beam is presented.

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  • Numerical examination of the operation modes of a weakly relativistic oversized backward wave oscillator Reviewed

    Hoshiyuki Yamazaki, Hirokazu Takagi, Hidekazu Tanaka, Kazuo Ogura

    JOURNAL OF PLASMA PHYSICS   72 ( 6 )   915 - 918   2006.12

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    Backward wave oscillators (BWOs) have been studied as a candidate high-power microwave source. To increase the operation frequency, an oversized slow-wave Structure (SWS) is used. The operation at reduced voltage is preferable for practical applications. This work is aimed at numerically examining the operation mode of a weakly relativistic oversized BWO. We examine not only the axisymmetric transverse magnetic mode but also the non-axisymmetric hybrid modes of the oversized SWS. Both of them are candidates for the operation modes. These modes are surface waves whose fields are concentrated near the SWS wall. They overlap in frequency and are not separated by stop-bands. For an efficient beam interaction, the injected electron beam needs to be controlled more accurately than in the non-oversized SWS case.

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  • Simultaneous measurements of ion and electron currents using a novel compact electrostatic end-loss-current detector Reviewed

    M. Hirata, Y. Miyake, T. Cho, J. Kohagura, T. Numakura, K. Shimizu, M. Ito, S. Kiminami, N. Morimoto, K. Hirai, T. Yamagishi, Y. Miyata, Y. Nakashima, S. Miyoshi, K. Ogura, T. Kondoh, T. Kariya

    REVIEW OF SCIENTIFIC INSTRUMENTS   77 ( 10 )   10E719-1 - 10E719-3   2006.10

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    For the purpose of end-loss-ion and -electron analyses in open-field plasmas, a compact-sized electrostatic end-loss-current detector is proposed on the basis of a self-collection principle for suppressing the effects of secondary-electron emission from a metal collector. For employing this specific method, it is worth noting that no further additional magnetic systems except the ambient open-ended magnetic fields are required in the detector operation. This characteristic property provides a compactness of the total detection system and availability for its use in plasma confinement devices without disturbing plasma-confining magnetic fields. The detector consists of a set of parallel metal plates with respect to lines of ambient magnetic forces of a plasma device for analyzing incident ion currents along with a grid for shielding the collector against strays due to the metal-plate biasing. The characterization experiments are carried out by the use of a test-ion-beam line along with an additional use of a Helmholtz coil system for the formation of open magnetic fields similar to those in the GAMMA 10 end region. The applications of the developed end-loss-current detector in the GAMMA 10 plasma experiments are demonstrated under the conditions with simultaneous incidence of energetic electrons produced by electron-cyclotron heatings for end-loss-plugging potential formation. (c) 2006 American Institute of Physics.

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  • Experimental estimation of the local energy balance of the potential-confining electrons in tandem-mirror plasmas Reviewed

    T. Numakura, T. Cho, J. Kohagura, M. Hirata, R. Minami, Y. Miyata, Y. Tomii, Y. Miyake, S. Kiminami, K. Shimizu, N. Morimoto, M. Itou, T. Imai, S. Miyoshi, K. Ogura

    REVIEW OF SCIENTIFIC INSTRUMENTS   77 ( 10 )   10F302-1 - 10F302-3   2006.10

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    Our proposed "matrix-type" semiconductor detectors are applied for studying the local energy balance of bulk electrons in the tandem-mirror GAMMA 10. The matrix-type detector array consists of compactly produced six "rows" having different thicknesses of thin dead layers (SiO2) on its surface. Each row has seven channel units ("columns") for measuring radiation profiles in the radial direction of plasmas. These various SiO2 layers are, thus, employed as "unbreakable ultrathin radiation-absorption filters" having various thicknesses to distinguish x rays from charge-exchange neutral particles and analyze the radial profiles of both plasma ion and electron temperatures simultaneously. The radial profiles of the energy confinement time and the thermal diffusivity obtained from the local energy balance analysis imply that the improvement of the plasma confinement is associated with the strong shear of radial electric fields due to a high plasma confining potentials. (c) 2006 American Institute of Physics.

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  • X-ray diagnostics for investigating electron distribution functions in the central cell of the GAMMA 10 tandem mirror Reviewed

    J. Kohagura, T. Cho, M. Hirata, T. Numakura, T. Fukai, Y. Tomii, S. Kiminami, N. Morimoto, T. Ikuno, S. Namiki, K. Shimizu, M. Ito, Y. Miyata, R. Minami, S. Miyoshi, K. Ogura, N. Saito, T. Saito, T. Kariya

    REVIEW OF SCIENTIFIC INSTRUMENTS   77 ( 10 )   10F332-1 - 10F332-3   2006.10

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    The quantum efficiency of an ultralow-energy-sensitive pure-Ge (ULE Ge) detector is investigated using synchrotron radiation from the storage ring at AIST especially for x-ray pulse-height analyses (PHAs), down to a few hundred eV. Several types of x-ray diagnostics such as x-ray PHA, x-ray absorption methods, and x-ray tomography using the ULE Ge detector, a NaI (Tl) detector, as well as a microchannel-plate tomography system are employed for investigating electron distribution functions and electron temperature profiles with preliminary central electron-cyclotron heating in the central cell of the GAMMA 10 tandem mirror. These measurements play an important role in studying an essential physics scaling of the electron temperature as a function of electron confining potential in tandem mirror plasmas. (c) 2006 American Institute of Physics.

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  • Numerical Study of Electromagnetic Surface Wave on Corrugated Metal Surface Reviewed

    O. Watanabe, T. Watanabe, K. Ogura, T. Imai, T. Cho

    Journal of Plasma and Fusion Research   1   025-1 - 025-2   2006.1

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    The dispersion characteristics of surface wave propagated on a deeply corrugated metal surface are analyzed. Surface wave becomes slow wave, because surface wave is evanescent wave to the direction away from the corrugated metal surface. The surface wave is possible to be backward wave, due to the periodic nature of the corrugation of metal surface. Because the Rayleigh hypothesis has failed for the analysis of an electromagnetic field upon a deeply corrugated surface, the dispersion relations are solved by a direct numerical computation of wave equations.

    DOI: 10.1585/pfr.1.025

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  • High-power ECRH experiments in the GAMMA 10 tandem mirror Reviewed

    Tatematsu, Y., Cho, T., Higaki, H., Hirata, M., Hojo, H., Ichimura, M., Imai, T., Ishii, K., Islam, M. K., Itakura, A., Katanuma, I., Kohagura, J., Nakashima, Y., Numakura, T., Saito, T., Watanabe, O., Yoshikawa, M., Machida, N., Nagai, D., Nozaki, K., Yamaguchi, Y., Sakamoto, K.

    Journal of the Korean Physical Society   49   S406 - S411   2006

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    Power-up of gyrotrons was carried out and corresponding launcher systems were designed for plug and central-cell ECRH systems in the GAMMA 10 tandem mirror. Then, a high-power ECRH experiment was started. For the plug ECRH, new 500-kW gyrotrons produced a new record value of the confining potential. For the central-cell ECRH, development of a new antenna system has increased the transmission rate of incident microwave power and focused it onto the machine axis in the resonance surface. As a result, a clear increase of the diamagnetism was observed during the pulse of ECRH.

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  • Progress in potential formation and findings in the associated radially sheared electric-field effects on suppressing intermittent turbulent vortex-like fluctuations and reducing transverse losses Reviewed

    T Cho, J Kohagura, M Hirata, T Numakura, H Higaki, H Hojo, M Ichimura, K Ishii, KM Islam, A Itakura, Katanuma, I, Y Nakashima, T Saito, Y Tatematsu, M Yoshikawa, Y Takemura, A Kojima, T Kobayashi, Y Yamaguchi, Y Miyata, N Yokoyama, Y Tomii, Y Miyake, S Kiminami, K Shimizu, Y Kubota, H Saimaru, Y Higashizono, A Mase, Y Yasaka, K Ogura, K Sakamoto, M Yoshida, VP Pastukhov, T Imai, S Miyoshi

    NUCLEAR FUSION   45 ( 12 )   1650 - 1657   2005.12

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    Following the 19th IAEA Fusion Energy Conference (Lyon, 2002), (1) three-time progress in the formation of ion-confining potential heights phi(c) including a record of 2.1 W in comparison to those attained 1992-2002 is achieved for tandem-mirror plasmas in the hot-ion mode with ion temperatures of several kiloelectronvolts. (2) The advance in the potential formation gives the bases for finding the remarkable effects of radially produced shear of electric fields E,, or non-uniform sheared plasma rotation on the suppression of intermittent vortex-like turbulent fluctuations. (i) Such a shear effect is visually highlighted by x-ray tomography diagnostics; that is, spatially and temporally intermittent vortex-like fluctuated structures are clearly observed as two-dimensionally reconstructed visual structures for the first time in kiloelectronvolt order ion-cyclotron heated plasmas having a weak shear in GAMMA 10. (ii) However, during the application of plug electron-cyclotron heatings (ECH), the associated potential rise produces a stronger shear (dE(r)/dr = several 10kVm(-2)) resulting in the disappearance of such intermittent turbulent vortices with plasma confinement improvement. X-ray observations also show elongation of a vortex structure from a circular into an ellipsoidal shape, as depicted in H-mode theories, with an outward shift. (3) For the physics interpretations and control of such potential and the associated shear formation, the validity of our proposed theory of the potential formation is extensionally tested under the conditions with auxiliary heating. The data described above fit well to the extended surfaces calculated from our proposed consolidated theory of the strong ECH theory (plateau formation) with Pastukhov's theory on energy confinement.

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  • Study of Relations between the Spatial Structure of Potential-Trapped Electron Distribution Functions and the Physics Scaling Law of Plasma Confining Potentials

    M.,Hirata, T.,Cho, J.,Kohagura, T.,Numakura, T.,Fukai, N.,Yokoyama, S.,Tokioka, Y.,Tomii, Y.,Miyake, K.,Ogura, Y.,Suzuki, K.,Komiyama, H.,Saito

    Annual Report of National Institute for Fusion Science   April 2004-March 2005   463   2005.11

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  • Performance of Weakly Relativistic Oversized Backward Wave Oscillators Reviewed

    Kazuo Ogura, Kiyofumi Komiyama, Masakazu Sakai, Daisuke Yamada, Hiroki Saito, Hoshiyuki Yamazaki

    IEEJ Transactions on Fundamentals and Materials   125 ( 9 )   733 - 738   2005

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    Performance of oversized backward wave oscillators (BWOs) is investigated. Due to the axial mode operation, there exists a critical value of beam energy for the oscillation, i.e., a starting energy. The output power depends on the beam radius and voltage. The maximum output powers are above 100 kW (K-band) and above 50 kW (Q-band). The corresponding quality factor Pf2 is about 6×104 [kW·GHz2]. By changing the condition at the SWS end, an enhanced performance of the K-band oversized BWO is observed in a low magnetic field region about 0.4 T. © 2005, The Institute of Electrical Engineers of Japan. All rights reserved.

    DOI: 10.1541/ieejfms.125.733

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  • Nonaxisymmetric Instabilities in Periodically Corrugated Cylindrical Waveguide with Low Magnetic Field Reviewed

    Hoshiyuki Yamazaki, Makoto Iwai, Yoshitaka Suzuki, Hirokazu Takagi, Osamu Watanabe, Kazuo Ogura

    IEEJ Transactions on Fundamentals and Materials   125 ( 9 )   739 - 743   2005

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    Nonaxisymmetric Cherenkov and slow cyclotron instabilities in a backward wave oscillator are investigated by using a new version of self-consistent linear theory. The slow cyclotron instability as well as Cherenkov instability can be driven by an axial electron beam without any initial perpendicular velocity. In a low magnetic field region, the radial displacement of beam plays an important role in the beam interactions. The slow cyclotron instability becomes strong, when the perturbed cyclotron motion and the electromagnetic wave rotate in the same direction. The rotational direction of electromagnetic wave also affects the Cherenkov instability. © 2005, The Institute of Electrical Engineers of Japan. All rights reserved.

    DOI: 10.1541/ieejfms.125.739

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  • Study on Oscillation Starting Condition of K-Band Oversized Backward Wave Oscillator Driven by a Weakly Relativistic Electron Beam Reviewed

    K. Ogura, R. Yoshida, K. Komiyama, M. Sakai, H. Yamazaki

    Journal of Plasma and Fusion Research SERIES   6   703 - 706   2004.12

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  • Numerical Examination of Electromagnetic Field Properties in a Cylindrical Periodic Slow Wave Structure Reviewed

    H. Yamazaki, K. Ogura, T. Watanabe

    Journal of Plasma and Fusion Research SERIES   6   719 - 722   2004.12

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  • Cherenkov and Slow Cyclotron Instability in Periodically Corrugated Cylindrical Waveguide with Low Magnetic Field Region Reviewed

    Hoshiyuki Yamazaki, Yuichiro Yamashita, Makoto Iwai, Yoshitaka Suzuki, Kazuo Ogura, Osamu Watanabe

    The transactions of the Institute of Electrical Engineers of Japan.A   124 ( 6 )   477 - 482   2004

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    Cherenkov and slow cyclotron instabilities driven by an axially injected electron beam in periodically corrugated cylindrical waveguide are studied by using a new version of self-consistent linear theory considering three dimensional beam perturbations. For the bounded microwave systems, the self-consistent boundary conditions require all field components and the normal modes in the beam are hybrid of transverse magnetic (TM) and transverse electric (TE) modes, even in the axisymmetric case. The slow cyclotron instability as well as Cherenkov instability can be driven by the axially streaming electron beam without any initial perpendicular velocity. In the low magnetic field region, the charge caused by the radial displacement of the beam plays an important role in the beam interaction with the electromagnetic mode. The radial displacement become large by decreasing the magnetic field and the slow cyclotron instability becomes strong and compete with the Cherenkov instability. For the axisymmetric case, the Cherenkov instability is dominant and suppresses the slow cyclotron instability, On the other hand, the slow cyclotron instability becomes dominant and suppresses the Cherenkov instability, for the nonaxisymmetric mode with the left-hand circular polarization. © 2004, The Institute of Electrical Engineers of Japan. All rights reserved.

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  • Experimental Demonstration of Mode Change in a Q-Band Oversized Backward Wave Oscillator due to Corrugation Number Reviewed

    Kazuo Ogura, Ryo Yoshida, Kiyofumi Komiyama, Masakazu Sakai, Hoshiyuki Yamazaki

    The transactions of the Institute of Electrical Engineers of Japan.A   124 ( 6 )   456 - 460   2004

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    Operation mode of an oversized backward wave oscillator is studied experimentally, using an oversized slow-wave structure. The dispersion characteristics of the slow-wave structure are determined by the average radius, corrugation amplitude and pitch length of the periodic waveguide. The corrugation amplitude and the corrugation period mainly determine the upper cutoff frequency of the lowest mode. The lower cutoff frequency is determined by the average radius. In this work, a Q-band periodic slow-wave structure is fabricated from aluminum. The diameter of the slow-wave structure is about 4 times free space wavelength. The beam voltage is weakly relativistic, around 50 kV, and the beam current is in the range of 100 A. The output powers of several 10 kW are obtained in the Q-band, i.e., the estimated frequency is in the range of 34–41 GH. The output modes are examined by measuring the radiation patterns. Nonaxisymmetric as well as axisymmetric modes are observed. It is demonstrated for the first time that the nonaxisymmetric and axisymmetric operations of the oversized BWO can be controlled by changing the corrugation number of slow-wave structure. © 2004, The Institute of Electrical Engineers of Japan. All rights reserved.

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  • Cherenkov instability due to unmagnetized electron beam in periodically corrugated waveguide Reviewed

    K Ogura, H Yamazaki, O Watanabe, MR Amin

    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS   42 ( 11 )   7095 - 7103   2003.11

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    Cherenkov instability driven by an unmagnetized electron beam in a periodically corrugated waveguide is studied by developing a new version of self-consistent linear theory. The conventional space-charge and cyclotron modes of magnetized beam degenerate in this case. The normal electromagnetic modes are pure transverse magnetic (TM) and transverse electric (TE) modes in axisymmetric cases and are hybrid modes having both TM and TE components in nonaxisymmetric cases. Using the developed linear theory, the axisymmetric and nonaxisymmetric Cherenkov instabilities due to the unmagnetized beam in the periodic system are examined numerically. The unmagnetized beam can excite the axisymmetric TM and nonaxisymmetric hybrid modes. A comparison of the numerically obtained results is made with those of the recent C-band Pasotron experiment.

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  • Calibration experiments of He-3 neutron detectors for analyzing neutron emissivity in the hot-ion mode on the GAMMA 10 tandem mirror Reviewed

    J Kohagura, T Cho, M Hirata, H Watanabe, R Minami, T Numakura, M Yoshida, H Ito, Y Tatematsu, K Yatsu, S Miyoshi, K Ogura, T Kondoh, T Nishitani, M Kwon, AC England

    REVIEW OF SCIENTIFIC INSTRUMENTS   74 ( 3 )   1757 - 1760   2003.3

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    Under the international fusion cooperating research, He neutron detectors in the GAMMA 10 tandem mirror are calibrated by the use of a Cf-252 spontaneous fission neutron source (8.96 x 10(4) n/s). The calibration experiments are carried out with a "rail system" placed along the, magnetic axis of the GAMMA 10 central-cell region, where hot ions in the plasma experiments with the bulk temperatures of similar to10 keV are produced. As compared to a previous neutron monitoring system with a BF3 detector in GAMMA 10, the present He-3 systems are designed with about two orders-of-magnitude higher neutron-counting efficiency for analyzing a neutron emissivity from the plasmas in a single plasma discharge alone. Two He-3 systems. are installed near the middle and the end of the central cell so as to identify the central-cell hot-ion axial profile. The filling pressure of He-3, the effective length, and the diameter of the detector are designed as 5 bar, 300 mm, and 50 mm, respectively. The detector output spectra are carefully analyzed by the use of a preamplifier, a shaping amplifier, as well as a multichannel analyzer for each He-3 detector. In the present article, the neutron-counting data from the two He-3 detectors due to the on-axis Cf-252 scan are interpreted in terms of the d(-2) intensity dependence (d being the distance between the detector and the neutron source) as well as the effects of the central-cell magnetic coils and the other machine structural components. (C) 2003 American Institute of Physics.

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  • A novel method for simultaneous observations of plasma ion and electron temperatures using a semiconductor-detector array Reviewed

    T. Cho, T. Numakura, J. Kohagura, M. Hirata, R. Minami, H. Watanabe, T. Sasuga, Y. Nishizawa, M. Yoshida, S. Nagashima, Y. Nakashima, K. Ogura, T. Tamano, K. Yatsu, S. Miyoshi

    Nuclear Instruments and Methods in Physics Research, Section A: Accelerators, Spectrometers, Detectors and Associated Equipment   477 ( 1-3 )   204 - 209   2002.1

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    A new method for a simultaneous observation of both plasma ion and electron temperatures is proposed using one semiconductor-detector array alone. This method will provide a new application of semiconductor-detector arrays for monitoring the key parameter set of nuclear-fusion triple product (i.e., ion temperatures, densities, and confinement time) as well as for clarifying physics mechanisms of energy transport between plasma ions and electrons under various plasma confining conditions. This method is developed on the basis of an alternative "positive" use of a semiconductor "dead layer"
    that is, an SiO2 layer is employed as a reliable ultra-thin energy analysis filter for low-energy charge-exchanged neutral particles from plasmas ranging in ion temperatures from 0.1 to several tens of kilo-electron-volts. Using recent fabrication techniques for the thin and uniform SiO2 layers of the order of tens to hundreds of angstrom, our computer simulation and its experimental verification show the availability of such semiconductors for distinguishing neutral particles (for ion temperatures) from X-rays (for electron temperatures). These are simultaneously emitted from the plasmas into semiconductor detectors
    however, we employ their quite different penetration lengths and the resultant different deposition depths and profiles in semiconductor materials. As a result, their output signals are distinguishable for these two different and fundamental species of plasmas. © 2002 Elsevier Science B.V. All rights reserved.

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  • Self-consistent linear analysis of slow cyclotron and Cherenkov instabilities Reviewed

    O. Watanabe, K. Ogura, T. Cho, Md. R. Amin

    Physical Review E   63 ( 5 )   056503-1 - 056503-9   2001.4

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    DOI: 10.1103/physreve.63.056503

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  • Slow Wave Electron Cyclotron Maser Utilizing Periodically Corrugated Waveguide Reviewed

    Kazuo Ogura, Osamu Watanabe, Daizo Kamiyama

    Fusion Technology   39 ( 1T )   320 - 323   2001.1

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    DOI: 10.13182/fst01-a11963470

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  • Normal Modes and Their High-Frequency Instabilities in Unbounded and Bounded Systems with Magnetied Electron Beam Reviewed

    O.Watanabe, K.Ogura

    Journal of Plasma and Fusion Research SERIES   3   601 - 604   2000.12

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  • Interaction of axially streaming electron beam with axisymmetric TM mode in a periodical slow wave structure with finite magnetic field Reviewed

    K Ogura, T Azegami, O Watanabe, T Watanabe

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   67 ( 10 )   3462 - 3470   1998.10

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    Interaction between an axially streaming electron beam and an axisymmetric TM mode in a periodically corrugated waveguide is analyzed using a linear fluid model. Effect of the perpendic ular perturbation of the beam by a finite magnetic field is considered. There are two mechanisms of Cherenkov interaction between a beam and a TM mode. One is the conventional mechanism attributed to a longitudinal perturbation. The other is attributed to the vertical perturbation of the beam surface and is dominant in the low magnetic field region. The slow cyclotron mode on an axially streaming beam is able to interact with an axisymmetric TM mode only if beam surface modulation is taken into account. The Cherenkov and cyclotron interactions degenerate for zero magnetic fields. This interaction has higher growth rate compared to the conventional Cherenkov interaction in the region of high current and weakly relativistic energy.

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  • Determination of the Starting Energy for a Large Diameter K-band Backward Wave Oscillator Reviewed

    Md. R. Amin, Md. A. Goffar Khan, K. Ogura

    IE(I) Journal-ET   79   15 - 20   1998.9

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  • Experimental demonstration of a high-power slow-wave electron cyclotron maser based on a combined resonance of Cherenkov and anomalous Doppler interactions Reviewed

    K Ogura, MR Amin, K Minami, XD Zheng, Y Suzuki, WS Kim, T Watanabe, Y Carmel, VL Granatstein

    PHYSICAL REVIEW E   53 ( 3 )   2726 - 2729   1996.3

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    A slow-wave electron cyclotron maser consisting of an oversized corrugated waveguide and an axially injected electron beam has been demonstrated experimentally. At resonance, the output rf power is strongly enhanced. Maximum output power of 200 kW with an electronic efficiency of 4% at 19.5 GHz is obtained for an electron beam with voltage of 35 kV and current of 150 A. The oscillation is observed to be a periodic TM(01) mode. The enhancement of microwave radiation is estimated to be caused by the combined resonance of Cherenkov interactions and an anomalous Doppler shifted electron cyclotron interaction.

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  • Plasma influence on the dispersion properties of finite-length, corrugated waveguides Reviewed

    A Shkvarunets, S Kobayashi, J Weaver, Y Carmel, J Rodgers, TM Antonsen, VL Granatstein, WW Destler, K Ogura, K Minami

    PHYSICAL REVIEW E   53 ( 3 )   R2045 - R2048   1996.3

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    We present an experimental study of the electromagnetic properties of transverse magnetic modes in a corrugated-wall cavity filled with a radially inhomogeneous plasma. The shifts of the resonant frequencies of a finite-length, corrugated cavity were measured as a function of the background plasma density and the dispersion diagram was reconstructed up to a peak plasma density of 10(12) cm(-3). Good agreement with a calculated dispersion diagram is obtained for plasma densities below 5 X 10(11) cm(-3).

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  • Electromagnetic field properties of axial modes in a finite length X-band slow wave structure Reviewed

    MR Amin, K Ogura, T Kobayashi, Y Suzuki, T Watanabe

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   65 ( 2 )   627 - 634   1996.2

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    The electromagnetic field properties of axisymmetric transverse magnetic (TM) modes in a specific slow wave structure (SWS) typically used in high power X-band backward wave oscillators are studied numerically. The dispersion relations, electric field distributions, and quality factors of the axial resonant modes are calculated. It is found that some of the axial modes can be switched from the volume modes to the surface ones by changing only the axial boundary of the SWS while the dispersion relations do not alter. This causes a drastic change in quality factors and can be of practical interest for controlling the coupling between beam and TM modes in high-power microwave devices. The calculated dispersion relations are verified experimentally for the TM(01) mode.

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  • RESONANT ENHANCEMENT OF RADIATION FROM A BACKWARD-WAVE OSCILLATOR UTILIZING LARGE-DIAMETER CORRUGATED METAL STRUCTURE Reviewed

    MR AMIN, K MINAMI, K OGURA, XD ZHENG, T WATANABE

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   64 ( 11 )   4473 - 4484   1995.11

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    An experiment on a backward wave oscillator (BWO) utilizing a large diameter corrugated metal wall slow wave structure (SWS) has been presented. Measurements are made above and below the starting beam energy for conventional BWO operation. For the latter case, an excited noise-level backward wave at 20 GHz (TM(01) mode) is coupled at the ends of the SWS to a forward anomalous Doppler shifted electron cyclotron (EC) beam mode which amplifies the original oscillation by an amount of 50 dB. Resultant microwave output powers of 200 kW with 4.5% electronic efficiency are observed near the condition of resonant magnetic field for an electron beam with energy 35 keV. Unlike the well-known fast wave devices, our slow wave EC device is simple to operate utilizing an electron beam with dominant parallel velocity in a uniform magnetic field.

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  • STARTING ENERGY AND CURRENT FOR A LARGE-DIAMETER FINITE-LENGTH BACKWARD-WAVE OSCILLATOR OPERATED AT THE FUNDAMENTAL MODE Reviewed

    K MINAMI, K OGURA, Y AIBA, MR AMIN, XD ZHENG, T WATANABE, Y CARMEL, WW DESTLER, VL GRANATSTEIN

    IEEE TRANSACTIONS ON PLASMA SCIENCE   23 ( 2 )   124 - 132   1995.4

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    We study the starting conditions for a large diameter (diameter/wavelength = 4.8) finite length backward wave oscillator designed for 24-GHz operation at the fundamental TM(01) mode. This geometry is very promising for high power handling capability. We analyze two separate threshold conditions. First, finite length effects give rise to a threshold in electron beam energy below which oscillations cannot be sustained at any beam current. The second is the more familiar current threshold known as a start current. It is also found that the growth rate for the fundamental mode can be much larger than those of other higher order modes thus leading to coherent operation of large diameter sources free from mode competition.

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  • ANALYSIS OF THE ELECTROMAGNETIC-WAVES IN AN OVERMODED FINITE-LENGTH SLOW-WAVE STRUCTURE Reviewed

    MR AMIN, K OGURA, H KITAMURA, K MINAMI, T WATANABE, Y CARMEL, W MAIN, J WEAVER, WW DESTLER, VL GRANATSTEIN

    IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES   43 ( 4 )   815 - 822   1995.4

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    The electromagnetic fields of the higher order axial resonant modes in a slow wave structure are analyzed and found to have considerably different characteristics from those of the conventional fundamental mode. Here, the reflections at both ends produce axial resonant modes corresponding to axisymmetric transverse magnetic (TM) modes. The period of field modulation of some of the higher order axial modes is shorter than that of the usual mode in a cylindrical waveguide, which could be of practical interest for higher power, higher frequency operation of backward wave oscillators, A perturbation technique is used to ascertain the field distribution inside the resonant cavity, and the numerical results thus obtained are compared to some experimental data.

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  • EXPERIMENT ON A LARGE-DIAMETER PLASMA-FILLED BACKWARD-WAVE OSCILLATOR Reviewed

    K OGURA, K MINAMI, K KURASHINA, W KIM, T WATANABE, K ISHII, S SUGITO

    FUSION ENGINEERING AND DESIGN   26 ( 1-4 )   365 - 373   1995.1

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    A large-diameter plasma-filled backward-wave oscillator (BWO) is investigated experimentally. The parameters of slow wave structure are chosen so that the oscillation frequency is about 20 GHz at 60 keV beam energy. Plasma is produced by the beam and has favorable effects for beam propagation and Cerenkov oscillations. The output power of the BWO with plasma is observed to be three to six times that of vacuum BWO. The power level is several kilowatts and the efficiency is about 0.01%. For Cerenkov oscillations of a large-diameter BWO, the beam energy mainly determines the starting conditions for oscillation. The output power is strongly enhanced when the guiding magnetic field approaches the fundamental electron cyclotron resonance. This mechanism is closely related to the anomalous Doppler cyclotron resonance. The maximum power of 480 kW with an efficiency of 5% is achieved even for a relatively low beam energy of 60 keV.

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  • ELECTROMAGNETIC PROPERTIES OF OPEN AND CLOSED OVERMODED SLOW-WAVE RESONATORS FOR INTERACTION WITH RELATIVISTIC ELECTRON-BEAMS Reviewed

    W MAIN, Y CARMEL, K OGURA, J WEAVER, GS NUSINOVICH, S KOBAYASHI, JP TATE, J RODGERS, A BROMBORSKY, S WATANABE, MR AMIN, K MINAMI, WW DESTLER, VL GRANATSTEIN

    IEEE TRANSACTIONS ON PLASMA SCIENCE   22 ( 5 )   566 - 577   1994.10

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    Specific slow wave structures are needed in order to produce coherent Cherenkov radiation in overmoded relativistic generators. The electromagnetic characteristics of such slow wave, resonant, finite length structures commonly used in relativistic backward wave oscillators have been studied both experimentally and theoretically. In experiments, perturbation techniques were used to study both the fundamental and higher order symmetric transverse magnetic (TM) modes. Finite length effects lead to end reflections and quantization of the wave number. The effects of end reflections in open slow wave structures were found from the spectral broadening of the discrete resonances of the different axial modes. The measured axial and radial field distributions are in excellent agreement with the results of a 2-D code developed for the calculation of the fields in these structures.

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  • HIGH-POWER BACKWARD-WAVE OSCILLATOR DRIVEN BY AN INTENSE RELATIVISTIC ELECTRON-BEAM WITH TAPERED SLOW-WAVE STRUCTURE FOR IMPROVED PERFORMANCES Reviewed

    T WATANABE, K OGURA, S WATANABE, K MINAMI

    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT   331 ( 1-3 )   134 - 139   1993.7

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    A new theoretical and computational method, which can analyze uniformly the working of slow wave oscillators with various shapes of the waveguide, is developed. Time evolution of nonlinear boundary value problems in 2D space are reduced to 1D space boundary value problems by the power expansion method, and the reduced equations can be solved numerically by the new numerical scheme HIDM (higher order implicit difference method) with high accuracy. Dynamics of the backward wave oscillator driven by an intense relativistic electron beam are analyzed by this method. It is found that a throttled shape waveguide is preferable to obtain uniform output power of microwave.

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  • Reply to "Comment on: A theory on the x-ray sensitivity of a silicon surface-barrier detector including a thermal charge-diffusion effect" (J. Appl. Phys. 72, 3363 (1992))

    T. Cho, M. Hirata, E. Takahashi, T. Teraji, J. Kohagura, N. Yamaguchi, K. Matsuda, A. Takeuchi, K. Ogura, T. Kondoh, A. Osawa, K. Yatsu, T. Tamano, S. Miyoshi

    Journal of Applied Physics   74 ( 2 )   1463 - 1464   1993

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    The effect of thermal-diffusion charge on the x-ray energy response of silicon surface-barrier (SSB) detectors have generally been ignored; consequently, the SSB response has been believed to be analyzed using the thickness of the depletion layer alone. Our new theory on the SSB x-ray response [J. Appl. Phys. 72, 3363 (1992)] was prepared for addressing recent confusion on plasma x-ray analyses using SSB detectors [Rev. Sci. Instrum. 59, 1380 (1988); 61, 693 (1990); 63, 4850 (1992)]. This approach was made under the assumption of a dominant contribution of the diffusion-charge signal in the vicinity of the x-ray incident location because of the strong reduction of the x-ray produced charge within the thermal-diffusion length. In this report, the comparison between this approximation (having an approximated solution) and the exact numerical calculation (using an integral form) is carried out. Necessity and importance of such three-dimensional treatments for the data analyses as well as the design of multichannel semiconductor-array detectors developed for plasma x-ray tomography diagnostics are highlighted. Furthermore, for the total diffusing-charge amount, the calculated results from our theory and the values using the comment from Donolato agree well within the accuracy of 1%.

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  • ABSOLUTE INSTABILITY OF LOW-FREQUENCY ELECTROMAGNETIC-WAVES IN A PLASMA WAVE-GUIDE WITH PERIODIC BOUNDARIES Reviewed

    K OGURA, MM ALI, K MINAMI, S WATANABE, Y KAN, Y AIBA, A SUGAWARA, T WATANABE

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   61 ( 11 )   4022 - 4032   1992.11

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    The linear dispersion relation of low frequency electromagnetic plasma waves in a corrugated plasma waveguide is analyzed successfully for a particular model in which difficulties for satisfying Floquet theorem rigorously are overcome. The resultant absolute instabilities are investigated numerically in some detail.

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  • ANALYSIS ON FIELD LINES AND POYNTING VECTORS IN CORRUGATED WALL WAVE-GUIDES Reviewed

    K OGURA, K MINAMI, MM ALI, Y KAN, T NOMURA, Y AIBA, A SUGAWARA, T WATANABE

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   61 ( 11 )   3966 - 3976   1992.11

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    Field patterns and Poynting vectors of TM01 mode in sinusoidally corrupted waveguides are analyzed numerically. It is shown that a plasma column new the axis excludes the rf electric field lines towards the peripheral region, resulting in Poynting vectors in the axial direction there. The excitation of TM01 mode in corrugated waveguides is shown to be classified into two cases; surface and the volume waves. A possible physical explanation for the enhanced radiation observed previously from plasma filled backward wave oscillators is tried from the present results.

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  • A THEORY ON THE X-RAY-SENSITIVITY OF A SILICON SURFACE-BARRIER DETECTOR INCLUDING A THERMAL CHARGE-DIFFUSION EFFECT Reviewed

    T CHO, M HIRATA, E TAKAHASHI, T TERAJI, N YAMAGUCHI, K MATSUDA, A TAKEUCHI, J KOHAGURA, K OGURA, T KONDOH, A OSAWA, K YATSU, T TAMANO, S MIYOSHI

    JOURNAL OF APPLIED PHYSICS   72 ( 8 )   3363 - 3373   1992.10

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    An analytical method based on a new theoretical model for the x-ray energy responses of silicon surface-barrier (SSB) detectors has been proposed. This method may address a recent confusing issue in the x-ray detection characteristics of SSB semiconductor detectors; that is, the x-ray responses of SSB detectors as well as p-i-n diodes used in underbiased operations were recently found to be contrary to the commonly held belief that the x-ray sensitivity of an SSB detector is determined by the thickness of the depletion layer. The model presented includes a signal contribution from thermally diffusing charge that is created in the field-free substrate region within a diffusion length from the depletion layer along with a signal contribution from charge created in the depletion layer. This model predicts a large signal contribution from the charge-diffusion effect on the SSB responses to high-energy x rays. Formulas and calculated results supporting SSB calibration data have been represented. These analytical methods might be developed to apply the analyses and predictions of energy responses of various types of silicon detectors including p-i-n diodes as well as charge-coupled devices.

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  • ANALYSIS OF STARTING CURRENTS IN A BACKWARD-WAVE OSCILLATOR WITH FINITE STRUCTURE LENGTH Reviewed

    K MINAMI, MM ALI, K OGURA, W KIM, T WATANABE

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   61 ( 10 )   3566 - 3575   1992.10

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    Starting current conditions for initiating radiation from a backward oscillator with finite structure length and with non-zero end reflections are analyzed numerically. Because of the leak of radiation at both ends, the beam starting current for initiating oscillation cannot be Zero. Various models for computing the condition are compared and discussed from the stand point of actual experiments.

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  • X-RAY-DETECTOR CHARACTERIZATION AND APPLICATIONS FOR PLASMA RESEARCH Reviewed

    T CHO, M HIRATA, E TAKAHASHI, N YAMAGUCHI, T KONDOH, T KUWABARA, K YATSU, K OGURA, S AOKI, H MAEZAWA, S MIYOSHI

    NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION B-BEAM INTERACTIONS WITH MATERIALS AND ATOMS   66 ( 4 )   485 - 491   1992.5

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    Using synchrotron radiation, the detection characteristics of microchannel plates, silicon surface barrier detectors and gold photocathodes are investigated; in particular, the detailed structures of the detection efficiency including an extended X-ray absorption fine structure (EXAFS), an X-ray absorption near-edge structure (XANES) and a chemical shift is reported along the with discussion on the physical mechanisms. Also, the applications of these detectors to X-ray tomography diagnostics for the observation of the cross-sections of fusion-oriented tandem-mirror plasmas are described. These data give information on the spatial distribution of the hot electrons which play an important role in the formation of thermal-barrier potentials phi(b). Also, the tomographic reconstructed X-ray data in the central cell show the effect of phi(b) formation on the improvement in the central-cell electron confinement for the first time.

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  • EFFECT OF BEAM ENERGY SPREAD ON RADIATION INTENSITY IN A HIGH-POWER BACKWARD-WAVE OSCILLATOR WITH FINITE LENGTH Reviewed

    T WATANABE, K OGURA, K MINAMI, M ALI

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   61 ( 4 )   1136 - 1140   1992.4

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    Numerical analysis for radiation level in a high-power backward wave oscillator with a finite-length slow-wave structure with end reflections has been made using an algorithm called the higher-order implicit difference method (HIDM). Spatial and temporal evolutions of a small localized disturbance in an RF field are followed by relativistic fluid equations and Maxwell equations. The radiation intensity of the oscillation decreases substantially with increasing energy spread beyond 10% of the beam.

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  • LINEAR-ANALYSIS OF A FINITE LENGTH PLASMA-FILLED BACKWARD-WAVE OSCILLATOR Reviewed

    MM ALI, K OGURA, K MINAMI, T WATANABE, WW DESTLER, VL GRANATSTEIN

    PHYSICS OF FLUIDS B-PLASMA PHYSICS   4 ( 4 )   1023 - 1032   1992.4

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    Absolute instability in a plasma-filled backward wave oscillator with sinusoidally corrugated slow wave structure driven by an intense relativistic electron beam has been analyzed numerically. The maximum spatial growth rate of the plasma-filled waveguide is found to be larger than that of an optimally designed vacuum structure. The excitation of a finite length structure is investigated. Although the spatial growth rates obtained in the linear theory increase with plasma density in the finite length plasma-filled structure for the fundamental TM01 mode of oscillation, negative global spatial growth rates prevent the coherent oscillation for intermediate ranges of plasma density, beam current, and even for structure length.

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  • X-RAY STUDIES OF VARIOUS SHAPES OF ELECTRON-VELOCITY DISTRIBUTION-FUNCTIONS AND OF ELECTRON CONFINEMENT AFFECTED BY KILOVOLT-RANGE ELECTROSTATIC POTENTIALS Reviewed

    T CHO, M HIRATA, E TAKAHASHI, K OGURA, K MASAI, N YAMAGUCHI, T KONDOH, K MATSUDA, H HOJO, M INUTAKE, K ISHII, Y KIWAMOTO, A MASE, T SAITO, K YATSU, S MIYOSHI

    PHYSICAL REVIEW A   45 ( 4 )   2532 - 2545   1992.2

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    Several types of x-ray diagnostics, such as x-ray energy spectrum analyses, x-ray absorption methods, and x-ray tomographic reconstructions using various types of x-ray detectors (i.e., a Si(Li), a pure Ge, a NaI(T1), Si surface-barrier detectors, as well as microchannel plates) have been employed for obtaining various shapes of electron-velocity distribution functions as well as their spatial profiles: (i) a plateau-shaped electron-velocity distribution function in the plug region, supporting a scaling theory between thermal-barrier potentials and ion-confining potentials (Cohen's strong electron-cyclotron heating theory); (ii) mirror-trapped 60-keV relativistic Maxwellian electrons in the thermal-barrier region; and (iii) two-component Maxwellian electrons in the central cell have been observed in the tandem-mirror GAMMA 10. During experiments with thermal barriers, it has been observed that the bulk-electron temperature and its evolution with time in the central cell are quite different from the electron energy and its temporal evolution in the plug region. These differences as well as the different shape of the electron-velocity distribution function in each region have clearly demonstrated the existence of a thermal-isolation effect due to the thermal barriers between the central cell and the plug region. X-ray tomography data in these three regions have shown good axisymmetric radial profiles peaked on the magnetic axis; this axisymmetric shape is useful for reducing nonambipolar radial particle losses. Furthermore, the validity of the Pastukhov theory for electron-energy confinement that is enhanced due to the formation of thermal-barrier potentials has been demonstrated using the electron-energy balance analyses. These data have represented a good electron-energy confinement capability due to the formation of thermal barriers.

    DOI: 10.1103/PhysRevA.45.2532

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  • A New Theory and Its Application to the Fitting of the X-ray Energy-Response Data of Silicon Surface-Barrier Detectors

    T., Cho, E., Takahashi, M., Hirata, N., Yamaguchi, T., Teraji, J., Kohagura, T., Tamano, S., Miyoshi, K., Ogura, S., Aoki, H., Maezawa, X, W. Zhang

    Photon Factory Activity Report 1992   10   376   1992.1

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  • EQUILIBRIA OF RF TOKAMAK PLASMAS DURING CURRENT START-UP Reviewed

    T MAEKAWA, K OGURA, H TANAKA, M NAKAMURA, Y TERUMICHI, S TANAKA

    PLASMA PHYSICS AND CONTROLLED FUSION   33 ( 14 )   1723 - 1733   1991.11

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    Equilibria of r.f. Tokamak plasmas during lower hybrid (LH) wave-driven current start-up experiments in the WT-2 and WT-3 Tokamaks are studied by comparing spatial profiles of tail and bulk electrons with simple model equilibria for the electron tail. When the plasma current I(p) is smaller than the Alfven critical current I(A), the confinement areas of the tail and bulk electrons are not coincident. The cross-section of the outermost flux surface is always found to be larger than the tail cross-section. Particularly in the case of the small Tokamak WT-2 (a(L) = 9 cm) is the outermost flux surface coincident with the limiter circle and much larger than the tail cross-section, indicating that good confinement of bulk electrons which carry LH waves and provide electrons to the tail is crucial for r.f. current start-up.

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  • NONINDUCTIVE CURRENT DRIVE USING 2ND HARMONIC ELECTRON-CYCLOTRON WAVES ON THE WT-3 TOKAMAK Reviewed

    H TANAKA, K OGURA, A ANDO, S IDE, M IIDA, K HANADA, T MINAMI, M YOSHIDA, M NAKAMURA, T MAEKAWA, Y TERUMICHI, S TANAKA

    NUCLEAR FUSION   31 ( 9 )   1673 - 1687   1991.9

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    A plasma current of up to 70 kA has been sustained in WT-3 discharges by second harmonic (2-OMEGA-e) electron cyclotron (EC) waves alone, with zero loop voltage, after shutting off the Ohmic heating power. Further, in the case of high power EC wave injection, ramp-up discharges have been obtained. Pulse height analysis of hard X-rays in the line of sight at various angles to the toroidal field shows that the velocity distribution function of the high energy tail electrons is asymmetric in the toroidal direction. The 2-OMEGA-e EC wave is mainly absorbed by the tail electrons, and a 2-OMEGA-e EC driven current is generated by enhancing the asymmetry of the distribution. The figure of merit of 2-OMEGA-e EC current drive (ECCD) is eta-EC(2) = (3.2-6.4) x 10(-2) (10(19) A/W.m2), which is one order of magnitude smaller than that of lower hybrid current drive in WT-3. This low value of eta-EC(2) can be attributed to low confinement of the current carrying, high energy tail electrons produced by 2-OMEGA-e ECCD.

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  • LINEAR-ANALYSIS OF A LOCALIZED PLASMA-LOADED BACKWARD-WAVE OSCILLATOR DRIVEN BY AN ANNULAR INTENSE RELATIVISTIC ELECTRON-BEAM Reviewed

    MM ALI, K MINAMI, S AMANO, K OGURA, T WATANABE

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   60 ( 8 )   2655 - 2664   1991.8

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    The linear theory of electromagnetic radiation from a localized plasma-loaded backward wave oscillator with sinusoidally corrugated slow wave structure driven by an annular intense relativistic electron beam has been derived and analyzed numerically. The enhanced radiation from a plasma-loaded structure is attributed to the increase in the spatial growth rate of the absolute instability. The backward wave oscillator instability without plasma is found to be most effective in a case where the beam travels near the wall of the slow wave structure. For the given number of plasma particles per unit length of the structure, the decrease in the plasma column radius enhances the output radiation.

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  • STUDY OF THE FAST ELECTRON-DISTRIBUTION FUNCTION IN LOWER HYBRID AND ELECTRON-CYCLOTRON CURRENT DRIVEN PLASMAS IN THE WT-3 TOKAMAK Reviewed

    K OGURA, H TANAKA, S IDE, M IIDA, K HANADA, M YOSHIDA, T MINAMI, T CHO, M NAKAMURA, T MAEKAWA, Y TERUMICHI, S TANAKA

    NUCLEAR FUSION   31 ( 6 )   1015 - 1033   1991.6

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    The distribution function f(--&gt; p) of fast electrons produced by lower hybrid current drive (LHCD) is investigated in the WT-3 tokamak, using a combination of measurements of the hard X-ray (HXR) angular distribution with respect to the toroidal magnetic field and observations of the HXR radial profile. The data obtained indicate the formation of a plateau-like region in f(--&gt;p) which corresponds to a region of resonant interaction between the lower hybrid (LH) wave and the electrons. The energy of the fast electrons in the peripheral plasma region is observed to be higher than that in the central plasma region under operational conditions with a high plasma current (I(p) greater-than-or-equal-to 80 kA). At low current (I(p) less-than-or-similar-to 50 kA), however, the energy of fast electrons is constant along the plasma radius. In the current ramp-up phase, fast electrons are generated in the directions normal to and opposite to the LH wave propagation. The latter case is ascribed to a negatively biased toroidal electric field induced by the current ramp-up. To study the characteristic change of f(--&gt;p) for various current drive mechanisms, HXR measurements are performed in electron cyclotron current driven (ECCD) plasma and in Ohmic heating (OH) plasma. In ECCD plasma, the perpendicular energy of fast electrons increases, which indicates that fast electrons are accelerated perpendicularly by electron cyclotron heating. In both LHCD and ECCD plasmas, fast electrons flow in the direction opposite to the wave propagation, while no such fast electrons are formed in OH plasma.

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  • TEMPORAL BEHAVIOR OF THE POTENTIAL CONFINED ELECTRONS IN THE CENTRAL CELL AND IN THE PLUG REGION DURING A PERIOD WITH THERMAL BARRIERS Reviewed

    M HIRATA, T CHO, E TAKAHASHI, K MASAI, K OGURA, K KOGANEZAWA, N YAMAGUCHI, T KATO, T KONDOH, K ISHII, T SAITO, Y KIWAMOTO, K YATSU, S MIYOSHI

    NUCLEAR FUSION   31 ( 4 )   752 - 756   1991.4

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    An increase with time of the central-cell electron temperature during a period with thermal barrier potentials has been observed. The increase is explained by an improvement of the electron energy confinement due to the presence of thermal barriers. Different evolutions of the electron energy in the plug region have been observed; these are closely related with the variation in time of the confining potential of the plug electrons. The observed behaviour of the potential confined electrons provides the first data set for the evolution of the effect of thermal isolation caused by the formation of a thermal barrier in the kilovolt range.

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  • COMPUTER-TOMOGRAPHY OF M=1 MODE DURING SAWTOOTH OSCILLATION WITH 3 SOFT-X-RAY DETECTOR ARRAYS ON THE WT-3 TOKAMAK Reviewed

    K HANADA, K OGURA, S IDE, H TANAKA, M IIDA, T ITO, M IWAMASA, M YOSHIDA, T MINAMI, M NAKAMURA, T MAEKAWA, Y TERUMICHI, S TANAKA

    PLASMA PHYSICS AND CONTROLLED FUSION   32 ( 14 )   1289 - 1299   1990.12

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    Soft X-rays (SXRs) emitted from plasma in the WT-3 Tokamak were measured by three SXR detector arrays, viewing the plasma from three different angles. From these experimental data, we reconstructed the two dimensional (2-D) contour of constant SXR emissivity as a function of time, using the technique of computer tomography (CT). Computer simulation results show that data from three or more sets of detector arrays are required to reconstruct the 2-D emissivity structure with sufficient accuracy to distinguish Kadomtsev's model from the quasi-interchange (Wesson's) model of sawtooth crash. Further, it is shown that if the noise amplitude is more than 1.5%, reconstruction of the real 2-D SXR emissivity structure is difficult.

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  • ABSOLUTE INSTABILITY FOR ENHANCED RADIATION FROM A HIGH-POWER PLASMA-FILLED BACKWARD-WAVE OSCILLATOR Reviewed

    MM ALI, K MINAMI, K OGURA, T HOSOKAWA, H KAZAMA, T OZAWA, T WATANABE, Y CARMEL, VL GRANATSTEIN, WW DESTLER, RA KEHS, WR LOU, D ABE

    PHYSICAL REVIEW LETTERS   65 ( 7 )   855 - 858   1990.8

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    DOI: 10.1103/PhysRevLett.65.855

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  • LINEAR-THEORY OF ELECTROMAGNETIC-WAVE GENERATION IN A PLASMA-LOADED CORRUGATED-WALL RESONATOR Reviewed

    K MINAMI, Y CARMEL, VL GRANATSTEIN, WW DESTLER, W LOU, DK ABE, RA KEHS, MM ALI, T HOSOKAWA, K OGURA, T WATANABE

    IEEE TRANSACTIONS ON PLASMA SCIENCE   18 ( 3 )   537 - 545   1990.6

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    DOI: 10.1109/27.55925

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  • TOROIDAL PLASMA CURRENT STARTUP AND SUSTAINMENT BY LOWER HYBRID WAVES IN THE WT-3 TOKAMAK Reviewed

    K OGURA, H TANAKA, S IDE, M IIDA, K HANADA, M YOSHIDA, T MINAMI, M NAKAMURA, T MAEKAWA, Y TERUMICHI, S TANAKA

    NUCLEAR FUSION   30 ( 4 )   611 - 624   1990.4

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  • OBSERVATION OF A PLATEAU ELECTRON-DISTRIBUTION FUNCTION DUE TO ELECTRON-CYCLOTRON HEATING FOR AN EFFICIENT PLUG POTENTIAL FORMATION Reviewed

    T CHO, M HIRATA, K OGURA, E TAKAHASHI, T KONDOH, N YAMAGUCHI, K MASAI, K HAYASHI, KATANUMA, I, K ISHII, T SAITO, Y KIWAMOTO, K YATSU, S MIYOSHI

    PHYSICAL REVIEW LETTERS   64 ( 12 )   1373 - 1376   1990.3

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    DOI: 10.1103/PhysRevLett.64.1373

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  • INVESTIGATION OF HIGH-ENERGY ELECTRONS IN LOWER HYBRID CURRENT DRIVE PLASMA WITH ELECTRON-CYCLOTRON EMISSION MEASUREMENT IN WT-3 Reviewed

    S IDE, K OGURA, H TANAKA, M IIDA, K HANADA, T ITOH, M IWAMASA, H SAKAKIBARA, T MINAMI, M YOSHIDA, T MAEKAWA, Y TERUMICHI, S TANAKA

    NUCLEAR FUSION   29 ( 8 )   1325 - 1338   1989.8

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  • Formation and Distribution Function of Fast Electron during RF Current Drive

    Kazuo Ogura

    1989.5

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  • Toroidal plasma current startup and sustainment by RF in the WT-3 tokamak.

    Ogura Kazuo, Tanaka Hitoshi, Ide Shunsuke, Iida Motomi, Hanada Kazuaki, Itou Takehiko, Iwamasa Mikito, Maekawa Takasi, Terumichi Yasushi, Tanaka Shigetoshi

    Journal of Plasma and Fusion Research   61 ( 2 )   106 - 127   1989

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    The toroidal plasma current is started up by rf power alone and is ramped up to above 20 kA in a low density plasma. The fraction ε<SUB><I>R</I></SUB> of injected LHW power is converted into poloidal magnetic field energy and its maximum value is about 5 %. For high density cases, a quasi-steady state discharge is obtained and the figure of merit η<SUB><I>CD</I></SUB> for steady current drive by LHW is about 0.04 × 10<SUP>19</SUP> (A·m<SUP>-2</SUP>/W). The direct loss of fast electrons from the plasma is very large and results in the low ε<SUB><I>R</I></SUB> and η<SUB><I>CD</I></SUB> in our experiments.

    DOI: 10.1585/jspf1958.61.106

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  • High frequency range lower-hybrid current drive on the WT-3 Tokamak.

    Iida Motomi, Ide Shunsuke, Tanaka Hitoshi, Ogura Kazuo, Hanada Kazuaki, Iwamasa Mikito, Itou Takehiko, Maekawa Takashi, Terumichi Yasushi, Tanaka Shigetoshi

    Journal of Plasma and Fusion Research   61 ( 4 )   241 - 257   1989

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    The lower-hybrid current drive (LHCD) experiments with a high frequency range such as ω= (2-3) × (Ω<SUB>e</SUB>Ω<SUB>i</SUB>) <SUP>1/2</SUP> on the WT-3 tokamak are reported. Experimental results on current sustainment and ramp-up in the low density region are basically consistent with the predictions based on the quasi-linear theory with the finite fast electron confinement time. But the density limit for LHCD is lower than that expected from ω<SUP>2</SUP>-scaling. It seems that the density limit is given by ω<SUB>pe</SUB><SUP>2</SUP>/Ω<SUB>e</SUB><SUP>2</SUP>=1 for the high frequency range. It is concluded that increase of ω is not effective to increase the density limit for LHCD in the high frequency range.

    DOI: 10.1585/jspf1958.61.241

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  • Stabilization and Destabilization of Sawtooth Oscillations by Lower Hybrid Current Drive in the WT-3 Tokamak

    Iida Motomi, Maekawa Takashi, Tanaka Hitoshi, Ide Shunsuke, Ogura Kazuo, Hanada Kazuaki, Iwamasa Mikito, Itoh Takehiko, Terumichi Yasushi, Tanaka Shigetoshi

    J Phys Soc Jpn   57 ( 11 )   3661 - 3664   1988.11

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    Sawtooth oscillations appearing in Ohmically heated (OH) plasmas are suppressed by the lower hybrid current drive (LHCD) in the WT-3 tokamak ($R{=}65$ cm, $a{=}20$ cm, $I_{\text{p } }{\simeq}100$ kA, $\bar{n}_{\text{e } }{=}1-2\times 10^{13}$ cm-3, $q_{\text{a } }{\simeq}4.5$, and $P_{\text{LH } }{\gtrsim}100$ kW). After the suppression, sawteeth reappear following $m{=}1$ oscillations in the LHCD plasmas. The latter sawteeth have a large amplitude and long period ($T_{\text{s } }{=}2\text{--}5$ msec), compared with the former one ($T_{\text{s } }{=}0.5\text{--}1.5$ msec). Furthermore, they do not accompany a precursor and crash very fast.

    DOI: 10.1143/JPSJ.57.3661

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  • ELECTRON-CYCLOTRON CURRENT DRIVE AT THE 2ND HARMONIC IN THE WT-3 TOKAMAK Reviewed

    H TANAKA, A ANDO, K OGURA, S IDE, M IIDA, K OHO, S OZAKI, K IWAMURA, A YAMAZAKI, M NAKAMURA, T MAEKAWA, Y TERUMICHI, S TANAKA

    PHYSICAL REVIEW LETTERS   60 ( 11 )   1033 - 1036   1988.3

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    DOI: 10.1103/PhysRevLett.60.1033

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  • Electron cyclotron current drive on WT-III by a56 GHz gyrotron Reviewed

    Y. Terumichi, H. Tanaka, A. Ando, K. Ogura, S. Ide, M. Iida, K. Oho, S. Ozaki, K. Iwamura, A. Yamazaki, M. Nakamura, T. Maekawa, S. Tanaka

    International Journal of Electronics   65 ( 3 )   691 - 697   1988

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    Electron cyclotron current drive (EC-CD) experiments have been carried out atthe fundamental and the second harmonics onthe WT-III tokamak using extraordinary moderadiation at 56 GHz launched from the low field side. The EC driven current of 24 kAisattained at the power level of 100 kW and the plasma with the density of 2 ×1012cm−3 and the electron temperature of several hundredseV can be sustained during the EC pulse. The efficiency of EC-CD is 1·0 × 10−2 (1019m−2 A W−1) atthe fundamental and 3·5 × 10−2 at the second harmonic. Theunidirectional high energy electrons in theinitial target plasma is necessary for EC-CD. © 1988 Taylor &amp
    Francis Group, LLC.

    DOI: 10.1080/00207218808945266

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  • Electron Cyclotron Current Drive Experiments in the WT-3 Tokamak Reviewed

    H.Tanaka, K.Ogura, A.Ando, S.Ide, M.Iida, K.Iwamura, A.Yamazaki, T.Itoh, M.Iwamasa, K.Hanada, M.Nakamura, T.Maekawa, Y.Terumichi, S.Tanaka

    Proc. of the 15th European Conference on Controlled Fusion and Plasma Heating   1031   1988

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  • Electron Cyclotron Emission from Lower Hybrid Current Drive Plasma on the WT-3 Tokamak Reviewed

    Shunsuke Ide, Motomi Iida, Kazuo Ogura, Hitoshi Tanaka, Akira Yamazaki, Kazuaki Iwamura, Kazuaki Hanada, Takehiko Itou, Mikito Iwamasa, Yasushi Terumichi, Shigetoshi Tanaka, Takashi Maekawa, Akira Ando, Masahiko Nakamura

    Journal of the Physical Society of Japan   57 ( 8 )   2605 - 2608   1988

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    Electron cyclotron emission (ECE) from the lower hybrid current drive (LHCD) as well as the ohmic heating (OH) plasmas in WT-3 were measured along the horizontal chord in the equatorial plane and the vertical chord where the magnitude of the toroidal field is constant, respectively. Measurements show that the high energy tail electrons carrying the plasma current build up within 10 msec after the injection of the lower hybrid wave. The ECE spectrum from the LHCD plasma in a quasi-steady state can be fitted with a numerically calculated spectrum assuming that the electron velocity distribution function is Maxwellian with the temperature T=50 keV. © 1988, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

    DOI: 10.1143/JPSJ.57.2605

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  • OBSERVATION OF HOT-ELECTRONS PRODUCED BY SECOND-HARMONIC ELECTRON-CYCLOTRON HEATING IN THE AXISYMMETRICAL TANDEM MIRROR GAMMA-10 Reviewed

    T CHO, T KONDOH, M HIRATA, A SAKASAI, N YAMAGUCHI, A MASE, Y KIWAMOTO, A HIROSE, K OGURA, S TANAKA, S MIYOSHI

    NUCLEAR FUSION   27 ( 9 )   1421 - 1438   1987.9

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  • CYCLIC TOKAMAK OPERATION IN THE WT-2 DEVICE Reviewed

    M NAKAMURA, K OGURA, A ANDO, H TANAKA, M IIDA, S IDE, K OHO, S OZAKI, T MAEKAWA, Y TERUMICHI, S TANAKA

    NUCLEAR FUSION   27 ( 5 )   779 - 785   1987.5

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  • Electron Cyclotron and Lower Hybrid Current Drive Experiments in the WT-III Tokamak Reviewed

    S.Tanaka, Y.Terumichi, T.Maekawa, M.Nakamura, A.Ando, K.Ogura, H.Tanaka, M.Iida, S.Ide, K.Oho, S.Ozaki, K.Iwamura, A.Yamazaki, H.Takase

    Proc. of the 14th European Conference on Controlled Fusion and Plasma Physics   3   886   1987.2

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  • PLASMA CURRENT SUSTAINMENT AND RAMP-UP BY ELECTRON-CYCLOTRON WAVES IN THE WT-2 TOKAMAK Reviewed

    A ANDO, K OGURA, H TANAKA, M IDA, S IDE, K OHO, S OZAKI, M NAKAMURA, T CHO, T MAEKAWA, Y TERUMICHI, S TANAKA

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   55 ( 12 )   4259 - 4271   1986.12

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  • TOROIDAL PLASMA PRODUCTION BY ELECTRON-CYCLOTRON HEATING IN THE WT-2 DEVICE Reviewed

    T CHO, K OGURA, A ANDO, H TANAKA, M NAKAMURA, S NAKAO, T SHIMOZUMA, S KUBO, T MAEKAWA, Y TERUMICHI, S TANAKA

    NUCLEAR FUSION   26 ( 3 )   349 - 359   1986.3

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  • FORMATION OF HIGH-ENERGY ELECTRON TAIL DURING RF PLASMA CURRENT START-UP IN THE WT-2 TOKAMAK Reviewed

    K OGURA, T CHO, A ANDO, H TANAKA, M IIDA, S IDE, M NAKAMURA, T MAEKAWA, Y TERUMICHI, S TANAKA

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   55 ( 1 )   13 - 16   1986.1

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  • ENHANCEMENT OF EFFICIENCY FOR LOWER HYBRID CURRENT DRIVE BY ELECTRON-CYCLOTRON HEATING IN THE WT-2 TOKAMAK Reviewed

    A ANDO, K OGURA, H TANAKA, M IIDA, S IDE, M NAKAMURA, T MAEKAWA, Y TERUMICHI, S TANAKA

    NUCLEAR FUSION   26 ( 1 )   107 - 111   1986.1

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    DOI: 10.1088/0029-5515/26/1/010

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  • Plasma current generation and sustainment by electron cyclotron waves in the WT-2 Tokamak Reviewed

    A. Ando, K. Ogura, H. Tanaka, M. Iida, S. Ide, K. Oho, S. Ozaki, M. Nakamura, T. Cho, T. Maekawa, Y. Terumichi, S. Tanaka

    Physical Review Letters   56 ( 20 )   2180 - 2183   1986

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    By injection of microwave power PEC near the electron cyclotron (EC) frequency into an Ohmically heated (OH) plasma in the WT-2 tokamak after OH power is shut off, the plasma current is sustained and ramped up by the EC wave only, without OH power. Here, EC-driven current is generated by EC heating of the suprathermal electron beam in OH plasma. Further, when PEC is injected into plasma sustained by lower-hybrid- (LH-) driven current, the plasma current and its rampup rate increase. Here, EC-driven current is generated by EC heating of the mildly relativistic electrons in LH-driven plasma. © 1986 The American Physical Society.

    DOI: 10.1103/PhysRevLett.56.2180

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  • Electron Cyclotron and Lower Hybrid Current Drive experiments in the WT-2 and WT-3 Tokamaks Reviewed

    S.Tanaka, Y.Terumichi, T.Maekawa, M.Nakamura, T.Cho, A.Ando, K.Ogura, H.Tanaka, M.Iida, S.Ide,K.Oho, S.Ozaki, R.Itatani, H.Abe, Y.Yasaka, M.Fukao, K.Ishii, A.Mohri, S.Kubo

    Proc. of the 11th International Conference on Plasma Physics and Controlled Nuclear Fusion Research   1   553   1986

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  • Preliminary experiment on electron beam injection for tokamak current drive Reviewed

    Hitoshi Tanaka, Akira Ando, Kazuo Ogura, Takashi Maekawa, Yasushi Terumichi, Shigetoshi Tanaka, Akihiro Mohri, Shin Kubo, Mitsuru Hasegawa, Kazumichi Narihara

    Japanese Journal of Applied Physics   24 ( 8 )   644 - 646   1985

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    DOI: 10.1143/JJAP.24.L644

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  • Study of Low Frequency Density Fluctuations in the WT-2 Tokamak by mm and Submm Wave Scattering Reviewed

    Y.Terumichi, S.Kubo, A.Ando, Y.Yanagimoto, K.Ogura, H.Tanaka, J.Takahashi, I.Tonai, M.Nakamura, T.Maekawa, S.Tanaka, T.Idehara

    Proc. of the Ninth International Conference on Infrared and Millimeter Waves   Th-8-5   1984

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  • Current Sustainment by Lower Hybrid Waves in the WT-2 Tokamak Reviewed

    Masahiko Nakamura, Teruji Cho, Shin Kubo, Takashi Shimozuma, Akira Ando, Kazuo Ogura, Takashi Maekawa, Yasushi Terumichi, Shigetoshi Tanaka

    Journal of the Physical Society of Japan   53 ( 10 )   3399 - 3407   1984

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    When RF power PLHH near the lower hybrid frequency is injected into the ohmically heated plasma in the WT-2 tokamak, the RF-driven current is generated (Irf~-12 kA) and the plasma (ne~-3 x 1012 cm-3)is sustained by this current without ohmic current during the injection of PLhh- The efficiency ofRF current drive is obtained as ITf=0.06PWH/ne R (kA, kW, 1013 cm-3, m),where R is the major radius. The current 7rf is carried by suprathermal electrons which interact resonantly with lower hybrid waves. A high frequency instability and associated relaxation oscillation are observed, which can be suppressed by a simultaneous injection of the electron cyclotron heating power. © 1984, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

    DOI: 10.1143/JPSJ.53.3399

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  • Plasma Current Start-Up and Sustainment by RF(Lower Hybrid and Cyclotron) Waves in WT-2 Tokamak Reviewed

    S.Tanaka, Y.Terumichi, T.Maekawa, M.Nakamura, T.Cho, S.Kubo, T.Shimozuma, A.Ando, K.Ogura, H.Tanaka, J.Takahashi, I.Tonai, Y.Yanagimoto

    Proc. of Tenth International Conference on Plasma Physics and Controlled Nuclear Fusion Research   1   623   1984

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  • Toroidal Plasma Current Start-Up and Sustainment by rf in the WT-2 Toroidal Device Reviewed

    Shin Kubo, Teruji Cho, Masahiko Nakamura, Shuji Nakao, Takashi Shimozuma, Akira Ando, Kazuo Ogura, Takashi Maekawa, Yasushi Terumichi, Shigetoshi Tanaka

    Journal of the Physical Society of Japan   53 ( 3 )   1047 - 1057   1984

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    When rf power in the range of lower hybrid frequency was injected into the microwave discharge plasma at the electron cyclotron resonance in the WT-2 toroidal device, the toroidal plasma current is generated, started up to Ip~5KA, and sustained by rf power alone, without the Ohmic heating power (so-called rf tokamak). This lower-hybrid-wave driven current is produced only when high-energy tail electrons, which interact resonantly with the lower hybrid wave, are present in the initial electron cyclotron resonance plasma. © 1984, THE PHYSICAL SOCIETY OF JAPAN. All rights reserved.

    DOI: 10.1143/JPSJ.53.1047

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  • Toroidal Plasma Current Start-up and Sustainment by RF in the WT-2 Tokamak Reviewed

    S.Tanaka, S.Kubo, M.Nakamura, T.Cho, S.Nakao, T.Shimozuma, A.Ando, K.Ogura, T.Maekawa, Y.Terumichi

    Proc. of the IAEA Technical Committee Meeting on Non-Inductive Current Drive in Tokamaks   327 - 335   1983

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  • TOROIDAL PLASMA CURRENT STARTUP AND SUSTAINMENT BY RF IN THE WT-2 TOKAMAK Reviewed

    S KUBO, M NAKAMURA, T CHO, S NAKAO, T SHIMOZUMA, A ANDO, K OGURA, T MAEKAWA, Y TERUMICHI, S TANAKA

    PHYSICAL REVIEW LETTERS   50 ( 25 )   1994 - 1997   1983

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  • PARTICLE LOSS FROM AN ELECTRON-CYCLOTRON RESONANCE DISCHARGE PLASMA IN THE WT-2 DEVICE Reviewed

    S NAKAO, K OGURA, Y TERUMICHI, S TANAKA

    PHYSICS LETTERS A   96 ( 8 )   405 - 408   1983

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  • Suppression of hf instability due to rf-driven current by applying ech in the wt-2 tokamak Reviewed

    T. Maekawa, T. Cho, M. Nakamura, S. Nakao, S. Kubo, T. Shimozuma, A. Ando, K. Ogura, Y. Terumichi, S. Tanaka

    Nuclear Fusion   23 ( 2 )   242 - 246   1983

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    By application of electron cyclotron heating (ECH) to the WT-2 tokamak, the high-frequency instability (relaxation oscillation) excited by the lower-hybrid-wave-driven current is suppressed and the loop voltage decreases without voltage spikes, implying that the driven current increases. This suppression can be ascribed to the isotropization of the current-carrying beam electrons by ECH. © 1983 IOP Publishing Ltd.

    DOI: 10.1088/0029-5515/23/2/012

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  • Plasma Current Start-Up by RF only(EC&LH) on WT-2 Reviewed

    Y.Terumichi, A.Ando, K.Ogura, K.Inoue, H.Tanaka, T.Shimozuma, S.Kubo, S.Nakao, T.Cho, M.Nakamura, T.Maekawa, S.Tanaka

    Proc. of the Fifth Topical Conference on Radio Frequency Plasma Heating   330   1983

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  • Development of 70GHz Gyrotron using Super Conducting Magnets Reviewed

    N.Sato, T.Kanemaki, T.Idehara, T.Yagi, A.Ando, K.Ogura, Y.Terumichi, S.Tanaka, M.Nagata, K.Sugimori, K.Fujita

    Kakuyugo Kenkyu   49 ( 2 )   133 - 142   1983

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    DOI: 10.1585/jspf1958.49.133

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  • Electron Cyclotron Heating and Preionization in the WT-2 Tokamak Reviewed

    S.Tanaka, T.Cho, M.Nakamura, S.Nakao, S.Kubo, T.Shimozuma, H.Kawai, K.Yamazaki, A.Ando, K.Ogura, T.Maekawa, Y.Terumichi

    Proc. of the International Conference on Plasma Physics   14a6   84   1982

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MISC

  • Backward Wave Oscillators and Smith-Purcell Radiations Driven by Weakly Relativistic Electron Beam

    OGURA Kazuo

    88 ( 10 )   589 - 593   2012.10

  • Fundamentals and Physics of Mili and Terahertz Waves Radiation Utilizing Electron Beams Invited

    Journal of Plasma and Fusion Research   88 ( 10 )   584   2012.10

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  • 28aGY-3 Experimental study on cylindrical surface wave oscillation of K-Band

    Yambe Kiyoyuki, Hasegawa Shinzi, Shinada Takaki, Yamamoto Kazumasa, Ogura Kazuo

    Meeting abstracts of the Physical Society of Japan   66 ( 1 )   267 - 267   2011.3

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  • Operation Mode of Oversized Backward Wave Oscillator Driven by Weakly Relativistic Electron Beam

    OGURA K., MIYAZAWA Y., KIUCHI Y., AOYAMA S., TANAKA H., SUGAWARA A.

    2006 ( 54 )   29 - 33   2006.8

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  • 30pUG-5 Weakly Relativistic Oversized Slow-Wave Generators

    Ogura K., Saito H., Yamada D., Miyazawa Y., Aoyama S.

    Meeting abstracts of the Physical Society of Japan   61 ( 1 )   251 - 251   2006.3

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  • Experimental Study of High-Power Oversized Backward Wave Oscillator

    SAITO Hiroki, YAMADA Daisuke, AOYAMA Satoshi, MIYAZAWA Yushi, OGURA Kazuo

    2005 ( 10 )   17 - 22   2005.5

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  • 30aC16P Liner analysis of interaction between surface wave and electron beam

    WATANABE O., WATANABE T., OGURA K., IMAI T., CHO T.

    ( 22 )   149 - 149   2005

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  • Introduction to Pulsed Radiation of Millimeter and Submillimeter Waves Using Plasma

    K. Ogura, N. Yugami, K. Kamada, T. Higashiguchi

    Journal of Plasma and Fusion Research   79 ( 2 )   164 - 171   2003.12

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  • Axisymmetric Cherenkov and Slow Cyclotron Instability in Periodically Corrugated Cylindrical Waveguide with Low Magnetic Field

    YAMAZAKI H., YAMASHITA Y., IWAI M., SUZUKI Y., OGURA K.

    2003 ( 45 )   57 - 61   2003.10

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  • Experimental Demonstration of Mode Change in a Q-Band Oversized Backward Wave Oscillator due to Corrugation Number

    OGURA K., YOSHIDA R., KOMIYAMA K., SAKAI M., YAMAZAKI H.

    2003 ( 45 )   63 - 66   2003.10

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  • Slow cyclotron instability with lower magnetic field from Backward Wave Oscillators

    Yamazaki H., Yamashita Y., Iwai M., Suzuki Y., Ogura K.

    Meeting abstracts of the Physical Society of Japan   58 ( 2 )   154 - 154   2003.8

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  • Starting Currents of axisymmetric TM mode in a Backward Wave Oscillator with Finite Structure Length

    Yamashita Y., Yamazaki H., Iwai M., Suzuki Y., Ogura K.

    Meeting abstracts of the Physical Society of Japan   58 ( 2 )   154 - 154   2003.8

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  • Hybrid Mode in Slow Wave Structure with Magnetized Electron Beam

    Yamazaki H., Kato K., Yamashita Y., Suzuki Y., Iwai M., Ogura K., Watanabe O.

    Meeting abstracts of the Physical Society of Japan   58 ( 1 )   208 - 208   2003.3

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  • Experiment on Oversized Backward Wave Oscillator II : Dependence of Operation Mode on Total Length of Corrugated Waveguide

    Yoshida R., Sakurai Y., Yamazaki H., Komiyama K., Sakai M., sakurai T., Ogura K.

    Meeting abstracts of the Physical Society of Japan   58 ( 1 )   213 - 213   2003.3

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  • Experiment on Oversized Backward Wave Oscillator I : Dependence of Operation Mode on Magnetic Field

    Sakurai Y., Yoshida R., Komiyama K., Sakai M., sakurai T., Yamazaki H., Watanabe O., Ogura K.

    Meeting abstracts of the Physical Society of Japan   57 ( 2 )   195 - 195   2002.8

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  • Study of Non axisymmetric Modes in Cylindrical Waveguide

    K. Kousei, Watanabe O., Yamazaki H., Tamashita Y., Iwai M., Suzuki Y., Ogura K.

    Meeting abstracts of the Physical Society of Japan   57 ( 2 )   195 - 195   2002.8

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  • Experiment on Oversized Backward Wave Oscillator Driven by Weakly Relativistic Electron Beam

    OGURA K., SAKURAI Y., YOSHIDA R., WATANABE O., YAMAZAKI H.

    2002 ( 17 )   41 - 44   2002.8

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  • Cherenkov and slow cyclotron instabilities of non-axisymmetric modes in periodic slow wave structure

    WATANABE O., YAMASHITA Y., YAMAZAKI H., OGURA K.

    2002 ( 17 )   45 - 48   2002.8

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  • 27aB02P Characterization and Optimization of High-Efficiency He3 Neutron Detectors for Deuterium-Deuterium Bulk Plasma Fusion Experiments in the GAMMA 10 Tandem Mirror

    Watanabe H., Cho T., Kohagura J., Hirata M., Numakura T., Minami R., Yoshida M., Nagashima S., Ito H., Kwon M., England A.C.

    ( 19 )   104 - 104   2002

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  • Study of Slow Cyclotron Maser Operation

    Watanabe Osamu, Katou Kousei, Ogura Kazuo

    Meeting abstracts of the Physical Society of Japan   56 ( 1 )   163 - 163   2001.3

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  • Microwave generation in millimeter-range by electron beam propagating in gas-filled waveguide

    Saitoh Y., Kamiyama D., Watanabe O., Ogura K.

    Meeting abstracts of the Physical Society of Japan   56 ( 1 )   162 - 162   2001.3

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  • 30pA08P Characterization and Optimization of High-Efficiency He^3 Neutron Detectors for Deuterium-Deuterium Bulk Plasma Fusion Experiments in the GAMMA 10 Tandem Mirror

    Cho T., Kohagura J., Watanabe H., Hirata M., Minami R., Numakura R., Yoshida M., Nagashima T., Itoh K., Kwon M., England A. C.

    ( 18 )   177 - 177   2001

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  • Study of Slow Cyclotron Maser due to Anomalous Doppler Effect

    Watanabe O., Kamiyama D., Kato K., Sano Y., Ogura K.

    Meeting abstracts of the Physical Society of Japan   55 ( 2 )   147 - 147   2000.9

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  • Study on Operation Modes of Backward Wave Oscillator without Magnetic Field

    kamiyama D., watanabe O, kohsei K., sano Y., ogura K.

    Meeting abstracts of the Physical Society of Japan   55 ( 2 )   147 - 147   2000.9

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  • 24pYG-9 Hybrid Modes in the Cylindrical Wave Guide with Magnetized Electron Beam.

    Watanabe O, Kondo T, Kamiyama D, Ogura K

    Meeting abstracts of the Physical Society of Japan   54 ( 2 )   148 - 148   1999.9

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  • 24pYG-7 Experimental on Large Diameter Backward Wave Oscillator without Magnetic Field II

    Ono A, Watanabe O, Tabei M, Saito Y, Ogura K

    Meeting abstracts of the Physical Society of Japan   54 ( 2 )   147 - 147   1999.9

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  • 24pYG-8 Linear Analysis of Backward Wave Oscillator without Magnetic Field

    Kondo T, Watanabe O, Kamiyama D, Ogura K

    Meeting abstracts of the Physical Society of Japan   54 ( 2 )   148 - 148   1999.9

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  • 29a-XH-4 Experiment on Large Diameter Backward Wave Oscillator without Magnetic Field

    Ogura K., Sekikawa K., Ono A., Watanabe O.

    Meeting abstracts of the Physical Society of Japan   54 ( 1 )   801 - 801   1999.3

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  • 29a-XH-3 Selfconsistent analysis of alow cyclotron and cherenkov instability for a cylindrical alow wave guide system.

    Watanabe O., Azegami T., Kondo T., Ogura K.

    Meeting abstracts of the Physical Society of Japan   54 ( 1 )   801 - 801   1999.3

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  • Generation and Propagation of High-Power Electron Beam Produced by Glow Discharge

    OGURA Kazuo, SEKIKAWA Keizou, ONO Atsusi, HAGINO Kohji

    1998 ( 51 )   1 - 4   1998.7

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  • Liner analysis of slow cyclotron resonance interaction

    WATANABE O., KAMIYA J., KONDO T., TOMODA M., OGURA K.

    Meeting abstracts of the Physical Society of Japan   53 ( 1 )   848 - 848   1998.3

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  • Linear Analysis of Cherenkov instability and Cyclotron instability with Low Magnetic Field

    AZEGAMI T., TAGATA K., WATANABE O., KONDOU T., OGURA K.

    Meeting abstracts of the Physical Society of Japan   53 ( 1 )   848 - 848   1998.3

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  • 6a-YN-10 Experimental study of microwave generation using SWS with a dielectric substance electron beam guide

    ENYA Kouji, SEKIKAWA Keizou, TAGATA Kei, ONO Atusi, OGURA Kazuo

    Meeting abstracts of the Physical Society of Japan   52 ( 2 )   926 - 926   1997.9

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  • 6a-YN-9 Linear analysis of slow cyclotron maser with axialy propagating electron beam.

    Watanabe O., Azegami T., Kondo T., Tomoda M., Ogura K.

    Meeting abstracts of the Physical Society of Japan   52 ( 2 )   926 - 926   1997.9

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  • Design Study of a Large Diameter Backward Wave Oscillator Operating at 24 GHz

    KIM Wonsop, MINAMI Kazuo, OGURA Kazuo, INADA Haruo, WATANABE Tsuguhiro

    Journal of plasma and fusion research   72 ( 4 )   338 - 346   1996.4

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    A detailed design study is carried out on high power large diameter backward wave oscillator operating at 24 GHz for a beam energy of 100 keV. The ratio of the mean diameter of the slow wave structure to the wavelength of output microwaves is increased to be 4.8. Analysis is made within the scope of linear theory of absolute instability. The output power with efficiency 0.17% and oscillation frequency 20 GHz for 65 keV beam energy are obtained experimentally. The large diameter backward wave oscillator may be an attractive alternative source of high power millimeter microwaves which has simpler structure than that of conventional gyrotrons.

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    Other Link: http://dl.ndl.go.jp/info:ndljp/pid/10452347

  • Experiment of Large Diameter Plasma-Filled Backward Wave Oscillator

    KIN Wonsop, OGURA Kazuo, MINAMI Kazuo, INADA Haruo, WATANABE Tsuguhiro

    Journal of plasma and fusion research   71 ( 9 )   876 - 889   1995.9

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    A Large diameter plasma-filled backward wave oscillator (BWO) utilizing sinusoidally corrugated slow wave structure (SWS) has been studied experimentally. The size parameters of the SWS are so selected that the device oscillates around 24GHz when it is driven by the electron beam of energy 100keV. The enhancement of 20GHz microwave radiation with maximum efficiency of 0.17% for the beam energy of 65keV from our designed large diameter BWO has been observed when plasma was introduced in the devices.

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  • Observation of Localized Density Rises Caused by High-Power Microwaves in a Plasma-Filled Corrugated Wall Waveguide

    Sugawara Akira, Naito Yuichi, Ogura Kazuo, Minami Kazuo, Watanabe Tuguhiro

    Journal of plasma and fusion research   69 ( 12 )   p1498 - 1506   1993.12

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    Axial density gratings with local rises in a plasma filled corrugated wall waveguide are experimentally found to be created by incident high-power microwaves. The density rises and the maxima of standing waves of the axial RF electric field are observed at the identical axial positions where the radius of the corrugated wall is minimum. A nonlinear plasma model to explain the physical meaning of the observed results is proposed.

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  • 12p-N-12 Experiment on High-Power Microwave Generation of Large-Diameter Plasma Backward-Wave Oscillator

    Kurashina K., Kim W.S., Motoi Y., Ogura K., Minami K., Ishii K., Watanabe T.

    Abstracts of the meeting of the Physical Society of Japan. Sectional meeting   1993 ( 4 )   199 - 199   1993.9

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  • 12p-M-4 Measuement of Local Density Rises in a Plasma-Filled Slow Wave Structure

    Sugawara A., Naito Y., Minami K., Ogura K., Ishii K., Watanabe T.

    Abstracts of the meeting of the Physical Society of Japan. Sectional meeting   1993 ( 4 )   182 - 182   1993.9

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  • Computer Analysis of Backward Wave Oscillator for High-Power and High Quality Microwaves(Special Features on Nuclear Fusion)

    WATANABE Tsuguhiro, OGURA Kazuo

    Journal of the Japan Society for Simulation Technology   12 ( 2 )   107 - 118   1993.6

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    New computational treatment is shown to study the analysis of backward wave oscillator, which is one of a high-power microwave generator excited by an intensive relativistic electron beam. The frequency range of the generated microwaves is of the order of the 10 GHz. Dynamics of backward wave oscillator is solved by coupled systems of equations composed of relativistic fluid equations for electron beam and Maxwell's equation for microwave in a slow-wave structure. Newly developed analytical method, power expansion method reduce the original coupled system of partial differential equations in (r, z, t ) space into a coupled system of those in (z, t ) space, in which the spatial variation of waveguide radius is included. The reduced time evolutionary partial differential equations for nonlinear boundary value problems are solved numerically by newly developed numerical scheme, HIDM (Higher order Implicit Difference Method). It is shown that throttled type slow-wave structure is favorable for the production of high power and high quality microwaves.

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  • 29p-ZE-2 Measurements of Cavitons in a Plasma Loaded Slow Wave Structure

    Sugawara A., koide M., Naitoh Y., Nakamura Y., Ogura K., Minami K., Ishii K.

    Abstracts of the meeting of the Physical Society of Japan. Annual meeting   48 ( 4 )   144 - 144   1993.3

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  • 1a-ZD-10 Computational Study of Throttled Type Backward Wave Oscillator for High Quality and High Power Microwave

    Watanabe T., Ogura K., Watanabe S., Minami K.

    Abstracts of the meeting of the Physical Society of Japan. Annual meeting   48 ( 4 )   218 - 218   1993.3

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  • 27p-A-6 Relation between Wave Guide Structure and Nolinear Behavior of Back Ward Oscillator

    Watanabe T, Ogura K, Watanabe S, Minami K

    1992 ( 4 )   187 - 187   1992.9

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  • 27p-A-7 Analysis on the starting Currents in a Backward Wave Oscellator

    Minami K, Ali M.M, Ogura K, Watanabe T

    1992 ( 4 )   188 - 188   1992.9

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  • 27p-A-5 Measurements of Dispersion Relation of a Waveguide with Periodic Boundaries

    Sugawara A, Koede M, kan Y, Naito Y, Ogura K, Minami K

    1992 ( 4 )   187 - 187   1992.9

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  • 27p-A-3 Design of a Large-Diamater Backward Wave Oscillator

    Watanabe S, Minami K, Ogura K, Aiba Y

    1992 ( 4 )   186 - 186   1992.9

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  • 28p-H-4 Radiation from a High-Power Backward Wave Oscillator

    Ogura K., Watanabe T., Minami K., Ali M., Watanabe S., Kan Y.

    46 ( 4 )   206 - 206   1991.9

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  • 27a-G-11 Computer Analysis on Particle Acceleration and Current Drive by μ-Wave in Slow Wave Structure

    Watanabe T., Ogura K., Ali M., Minami K.

    46 ( 4 )   152 - 152   1991.9

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  • 27a-E-9 Oscillation Condition for Plasma-Filled Backward Wave Oscillator

    Ali M.M., Minami K., Ogura K., Watanabe T.

    1991 ( 4 )   196 - 196   1991.3

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  • 27a-E-10 Nonlinear Analysis of a Plasma-Filled Backward Wave Oscillator

    Ogura K., Watanabe T., Ali M.M., Itakura M., Minami K.

    1991 ( 4 )   197 - 197   1991.3

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  • 26p-E-7 X-ray diagnostics in GAMMA 10 V : Observation of electron temperature in the central cell of GAMMA 10

    Takahashi E., Cho T., Hirata M., Matsuda K., Ogura K., Yamaguchi N., Masai K., Ishii K., Saito T., Kiwamoto Y., Miyoshi S.

    1991 ( 4 )   177 - 177   1991.3

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  • 3p-S-9 Dispersion Relations of Electromagnetic Waves in a Plasma with Periodic Boundaries

    Ogura K., Minami K., Watanabe T., Nomura T., Kato K., Ali M.M., Hosokawa T.

    1990 ( 4 )   183 - 183   1990.9

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  • 2a-R-5 Nonlinear Computer Analysis of a Backward Wave Oscillator

    Watanabe T., Ogura K., Ali M., Minami K.

    1990 ( 4 )   125 - 125   1990.9

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  • 3p-S-10 500keV Linac for Plasma Backward Wave Tube

    Yanagase H., Ogura K., Sugawara A., Ali M.M., Kato K., Minami K.

    1990 ( 4 )   183 - 183   1990.9

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  • LOCAL SURFACE HEATING BY SKIN CURRENT

    NAKAMURA M.

    45 ( 4 )   152 - 152   1990.3

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  • X-ray Diagnostics in GAMMA 10 I : Observation of Plateau Electron Distribution Functions

    Cho T., Hirata M., Takahashi E., Ogura K., Yamaguchi N., Masai K., Hayashi K., Ishii K., Saito T., Kiwamoto Y., Miyoshi S.

    45 ( 4 )   195 - 195   1990.3

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  • X-ray Diagnostics in GAMMA10 II : Observation of Thermal Isolation Effects due to Theramal Barriers

    Hirata M., Cho T., Takahashi E., Ogura K., Yamaguchi N., Masai K., Ishii K., Saito T., Kiwamoto Y., Miyoshi S.

    45 ( 4 )   195 - 195   1990.3

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  • X-Ray Tomography and Potential Studies in GAMMA 10

    T. Cho, M. Hirata, E. Takahashi, N. Yamaguchi, K. Koganezawa, K. Masai, K. Ogura, T. Kondo, K. Ishii, A. Itakura, T. Saito, A. Mase, Y. Kiwamoto, K. Yatsu, S. Miyoshi

    350 - 351   1990

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  • 6a-J-5 BOUNDARY PLASMA OF WT-3 TOKAMAK

    NAKAMURA M.

    1989 ( 4 )   251 - 251   1989.9

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  • 29p-TE-3 High Frequency Range (ω/√<ΩeΩi>>2) LHCD

    Iida Motomi

    44 ( 4 )   151 - 151   1989.3

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  • 29p-TE-2 MHD oscillation during ECH in the WT-3 tokamak

    Tanaka H., Sakakibara H., Minami T., Yoshida M., Itoh T., Iwamasa M., Hanada K., Ide S., Iida M., Ogura K., Ando A., Nakamura M., Maekawa T., Terumichi Y., Tanaka S., WT-3 group

    44 ( 4 )   150 - 150   1989.3

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  • 29p-TE-4 Production of high βp plasma by bi-directional LHCD

    Maekawa Takashi

    44 ( 4 )   151 - 151   1989.3

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  • 29p-TE-5 Behaviour of high energy electrons in LHW & ECW combined current drive plasma

    IDE Shunsuke

    44 ( 4 )   152 - 152   1989.3

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  • 29p-TE-9 BOUNDARY PLASMA OF WT-3 TOKAMAK

    NAKAMURA M.

    44 ( 4 )   154 - 154   1989.3

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  • 29p-TE-7 Sawtooth Oscillation and suppression during LHCD

    HANADA Kazuaki

    44 ( 4 )   153 - 153   1989.3

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  • 29p-TE-6 The figure of merit for the LHCD plasma and the confinement of the tail electrons

    Ogura

    44 ( 4 )   152 - 152   1989.3

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  • 5a-E6-1 WT-IIILHCDプラズマ中の高速電子のECE計測による解析

    井手 俊介, 榊原 久芳, 南 貴司, 吉田 光宏, 伊藤 岳彦, 岩政 幹人, 花田 和明, 飯田 素身, 田中 仁, 小椋 一夫, 中村 正彦, 前川 孝, 曄道 恭, 田中 茂利, 澤田 圭司, 末満 英俊, 平田 洋介, 深尾 正之, 須川 正雄, 管谷 礼爾, 百々 太郎

    秋の分科会講演予稿集   1988 ( 4 )   193 - 193   1988.9

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  • 5a-E6-4 WT-IIIにおけるLHCDによるTearing modeの抑制とDisruption

    飯田 素身, 吉田 光宏, 榊原 久芳, 南 貴司, 伊藤 岳彦, 岩政 幹人, 花田 和明, 井手 俊介, 田中 仁, 小椋 一夫, 中村 正彦, 前川 孝, 曄道 恭, 田中 茂利, 澤田 圭司, 末満 英俊, 平田 洋介, 深尾 正之

    秋の分科会講演予稿集   1988 ( 4 )   195 - 195   1988.9

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  • 5a-E6-2 WT-IIIにおけるrf電流駆動時の高速電子とX線計測

    小椋 一夫, 花田 和明, 吉田 光宏, 榊原 久芳, 南 貴司, 伊藤 岳彦, 岩政 幹人, 井手 俊介, 飯田 素身, 田中 仁, 中村 正彦, 前川 孝, 曄道 恭, 田中 茂利, 澤田 圭司, 末満 英俊, 平田 洋介, 深尾 正之

    秋の分科会講演予稿集   1988 ( 4 )   194 - 194   1988.9

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  • 1p-H1-2 WT-IIIトカマクにおけるLHH V(磁場,密度依存)(プラズマ物理・核融合(WT-III))

    飯田 素身, 伊藤 岳彦, 岩政 幹人, 花田 和明, 岩村 和昭, 山崎 晃, 井出 俊介, 田中 仁, 安藤 晃, 小椋 一夫, 中村 正彦, 前川 孝, 嘩道 恭, 田中 茂利, 澤田 圭司, 宮地 忍, 末満 英俊, 平田 洋介, 深尾 正之

    年会講演予稿集   43 ( 4 )   156 - 156   1988.3

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  • 27p-Y2-2 WT-IIIトカマクにおけるLHH III(高い密度でのLHCD)

    飯田 素身, 伊藤 岳彦, 岩政 幹人, 花田 和明, 山崎 晃, 岩村 和昭, 井手 俊介, 田中 仁, 安藤 晃, 小椋 一夫, 中村 正彦, 前川 孝, 曄道 恭, 田中 茂利, 宮地 忍, 末満 英俊, 平田 洋介, 深尾 正之

    秋の分科会講演予稿集   1987 ( 4 )   147 - 147   1987.9

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  • 27p-Y2-4 WY-IIIトカマクにおけるLHH IV(Sawtooth scillationとLHCD)

    前川 孝, 伊藤 岳彦, 岩政 幹人, 花田 和明, 山崎 晃, 岩村 和昭, 井手 俊介, 飯田 素身, 田中 仁, 安藤 晃, 小椋 一夫, 中村 正彦, 曄道 恭, 田中 茂利, 宮地 忍, 末満 英俊, 平田 洋介, 深尾 正之

    秋の分科会講演予稿集   1987 ( 4 )   148 - 148   1987.9

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  • 27p-Y2-3 WT-IIIトカマクにおけるECH III(ECCD)

    田中 仁, 伊藤 岳彦, 岩政 幹人, 花田 和明, 山崎 晃, 岩村 和昭, 井手 俊介, 飯田 素身, 安藤 晃, 小椋 一夫, 中村 正彦, 前川 孝, 曄道 恭, 田中 茂利, 宮地 忍, 末満 英俊, 平田 洋介, 深尾 正之, 和田 修己, 中島 将光

    秋の分科会講演予稿集   1987 ( 4 )   148 - 148   1987.9

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  • 28a-M-9 WT-IIIにおけるECH

    曄道 恭, 和田 修己, 中島 将光, 岩村 和昭, 山崎 晃, 大穂 健介, 尾崎 成則, 飯田 素身, 井手 俊介, 田中 仁, 小椋 一夫, 安藤 晃, 中村 正彦, 前川 孝, 田中 茂利, 宮地 忍, 末満 英俊, 藤本 孝, 石井 慶之, 深尾 正之, 八坂 保能, 阿部 宏尹, 板谷 良平

    秋の分科会講演予稿集   1986 ( 4 )   207 - 207   1986.9

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  • 28a-M-7 WT-2におけるACトカマク実験

    中村 正彦, 大穂 健介, 尾崎 成則, 井手 俊介, 飯田 素身, 田中 仁, 小椋 一夫, 安藤 晃, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1986 ( 4 )   206 - 206   1986.9

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  • 28a-M-8 WT-IIIにおけるジュール加熱プラズマ

    田中 茂利, 岩村 和昭, 山崎 晃, 大穂 健介, 尾崎 成則, 飯田 素身, 井手 俊介, 田中 仁, 小椋 一夫, 安藤 晃, 中村 正彦, 前川 孝, 曄道 恭, 宮地 忍, 末満 英俊, 藤木 孝, 石井 慶之, 深尾 正之, 八坂 保能, 阿部 宏尹, 板谷 良平, 佐々木 敏博, 伊藤 進

    秋の分科会講演予稿集   1986 ( 4 )   206 - 206   1986.9

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  • 28a-M-10 WT-IIIにおけるLHH

    前川 孝, 岩村 和昭, 山崎 晃, 大穂 健介, 尾崎 成則, 飯田 素身, 井手 俊介, 田中 仁, 小椋 一夫, 安藤 晃, 中村 正彦, 曄道 恭, 田中 茂利, 宮地 忍, 末満 英俊, 藤本 孝, 石井 慶之, 深尾 正之, 八坂 保能, 阿部 宏尹, 板谷 良平

    秋の分科会講演予稿集   1986 ( 4 )   207 - 207   1986.9

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  • 29p-BA-12 WT-2トカマクの電流駆動 IX : 高n_<11>スペクトラムの印加(プラズマ物理・核融合(ヘリオトロン,トカマク))

    飯田 素身, 尾崎 成則, 大穂 健介, 井手 俊介, 田中 仁, 小椋 一夫, 安藤 晃, 中村 正彦, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   41 ( 4 )   146 - 146   1986.3

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  • 29a-BC-2 ガンマ10バリア部のECH生成プラズマによるX線輻射計測ii : 高温電子生成機構(プラズマ物理・核融合(開放端系))

    長 照二, 平田 真史, 近藤 貴, 大澤 明彦, 山口 直洋, 澤田 克郎, 三好 昭一, 加藤 隆子, 政井 邦昭, 小椋 一夫, 前川 隆, 田中 茂利

    年会講演予稿集   41 ( 4 )   163 - 163   1986.3

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  • 29p-BA-13 WT-2トカマクの電子ビーム入射による電流駆動 IV(プラズマ物理・核融合(ヘリオトロン,トカマク))

    田中 仁, 毛利 明博, 成原 一途, 久保 伸, 中村 正彦, 安藤 晃, 小椋 一夫, 飯田 素身, 井手 俊介, 大穂 健介, 尾崎 成則, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   41 ( 4 )   147 - 147   1986.3

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  • 2a-L-13 WT-2トカマクの電子ビーム入射による電流駆動 III

    田中 仁, 毛利 明博, 成原 一途, 久保 伸, 中村 正彦, 安藤 晃, 小椋 一夫, 飯田 素身, 井手 俊介, 大穂 健介, 尾崎 成則, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1985 ( 4 )   231 - 231   1985.9

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  • 2a-L-11 WT-2(RF-トカマク)のECH

    安藤 晃, 大穂 健介, 尾崎 成則, 井手 俊介, 飯田 素身, 田中 仁, 小椋 一夫, 中村 正彦, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1985 ( 4 )   230 - 230   1985.9

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  • 2a-L-10 WT-2トカマク(RFトカマク)の高速電子とX線計測

    小椋 一夫, 中村 正彦, 安藤 晃, 田中 仁, 飯田 素身, 井手 俊介, 大穂 健介, 尾崎 成則, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1985 ( 4 )   230 - 230   1985.9

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  • 2a-L-12 WT2トカマク(RFトカマク)における逆電場の影響

    中村 正彦, 井手 俊介, 飯田 素身, 安藤 晃, 小椋 一夫, 田中 仁, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1985 ( 4 )   231 - 231   1985.9

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  • 31p-E4-8 WT-2トカマクの電子ビーム入射による電流駆動(プラズマ物理・核融合)

    田中 仁, 毛利 明博, 成原 一途, 久保 伸, 長谷川 満, 中村 正彦, 安藤 晃, 小椋 一夫, 高橋 淳一, 唐内 一郎, 柳本 吉之, 飯田 素身, 井手 俊介, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   40 ( 4 )   151 - 151   1985.3

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  • 31p-E4-7 高トロイダル磁場中へのEビーム入射におけるECRプラズマ電場の効用 : WT-2トカマクの実験(プラズマ物理・核融合)

    毛利 明博, 成原 一途, 久保 伸, 長谷川 満, 田中 茂利, 曄道 恭, 前川 孝, 安藤 晃, 小椋 一夫, 田中 仁

    年会講演予稿集   40 ( 4 )   150 - 150   1985.3

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  • 31p-E4-6 WT-2トカマクの高周波電流駆動VIII(プラズマ物理・核融合)

    前川 孝, 中村 正彦, 安藤 晃, 小椋 一夫, 田中 仁, 高橋 淳一, 唐内 一郎, 柳本 吉之, 飯田 素身, 井手 俊介, 曄道 恭, 田中 茂利

    年会講演予稿集   40 ( 4 )   150 - 150   1985.3

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  • 2p-G-3 WT-2トカマクにおけるRF電流駆動VII : X線の波高分析

    小椋 一夫, 唐内 一郎, 長 照二, 中村 正彦, 安藤 晃, 田中 仁, 高橋 淳一, 柳本 吉之, 飯田 素身, 井出 俊介, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1984 ( 4 )   111 - 111   1984.9

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  • 2p-G-2 WT-2トカマクにおけるRF電流駆動 VI : 電流の立ち上げ

    田中 仁, 中村 正彦, 安藤 晃, 小椋 一夫, 高橋 淳一, 唐内 一郎, 柳本 吉之, 飯田 素身, 井出 俊介, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1984 ( 4 )   110 - 110   1984.9

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  • 2p-G-4 WT-2トカマクのICH(I)

    中村 正彦, 八坂 保能, 板谷 良平, 安藤 晃, 小椋 一夫, 田中 仁, 高橋 淳一, 唐内 一郎, 柳本 吉之, 飯田 素身, 井出 俊介, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1984 ( 4 )   111 - 111   1984.9

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  • 4a-RB-13 WT-2トカマクにおけるRF電流駆動V(サブミリ波散乱計測)

    久保 伸, 柳本 吉之, 前川 孝, 中村 正彦, 長 照二, 下妻 隆, 安藤 晃, 小椋 一夫, 井上 考, 田中 仁, 高橋 淳一, 唐内 一郎, 曄道 恭, 田中 茂利

    年会講演予稿集   39 ( 4 )   155 - 155   1984.3

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  • 4a-RB-11 WT-2トカマクにおけるRFによるトロイダル電流の立ち上げ

    中村 正彦, 田中 仁, 井上 考, 安藤 晃, 小椋 一夫, 下妻 隆, 久保 伸, 長 照二, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   39 ( 4 )   154 - 154   1984.3

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  • 4a-RB-12 WT-2トカマクにおけるRF電流駆動IV(軟X線の波高分析)

    前川 孝, 長 照二, 小椋 一夫, 田中 仁, 井上 考, 唐内 一郎, 中村 正彦, 久保 伸, 下妻 隆, 安藤 晃, 高橋 淳一, 柳本 吉之, 嘩道 恭, 田中 茂利

    年会講演予稿集   39 ( 4 )   154 - 154   1984.3

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  • 12p-DJ-1 ミリ波帯ジャイロトロンE3953の発振特性II

    印牧 知廣, 佐藤 信之, 出原 敏孝, 安藤 晃, 小椋 一夫, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1983 ( 4 )   158 - 158   1983.9

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  • 13a-DG-7 WT-2トカマクにおけるRF電流駆動(III) : 逆電場の影響

    中村 正彦, 井上 考, 田中 仁, 安藤 晃, 小椋 一夫, 下妻 隆, 久保 伸, 長 照二, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1983 ( 4 )   167 - 167   1983.9

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  • 13a-DG-8 WT-2トカマクでのRF電流駆動シミュレーション

    下妻 隆, 井上 考, 田中 仁, 安藤 晃, 小椋 一夫, 久保 伸, 長 照二, 中村 正彦, 前川 孝, 曄道 恭, 田中 茂利, 岡本 正雄

    秋の分科会講演予稿集   1983 ( 4 )   167 - 167   1983.9

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  • 13a-DG-6 WT-2トカマクにおけるRF電流駆動(II) : RFのみによる電流立ち上げと保持 RFトカマク

    久保 伸, 井上 考, 田中 仁, 安藤 晃, 小椋 一夫, 下妻 隆, 長 照二, 中村 正彦, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1983 ( 4 )   166 - 166   1983.9

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  • 13a-DG-5 WT-2トカマクにおけるRF電流駆動(I) : 電流駆動に必要なECR-プラズマに関して

    長 照二, 中村 正彦, 久保 伸, 下妻 隆, 小椋 一夫, 安藤 晃, 井上 考, 田中 仁, 高橋 淳一, 柳本 吉之, 唐内 一郎, 前川 孝, 曄道 恭, 田中 茂利

    秋の分科会講演予稿集   1983 ( 4 )   166 - 166   1983.9

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  • 30a-SB-10 ミリ波帯ジャイロトロンの試作

    印牧 知広, 佐藤 信之, 出原 敏孝, 八木 寿郎, 安藤 晃, 小椋 一夫, 曄道 恭, 田中 茂利

    年会講演予稿集   38 ( 4 )   148 - 148   1983.3

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  • 28a-A-2 WT-2トカマクのLHH(XII)(RF駆動電流によるプラズマの保持)

    久保 伸, 中村 正彦, 長 照二, 中尾 修治, 下妻 隆, 安藤 晃, 小椋 一夫, 井上 考, 田中 仁, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   38 ( 4 )   102 - 102   1983.3

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  • 28a-A-1 WT-2トカマクのLHH(XI)(RF駆動によるプラズマ電流の立ち上げ)

    中尾 修治, 中村 正彦, 長 照二, 久保 伸, 下妻 隆, 安藤 晃, 小椋 一夫, 田中 仁, 井上 考, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   38 ( 4 )   102 - 102   1983.3

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  • 30a-CG-4 70GHz ジャイロトロンの試作

    安藤 晃, 小椋 一夫, 曄道 恭, 田中 茂利, 印牧 知広, 佐藤 信之, 出原 敏孝, 八木 寿郎

    年会講演予稿集   37 ( 4 )   105 - 105   1982.9

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  • 30a-CE-6 WT-2トカマクのLHH X : RF電流保持プラズマの比例則とエネルギーバランス

    長 照二, 中村 正彦, 中尾 修治, 久保 伸, 下妻 隆, 安藤 晃, 小椋 一夫, 井上 考, 田中 仁, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   37 ( 4 )   93 - 93   1982.9

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  • 30a-CE-4 WT-2トカマクのLHH VIII : 電流駆動の密度限界

    中村 正彦, 長 照二, 中尾 修治, 久保 伸, 下妻 隆, 安藤 晃, 小椋 一夫, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   37 ( 4 )   92 - 92   1982.9

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  • 30a-CE-5 WT-2トカマクのLHH IX : LHHとECHによる複合電流駆動

    久保 伸, 中村 正彦, 長 照二, 中尾 修治, 下妻 隆, 安藤 晃, 小椋 一夫, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   37 ( 4 )   93 - 93   1982.9

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  • 30a-CG-3 WT-2トーラスにおけるECRプラズマ生成 II

    中尾 修治, 長 照二, 小椋 一夫, 安藤 晃, 中村 正彦, 久保 伸, 下妻 隆, 井上 考, 田中 仁, 前川 孝, 曄道 恭, 田中 茂利

    年会講演予稿集   37 ( 4 )   105 - 105   1982.9

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  • 31p-W-13 WT-2トーラスにおけるECRプラズマ生成

    小椋 一夫, 安藤 晃, 河合 秀樹, 山崎 孝二, 下妻 隆, 久保 伸, 中尾 修治, 中村 正彦, 長 照二, 前川 孝, 曄道 恭, 田中 茂利

    春の分科会予稿集   1982 ( 4 )   108 - 108   1982.3

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  • 31p-W-11 WT-2トカマクのLHH(VI)(サブミリ波による散乱測定)

    久保 伸, 中村 正彦, 長 照二, 中尾 修治, 下妻 隆, 河合 秀樹, 山崎 孝二, 安藤 晃, 小椋 一夫, 前川 孝, 曄道 恭, 田中 茂利

    春の分科会予稿集   1982 ( 4 )   107 - 107   1982.3

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  • 31p-W-14 WT-2トカマクのECH(IV)

    安藤 晃, 小椋 一夫, 河合 秀樹, 山崎 孝二, 下妻 隆, 久保 伸, 中尾 修治, 中村 正彦, 長 照二, 前川 孝, 曄道 恭, 田中 茂利

    春の分科会予稿集   1982 ( 4 )   108 - 108   1982.3

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  • 31p-W-16 WT-2トカマクのECR放電洗浄

    中尾 修治, 小椋 一夫, 長 照二, 中村 正彦, 久保 伸, 下妻 隆, 河合 秀樹, 山崎 孝二, 安藤 晃, 前川 孝, 嘩道 恭, 田中 茂利

    春の分科会予稿集   1982 ( 4 )   109 - 109   1982.3

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  • 31p-W-9 WT2トカマクのLHH(IV)RFによるトロイダル電流

    中村 正彦, 長 照二, 中尾 修治, 久保 伸, 下妻 隆, 河合 秀樹, 山崎 孝二, 安藤 晃, 小椋 一夫, 前川 孝, 曄道 恭, 田中 茂利

    春の分科会予稿集   1982 ( 4 )   106 - 106   1982.3

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  • 31p-W-10 WT-2トカマクのLHH(V)(電子の分布函数と輻射測定)

    長 照二, 中村 正彦, 中尾 修治, 久保 伸, 下妻 隆, 山崎 孝二, 河合 秀樹, 小椋 一夫, 安藤 晃, 前川 孝, 嘩道 恭, 田中 茂利

    春の分科会予稿集   1982 ( 4 )   106 - 106   1982.3

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  • 2p-NW-16 WT-2トカマクのECH(III)

    曄道 恭, 安藤 晃, 小椋 一夫, 河合 秀樹, 山崎 孝二, 下妻 隆, 久保 伸, 中尾 修治, 長 照二, 中村 正彦, 前川 孝, 田中 茂利

    秋の分科会講演予稿集   1981 ( 4 )   79 - 79   1981.9

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Presentations

  • Non-axisymmetric Radiation from Surface Wave Oscillator Driven by Weakly Relativistic Electron Beam International conference

    Yuta Annaka, Kazuo Ogura, Kosuke Ozawa, Makoto Nakasone, Yuki Sato

    12th International Conference on Open Magnetic Systems for Plasma Confinement  2018.8 

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    Venue:Tsukuba, Japan  

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  • Study of Spoof Plasmon Formed on Periodically Corrugated Metal Surface Based on Cavity Resonance Method International conference

    Kazuo Ogura, Kei Sekine, Yuta Annaka, Min, Thu San

    12th International Conference on Open Magnetic Systems for Plasma Confinement  2018.8 

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  • Spoof Plasmon on Periodically Corrugated Metal Cylinder International conference

    Min Thu San, Kazuo Ogura, Kei Sekine, Yuta Annaka, Akira Sugawara, Kiyoyuki Yambe, Shin Kubo, Takashi Shimozuma, Sakuji Kobayashi, Kohji Okada

    The 26th International Toki Conference and The 11th Asia Plasma and Fusion Association Conference  2017.12 

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    Venue:Toki, Japan  

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  • Terahertz Wave Generation Based on Surface Wave Resonator International conference

    Kazuo Ogura, Yuta Annaka, Kazuma Iwato, Kiyoyuki Yambe, Teruo Saito

    The 6th International Workshop on Far-Infrared Technologies and The 2nd International Symposium on Development of High Power Terahertz Science and Technology  2017.3 

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    Venue:Fukui, Japan  

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  • Study on Intense Sub-Terahertz Radiation by Oversized Surface Wave Oscillator International conference

    Min Thu San, Kazuo Ogura, Kiyoyuki Yambe, Yuta Annaka, Shaoyan Gong

    The 18th International Congress on Plasma Physics  2016.6 

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    Venue:Kaohsiung, Taiwan  

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  • “Experimental Study on Slow Cyclotron Interaction under Anomalous Doppler Effect in W-Band Backward Wave Oscillator International conference

    Yuta Annaka, Kazuo Ogura, June Kawamura, Takuro Miura, Takuro Kawamura, Sho Takanashi

    The 25nd International Toki Conference  2015.11 

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    Venue:Toki, Japan  

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  • Experimental Study on W-band Oversized Surface Wave Oscillator Driven by Weakly Relativistic Electron Beam International conference

    Min Thu San, Kazuo Ogura, Kiyoyuki Yambe, Yuta Annaka, Shaoyan Gong, Jun Kawamura, Takuro Miura, Shin Kubo, Takashi Shimozuma, Sakuji Kobayashi, Kohji Okada

    The 25nd International Toki Conference  2015.11 

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    Venue:Toki, Japan  

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  • Oscillation Starting Condition for Oversized G-Band Backward Wave Oscillator Driven by a Weakly Relativistic Electron Beam International conference

    Shaoyan Gong, Kazuo Ogura, Shintaro Nomizu, Kosuke Yamazaki, Kiyoyuki Yambe, Shin Kubo, Takashi Shimozuma, Sakuji Kobayashi, Kohji Okada

    The 5th Euro-Asian Pulsed Power Conference  2014.9 

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    Venue:Kumamoto, Japan  

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  • Beam Interactions with Surface Waves and Higher Order Modes in Oversized G-band Slow-Wave Structure International conference

    Kazuo Ogura, Akihiro Shirai, Masahiko Ogata, Kiyoyuki Yambe

    The 5th Euro-Asian Pulsed Power Conference  2014.9 

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    Venue:Kumamoto, Japan  

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  • Enhancement of Smith-Purcell Radiations by Self-Bunched Electron Beams in Oversized Backward Wave Oscillator International conference

    Kazuo Ogura, Kiyoyuki Yambe, Takayuki Iwasaki, Shota Magori, Junpei Kojima

    The 41st IEEE International Conference on Plasma Science and the 20th International Conference on High-Power Particle Beams  2014.5 

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    Venue:Washington, DC, USA  

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  • Surface Waves in Oversized G-Band Slow-Wave Structures with Rectangular Corrugations International conference

    Kazuo Ogura, Akihiko Kojima, Fumiaki Kawabe, Kiyoyuki Yambe, Md. Ruhul Amin

    23nd International Toki Conference  2013.11 

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    Venue:Toki, Japan  

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  • Experimental Study on G-band Oversized Backward Wave Oscillator Driven by Weakly Relativistic Electron Beam International conference

    Shota Magori, Kazuo Ogura, Takayuki Iwasaki, Junpei Kojima, Kiyoyuki Yambe, Shin Kubo, Takashi Shimozuma, Sakuji Kobayashi, Kohji Okada

    23nd International Toki Conference  2013.11 

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    Venue:Toki, Japan  

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  • Beam Interactions with Surface Waves and Higher Order Modes in Oversized Backward Wave Oscillators International conference

    Kazuo Ogura, Akihiko Kojima, Fumiaki Kawabe, Kiyoyuki Yambe

    9th Asia Plasma and Fusion Association Conference  2013.11 

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    Venue:Gyeongju, Korea  

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  • Experimental Study on Smith-Purcell Radiations of Weakly Relativistic Oversized Backward Wave Oscillators International conference

    Takayuki Iwasaki, Kazuo Ogura, Shota Magori, Junpei Kojima, Kiyoyuki Yambe

    9th Asia Plasma and Fusion Association Conference  2013.11 

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    Venue:Gyeongju, Korea  

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  • Higher Order Mode Radiations of Weakly Relativistic Oversized Backward Wave Oscillator International conference

    K. Ogura, K. Yambe, S. Hasegawa, T. Iwasaki, K. Yamamoto, Y. Kobari

    22nd International Toki Conference  2012.11 

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    Venue:Toki, Japan  

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  • Normal Modes and Slow-Wave Instabilities in Oversized Coaxial Slow-Wave Structure with Rectangular Corrugations International conference

    Kazuo Ogura, Kiyoyuki Yambe, Kazumasa Yamamoto, Yoshihiro Kobari

    4th Euro-Asian Pulsed Power Conference and 19th International Conference on High-Power Beams  2012.9 

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    Venue:Karlsruhe, Germany  

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  • Experimental Study on Generation of Electron Beam Utilizing Cold Cathode in the Weakly Relativistic Energy Region International conference

    Kiyoyuki Yambe, Kazuo Ogura, Shinji Hasegawa, Takaki Shinada, Takayuki Iwasaki, Tsubasa Furuichi

    4th Euro-Asian Pulsed Power Conference and 19th International Conference on High-Power Beams  2012.9 

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    Venue:Karlsruhe, Germany  

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  • Smith-Purcell Radiation Based on Cylindrical Surface Waves International conference

    S. Hasegawa, K. Ogura, T. Iwasaki, K. Yambe

    oint conference of 9th International Conference on Open Magnetic Systems for Plasma Confinement and 3rd International Workshop on Plasma Material Interaction Facilities for Fusion  2012.8 

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    Venue:Tsukuba, Japan  

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  • Normal Modes and Slow-Wave Instabilities in Oversized Coaxial Slow-Wave Structure with Rectangular Corrugations International conference

    Kazuo Ogura, Kiyoyuki Yambe, Kazumasa Yamamoto, Yoshihiro Kobari

    Joint conference of 9th International Conference on Open Magnetic Systems for Plasma Confinement and 3rd International Workshop on Plasma Material Interaction Facilities for Fusion  2012.8 

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    Venue:Tsukuba, Japan  

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  • Cylindrical Surface Wave on Periodically Corrugated Metal Cylinder International conference

    H. Iiduka, K. Ogura, K. Yambe

    21st International Toki Conference on Integration of Fusion Science and Technology for Steady State Operation  2011.11 

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    Venue:Toki, Japan  

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  • Numerical Study of Slow-Wave Instabilities in Oversized Coaxial Slow-Wave Structure International conference

    K. Ogura, S. Abe, H. Kimura, K. Yamamoto, K. Yambe, Md. R. Amin

    3rd Euro-Asian Pulsed Power Conference and 18th International Conference on High-Power Beams  2010.10 

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    Venue:Jeju Island, Korea  

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  • Experimental Study on Weakly Relativistic Oversized Backward Wave Oscillator with Coaxial Rectangular Corrugations International conference

    M. Takahashi, K. Ogura, H. Yoshimura, H. Iiduka, A. Sugawara, K. Yambe, W. S. Kim

    3rd Euro-Asian Pulsed Power Conference and 18th International Conference on High-Power Beams  2010.10 

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    Venue:Jeju Island, Korea  

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Awards

  • The Sir Thomas Ward Memorial Medal

    2000.1   The Institute of Engineer (India)  

    Md. R. Amin, Md. A. Goffar Khan, K. Ogura

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Research Projects

  • Study on Broadband Pulsed Surface Wave Oscillator with Double-Corrgation

    2011.11 - 2014.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research(B)

    Kazuo Ogura

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\13300000 ( Direct Cost: \9310000 、 Indirect Cost:\3990000 )

    Study on Broadband Pulsed Surface Wave Oscillator with Double-Corrugation
    Broadband pulsed surface wave oscillators with slow-wave structure composed of double-corrugation are examined. The dispersion characteristics of surface wave can be controlled by the corrugation parameters. The surface waves in the range from 20GHz to 40GHz are examined numerically and experimentally. Weakly relativistic electron beams are generated by a disk type cold cathode, not by a hot cathode. By injecting the beam into the double-corrugation, an intense surface wave excitation and a frequency tunability of about 20 percent are demonstrated based on the double-corrugation. And high frequency operation based on the higher order modes of double-corrugation are examined numerically and relatively strong radiations of higher order mode are demonstrated experimentally. Moreover, the intense surface wave excitation is extended up to 170GHz-band. The higher order and extended surface wave operations are of considerable interest for an intense broadband terahertz wave source.

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  • 異常ドップラー効果による表面波励起を用いた弱い相対論的大電力遅波ミリ波源の研究

    2005.4 - 2008.3

    日本学術振興会  科学研究費助成事業  基盤研究(B)

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    Grant type:Competitive

    Grant amount:\14800000 ( Direct Cost: \14560000 、 Indirect Cost:\240000 )

    本研究では弱い相対論的電子ビームによりオーバーサイズ遅波導波管の表面波を励起することを目指した。まず,弱い相対論的領域では大電流の電子ビーム生成そのものも解決すべき重要な問題である。新しくディスクタイプの冷陰極を提案し,弱い相対論的領域で均一性の良いビームを発生させることができた。ビーム回収ポートについては,今後さらに検討する必要がある。
    電子ビームとオーバーサイズ遅波導波管特性の改善により20GHz帯で約500kW,40GHz帯で約200kWまで出力が上昇した。また,軸対称モードと非軸対称モードの制御が可能であることを実証した。遅波構造として矩形を採用して平坦なアッパーカットオフを実現し,比較的エネルギーの低い領域でチェレンコフ相互作用と遅波サイクロトロン相互作用が共鳴した異常ドップラー効果による表面波励起を行った。低磁場と低エネルギー領域での表面波励起とモード制御の成果であり,将来性の見込める成果といえる。
    オー

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  • 異常ドップラー効果による遅波サイクロトロンメーザの研究

    2000.4 - 2003.3

    日本学術振興会  科学研究費助成事業  基盤研究(B)

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    Grant type:Competitive

    Grant amount:\14600000 ( Direct Cost: \14600000 )

    本研究では,異常ドップラー効果による遅波サイクロトロン共鳴相互作用の誘導放射を利用し単一スペクトルの電磁波を得る遅波サイクロトロンメーザを提案した。研究成果の概要を箇条書きにまとめる。
    ・磁場システム製作と電子ビーム制御
    磁場配意が可変な磁場システムを新たに構築した。磁場コイルの電流分布と磁場配位の関係を定量的に調べ,軸方向414mm,半径方向60mmの範囲で変化率5%以内の磁場が得られた。この磁場による制御により,高真空状態において,60kV程度,数100Aの電子ビームを360mm以上伝搬させることができた。
    ・異常ドップラー効果による遅波サイクロトロンメーザの研究
    遅波サイクロトロンメーザ動作の理論的解析結果は,米国の雑誌Phys. Rev. Eに論文として掲載された。また,K-Band大口径波形導波管により,チェレンコフ相互作用と遅波サイクロトロン相互作用によるマイクロ波発生について調べた。発振周波数は20-25GHz,発振電力は最大で約100kW(約2%)が

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Teaching Experience (researchmap)

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Teaching Experience

  • プロジェクト研究特別概説

    2021
    Institution name:新潟大学

  • 電気磁気エネルギー工学

    2021
    Institution name:新潟大学

  • 電子情報通信実験IIIB

    2020
    Institution name:新潟大学

  • 論文輪講I

    2020
    Institution name:新潟大学

  • 電子情報通信設計製図

    2020
    Institution name:新潟大学

  • 論文輪講II

    2020
    Institution name:新潟大学

  • 電子情報通信実験IIIA

    2020
    Institution name:新潟大学

  • 工学リテラシー入門(情報電子分野)

    2019
    Institution name:新潟大学

  • 電子情報通信実験IIB

    2019
    Institution name:新潟大学

  • 科学技術者の倫理

    2019
    Institution name:新潟大学

  • 電子情報通信実験IIA

    2019
    Institution name:新潟大学

  • 電子情報通信実験IB

    2018
    Institution name:新潟大学

  • 電子情報通信実験IA

    2018
    Institution name:新潟大学

  • 総合工学概論

    2017
    Institution name:新潟大学

  • 総合技術科学演習

    2017
    -
    2020
    Institution name:新潟大学

  • 電気情報工学博士セミナーⅠ

    2015
    Institution name:新潟大学

  • 電気電子工学研究発表(外部発表)

    2014
    -
    2015
    Institution name:新潟大学

  • 電気情報工学特定研究Ⅲ

    2014
    Institution name:新潟大学

  • 電気電子工学特定研究Ⅱ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学セミナーⅡ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学特定研究Ⅰ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学文献詳読Ⅱ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学研究発表演習(中間発表)

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学セミナーⅠ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気電子工学文献詳読Ⅰ

    2013
    -
    2015
    Institution name:新潟大学

  • 電気情報工学特定研究Ⅱ

    2013
    Institution name:新潟大学

  • 外国語論文解説・討論Ⅱ

    2013
    Institution name:新潟大学

  • 技術英語入門

    2013
    Institution name:新潟大学

  • 電気電子工学研究発表演習(外部発表)

    2013
    Institution name:新潟大学

  • 中間発表

    2013
    Institution name:新潟大学

  • 電気電子工学コースセミナーⅡ

    2013
    Institution name:新潟大学

  • 電気電子工学コース演習

    2012
    -
    2015
    Institution name:新潟大学

  • 電気情報工学特定研究Ⅰ

    2012
    -
    2015
    Institution name:新潟大学

  • 外国語論文解説・討論Ⅰ

    2012
    -
    2015
    Institution name:新潟大学

  • 電気電子工学コースセミナーⅠ

    2012
    Institution name:新潟大学

  • 物理工学特論1

    2011
    Institution name:新潟大学

  • 電気電子設計製図

    2010
    -
    2018
    Institution name:新潟大学

  • 電気電子創造設計

    2010
    -
    2016
    Institution name:新潟大学

  • 卒業研修

    2009
    Institution name:新潟大学

  • 工学リテラシー入門(電気電子工学科)

    2009
    -
    2016
    Institution name:新潟大学

  • 電磁気学演習I

    2009
    -
    2010
    Institution name:新潟大学

  • 自然科学総論Ⅴ

    2008
    Institution name:新潟大学

  • スタディスキルズ(電気電子工学)

    2008
    Institution name:新潟大学

  • 物理工学IV

    2007
    Institution name:新潟大学

  • 高電圧工学

    2007
    Institution name:新潟大学

  • 卒業研究

    2007
    Institution name:新潟大学

  • プラズマ応用工学

    2007
    Institution name:新潟大学

  • 論文輪講

    2007
    -
    2019
    Institution name:新潟大学

  • 物理工学II

    2007
    -
    2018
    Institution name:新潟大学

  • 電気電子工学実験III

    2007
    -
    2018
    Institution name:新潟大学

  • 電気電子工学実験IV

    2007
    -
    2018
    Institution name:新潟大学

  • 電気電子工学実験I

    2007
    -
    2017
    Institution name:新潟大学

  • 電気電子工学実験II

    2007
    -
    2017
    Institution name:新潟大学

  • エレクトロニクスへの招待

    2007
    -
    2016
    Institution name:新潟大学

  • 電気磁気エネルギー工学

    2007
    -
    2016
    Institution name:新潟大学

  • 電気電子演習

    2007
    -
    2009
    Institution name:新潟大学

  • 卒業基礎研究

    2007
    -
    2008
    Institution name:新潟大学

  • 物理工学III

    2007
    -
    2008
    Institution name:新潟大学

  • 物理工学特論II

    2007
    Institution name:新潟大学

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