Researcher Profile and Settings

Master

Affiliation (Master)

• Faculty of Engineering　Applied Quantum Science and Engineering　Quantum Engineering for Materials

Affiliation (Master)

• Faculty of Engineering　Applied Quantum Science and Engineering　Quantum Engineering for Materials

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Profile and Settings

Profile and Settings

• Name (Japanese)

  Tomita

• Name (Kana)

  Kentaro

• Name

  201901020432931575

Achievement

Research Interests

• measurements of electron density and temperature   Soft X-ray light source   EUV light source   laser-aided spectroscopy   plasma electronics   

Research Areas

• Energy / Applied plasma science / plasma spectroscopy
• Energy / Basic plasma science / laser spectroscopy

Research Experience

• 2020/07 - Today Hokkaido University Division of Quantum Science and Engineering, Graduate School of Engineering Associate professor
• 2007/04 - 2020/06 九州大学
• 2006/11 - 2007/03 九州大学

Education

• 2004/04 - 2006/10  Kyushu University  Interdisciplinary Graduate School of Engineering Sciences  Department of Applied Science for Electronics and Materials
• 2002/04 - 2004/03  Kyushu University  Interdisciplinary Graduate School of Engineering Sciences  Department of Applied Science for Electronics and Materials
• 1998/04 - 2002/03  Kyushu University

Awards

• 2022/01 Center for Low-temperature Plasma Sciences, Nagoya University Plasma Materials Science Awards
   Study of high spatio-temporal resolution measurement of plasma electron density 

  受賞者: Kentaro Tomita受賞理由：「プロセスプラズマからEUV光源プラズマまで多様な対象に対するレーザトムソン散乱法によるプラズマ電子密度の高時空間分解能測定の研究成果は、世界をけん引する顕著な業績であり、プラズマ材料科学の進展に大きく貢献するものである」
• 2020/11 量子科学技術研究開発機構 核融合エネルギー部門 令和元年度JT-60共同研究優秀賞
   レーザー光脱離およびトムソン散乱法を用いたNBI用負イオン源内の負イオン分布計測 

  受賞者: 富田 健太郎、小島 有志、平塚;淳一、柏木 美恵子、市川雅浩
• 2019/04 Ministry of Education, Culture, Sports, Science and Technology The Commendation for Science and Technology by the Minister of Education, The Young Scientists’ Prize Culture, Sports, Science and Technology
   

  受賞者: Kentaro Tomita
• 2018/03 日本応用物理学会プラズマエレクトロニクス分科会 2018 Plasma Electronics Award
   

  受賞者: Kentaro Tomita
• 2018/02 一般社団法人照明学会 2018年度(第30回)照明学会論文賞
   

  受賞者: 堀内 誠;山形 幸彦;堤 晋一;富田 健太郎;真鍋 由雄
• 2014/08 電気学会 電気学会優秀論文発表A賞
   

  受賞者: Kentaro Tomita
• 2014/05 5th International Conference on Plasma Medicine (ICPM5), J. M. Pouvesle, The Award Committee of ICPM5 Early Career Presentation Awards (ECPA)
   

  受賞者: Kentaro Tomita
• 2014/04 大阪大学レーザーエネルギー学研究センター 大阪大学レーザーエネルギー学研究センターシンポジウム2014ベストポスター賞
   

  受賞者: 富田健太郎
• 2013/09 電気学会 優秀論文発表賞
   

  受賞者: 富田健太郎
• 2007/09 応用物理学会 講演奨励賞
   

  受賞者: 富田健太郎
• 2004/10 応用物理学会 プラズマエレクトロニクスサマースクール優秀講演賞
   

  受賞者: 富田健太郎

Published Papers

• Direct observations of pure electron outflow in magnetic reconnection

  K. Sakai, T. Moritaka, T. Morita, K. Tomita, T. Minami, T. Nishimoto, S. Egashira, M. Ota, Y. Sakawa, N. Ozaki, R. Kodama, T. Kojima, T. Takezaki, R. Yamazaki, S. J. Tanaka, K. Aihara, M. Koenig, B. Albertazzi, P. Mabey, N. Woolsey, S. Matsukiyo, H. Takabe, M. Hoshino, Y. Kuramitsu

  Scientific Reports 12 (1) 2022/12 

  Abstract Magnetic reconnection is a universal process in space, astrophysical, and laboratory plasmas. It alters magnetic field topology and results in energy release to the plasma. Here we report the experimental results of a pure electron outflow in magnetic reconnection, which is not accompanied with ion flows. By controlling an applied magnetic field in a laser produced plasma, we have constructed an experiment that magnetizes the electrons but not the ions. This allows us to isolate the electron dynamics from the ions. Collective Thomson scattering measurements reveal the electron Alfvénic outflow without ion outflow. The resultant plasmoid and whistler waves are observed with the magnetic induction probe measurements. We observe the unique features of electron-scale magnetic reconnection simultaneously in laser produced plasmas, including global structures, local plasma parameters, magnetic field, and waves.
• Detection of current-sheet and bipolar ion flows in a self-generated antiparallel magnetic field of laser-produced plasmas for magnetic reconnection research

  T. Morita, T. Kojima, S. Matsuo, S. Matsukiyo, S. Isayama, R. Yamazaki, S. J. Tanaka, K. Aihara, Y. Sato, J. Shiota, Y. Pan, K. Tomita, T. Takezaki, Y. Kuramitsu, K. Sakai, S. Egashira, H. Ishihara, O. Kuramoto, Y. Matsumoto, K. Maeda, Y. Sakawa

  Physical Review E 106 (5) 2470-0045 2022/11/10
• High-power laser experiment on developing supercritical shock propagating in homogeneously magnetized plasma of ambient gas origin

  S. Matsukiyo, R. Yamazaki, T. Morita, K. Tomita, Y. Kuramitsu, T. Sano, S. J. Tanaka, T. Takezaki, S. Isayama, T. Higuchi, H. Murakami, Y. Horie, N. Katsuki, R. Hatsuyama, M. Edamoto, H. Nishioka, M. Takagi, T. Kojima, S. Tomita, N. Ishizaka, S. Kakuchi, S. Sei, K. Sugiyama, K. Aihara, S. Kambayashi, M. Ota, S. Egashira, T. Izumi, T. Minami, Y. Nakagawa, K. Sakai, M. Iwamoto, N. Ozaki, Y. Sakawa

  Physical Review E 106 (2) 2470-0045 2022/08/26
• Feasibility study on reactive ion etching occurrence in EUV-induced photoionized hydrogen plasmas based on electron temperature and electron density measurements

  Kouichiro Kouge, Kentaro Tomita, Junya Hotta, Yiming Pan, Hiroaki Tomuro, Tatsuya Yanagida, Kiichiro Uchino, Naoji Yamamoto

  Japanese Journal of Applied Physics 0021-4922 2022/03/11 [Refereed][Not invited]
   

  Abstract Temporal evolutions of electron temperature (T_e) and electron density (n_e) of photoionized hydrogen plasmas, which were induced by radiation from laser-produced Sn-plasma EUV sources, were measured using the Laser Thomson Scattering (LTS) technique. Measured T_e and n_e ranged from 0.5–2.5 eV and 10¹⁶–10¹⁸ m^-3, respectively, for hydrogen pressures of 50–400 Pa. The T_e of this EUV-induced hydrogen plasma decayed with the thermal relaxation time between electrons and gases. The maximum value of T_e in the time variation depended on hydrogen pressure. The lower the pressure, the higher the maximum T_e, and it reached approximately 2 eV at 50 Pa. The sheath potential between the EUV-induced hydrogen plasma and the unbiased wall might be exceeded 6 eV at 50 Pa, which is sufficient to enhance the removal of Sn-debris from a Mo/Si multilayer mirror via reactive ion etching processes.
• High-power laser experiment forming a supercritical collisionless shock in a magnetized uniform plasma at rest

  R. Yamazaki, S. Matsukiyo, T. Morita, S. J. Tanaka, T. Umeda, K. Aihara, M. Edamoto, S. Egashira, R. Hatsuyama, T. Higuchi, T. Hihara, Y. Horie, M. Hoshino, A. Ishii, N. Ishizaka, Y. Itadani, T. Izumi, S. Kambayashi, S. Kakuchi, N. Katsuki, R. Kawamura, Y. Kawamura, S. Kisaka, T. Kojima, A. Konuma, R. Kumar, T. Minami, I. Miyata, T. Moritaka, Y. Murakami, K. Nagashima, Y. Nakagawa, T. Nishimoto, Y. Nishioka, Y. Ohira, N. Ohnishi, M. Ota, N. Ozaki, T. Sano, K. Sakai, S. Sei, J. Shiota, Y. Shoji, K. Sugiyama, D. Suzuki, M. Takagi, H. Toda, S. Tomita, S. Tomiya, H. Yoneda, T. Takezaki, K. Tomita, Y. Kuramitsu, Y. Sakawa

  Physical Review E 105 (2) 2470-0045 2022/02/11
• Functional nitrogen science based on plasma processing: quantum devices, photocatalysts and activation of plant defense and immune systems

  Toshiro Kaneko, KATO Hiromitsu, Muneaki Yamamoto, Tomoko Yoshida, Pankaj Attri, Kazunori Koga, Kazuyuki Kuchitsu, Sugihiro Ando, Yasuhiro Nishikawa, Kentaro Tomita, Ono Ryo, ITO Tsuyohito, Koji Eriguchi, Tomohiro Nozaki, Takayoshi TSUTSUMI, Kenji Ishikawa

  Japanese Journal of Applied Physics 61 (SA) SA0805  0021-4922 2021/12 [Refereed][Invited]
   

  Nitrogen is a very common element, comprising approximately 78% of Earth's atmosphere, and is an important component of various electronic devices while also being essential for life. However, it is challenging to directly utilize dinitrogen because of the highly stable triple bond in this molecule. The present review examines the use of non-equilibrium plasmas to generate controlled electron impacts as a means of generating reactive nitrogen species (RNS) with high internal energy values and extremely short lifetimes. These species include ground state nitrogen atoms, excited nitrogen atoms, etc. RNS can subsequently react with oxygen and/or hydrogen to generate new highly reactive compounds and can also be used to control various cell functions and create new functional materials. Herein, plasma-processing methods intended to provide RNS serving as short-lived precursors for a range of applications are examined in detail.
• Time-resolved two-dimensional measurements of the electron density, electron temperature, and drift velocity of laser-produced carbon plasmas using the ion feature of collective laser Thomson scattering

  Yiming Pan, Kentaro Tomita, Kiichiro Uchino, Atsushi Sunahara, Katsunobu Nishihara

  Applied Physics Express 14 (6) 066001 - 066001 1882-0778 2021/06/01 [Refereed]
  
• Time-resolved spatial profiles of electron density and temperature in hydrogen plasmas induced by radiation from laser-produced tin plasmas for extreme ultraviolet lithography light sources

  Kouichiro Kouge, Kentaro Tomita, Junya Hotta, Yiming Pan, Hiroaki Tomuro, Masayuki Morita, Tatsuya Yanagida, Kiichiro Uchino, Naoji Yamamoto

  Japanese Journal of Applied Physics 60 (6) 066002 - 066002 0021-4922 2021/06/01 [Refereed]
  
• Measurements of spatial distributions of electron density and temperature of 450 MHz UHF plasma using laser Thomson scattering

  Yiming Pan, Kentaro Tomita, Yoshinobu Kawai, Masaaki Matsukuma, Kiichiro Uchino

  Japanese Journal of Applied Physics 60 (SA) SAAB03 - SAAB03 0021-4922 2021/01/01 [Refereed]
  
• Collective Thomson scattering in non-equilibrium laser produced two-stream plasmas

  K. Sakai, S. Isayama, N. Bolouki, M. S. Habibi, Y. L. Liu, Y. H. Hsieh, H. H. Chu, J. Wang, S. H. Chen, T. Morita, K. Tomita, R. Yamazaki, Y. Sakawa, S. Matsukiyo, Y. Kuramitsu

  Physics of Plasmas 27 (10) 103104 - 103104 1070-664X 2020/10 [Refereed]
  
• Local plasma parameter measurements in colliding laser-produced plasmas for studying magnetic reconnection

  T. Morita, K. Tomita, K. Sakai, M. Takagi, K. Aihara, M. Edamoto, S. Egashira, T. Higuchi, N. Ishizaka, T. Izumi, S. Kakuchi, T. Kojima, Y. Kuramitsu, S. Matsukiyo, Y. Nakagawa, T. Minami, H. Murakami, Y. Nishioka, M. Ota, T. Sano, S. Sei, K. Sugiyama, S.J. Tanaka, R. Yamazaki, Y. Sakawa

  High Energy Density Physics 36 100754 - 100754 2020/08 [Refereed][Not invited]
  
• Measurement of electron velocity distribution function in a pulsed positive streamer discharge in atmospheric-pressure air

  Kentaro Tomita, Yuki Inada, Atsushi Komuro, Xiang Zhang, Kiichiro Uchino, Ryo Ono

  Journal of Physics D: Applied Physics {IOP} Publishing 2020/02 [Refereed][Not invited]
  
• Anomalous plasma acceleration in colliding high-power laser-produced plasmas

  T. Morita, K. Nagashima, M. Edamoto, K. Tomita, T. Sano, Y. Itadani, R. Kumar, M. Ota, S. Egashira, R. Yamazaki, S. J. Tanaka, S. Tomita, S. Tomiya, H. Toda, I. Miyata, S. Kakuchi, S. Sei, N. Ishizaka, S. Matsukiyo, Y. Kuramitsu, Y. Ohira, M. Hoshino, Y. Sakawa

  Phys. Plasmas 26 90702  2019/10 [Refereed][Not invited]
  
• Magnetic Reconnection in Self-Generated and Externally Applied Magnetic Fields in Laser-Produced Plasmas

  Taichi Morita, Masafumi Edamoto, Yuki Nishioka, Takayoshi Sano, Masato Ota, Shunsuke Egashira, Ryo Yamazaki, Shuta Tanaka, Sara Tomita, Hirofumi Toda, Itaru Miyata, Ayato Shinoda, Shin Kakuchi, Shuto Sei, Natsuki Ishizaka, Riko Kawamura, Kei Sugiyama, Daisuke Suzuki, Sara Takayama, Kentaro Tomita, Yasuhiro Kuramitsu, Takumi Minami, Kentaro Sakai, Shuichi Matsukiyo, Yumi Horie, Takumi Higuchi, Taichi Takezaki, Youichi Sakawa

  2019/09 [Not refereed][Not invited]
  
• Collective Thomson Scattering Measurements of Electron Feature Using Stimulated Brillouin Scattering in Laser-Produced Plasmas

  N. Boloukia, K. Sakai, T.Y. Huang, S. Isayama, Y.L. Liu, C.W. Peng, C.H. Chen, N. Khasanah, H.H. Chu, T. Moritaka, K. Tomita, Y. Sato, K. Uchino, T. Morita, S. Matsukiyo, Y. Hara, H. Shimogawara, Y. Sakawa, S. Sakata, S. Kojima, S. Fujioka, Y. Shoji, S. Tomiya, R. Yamazaki, M. Koenig, Y. Kuramitsu

  High Energy Density Physics DOI: 10.1016/j.hedp.2019.06.002 2019/06 [Refereed][Not invited]
  
• VHF Plasma CVD Synthesis of Photochromic ZnO Nanoparticle

  H. Kajiyama, S. Kuboyama, A. Otomo, H. Uyama, T. Matsuura, S. Inoue, Y. Matsumura, K. Takata, K. Tomita, K. Uchino

  MRS advances, https://doi.org/10.1557/adv. 2019/02 [Refereed][Not invited]
  
• Observation of the whole Thomson scattering spectrum of laser-produced plasmas for EUV light sources

  Y. Sato, R. Fukada, F. Ito, K. Tomita, K. Uchino

  Engineering Sciences Reports, Kyushu University 40 11 - 15 2019/02 [Refereed][Not invited]
  
• Investigation on chemically non-equilibrium arc behaviors of different gas media during arc decay phase in a model circuit breaker

  H. Sun, Y. Wu, Y. Tanaka, K. Tomita, M. Rong

  Journal of Physics D: Applied Physics 52 75202  2018/12 [Refereed][Not invited]
  
• Determination of Spatiotemporal Structure of Fluctuations by Statistical Averaging Method

  Y. Kawachi, S. Inagaki, K. Tomita, K. Yamasaki, F. Kin, Y. Kosuga, M. Sasaki, Y. Nagashima, N. Kasuya, K. Hasamada, B. Zhang, A. Fujisawa

  Plasma and Fusion Research 13 3401105  1880-6821 2018/08 [Refereed][Not invited]
   

  Spatiotemporal structure of fluctuation with 11 kHz excited in a linear magnetized plasma was observed in details by applying pattern recognition method based on statistical averaging. Statistical behaviors of instantaneous period of the fluctuation and the temporal behavior of the radial profile of the fluctuation are clarified. Two-dimensional structure of the fluctuation is reconstructed and distortion of the wave-front of the fluctuation was inferred. (C) 2018 The Japan Society of Plasma Science and Nuclear Fusion Research
• Magnetic reconnection driven by electron dynamics

  Y. Kuramitsu, T. Moritaka, Y. Sakawa, T. Morita, T. Sano, M. Koenig, C. D. Gregory, N. Woolsey, K. Tomita, H. Takabe, Y. L. Liu, S. H. Chen, S. Matsukiyo, M. Hoshino

  Nature communications 9 5109  2018/08 [Refereed][Not invited]
  
• Competition of magnetic reconnections driven by self-generated magnetic fields and an external magnetic field

  Y. Kuramitsu, K. Sakai, T.Y. Huang, N. Khasanah, N. Bolouki, H.H. Chu, T. Moritaka, Y. Sakawa, Y. Hara, T. Sano, K. Tomita, Y. Sato, K. Uchino, S. Matsukiyo, T. Morita, H. Takabe, R. Yamazaki

  2018/05 [Not refereed][Not invited]
  
• Study of driven magnetic reconnection in high-power laser- produced plasma

  T. Morita, K. Nagashima, M. Edamoto, Y. Itadani, T. Sano, R. Kumar, M. Ota, S. Egashira, R. Yamazaki, S. Tanaka, S. Tomiya, H. Toda, I. Miyata, S. Kakuchi, S. Sei, N. Ishizaka, S. Tomita, K. Tomita, Y. Kuramitsu, S. Matsukiyo, Y. Sakawa

  2018/05 [Not refereed][Not invited]
  
• Thermal re-ignition processes of switching arcs with various gas-blast using voltage application highly controlled by powersemiconductors

  Tomoyuki Nakano, Yasunori Tanaka, K. Murai, Y. Uesugi, T. Ishijima, K. Tomita, K. Suzuki, T. Shinkai

  Journal of Physics D: Applied Physics 51 (21) 215202  1361-6463 2018/04/30 [Refereed][Not invited]
   

  This paper focuses on a fundamental experimental approach to thermal arc re-ignition processes in a variety of gas flows in a nozzle. Using power semiconductor switches in the experimental system, the arc current and the voltage applied to the arc were controlled with precise timing. With this system, residual arcs were created in decaying phase under free recovery conditions arc re-ignition was then intentionally instigated by application of artificial voltage - i.e. quasi-transient recovery voltage - to study the arc behaviour in both decaying and re-ignition phases. In this study, SF6, CO2, N2, O2, air and Ar arcs were intentionally re-ignited by quasi-TRV application at 20 μs delay time from initiation of free recovery condition. Through these experiments, the electron density at the nozzle throat was measured using a laser Thomson scattering method together with high speed video camera observation during the re-ignition process. Temporal variations in the electron density from the arc decaying to re-ignition phases were successfully obtained for each gas-blast arc at the nozzle throat. In addition, initial dielectric recovery properties of SF6, CO2, air and Ar arcs were measured under the same conditions. These data will be useful in the fundamental elucidation of thermal arc re-ignition processes.
• The Development of a System for Measuring the Junction Temperatures of Multiple LEDs on a Package Simultaneously by Using Pulsed-laser Raman Scattering

  M. Horiuchi, Y. Yamagata, S. Tsutsumi, K. Tomita, Y. Manabe

  Journal of Science and Technology in Lighting 一般社団法人 照明学会 41 101 - 107 2018/03 [Refereed][Not invited]
   

  This paper details a novel method consisting of employing a pulsed-laser Raman scattering technique to estimate junction temperatures of several LED chips arranged in a straight line on a phosphor-less blue-LED package and a phosphor-resin coated blue-LED package. By using a sheet-shaped irradiation pattern, each of the GaN-E₂^H Raman spectra from several chips mounted straight on a phosphor-less blue LED package was observed at the same time and the junction temperature of each chip was estimated successfully by means of each Raman shift during operation despite the existence of strong LED emission. In addition, the GaN-E₂^H Raman signal from the phosphor-resin coated blue-LED was observed for the first time by using 633 nm laser to reduce the negative influence from the phosphor and light diffusing substances in the resin. It is concluded that this technique would be a useful method for a remote and standard system for 2D mapping of the junction temperatures of blue-LED packages.

• Evaluation of arc quenching characteristics of various gases using power semiconductors

  Tomoyuki Nakano, Yasunori Tanaka, K. Murai, Y. Uesugi, T. Ishijima, K. Tomita, K. Suzuki, T. Shinkai

  JOURNAL OF PHYSICS D-APPLIED PHYSICS 50 (48) 485602  0022-3727 2017/12 [Refereed][Not invited]
   

  This paper presents the arc quenching abilities of various gases studied using a power semiconductor switching technique. The technique uses an insulated gate bi-polar transistor (IGBT) to inject current and apply voltage to the plasma arc. Using this technique, arcs in free recovery condition after a 50 A steady state condition were investigated in SF6, CO2, O-2, N-2, air and Ar gas flows. Furthermore, at a specific time high voltages of about 1.1 kV and 1.7 kV mu s(-1) were applied to the residual decaying arcs by the IGBT to elucidate the arc re-ignition process and recovery properties. These systematic experiments further enabled us to estimate the interruption probability versus the voltage application time. From these results, the voltage application time for 50% successful interruption was estimated for various gases, with the results showing a direct relation to the interruption capabilities of the respective gases. These results were then compared to the electron density measurement results and numerical simulation results to confirm their validity. All data obtained from the experiments and simulation is expected to be useful for elucidating the arc quenching physics and also for the practical application of arc quenching phenomena.
• Design of compact dispersion interferometer with a high efficiency nonlinear crystal and a low power CO2 laser

  T. Akiyama, S. Yoshimura, K. Tomita, N. Shirai, T. Murakami, K. Urabe

  JOURNAL OF INSTRUMENTATION 12 C12028  1748-0221 2017/12 [Refereed][Not invited]
   

  When the electron density of a plasma generated in high pressure environment is measured by a conventional interferometer, the phase shifts due to changes of the neutral gas density cause significant measurement errors. A dispersion interferometer, which measures the phase shift that arises from dispersion of medium between the fundamental and the second harmonic wavelengths of laser light, can suppress the measured phase shift due to the variations of neutral gas density. In recent years, the CO2 laser dispersion interferometer has been applied to the atmospheric pressure plasmas and its feasibility has been demonstrated. By combining a low power laser and a high efficiency nonlinear crystal for the second harmonic component generation, a compact dispersion interferometer can be designed. The optical design and preliminary experiments are conducted.
• Time-resolved two-dimensional profiles of electron density and temperature of laser-produced tin plasmas for extreme-ultraviolet lithography light sources

  Kentaro Tomita, Yuta Sato, Syouichi Tsukiyama, Toshiaki Eguchi, Kiichiro Uchino, Kouichiro Kouge, Hiroaki Tomuro, Tatsuya Yanagida, Yasunori Wada, Masahito Kunishima, Georg Soumagne, Takeshi Kodama, Hakaru Mizoguchi, Atsushi Sunahara, Katsunobu Nishihara

  SCIENTIFIC REPORTS 7 12328  2045-2322 2017/10 [Refereed][Not invited]
   

  Time-resolved two-dimensional (2D) profiles of electron density (n(e)) and electron temperature (T-e) of extreme ultraviolet (EUV) lithography light source plasmas were obtained from the ion components of collective Thomson scattering (CTS) spectra. The highest EUV conversion efficiency (CE) of 4% from double pulse lasers irradiating a Sn droplet was obtained by changing their delay time. The 2D-CTS results clarified that for the highest CE condition, a hollow-like density profile was formed, i.e., the high density region existed not on the central axis but in a part with a certain radius. The 2D profile of the in-band EUV emissivity (eta(EUV)) was theoretically calculated using the CTS results and atomic model (Hullac code), which reproduced a directly measured EUV image reasonably well. The CTS results strongly indicated the necessity of optimizing 2D plasma profiles to improve the CE in the future.
• Magnetic reconnection experiment with an external magnetic field by using Gekko-XII laser

  Taichi MORITA, Satoshi MIURA, Masafumi EDAMOTO, Kentaro TOMITA, Yutaro ITADANI, Naoji YAMAMOTO, Shinsuke FUJIOKA, Youichi SAKAWA

  2017/09 [Not refereed][Not invited]
  
• Generation of counter-streaming plasmas for collisionless shock experiment

  Y. Sakawa, T. Ide, T. Morita, K. Tomita, K. Uchino, Y. Kuramitsu, N. Ohnishi, H. Takabe

  HIGH ENERGY DENSITY PHYSICS 23 207 - 211 1574-1818 2017/06 [Refereed][Not invited]
   

  The generation mechanism of counter-streaming plasmas, by irradiating an inner-surface of the 1st-plane of double-plane target, is investigated experimentally using optical imaging and collective Thomson scattering (CTS) ion-term measurement. The CTS measurement reveals that counter-streaming plasmas exist at the same time at the same position, which is the evidence for the collisionless interaction between the counter streaming plasmas. The generation of the 2nd-plane plasma is in two steps: First, the 2nd-plane is ablated nearly at the laser timing by radiation from the 1st-plane plasma. Then similar or equal to 5-7 ns later, when the plasma from the 1st-plane reaches the 2ns-plane, it induces higher-density plasma generation. (C) 2017 Elsevier B.V. All rights reserved.
• Measurements of electron density and electron temperature using laser Thomson scattering in PANTA

  K. Tomita, Y. Sato, N. Bolouki, T. Shiraishi, K. Uchino, Y. Miwa, T. Kobayashi, S. Inagaki

  Plasma and Fusion Research: Regular Articles 12 1401018  2017/03 [Refereed][Not invited]
  
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• Spatial and temporal plasma evolutions of magnetic reconnection in laser produced plasmas

  N. Khasanah, C.W. Peng, C.H. Chen, T.Y. Huang, N. Bolouki, T. Moritaka, Y. Hara, H. Shimogawara, T. Sano, Y. Sakawa, Y. Sato, K. Tomita, K. Uchino, S. Matsukiyo, Y. Shoji, S. Tomita, S. Tomiya, R. Yamazaki, M. Koenig, Y. Kuramitsu

  High Energy Density Physics 23 15 - 19 2017/02 [Refereed][Not invited]
  
• Development of junction temperature measurement system for blue LED in operation using pulsed-laser Raman scattering

  M. Horiuchi, S. Tsutsumi, Y. Yamagata, K. Tomita, Y. Manabe

  Engineering Sciences Reports, Kyushu University 九州大学大学院総合理工学府 38 (2) 1 - 7 1346-7883 2017/02 [Refereed][Not invited]
   

  A novel method by using a pulsed-laser Raman scattering technique was employed to estimate junction temperatures of a phosphor-less blue-LED module. Observation of GaN-E_2^H Raman spectra was done successfully and temperature dependent Raman spectra of GaN were detected. This technique was applied to simultaneous estimation of the junction temperatures of the several chips in the phosphor-less blue LED module in operation. It is concluded that this technique would be a useful method for remoteness and simultaneous multipoint measurement of the junction temperature of a LED module in which several chips are integrated.
• Spatial profiles of electron density, electron temperature, average ionic charge, and EUV emission of laser-produced Sn plasmas for EUV lithography

  Y. Sato, K. Tomita, S. Tsukiyama, T. Eguchi, K. Uchino, K. Kouge, H. Tomuro, T. Yanagida, Y. Wada, M. Kunishima, T. Kodama, H. Mizoguchi

  Jpn. J. Appl. Phys. Institute of Physics 56 (3) 36201 - 36201 0021-4922 2017/01 [Refereed][Not invited]
   

  Spatial profiles of the electron density (ne), electron temperature (Te), and average ionic charge (Z) of laser-produced Sn plasmas for EUV lithography, whose conversion efficiency (CE) is sufficiently high for practical use, were measured using a collective Thomson scattering (TS) technique. For plasma production, Sn droplets of 26 µm diameter were used as a fuel. First, a picosecond-pulsed laser was used to expand a Sn target. Next, a CO2laser was used to generate plasmas. By changing the injection timing of the picosecond and CO2lasers, three different types of plasmas were generated. The CEs of the three types of plasmas differed, and ranged from 2.8 to 4.0%. Regarding the different plasma conditions, the spatial profiles of ne, Te, and Z clearly differed. However, under all plasma conditions, intense EUV was only observed at a sufficiently high Te(> 25 eV) and in an adequate nerange [10²⁴–(2 × 10²⁵) m⁻³]. These plasma parameters lie in the efficient-EUV light source range, as predicted by simulations.
• Rayleigh Scattering Measurement of Neutral Atom Number Density Downstream of a Hall Thruster under Cold Flow Conditions

  Masataka Iwamoto, Naoji Yamamoto, Taichi Morita, Hideki Nakashima, Kentaro Tomita, Kiichiro Uchino

  TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 60 (5) 327 - 330 0549-3811 2017 [Refereed][Not invited]
  
• Influence of the gas flow rate on the nonchemical equilibrium N2 arc behavior in a model nozzle circuit breaker

  Yi Wu, Hao Sun, Yasunori Tanaka, Kentaro Tomita, Mingzhe Rong, Fei Yang, Yoshihiko Uesugi, Tatsuo Ishijima, Xiaohua Wang, Ying Feng

  Journal of Physics D: Applied Physics 49 (42) 425202  1361-6463 2016/09/22 [Refereed][Not invited]
   

  The influence of the gas flow rate on the N2 arc behavior was investigated based on a previously established nonchemical equilibrium (non-CE) model. This numerical non-CE model was adopted in the N2 nozzle arc in a model circuit breaker. The arc behaviors of both the arc burning and arc decay phases were obtained at different gas flow rates in both the non-CE and local thermal equilibrium (LTE) model. To better understand the influence of the gas flow rate, in this work we devised the concept of the nonequilibrium parameter. Additionally, the influences of convection, diffusion, and chemical reactions were examined separately to determine which one contributed most to the non-CE behavior. Finally, laser Thomson scattering (LTS) measurements at different gas flow rates were adopted to further demonstrate the validity of the non-CE model. The results of the macroscopic behaviors indicate that the deviations between the non-CE and LTE models during the arc burning phase are much fewer than those during the arc decay phase. By the nonequilibrium parameters, it clearly indicates that with an increase in the gas flow rate, the non-CE effect will be greatly enhanced. During the arc burning phase, this non-CE effect is mainly caused by radial diffusion of the particles. During the arc decay phase, for the charged particles, the chemical reactions had the greatest effect on the time variations of the particle number densities however, for the neutral particles the time variations of the number densities were mutually influenced by convections, diffusions, and chemical reactions. Finally, the LTS results further demonstrate the validity of the non-CE model at different gas flow rates.
• Diagnostics of atmospheric-pressure pulsed-dc discharge with metal and liquid anodes by multiple laser-aided methods

  Keiichiro Urabe, Naoki Shirai, Kentaro Tomita, Tsuyoshi Akiyama, Tomoyuki Murakami

  Plasma Sources Science and Technology 25 (4) 45004  1361-6595 2016/05/26 [Refereed][Not invited]
   

  The density and temperature of electrons and key heavy particles were measured in an atmospheric-pressure pulsed-dc helium discharge plasma with a nitrogen molecular impurity generated using system with a liquid or metal anode and a metal cathode. To obtain these parameters, we conducted experiments using several laser-aided methods: Thomson scattering spectroscopy to obtain the spatial profiles of electron density and temperature, Raman scattering spectroscopy to obtain the neutral molecular nitrogen rotational temperature, phase-modulated dispersion interferometry to determine the temporal variation of the electron density, and time-resolved laser absorption spectroscopy to analyze the temporal variation of the helium metastable atom density. The electron density and temperature measured by Thomson scattering varied from 2.4 1014 cm-3 and 1.8 eV at the center of the discharge to 0.8 1014 cm-3 and 1.5 eV near the outer edge of the plasma in the case of the metal anode, respectively. The electron density obtained with the liquid anode was approximately 20% smaller than that obtained with the metal anode, while the electron temperature was not significantly affected by the anode material. The molecular nitrogen rotational temperatures were 1200 K with the metal anode and 1650 K with the liquid anode at the outer edge of the plasma column. The density of helium metastable atoms decreased by a factor of two when using the liquid anode.
• Electrostatic collisionless shock in laser-produced counter-streaming plasmas

  Y. Sakawa, Y. Hara, H. Shimogawara, R. Kumar, Y. Sano, S. Fujioka, K. Tomita, K. Uchino, T. Morita, S. Matsukiyo, R. Yamazak, T. Moritaka, Y. Kuramitsu, R. Crowston, N. Woolsey, B. Albertazzi, M. Koeing, L. Van, Box Som, E. Falize, C. Michaut, P. Barroso, Y. T. Li, X. Pei, H. Wei, J. Y. Zhong, H. Sakagami, H. Takabe

  2016/05 [Not refereed][Not invited]
  
• Radiation Magneto-Hydrodynamics Simulations for Laser- Produced Collisionless Shock Experiment

  A. Ishii, N. Ohnishi, R. Yamazaki, Y. Shoji, S. Tomiya, Y. Sakawa, Y. Hara, H. Shimogawara, S. Matsukiyo, T. Morita, K. Tomita, S. Tanaka, Y. Teraki

  2016/05 [Not refereed][Not invited]
  
• Electron density change of atmospheric-pressure plasmas in helium flow depending on the oxygen/nitrogen ratio of the surrounding atmosphere

  K. Tomita, K. Urabe, N. Shirai, Y. Sato, S. Hassaballa, N. Bolouki, M. Yoneda, T. Shimizu, K. Uchino

  Jpn. J. Appl. Phys. Institute of Physics 55 (6) 66101 - 66101 0021-4922 2016/05 [Refereed][Not invited]
   

  Laser Thomson scattering was applied to an atmospheric-pressure plasma produced in a helium (He) gas flow for measuring the spatial profiles of electron density (ne) and electron temperature (Te). Aside from the He core flow, the shielding gas flow of N2or synthesized air ([Formula: see text]) surrounding the He flow was introduced to evaluate the effect of ambient gas components on the plasma parameters, eliminating the effect of ambient humidity. The neat the discharge center was 2.7 × 10²¹m⁻³for plasma generated with N2/O2shielding gas, 50% higher than that generated with N2shielding.
• Synthesis of photochromic nanoparticles and determination of the mechanism of photochromism

  Shuhei Inoue, Takahiro Kawamoto, Yukihiko Matsumura, Kentaro Tomita, Kiichiro Uchino, Keiji Takata, Hiroshi Kajiyama

  AIP ADVANCES 6 (5) 55214  2158-3226 2016/05 [Refereed][Not invited]
   

  Photochromic nanoparticles of zinc-silicon oxide were synthesized using plasma enhanced chemical vapor deposition. These particles turned black upon irradiating with ultraviolet light. We investigated this phenomenon using density functional theory calculations. Silicon inclusions create trap levels and oxygen defects that reduce the ionization potential of ZnO. This forms a quantum potential between ZnO and zinc-silicon oxide, and the excited electron is stable. Because oxygen defects also increase the bond overlap population between the zinc atoms in a ZnO crystal, they introduce further defects and help in the formation of quantum potentials. Growth of a perfect crystal of ZnO prevents the formation of oxygen defects, which is not desirable for photochromism. (C) 2016 Author(s).
• Measurement of electron density and electron temperature in decaying arcs containing decomposed gas from polymer

  H. Safwat, K. Tomita

  Engineering Sciences Reports, Kyushu University Interdisciplinary Graduate School of Engineering Sciences, Kyushu University 37 (2) 6 - 11 1346-7883 2016/02 [Refereed][Not invited]
   

  Electron density (ne) and electron temperature (Te) in arc discharges generated in the atmospheric air were measured using the laser Thomson scattering (LTS) technique. The arcs were generated using tungsten electrodes with a gap length of 2 mm. At the tip of the cathode electrode, a polymer material-polyoxymethylene (POM) or polytetrafluoroethylene (PTFE)-was inserted to generate the arcs containing the decomposed gas from polymer. LTS results showed that n_e in the arcs varied with the polymer material used. In particular, with POM, the decay speed of n_e was much higher than that with PTFE. The LTS results are qualitatively consistent with the results of previous numerical studies, which indicate that a POM ablation gas can decay the arc conductance more effectively than a PTFE ablation gas.
• Characteristics of extreme ultraviolet emission from high-Z plasmas

  H. Ohashi, T. Higashiguchi, Y. Suzuki, M. Kawasaki, C. Suzuki, K. Tomita, M. Nishikino, S. Fujioka, A. Endo, B. Li, T. Otsuka, P. Dunne, G. O'Sullivan

  8TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2013) 688 12079  1742-6588 2016 [Refereed][Not invited]
   

  We demonstrate the extreme ultraviolet (EUV) and soft x-ray sources in the 2 to 7 nm spectral region related to the beyond EUV (BEUV) question at 6.x nm and the water window source based on laser -produced high-Z plasmas. Resonance emission from multiply charged ions merges to produce intense unresolved transition arrays (UTAs), extending below the carbon K edge (4.37 nm). An outline of a microscope design for single -shot live cell imaging is proposed based on high-Z plasma UTA source, coupled to multilayer mirror optics.
• Collective scattering of an incident monochromatic circularly polarized wave in an unmagnetized non-equilibrium plasma

  S. Matsukiyo, Y. Kuramitsu, K. Tomita

  8TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2013) 688 12062  1742-6588 2016 [Refereed][Not invited]
   

  Collective scattering of an incident monochromatic circularly polarized electromagnetic wave in an unmagnetized non-equilibrium plasma is investigated. The wave equation of the scattered waves are numerically solved by giving wave spectra of the incident electromagnetic wave and a variety of longitudinal fluctuations of a plasma. In addition to the well known symmetric ion and electron features of frequency spectrum in an equilibrium plasma, some asymmetries are found in a frequency spectrum when anisotropic longitudinal wave propagation or the effect of the presence of a beam mode are taken into account.
• Thomson scattering measurement of a collimated plasma jet generated by a high-power laser system

  T. Ishikawa, Y. Sakawa, T. Morita, Y. Yamaura, Y. Kuramitsu, T. Moritaka, T. Sano, R. Shimoda, K. Tomita, K. Uchino, S. Matsukiyo, A. Mizuta, N. Ohnishi, R. Crowston, N. Woolsey, H. Doyle, G. Gregori, M. Koenig, C. Michaut, A. Pelka, D. Yuan, Y. Li, K. Zhang, J. Zhong, F. Wang, H. Takabe

  8TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2013) 688 12098  1742-6588 2016 [Refereed][Not invited]
   

  One of the important and interesting problems in astrophysics and plasma physics is collimation of plasma jets. The collimation mechanism, which causes a plasma flow to propagate a long distance, has not been understood in detail. We have been investigating a model experiment to simulate astrophysical plasma jets with an external magnetic field [Nishio et al., EPJ. Web of Conferences 59, 15005 (2013)]. The experiment was performed by using Gekko XII HIPER laser system at Institute of Laser Engineering, Osaka University. We shot CH plane targets (3 mm x 3 mm x 10 mu m) and observed rear-side plasma flows. A collimated plasma flow or plasma jet was generated by separating focal spots of laser beams. In this report, we measured plasma jet structure without an external magnetic field with shadowgraphy, and simultaneously measured the local parameters of the plasma jet, i.e., electron density, electron and ion temperatures, charge state, and drift velocity, with collective Thomson scattering.
• Spherical shock in the presence of an external magnetic field

  Y. Kuramitsu, S. Matsukiyo, S. Isayama, D. Harada, T. Oyama, R. Fujino, Y. Sakawa, T. Morita, Y. Yamaura, T. Ishikawa, T. Moritaka, T. Sano, K. Tomita, R. Shimoda, Y. Sato, K. Uchino, A. Pelka, R. Crowston, N. Woolsey, G. Gregori, M. Koenig, D. W. Yuan, C. L. Yin, Y. T. Li, K. Zhang, J. Y. Zhong, F. L. Wang, N. Ohnishi, K. Nagamine, H. Yoneda, H. Takabe

  8TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2013) 688 12056  1742-6588 2016 [Refereed][Not invited]
   

  We investigate spherical collisionless shocks in the presence of an external magnetic field. Spherical collisionless shocks are common resultant of interactions between a expanding plasma and a surrounding plasma, such as the solar wind, stellar winds, and supernova remnants. Anisotropies often observed in shock propagations and their emissions, and it is widely believed a magnetic field plays a major role. Since the local observations of magnetic fields in astrophysical plasmas are not accessible, laboratory experiments provide unique capability to investigate such phenomena. We model the spherical shocks in the universe by irradiating a solid spherical target surrounded by a plasma in the presence of a magnetic field. We present preliminary results obtained by shadowgraphy.
• Beyond Extreme Ultra Violet (BEUV) Radiation from Spherically symmetrical High-Z plasmas

  Kensuke Yoshida, Shinsuke Fujioka, Takeshi Higashiguchi, Teruyuki Ugomori, Nozomi Tanaka, Masato Kawasaki, Yuhei Suzuki, Chihiro Suzuki, Kentaro Tomita, Ryouichi Hirose, Takeo Eshima, Hayato Ohashi, Masaharu Nishikino, Enda Scally, Hiroaki Nshimura, Hiroshi Azechi, Gerard O'Sullivan

  8TH INTERNATIONAL CONFERENCE ON INERTIAL FUSION SCIENCES AND APPLICATIONS (IFSA 2013) 688 12046  1742-6588 2016 [Refereed][Not invited]
   

  Photo-lithography is a key technology for volume manufacture of high performance and compact semiconductor devices. Smaller and more complex structures can be fabricated by using shorter wavelength light in the photolithography. One of the most critical issues in development of the next generation photo-lithography is to increase energy conversion efficiency (CE) from laser to shorter wavelength light. Experimental database of beyond extreme ultraviolet (BEUV) radiation was obtained by using spherically symmetrical high-Z plasmas generated with spherically allocated laser beams. Absolute energy and spectra of BEUV light emitted from Tb, Gd, and Mo plasmas were measured with a absolutely calibrated BEUV calorimeter and a transmission grating spectrometer. 1.0 x 10(12) W/cm(2) is the optimal laser intensity to produced efficient BEUV light source plasmas with Tb and Gd targets. Maximum CE is achieved at 0.8% that is two times higher than the published CEs obtained with planar targets.
• Toward the generation of magnetized collisionless shocks with high-power lasers

  Yoshitaka Shoji, Ryo Yamazaki, Sara Tomita, Yushiro Kawamura, Yutaka Ohira, Satoshi Tomiya, Yoichi Sakawa, Takayoshi Sano, Yukiko Hara, Sarana Kondo, Hiroshi Shimogawara, Shuichi Matsukiyo, Taichi Morita, Kentaro Tomita, Hitoki Yoneda, Kazunori Nagamine, Yasuhiro Kuramitsu, Toseo Moritaka, Naofumi Ohnishi, Takayuki Umeda, Hideaki Takabe

  Plasma and Fusion Research 11 (2) 3401031  1880-6821 2016 [Refereed][Not invited]
   

  We have started a project of experimental generation of low Mach number collisionless shocks propagating into magnetized plasma, using high power lasers such as Gekko XII at Institute of laser engineering, Osaka University. We briefly present a result of our first experiments done in September 2014, in which Aluminum plane target was irradiated by main laser in ambient Helium gas with external magnetic field. Ejected Aluminum plasma had a bulk velocity of 430 km s-1, which is sufficient enough to excite the magnetized collisionless shock in our experimental setup. However, the ejected Aluminum plasma was decelerated before the shock was excited.
• The LTE thermofluid simulation of AR/SF6 gas-blast arcs in a nozzle space in an arc device

  Kosuke Murai, Tomoyuki Nakano, Yasunori Tanaka, Yoshihiko Uesugi, Tatsuo Ishijima, Kentaro Tomita, Katsumi Suzuki, Takanori Iijima, Takeshi Shinkai

  IEEJ Transactions on Power and Energy 136 (9) 741 - 748 1348-8147 2016 [Refereed][Not invited]
   

  The present paper describes numerical thermofluid simulation results of SF6, Ar, and Ar/SF6 arcs in a nozzle space at atmospheric pressure on the assumption of local thermodynamic equilibrium (LTE) condition. It is crucial to investigate fundamentals on arc extinction phenomena by numerical simulation approach as well as experimental approach. Two-dimensional temperature distributions in SF6, Ar, Ar/SF6 gas-blast arcs were calculated in a steady state at a direct current of 50 A. Furthermore, transient temperature distributions in these arcs were computed under free recovery condition for a fundamental study. We investigated dependences of the gas mixture ratio of SF6 to Ar and the gas flow velocity on the arc temperature and the arc voltage. The calculated arc voltage in the steady state and the transition of electron density under free recovery condition were compared with those obtained by laser Thomson scattering method in our experiments. As a result, the increasing admixture ratio of SF6 to Ar and the increasing gas flow velocity shrinks the arc plasma around nozzle throat inlet, leading to the higher arc resistance. Under free recovery condition, the arc plasma decay more rapidly there. Comparison in electron density shows the similar dependence on SF6 and Ar, while there is still some difference in the absolute value of electron density between the calculation results and experimental results.
• Computational non-chemically equilibrium model on the current zero simulation in a model N2 circuit breaker under the free recovery condition

  Hao Sun, Yasunori Tanaka, Kentaro Tomita, Yi Wu, Mingzhe Rong, Yoshihiko Uesugi, Tatsuo Ishijima

  Journal of Physics D: Applied Physics 49 (5) 55204  1361-6463 2015/12/23 [Refereed][Not invited]
   

  A non-chemically equilibrium (non-CE) model was established to investigate the N2 arc plasma in the decaying phase during the arc interruption, and was validated by comparison with the experimental results based on laser Thomson scattering. Unlike the conventional model assuming the local thermodynamic equilibrium (LTE), in this non-CE model, the magneto-hydro-dynamics (MHD) method was coupled with the reaction kinetics to obtain the time-dependent species compositions and properties. The current calculation took into account five species in hot gas and 22 chemical reactions in total. The time-dependent species compositions of hot N2 were derived from the mass conservation equation for each species, considering the effect of the convection, diffusion and the chemical reaction. The influence of the non-CE compositions on the arc decaying behavior was realized by updating the thermodynamic and transport properties at each iterative step. The results indicate that the non-CE model can result in the departure of the arc decaying behavior from the LTE model, because it alters the time evolution of the species composition and consequently changes the thermodynamic and transport properties. At the edge of the arc, the time evolutions of the species are dominant by both the diffusion and the chemical reactions while at the center of the arc they are mainly influenced by the chemical reactions. Generally, the non-CE effect can lead to the delay of all the particles' variations, particularly the electron decay, so that the arc interruption performance will be reduced compared with that in the LTE model.
• Fundamental investigation technique on gas-blast arc behaviors in decaying and re-ignition processes using power semiconductors

  Yasunori Tanaka, Takahiro Shimizu, Takayasu Fujino, Tomoyuki Nakano, Kentaro Tomita, Katsumi Suzuki

  IEEJ Transactions on Power and Energy 135 (11) 661 - 668 1348-8147 2015/11/01 [Refereed][Not invited]
   

  This paper has proposed a new fundamental investigation technique on arc behaviors in decaying and re-ignition processes under gas flow condition. This technique utilizes power semiconductors like insulated-gate bipolar transistors (IGBTs) to control the arc current and voltage with a high accuracy in time domain. The free recovery condition was created by switching-on an IGBT connected in parallel with the arc device to investigate decaying process of the arc plasma under gas flow condition. Then, the quasi-transient recovery voltage (quasi-TRV) was intentionally applied between the electrodes in the arc device under the free recovery condition by turning-off the IGBT again, to study the re-ignition process of the arc plasma. At the same time, the arc behavior in a nozzle was observed by a high speed video camera at a frame rate of 200,000 fps. In the present work, arc behaviors in gas flow such as SF6 and CO2 in a nozzle was fundamentally investigated under free recovery condition and then after quasi-TRV application. In addition, the timing of the quasi-TRV application was changed to examine the recovery property of residual arcs in SF6 and CO2 gas flow. Through these experiments, the probability of arc successful interruptions were statistically measured for these gas flow arcs. These results provide fundamental data for comparison of the arc interruption capability of different conditions.
• Development of a collective Thomson scattering system for laser-produced tin plasmas for extreme-ultraviolet light sources

  K. Tomita, Y. Sato, K. Nishikawa, K. Uchino, T. Yanagida, H. Tomuro, Y. Wada, M. Kunishima, T. Kodama, H. Mizoguchi, A. Sunahara

  Appl. Phys. Express Institute of Physics 8 (12) 126101 - 126101 1882-0778 2015/11 [Refereed][Not invited]
   

  Spatial profiles of electron density (ne) and electron temperature (Te) of laser-produced Sn plasmas for extreme-ultraviolet (EUV) light sources have been obtained using a new collective Thomson scattering system, which has been optimized for the measurement of the ion feature spectrum. The system has an 18 pm spectral resolution, a 5 ns temporal resolution, a 50 µm spatial resolution, and sufficient stray-light rejection near the probing laser wavelength. With this system, measurements of the laser-produced Sn plasmas in the parameter ranges of 3 × 10²³< ne< 10²⁵m⁻³and 10 < Te< 20 eV have been performed.
• STUDIES OF LASER-PRODUCED ELECTROSTATIC COLLISIONLESS SHOCK USING COLLECTIVE THOMSON SCATTERING ION-TERM MEASUREMENT

  Y. Hara, Y. Sakawa, K. Tomita, Y. Sato, K. Nishikawa, T. Morita, T. Sano, T. Moritaka, H. Takabe

  2015/09 [Not refereed][Not invited]
  
• Thomson scattering diagnostics of SF6 gas-blasted arcs confined by a nozzle under free-recovery conditions

  Kentaro Tomita, Daisuke Gojima, Takahiro Shimizu, Kiichiro Uchino, Tomoyuki Nakano, Yasunori Tanaka, Katsumi Suzuki, Takanori Iijima, Takeshi Shinkai

  Journal of Physics D: Applied Physics 48 (26) 265201  1361-6463 2015/07/08 [Refereed][Not invited]
   

  Collective Thomson scattering has been applied to gas-blasted arcs confined by a nozzle to measure their decay processes with respect to electron density (ne). Pure SF6 gas, an Ar/SF6 gas mixture (SF6 was 20, 40, 60, and 80% of the mixture), and pure Ar gas were used as arc-quenching media at atmospheric pressure. Copper-tungsten (40% copper) electrodes were installed inside a polytetrafluoroethylene (PTFE) nozzle and 50 mm-long gap arcs were generated between the electrodes. First, steady-state arcs were generated with 50 A current. Then, a semiconductor switch removed the arc current. It was found that after the current decreased to zero, ne exponentially decreased and the decay time constant of ne systematically decreased with an increasing SF6 gas ratio. Thomson scattering measured ne in the range 1021-1023 m-3. Self-emission measurements, which were performed with a high-speed camera at 200 000 frames per second, exhibited good agreement with the results of the Thomson scattering.
• Development of junction temperature estimation system for light-emitting LED using pulsed-laser Raman scattering

  M. Horiuchi, Y. Yamagata, S. Tsutsumi, K. Tomita, Y. Manabe

  J. Solid State Lighting 2 1 - 7 2015/07 [Refereed][Not invited]
  
• Collective Thomson scattering of electrostatic collisionlessshock

  Y. Hara, Y. Sakawa, K. Tomita, Y. Sato, K. Nishikawa, T. Morita, T. Sano, T. Moritaka, H. Takabe

  2015/04 [Not refereed][Not invited]
  
• High Power Laser Experiment of Planar Collisionless Shocks

  M. Nakanotani, S. Matsukiyo, T. Hada, Y. Sakawa, Y. Kuramitsu, T. Morita, K. Tomita, R. Fujino, S. Kubo, T. Sano, T. Moritaka, Y. Hara, R. Yamazaki, H. Takabe

  2015/04 [Not refereed][Not invited]
  
• Density and x-ray emission profile relationships in highly ionized high-Z laser-produced plasmas

  Kensuke Yoshida, Shinsuke Fujioka, Takeshi Higashiguchi, Teruyuki Ugomori, Nozomi Tanaka, Masato Kawasaki, Yuhei Suzuki, Chihiro Suzuki, Kentaro Tomita, Ryoichi Hirose, Takeo Ejima, Hayato Ohashi, Masaharu Nishikino, Atsushi Sunahara, Bowen Li, Padraig Dunne, Gerry O'Sullivan, Tatsuya Yanagida, Hiroshi Azechi, Hiroaki Nishimura

  APPLIED PHYSICS LETTERS 106 (12) 121109  0003-6951 2015/03 [Refereed][Not invited]
   

  We present a benchmark measurement of the electron density profile in the region where the electron density is 10(19) cm(-3) and where the bulk of extreme ultraviolet (EUV) emission occurs from isotropically expanding spherical high-Z gadolinium plasmas. It was found that, due to opacity effects, the observed EUV emission is mostly produced from an underdense region. We have analyzed time-resolved emission spectra with the aid of atomic structure calculations and find the multiple ion charge states around 18+ during the laser pulse irradiation. (C) 2015 AIP Publishing LLC.
• Development of Thomson Scattering Diagnostics for Cathode-Directed Streamer Discharges in Helium

  N. Bolouki, S. Hassaballa, K. Tomita, K. Uchino

  Engineering sciences reports, Kyushu University Interdisciplinary Graduate School of Engineering Sciences, Kyushu University 36 (2) 1 - 5 1346-7883 2015/02 [Refereed][Not invited]
   

  Laser Thomson scattering diagnostics has been developed for the study of the streamer moving toward the cathode in helium near atmospheric pressure. In order to avoid laser perturbation and obtain sufficient intensity of the Thomson scattering signal, two cylindrical lenses were used to optimize the spot size of a probing laser at a focusing point. At a position of 2 mm from the anode (needle electrode), the electron density and electron temperature were successfully measured to be ~ 10^18 m^-3 and ~ 2 eV, respectively, in the initial stage of the primary streamer.
• Evaluation on Current Interruption Ability of CO2 and SF6 using Current and Voltage Application Highly Controlled by Power Semiconductors

  Tomoyuki Nakano, Kosuke Murai, Yasunori Tanaka, Yoshihiko Uesugi, Tatsuo Ishijima, Tatsuro Shiraishi, Takahiro Shimizu, Kentaro Tomita, Katsumi Suzuki, Takeshi Shinkai

  2015 3RD INTERNATIONAL CONFERENCE ON ELECTRIC POWER EQUIPMENT - SWITCHING TECHNOLOGY (ICEPE-ST) 307 - 312 2015 [Refereed][Not invited]
   

  This paper reports a new simple test technique to evaluate current interruption ability of arc quenching gases. In the test, current and voltage applied to the arc was controlled using a insulated gate bipolar transistor (IGBT). Switching the IGBT enables us to produce free recovery conditions for a fundamental arc decay in nozzles. In addition to this, a voltage was intentionally applied to the free recovery arcs between the electrodes by switching-off IGBT again at the specified delay time t(d). This applied voltage is called quasi transient recovery voltage (quasi-TRV). We can evaluate successful interruption or interruption failure by measuring the current between the electrodes after quasi-TRV application. We compared the interruption ability of SF6 and CO2 through this developed technique. The experimental results show that a residual arc in SF6 gas flow decays four times more rapidly than that in CO2 gas flow. Influence of observation holes in the nozzles used in the experiments was also investigated, showing less influence of observation on the arc behavior.
• The LTF, Simulation on Decaying Arc Plasmas in Various Arc Quenching Gases in a Model Circuit Breaker

  Kosuke Murai, Tomoyuki Nakano, Yasunori Tanaka, Yoshihiko Uesugi, Tatsuo Ishijima, Tatsuro Shiraishi, Takahiro Shimizu, Kentaro Tomita, Katsumi Suzuki, Takayasu Fujino

  2015 3RD INTERNATIONAL CONFERENCE ON ELECTRIC POWER EQUIPMENT - SWITCHING TECHNOLOGY (ICEPE-ST) 146 - 151 2015 [Refereed][Not invited]
   

  The present report describes numerical thermofluid simulation results of various gas arcs in a nozzle space at atmospheric pressure on the assumption of local thermodynamic equilibrium condition. It is crucial to investigate fundamentals on arc extinction phenomena by numerical simulation approach as well as experimental approach. The SF6, Ar, CO2 and N-2 arcs in our experimental setup were treated for the present calculation because we can accurately control the voltage and arc current in our experimtants and we can perform accurate electron density measurements for fundamental investigation and comparison. Two-dimensional temperature distributions in various gas-blast arcs were calculated in a steady state at a direct current of 50 A. Furthermore, transient temperature distributions in these arcs were computed under free recovery condition. Then, we calculated transient responses under free recovery condition by using calculated results in the steady state. The calculated arc voltage in the steady state and the transition of electron density under free recovery condition were compared with those obtained by laser Thomson scattering method in our experiments.
• Temporal evolution of electron density and electron temperature profiles in a non-thermal atmospheric-pressure plasma measured by laser Thomson scattering

  Nima Bolouki, Kentaro Tomita, Safwat Hassaballa, Yukihiko Yamagata, Kiichiro Uchino

  JAPANESE JOURNAL OF APPLIED PHYSICS 54 (1) 16101  0021-4922 2015/01 [Refereed][Not invited]
   

  The laser Thomson scattering technique has been applied for measuring the spatiotemporal changes in the electron density (n(e)) and electron temperature (T-e) of a capacity-coupled micro-discharge generated in neon gas at near-atmospheric pressure. A significant difference has been observed in temporal behavior between n(e) and T-e after the discharge generation. The value of n(e) decreases monotonically from t = 25 ns when the electrical input is truncated. On the other hand, T-e is approximately 1.7 eV at 15 ns and, after this point, T-e rapidly decreases to about 0.8 eV. Subsequently, T-e decreases gradually. These features are discussed on the basis of the recombination processes. (C) 2015 The Japan Society of Applied Physics
• Experimental Investigation on Decaying Arc Behaviors in Alternative Gas Flow using Semiconductors

  Y.,Tanaka, T.,Nakano, K.,Tomita, Fujino,Takayasu, K.,Suzuki

  IEEJ 9th International Workshop on High Voltage Engineering (ED-14-084, SP-14-040, HV-14-09) 2014/11 [Not refereed][Not invited]
  
• Measurements of Electron Density and Electron Temperature of Arc Discharge Plasmas Containing Metallic Vapors Using Laser Thomson Scattering

  Kentaro Tomita, Shinya Yoshitake, Kiichiro Uchino, Daigo Takenaka, Hiroaki Toda, Masayuki Hikita, Katsumi Suzuki

  ELECTRICAL ENGINEERING IN JAPAN 188 (4) 1 - 8 0424-7760 2014/09 [Refereed][Not invited]
   

  Laser Thomson scattering (LTS) was applied to arc discharges generated in the atmosphere to measure electron density (ne) and electron temperature (Te). The electrode gap was 0.8 mm, and the electrode diameter was 1 mm. The applied voltage was 6 kV, the peak current was 600 A, and the decay time of the voltage and current was 25 s. The spatiotemporal evolution of ne and Te was measured 10, 30, and 50 s after discharge initiation. At these times, the obtained values of ne and Te were estimated to be in the ranges of (0.8 to 2.0) x 1023 m-3 and 1.0 to 2.2eV, respectively. These values were consistent with those evaluated using Saha's thermodynamic equation at 1 atm. It was also found that the decay of the arc discharge produced using the tungsten-copper electrodes was much faster than that produced using the tungsten electrodes.
• Experimental study on jet formation and propagation by use of Gekko-XII laser system

  Taichi MORITA, Youichi Sakawa, Kentaro Tomita, Robert Crowston, Ryosuke Fujino, Daisuke Harada, Shogo Isayama, Taishi Ishikawa, Kai Zhang, Michel Koenig, Yasuhiro Kuramitsu, Yutong Li, Shuichi Matsukiyo, Claire Michaut, Toseo Moritaka, Kazuyoshi Nagamine, Tatsuya Oyama, Alexander Pelka, Takayoshi Sano, Yuta Sato, Ryo Shimoda, Tomoya Wadagaki, Nigel Woolsey, Yuta Yamaura, Chuanlei Yin, Hitoki Yoneda, Dawei Yuan, Roman Yurchak, Zhang Zhe, Jiayong Zhong, Hideaki Takabe

  2014/05 [Not refereed][Not invited]
  
• Collisionless shock experiments using large-scale lasers

  Y. Sakawa, T Morita, Y. Yamaura, T. Ishikawa, K. Tomita, R. Crowston, R. Fujino, G. Gregori, C. Huntington, D. Harada, S. Isayama, N. Kugland, Z. Kai, M. Koenig, Y. Kuramitsu, Y- T. Li, S. Matsukiyo, C. Michaut, T. Moritaka, K. Nagamine, T. Oyama, H. S. Park, A. Pelka, B. Remington, T. Sano, Y. Sato, R. Shimoda, A. Spitkovsky, T. Wadagaki, N. Woolsey, C. Yin, H. Yoneda, D. Yuan, R. Yurchak, Z. Zhang, J. Zhong, H. Takabe

  2014/05 [Not refereed][Not invited]
  
• Temperature measurement of junction of light-emitting LED using pulsed-laser Raman scattering

  山形 幸彦, 堀内 誠, 富田 健太郎, 真鍋 由雄

  Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 電気・情報関係学会九州支部連合大会委員会 2014 98 - 98 2014 

  集積化，大電流動作された照明用LEDでは，ジャンクション部の温度上昇がもたらす効率及び寿命の著しい低下，動作の不安定化が大きな課題である．そのため照明用LED開発では，発光中LEDのジャンクション部の温度測定を基にしたデバイス全体の放熱設計が最重要である．しかしながら，その直接測定はできておらず，標準的な温度計測技術の開発が切望されている．本研究ではパルスレーザーラマン散乱法を用いて，外乱光に強く，リモート計測可能な発光中LEDの温度計測システムを開発した．今回，GaN-E₂^Hのラマンシフトの温度依存性を観測し，発光中LEDのジャンクション部の温度計測に成功したので報告する．
• Thomson scattering diagnostics of atmospheric plasmas in contact with ionic liquids

  Kentaro Tomita, Kazuhiko Nagai, Takahiro Shimizu, Nima Bolouki, Yukihiko Yamagata, Kiichiro Uchino, Toshiro Kaneko

  Applied Physics Express 7 (6) 66101  1882-0786 2014 [Refereed][Not invited]
   

  Laser Thomson scattering has been applied to a nonequilibrium atmospheric plasma in contact with an ionic liquid to measure both electron density (n e) and electron temperature (Te). The discharge plasma was produced between a needle and a plane ionic-liquid electrode separated by a 3mm gap. In comparison with a conventional metal electrode, distinct differences were found in spatial profiles of ne and Te of the plasma produced with the ionic-liquid electrode. © 2014 The Japan Society of Applied Physics.
• Efficient extreme ultraviolet emission from one-dimensional spherical plasmas produced by multiple lasers

  Kensuke Yoshida, Shinsuke Fujioka, Takeshi Higashiguchi, Teruyuki Ugomori, Nozomi Tanaka, Hayato Ohashi, Masato Kawasaki, Yuhei Suzuki, Chihiro Suzuki, Kentaro Tomita, Ryoichi Hirose, Takeo Ejima, Masaharu Nishikino, Atsushi Sunahara, Enda Scally, Bowen Li, Tatsuya Yanagida, Hiroaki Nishimura, Hiroshi Azechi, Gerry O'Sullivan

  Applied Physics Express 7 (8) 86202  1882-0786 2014 [Refereed][Not invited]
   

  We demonstrate high conversion efficiency for extreme ultraviolet (EUV) emission at 6.5-6.7nm from multiple laser beam-produced onedimensional spherical plasmas. Multiply charged-state ions produce strong resonance emission lines, which combine to yield intense unresolved transition arrays (UTAs) in Gd, Tb, and Mo. At an optimum laser intensity of 1 × 1012W/cm 2, which is estimated to yield an electron temperature of around 100 eV, the maximum in-band EUV conversion efficiency (CE) was observed to be 0.8%, which is one of the highest values ever reported due to the reduction of plasma expansion loss. © 2014 The Japan Society of Applied Physics.
• Thomson scattering diagnostics of decay processes of Ar/SF6 gas-blast arcs confined by a nozzle

  Kentaro Tomita, Daisuke Gojima, Kazuhiko Nagai, Kiichiro Uchino, Ryo Kamimae, Yasunori Tanaka, Katsumi Suzuki, Takanori Iijima, Toshiyuki Uchii, Takeshi Shinkai

  Journal of Physics D: Applied Physics 46 (38) 382001  0022-3727 2013/09/25 [Refereed][Not invited]
   

  Because of its instability, it is difficult to measure precisely the electron density (ne) of a long-gap decaying arc discharge in a circuit breaker. However, it is well known that it is an essential parameter for the determination of success or failure of the current interruption in a circuit breaker. In this paper, the spatiotemporal evolutions of the electron density were successfully measured in decaying SF6 gas-blast arc discharges formed with a long gap (50 mm) in a confined nozzle using laser Thomson scattering. Pure Ar gas and an 80%Ar/20%SF6 mixture gas were used as the arc quenching media at atmospheric pressure. After reducing the current to zero, both the measured ne and arc radius in the Ar/SF6 gas arc clearly decayed more rapidly than in the pure Ar gas arc. © 2013 IOP Publishing Ltd.
• Diagnostics of VHF argon plasmas by laser Thomson scattering

  W. Chen, K. Ogiwara, K. Koge, K. Tomita, K. Uchino, Y. Kawai

  Plasma and Fusion Research 8 1306114  2013/09 [Refereed][Not invited]
  
• Investigation of VHF argon plasma at high pressure by balanced power feeding using laser Thomson scattering

  W. Chen, K. Ogiwara, K. Koge, K. Tomita, K. Uchino, Y. Kawai

  Engineering Sciences Reports, Kyushu University Interdisciplinary Graduate School of Engineering Sciences, Kyushu University 35 (1) 6 - 11 1346-7883 2013/09 [Refereed][Not invited]
   

  The dependences of the VHF plasma parameters on the gas pressure and power were examined by using the Laser Thomson scattering method, where the VHF plasma was produced in the high pressure region by the balanced power feeding method. It was found that the balanced power feeding method provides a high electron density plasma with low electron temperature at high pressures. This characteristics were confirmed by calculations using a 2-dimensional simulation code.
• Thomson scattering measurement of a shock in laser-produced counter-streaming plasmas

  T. Morita, Y. Sakawa, K. Tomita, T. Ide, Y. Kuramitsu, K. Nishio, K. Nakayama, K. Inoue, T. Moritaka, H. Ide, M. Kuwada, K. Tsubouchi, K. Uchino, H. Takabe

  PHYSICS OF PLASMAS 20 (9) 92115  1070-664X 2013/09 [Refereed][Not invited]
   

  We report the first direct measurement of temporally and spatially resolved plasma temperatures at a shock as well as its spatial structure and propagation in laser-produced counter-streaming plasmas. Two shocks are formed in counter-streaming collisionless plasmas early in time, and they propagate opposite directions. This indicates the existence of counter-streaming collisionless flows to keep exciting the shocks, even though the collisional effects increase later in time. The shock images are observed with optical diagnostics, and the upstream and downstream plasma parameters of one of the shocks are measured using Thomson scattering technique. (C) 2013 AIP Publishing LLC.
• Cosmic shocks and magnetic fields: an experiment at GEKKO

  Rob Crowston, Nigel Woolsey, Hugo Doyle, Jena Meinecke, Brian Reville, Youichi Sakawa, Yasuhiro Kuramitsu, Hideaki Takabe, Taichi Morita, Takayoshi Sano, Toseo Moritaka, Yuta Yamaura, Taishi Ishikawa, Hitoki Yoneda, Kazunori Nagamine, Michel Koenig, Alexander Pelka, Jean-Michel Boudenne, Claire Michaut, Kentaro Tomita, Kazuya Inoue, Ryo Shimoda, Jiayong Zhong, Kai Zhang, Feilu Wang, Yutong Li, David Yuan, Francesco Miniati, Gianluca Gregori

  2013/08 [Not refereed][Not invited]
  
• Laboratory astrophysical experiments using Gekko XII laser system

  Y. Sakawa, Y. Kuramitsu, T. Morita, T. Ishikawa, Y. Yamaura, T. Moritaka, T. Sano, H.Takabe, R. Shimoda, K. Tomita, K. Uchino, S. Matsukiyo, A. Mizuta, N. Ohnishi, R. Crowston, N. Woolsey, H. Doyle, G. Gregori, A. Ravasio, A. Pelka, M. Koenig, C. Michaut, D. Yuan, Y. Li, K. Zhang, J. Zhong, F. Wang, A. Spitkovsky, N. L. Kugland, J. S. Ross, H.-S. Park, B. Remington

  2013/08 [Not refereed][Not invited]
  
• Material dependence of shock waves in laser-produced Counter-streaming plasmas

  Y Yamaura, Y. Sakawa, Y Kuramitsu, T Morita, T. Ishikawa, T. Moritaka, T. Sano, R. Shimoda, K. Tomita, K. Uchino, S. Matsukiyo, A. Mizuta, N. Ohnishi, R. Crowston, N. Woolsey, H. Doyle, G. Gregori, A. Ravasio, A. Pelka, M. Koenig, C.Michaut, D. Yuan, Y. Li, K. Zhang, J. Zhong, F. Wang, H.Takabe

  2013/08 [Not refereed][Not invited]
  
• Collective Thomson Scattering diagnostics of Counter-Streaming Plasmas Produced by High-Power Laser Systems

  Kentaro TOMITA, Youichi SAKAWA, Taichi MORITA, Yasuhiro KURAMITSU, Toseo MORITAKA, Ryo SHIMODA, Kiichiro UCHINO, Hideaki TAKABE

  2013/08 [Not refereed][Not invited]
  
• A collective laser Thomson scattering system for diagnostics of laser-produced plasmas for extreme ultraviolet light sources

  K. Tomita, K. Nakayama, K. Inoue, A. Sunahara, K. Uchino

  Appl. Phys. Express 6 76101  2013/06 [Refereed][Not invited]
  
• Measurements of Electron Density and Electron Temperature in a Decay Process of Ar/SF₆ Gas Arc by Using Thomson Scattering

  合嶋 大輔, 永井 和彦, 富田 健太郎, 内野 喜一郎, 田中 康規, 鈴木 克己, 飯島 崇文, 内井 敏之, 新海 健

  Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 電気・情報関係学会九州支部連合大会委員会 2013 451 - 451 2013 

  電力用ガス遮断器内アーク現象の定量的把握を目指し、ArガスおよびAr/SF₆混合ガス中において、ガス吹き付けノズル内の長ギャップ電極間で生成されるアークの減衰過程における電子密度・電子温度の時間空間変化を、レーザートムソン散乱法により計測した。放電1回の計測から減衰アークの局所的な情報を得ることができ、SF₆ガスを混入した場合は、Ar(100%)ガスの場合と比較し、アーク半径が小さくなり、かつ電子密度の時間減衰が早くなることが確認された。
• Thomson scattering diagnostics in the plasma of an ion thruster

  N. Yamamoto, Y. Hiraoka, K. Sugita, T. Kurita, K. Tomita, K Uchino, H. Nakashima

  Trans. Jpn. Soc. for Aeronautical and Space Sci., Aerospace Technol. Jpn. THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 10 (28) Pb79 - Pb_83 1884-0485 2012/08 [Refereed][Not invited]
   

  In order to validate the grid erosion evaluation code for the lifetime validation of ion thrusters, the electron number density/temperature in the vicinity of a screen gird in a 30 W class microwave discharge ion thruster were measured by means of laser Thomson scattering (LTS) technique. A photon counting method and a triple grating spectrometer were used against a small Thomson scattering signal and a strong stray laser light. Observed Thomson scattering spectrum tells that the electron energy distribution function was Maxwellian. From this spectrum and the Rayleigh scattering calibration using nitrogen gas, electron number density and electron temperature were calculated to be (3.8±0.2)×10¹⁷m^-3 and 6.2±0.1 eV, respectively at incident microwave power of 8 W and krypton mass flow rate of 6.2 μg/s. The ion saturation currents estimated from the LTS measurement are in good agreement with ion beam currents through the screen grid for several conditions. These results show that LTS technique is a useful non-intrusive tool for measuring plasma property in the vicinity of the screen grid.
• Measurement of xenon plasma properties in an ion thruster using laser Thomson scattering technique

  N. Yamamoto, K. Tomita, K. Sugita, T. Kurita, H. Nakashima, K. Uchino

  REVIEW OF SCIENTIFIC INSTRUMENTS 83 (7) 73106  0034-6748 2012/07 [Refereed][Not invited]
   

  This paper reports on the development of a method for measuring xenon plasma properties using the laser Thomson scattering technique, for application to ion engine system design. The thresholds of photo-ionization of xenon plasma were investigated and the number density of metastable atoms, which are photo-ionized by a probe laser, was measured using laser absorption spectroscopy, for several conditions. The measured threshold energy of the probe laser using a plano-convex lens with a focal length of 200 mm was 150 mJ for a xenon mass flow rate of 20 mu g/s and incident microwave power of 6 W; the probe laser energy was therefore set as 80 mJ. Electron number density was found to be (6.2 +/- 0.4) x 10(17) m(-3) and electron temperature was found to be 2.2 +/- 0.4 eV at a xenon mass flow rate of 20 mu g/s and incident microwave power of 6 W. The threshold of the probe laser intensity against photo-ionization in a miniature xenon ion thruster is almost constant for various mass flow rates, since the ratio of population of the metastable atoms to the electron number density is little changed. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737144]
• LABORATORY EXPERIMENTS TO STUDY COLLISIONLESS SHOCKS

  Y. Sakawa, Y. Kuramitsu, T. Morita, T. Ide, K. Nishio, H. Ide, K. Tsubouchi, K. Tomita, K. Uchino, N. Woolsey, C. Murphy, G. Gregori, A. Ravasio, A. Pelka, M. Koenig, A. Spitkovsky, N. L. Kugland, J. S. Ross, H.-S. Park, B. Remington, H.Takabe

  2012/05 [Not refereed][Invited]
  
• Electron scale magnetic reconnection in a laser produced plasma

  Y. Kuramitsu, T. Moritaka, Y. Sakawa, T. Morita, T. Ide, K. Nishio, C. D. Gregory, J. N. Waugh, B. Loupias, G. Gregori, M. Koenig, N. Woolsey, T. Sano, K. Tomita, K. Uchino, M. Hoshino, H. Takabe

  2012/05 [Not refereed][Not invited]
  
• Two-dimensional Thomson scattering diagnostics of pulsed discharges produced at atmospheric pressure

  K. Tomita, N. Bolouki, H. Shirozono, Y. Yamagata, K. Uchino, K. Takaki

  JOURNAL OF INSTRUMENTATION 7 C02057  1748-0221 2012/02 [Refereed][Not invited]
   

  Laser Thomson scattering (LTS) method has been applied to measure two dimensional distributions of electron density (n(e)) and electron temperature (T-e) of a pulsed discharge in Ne gas at a pressure of 400 Torr. Such a discharge was produced with good reproducibility by using a set of electrodes composed of a needle and a hemisphere with a spacing gap of 0.5 mm. The values of n(e) and T-e at t = 25 ns after the start of the discharge and at the center of the discharge were evaluated to be 4.6 x 10(22) m(-3) and 1.0 eV, respectively. Based on the observed signal intensity and noise components, signal-to-noise ratios were examined and the way to apply present diagnostic system to the discharge plasma with an electron density as low as 10(18) m(-3) was discussed.
• Studies of non-thermel plasmas produced in atmospheric pressure using collective Thomson scattering.

  Nima Bolouki

  Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 電気・情報関係学会九州支部連合大会委員会 2012 508 - 508 2012 

  大気圧非熱平衡プラズマは、大気中での生成が可能であることや、ラジカル生成が容易であることなどから、オゾン生成や排ガス処理など、多くの応用例のある有用なプラズマである。しかし、プラズマ形成するパルスマイクロ放電は、微小、短命であるため、プラズマ内部の状態は明らかにされていない。本研究では、大気圧非熱平衡プラズマを形成するひとつのパルスマイクロ放電内の電子密度や電子温度の時間空間分解計測を、レーザートムソン散乱法を用いて行っている。測定対象としたのは、針対半球電極間で生成した容量連結型放電であり、これまでに、再結合過程における電子密度・電子温度の計測を達成した。
• Diagnostics of laser-produced plasmas for EUV light sources using collective Thomson scattering.

  井上 和哉, 下田 諒, 富田 健太郎, 内野 喜一郎

  Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 電気・情報関係学会九州支部連合大会委員会 2012 509 - 509 2012 

  半導体集積回路の高集積化は、光リソグラフィ光源の短波長化で実現されてきた。今後更なる高集積化の為に、レーザー生成プラズマ（LPP）方式や放電生成プラズマ（DPP）方式を用いた、波長13.5nmの極端紫外光（EUV）の実用化が期待されているが、発光強度、効率が目標値に達していない。EUVを高効率化するには、プラズマの電子密度・電子温度を制御する必要があるが、これらのEUVプラズマパラメータを診断する方法がないのが現状である。本研究では、レーザー生成EUV光源プラズマにレーザートムソン散乱法を適用し、プラズマの電子密度 （ne）・電子温度 （Te）・平均イオン価数（Z）の計測を確立し、EUV光源実用化へ寄与することを目的としている。
• Measurements of Electron Density and Electron Temperature of Arc Discharges Containing Metallic Vapors.

  Yoshitake Shinya, Tomita Kentaro

  Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 電気・情報関係学会九州支部連合大会委員会 2011 310 - 310 2011 

  電力用ガス遮断器は、系統事故時に発生する事故電流等を瞬時に遮断し、系統に接続されている機器の損傷や破壊から保護するために用いられている。遮断器の小型化・高信頼化のためには、アーク放電の基礎特性を把握することが重要である。特に、電流零点近傍における電子密度は、遮断性能を決定づける重要なパラメータである。しかし、アークが消弧する際に、電極などで用いられている金属による蒸気混入がアーク放電の電子密度・電子温度にどう関与するかを実験的に求めた報告例は乏しい。本研究では、大気中アーク放電に対してトムソン散乱測定法を適用し、金属蒸気混入がアーク放電の電子密度・電子温度に及ぼす影響を調査、比較した。
• Spectroscopic Studies of Micro Discharges for Efficient PDP

  Mikami Genichiro, Uchino Kiichiro, Tomita Kentaro, Hasui Yuya, Tanaka Hiroshi

  Record of Joint Conference of Electrical and Electronics Engineers in Kyushu 電気・情報関係学会九州支部連合大会委員会 2011 598 - 598 2011 

  プラズマディスプレイパネル(PDP)は、微小なセル内の放電により紫外線を発生させ、その紫外線をセル壁面に塗布された蛍光体で可視光に変換し、画像を表示するディスプレイである。これは蛍光灯と同様の発光形態であるがPDPの発光効率は蛍光灯の発光効率に比べ1/10以下と非常に低く、そこに大きな効率改善の余地がある。それに関し、維持電極の幅を従来の電極よりも狭くして放電長を制限することにより高Xe分圧下において効率が良くなることが報告されている。そこで、放電の構造が発光効率にどのように関わるかを明らかにするため、高発光効率PDPマイクロ放電に対し、分光計測を行った。その経過について、報告する。
• Relationship between Ba atom emission and electrode temperature in a low-pressure fluorescent lamp

  Yukihiko Yamagata, Makoto Kai, Sho Naito, Kentaro Tomita, Kiichiro Uchino, Yoshio Manabe

  THIN SOLID FILMS 518 (13) 3449 - 3452 0040-6090 2010/04 [Refereed][Not invited]
   

  A relationship between emission characteristics of Ba atom as an emitter material and temperature distributions of an electrode in a fluorescent lamp is described, which is measured by using laser-induced fluorescence and black-body radiation method, respectively. In a virgin lamp, a hot spot observed at the electrode edge connected to the power supply is the main source of Ba atom emission. In a long-term-used lamp, it is shown that Ba atom emission, thermionic electron emission in cathode half-cycle and electron collection in anode half-cycle are most active on the hot spot appearing on the center of the electrode. (C) 2009 Elsevier B.V. All rights reserved.
• Thomson-Scattering Diagnostics of Plasmas Produced in a Miniature Microwave Discharge Ion Engine

  Tomita Kentaro, Yamamoto Naoji, Yamasaki Naoto, Tsuru Teppei, Uchino Kiichiro, Nakashima Hideki

  JOURNAL OF PROPULSION AND POWER 26 (2) 381 - 384 0748-4658 2010/03 [Refereed][Not invited]
  
• Plasma Properties in a Miniature Microwave Discharge Ion Thruster

  EZAKI Toru, YAMAMOTO Naoji, TSURU Teppei, KOTANI Yusuke, NAKASHIMA Hideki, YAMASAKI Naoto, TOMITA Kentaro, UCHINO Kiichiro

  TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, SPACE TECHNOLOGY JAPAN THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES 8 (27) Pb_55 - Pb_59 1884-0485 2010 

  In order to improve the thrust performance of a 1-mN-class miniature microwave discharge ion thruster, we investigate the dependence of inner plasma properties inside the thruster on operational conditions, krypton mass flow rate, incident microwave power and magnet field strength by laser Thomson scattering (LTS) technique. With an increase in mass flow rate, the electron temperature decreases and the electron number density increases at an incident microwave power of 16 W and the number of magnets of twelve. These results indicate that there is an optimum mass flow rate, which is 0.6 sccm in this condition. The electron number density and temperature increase with incident microwave power and is saturated at 8 W for a mass flow rate of 0.4 sccm and the number of magnets of twelve. With an increase in magnetic field strength, the electron temperature and the electron density suddenly jump from 9.8×10¹⁷ m^-3 and 5.2 eV to 1.7×10¹⁸ m^-3 and 7.3 eV at the number of magnets of thirteen at a mass flow rate of 0.4 sccm and incident microwave power of 16 W.
• Measurements of electron density and temperature in a miniature microwave discharge ion thruster using laser Thomson scattering technique

  N. Yamamoto, K. Tomita, N. Yamasaki, T. Tsuru, T. Ezaki, Y. Kotani, K. Uchino, H. Nakashima

  Plasma Sources Science and Technology 19 (4) 45009  0963-0252 2010 [Refereed][Not invited]
   

  In order to improve the thrust performance of a miniature microwave discharge ion thruster, the relationship between electron number density/temperature and operational conditions, mass flow rate, incident microwave power and magnetic field strength were measured by means of laser Thomson scattering. A photon counting method and a triple grating spectrometer were used against a small Thomson scattering signal and a strong stray laser light. Electron number density increased with incident microwave power and was saturated at critical incident microwave power it was about 1.2 × 10 18 m-3 at incident microwave power > 8 W. In addition, electron number density increased with mass flow rate and became saturated it was about 1.7 × 1018 m-3 at mass flow rate > 0.04 mg s-1. The electron number density gradually increased with an increase in the number of magnets, i.e. magnetic field strength. There was a sudden jump at thirteen magnets, although the thruster failed to ignite at fourteen magnets. This is because there is an optimum distance between the antenna and the electron cyclotron resonance layer. These results suggest that future improvement in thrust efficiency in miniature microwave discharge ion thrusters may come from the fine adjustment of the magnetic field configuration inside the discharge chamber. © 2010 IOP Publishing Ltd.
• Measurements of distributions of Ba atom density and electrode temperature in low-pressure fluorescent lamp

  M. Naka, M. Kai, Y. Egashira, K. Tomita, Y. Manabe, Y. Yamagata, K. Uchino

  J. Plasma and Fusion Research SERIES 8 1308 - 1312 2009/09 [Refereed][Not invited]
  
• Laser Thomson scattering diagnostics of dielectric barrier discharge plasmas

  Y. Sonoda, S. Nishimoto, K. Tomita, S. Hassaballa, Y. Yamagata, K. Uchino

  J. Plasma and Fusion Research SERIES 8 696 - 699 2009/09 [Refereed][Not invited]
  
• Collective Thomson scattering diagnostics of EUV plasmas

  K. Tomita, T. Kagawa, K. Uchino, S. Katsuki, H. Akiyama

  J. Plasma and Fusion Research SERIES 8 488 - 491 2009/09 [Refereed][Not invited]
  
• Laser Thomson scattering and optical emission studies of striated PDP micro-discharge plasmas

  S Hassaballa, Y Sonoda, K Tomita, YK Kim, K Uchino

  JOURNAL OF THE SOCIETY FOR INFORMATION DISPLAY 13 (8) 639 - 645 1071-0922 2005/08 [Refereed][Not invited]
   

  Properties of a plasma-display-panel ( PDP) like discharge were examined by emission and laser Thomson scattering (LTS) measurements. Emission measurements were performed using an intensified CCD camera. By varying several external parameters such as the amplitude of the input voltage, gas composition, and pressure, the influence of these parameters on the discharge behavior was studied. Results of emission measurements showed that they were in good agreement with similar emission measurements on real PDP cells. LTS measurements were performed for the striated PDP-like discharge at a pressure of 100 Torr and the results showed clear modulations in both profiles of electron density and electron temperature.
• Laser Thomson scattering measurements of electron density and temperature profiles of a striated plasma in a plasma display panel (PDP)-like discharge

  S Hassaballa, K Tomita, YK Kim, K Uchino, H Hatanaka, YM Kim, CH Park, K Muraoka

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 44 (12-15) L442 - L444 0021-4922 2005 [Refereed][Not invited]
   

  A laser Thomson scattering technique has been used to directly measure the electron density (it,) and electron temperature (T,) profiles of a striated plasma in a plasma display panel (PDP)-like discharge. A modulation in n(e) was observed only on the anode side of an electrode substrate; this corresponds to a feature similar to that of the emission images obtained using an intensified charge-coupled device (ICCD) camera. Also, a modulation in T-e was observed and it was found to be out of phase from the modulation in it,.
• Laser Thomson Scattering and Optical Emission Studies of PDP

  Hassaballa Safwat, Tomita Kentaro, Kim Young Kee, Uchino Kiichiro

  九州大学大学院総合理工学報告 Interdisciplinary Graduate School of Engineering Sciences, Kyushu University 26 (3) 327 - 332 1346-7883 2004/12 

  Properties of a plasma display panel (PDP) like discharge were examined by emission and laser Thomson scattering (LTS) measurements. Emission measurements were performed using an intensified CCD camera. By varying several external parameters such as amplitude of the input voltage, gas composition and pressure, the influence of these parameters on the discharge behavior was studied. Results of emission measurements showed that they were in good agreement with similar emission measurements on real PDP cells. LTS measurements were performed for the discharge at a pressure of 100 Torr. The results yielded precise profiles of electron density and electron temperature of the striated PDP-like plasma for the first time.
• Two-dimensional structure of PDP micro-discharge plasmas obtained using laser Thomson scattering

  S Hassaballa, M Yakushiji, YK Kim, K Tomita, K Uchino, K Muraoka

  IEEE TRANSACTIONS ON PLASMA SCIENCE 32 (1) 127 - 134 0093-3813 2004/02 [Refereed][Not invited]
   

  Laser Thomson scattering (LTS) has been applied for measurements of the electron density and electron temperature in micro-discharge plasmas for plasma-display panel research. A brief description of the method for overcoming the sparsity of scattered photons by the data accumulation technique is presented. Then, the technique of applying LTS to micro-discharge plasmas is described where the use of a specially designed triple-grating spectrometer has turned out to be essential. Improvements in the experimental setup to allow, for the first time, to collect laser LTS spectra at heights as close as to 60 mum from the electrode surface are discussed. Spatial distributions of the electron density and electron temperature in the vertical direction above the electrode surface are presented. Finally, an extension of the measurements into two-dimensions, namely along the electrode surface and at different heights above the electrodes enabling to cover the discharge front to be made, are presented and compared with the results of optical emission measurements.
• Thomson scattering diagnostics of glow discharge plasmas produced in Raman active gases

  S Narishige, S Kitamura, S Sakemi, K Tomita, K Uchino, K Muraoka, T Sakoda

  JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS 41 (11A) L1259 - L1262 0021-4922 2002/11 [Refereed][Not invited]
   

  In Thomson scattering measurements of processing plasmas, rotational Raman scattering light from molecules sometimes overlaps the observed spectra. In order to solve this problem, a new method is proposed. This method involves separating the Thomson scattering component from the Raman scattering component by utilizing differences in the scattering characteristics depending on scattering wavelength and scattering geometry. By using this method, electron densities and electron temperatures of a microwave discharge plasma produced in a H-2/CH4 gas mixture at a moderate pressure were successfully measured for the first time.

MISC

• 半導体リソグラフィー用EUV-BEUV光源のイオンデブリの価数分離エネルギースペクトル—Charge-separated ionic debris spectra in EUV-BEUV sources for semiconductor lithography—フォトニクス・ワークショップ in 九州 : 福岡

  東口 武史, 中山 勇冬, 新沼 大登, 久米 真樹, 杉浦 使, 森田 大樹, 富田 健太郎, 砂原 淳, 難波 慎一, 江島 丈雄  レーザー学会研究会報告 = Reports the on topical meeting of the Laser Society of Japan  RTM22-  (26-31)  11  -16  2022/09/05
• レーザー生成プラズマ極端紫外光源から発生する高速イオンのエネルギースペクトル—Energy spectra of fast ions from a laser-produced plasma EUV source—放電・プラズマ・パルスパワー研究会・放電・プラズマ・パルスパワー一般

  東口 武史, 中山 勇冬, 新沼 大登, 久米 真樹, 森田 大樹, 砂原 淳, 富田 健太郎, 江 偉華, 難波 慎一, 江島 丈雄  電気学会研究会資料. EPP = The papers of technical meeting, IEE Japan / [放電・プラズマ・パルスパワー研究会] [編]  2022-  (60-65)  1  -6  2022/05/20
• Energy spectra of fast ions from a laser-produced plasma EUV source

  東口武史, 中山勇冬, 新沼大登, 久米真樹, 森田大樹, 砂原淳, 富田健太郎, JIANG Weihua, 難波慎一, 江島丈雄  電気学会研究会資料(Web)  (EPP-22-060-065)  2022
• Charge-separated ionic debris spectra in EUV-BEUV sources for semiconductor lithography

  東口武史, 中山勇冬, 新沼大登, 久米真樹, 杉浦使, 森田大樹, 富田健太郎, 砂原淳, 難波慎一, 江島丈雄  レーザー学会研究会報告  567th-  2022
• Experiments of generation of collisionless shocks propagating into magnetized plasma

  山崎了, 田中周太, 相原研人, 佐藤雄飛, 塩田珠里, 高田敦也, 松井啓一郎, 佐野孝好, 太田雅人, 江頭俊輔, 倉本織羽乃, 松本雄志郎, 蔵満康浩, 南卓海, 境健太郎, 西本貴博, 岩崎滉, 松清修一, 森田太智, 松尾涼人, 児島拓仁, 枝本雅史, 富田健太郎, 竹崎太智, 小口拓哉, 星野真弘, 大平豊, 梅田隆行, 石井彩子, 大西直文, 冨田沙羅, 坂和洋一  衝撃波シンポジウム講演論文集(CD-ROM)  2021-  2022
• レーザーアブレーションプラズマが駆動する磁気リコネクション研究(2019A-MORITA)

  森田太智, 高木麻理子, 西岡裕輝, 枝本雅史, 坂和洋一, 富田健太郎, 佐野孝好, 蔵満康浩, 山崎了, 田中周太, 松清修一, 大平豊, 太田雅人, 江頭俊輔, 泉智大, 境健太郎, 角地真, 瀬井柊人, 石坂夏槻, 杉山慧, 樋口琢己, 村上洋大  大阪大学レーザー科学研究所共同利用・共同研究成果報告書(Web)  2019-  2020
• 高出力レーザーを用いた磁気リコネクション実験における局所プラズマ・磁場計測

  森田太智, 枝本雅史, 西岡裕輝, 佐野孝好, 太田雅人, 江頭俊輔, 泉智大, 松清修一, 堀江由実, 樋口琢海, 山崎了, 田中周太, 遠田裕史, 宮田親, 角地真, 瀬井柊人, 石坂夏規, 冨田沙羅, 河村璃子, 杉山慧, 鈴木大介, 高山紗良, 富田健太郎, 蔵満康浩, 境健太郎, 南卓海, 坂和洋一  日本物理学会講演概要集(CD-ROM)  74-  (1)  ROMBUNNO.17aK309‐10  2019/03/22  [Not refereed][Not invited]
  
• レーザー生成対向プラズマ中における磁気リコネクション

  森田太智, 長島圭祐, 枝本雅史, 板谷佑太朗, 佐野孝好, KUMAR R, 太田雅人, 江頭俊輔, 山崎了, 田中周太, 冨谷聡志, 遠田裕史, 宮田親, 角地真, 瀬井柊人, 石坂夏規, 冨田沙羅, 富田健太郎, 蔵満康浩, 松清修一, 坂和洋一  日本物理学会講演概要集(CD-ROM)  73-  (2)  ROMBUNNO.9aC102‐6  2018/09/21  [Not refereed][Not invited]
  
• 高出力レーザーと外部磁場を用いた磁気リコネクション実験

  森田太智, 枝本雅史, 富田健太郎, 板谷佑太朗, 松清修一, 佐野孝好, 山崎了, 坂和洋一  日本物理学会講演概要集(CD-ROM)  73-  (1)  ROMBUNNO.25aK609‐3  2018/03/23  [Not refereed][Not invited]
  
• 磁気リコネクション実験

  坂和洋一, 江頭俊輔, 太田雅人, KUMAR Rajesh, LAW K. F. F, 南卓海, 藤田泰彦, 上林大介, 堺健太郎, 佐野孝好, 森田太智, BOLOUKI Nima, 金崎真聡, 福田祐仁, 松尾一輝, MORACE A, 藤岡慎介, 余語覚文, 乗松孝好, 羽原英明, 蔵満康浩, 尾崎典雅, 富田健太郎, 松清修一, 星野真弘, 山崎了, 田中周太, 米田仁紀, 森高外征雄, KOENIG Michel, CASNER Alexis, MICHAUT Claire  大阪大学レーザー科学研究所共同利用・共同研究成果報告書(CD-ROM)  2017-  ROMBUNNO.1‐17  2018/03  [Not refereed][Not invited]
  
• プラズマ衝撃波のマルチスケール構造の精密測定

  松清修一, 香月のどか, 初山凌介, 堀江由実, 坂和洋一, 佐野孝好, 森田太智, 富田健太郎, 枝本雅史, 太田雅人, 江頭俊輔, KUMAR Rajesh, 山崎了, BOLOUKI Nima, 蔵満康浩, 冨田沙羅, 田中周太  大阪大学レーザー科学研究所共同利用・共同研究成果報告書(CD-ROM)  2017-  ROMBUNNO.1‐3  2018/03  [Not refereed][Not invited]
  
• 磁化プラズマ中を伝播する低マッハ数の無衝突衝撃波の生成実験

  山崎了, 冨谷聡志, 遠田裕史, 宮田親, 安部大晟, 石坂夏規, 角地真, 瀬井柊人, 冨田沙羅, 坂和洋一, 佐野孝好, 江頭俊輔, 太田雅人, KUMAR Rajesh, 蔵満康浩, 松清修一, 森田太智, 富田健太郎, 枝本雅史, 小沼杏奈, 浅井晴貴, 飯田浩祐, 米田仁紀, 田中周太, 大西直文, 井上剛志, 梅田隆行, 高部英明, 星野真弘, 大平豊, 石井彩子, 寺木悠人  大阪大学レーザー科学研究所共同利用・共同研究成果報告書(CD-ROM)  2017-  ROMBUNNO.1‐1  2018/03  [Not refereed][Not invited]
  
• 高出力レーザーを用いた磁気リコネクション実験

  森田太智, 長島圭祐, 枝本雅史, 板谷佑太朗, 佐野孝好, KUMAR Rajesh, 太田雅人, 江頭俊輔, 山崎了, 田中周太, 冨谷聡志, 遠田裕史, 宮田親, 角地真, 瀬井柊人, 石坂夏槻, 冨田沙羅, 富田健太郎, 蔵満康浩, 松清修一, 坂和洋一  プラズマ・核融合学会年会(Web)  35th-  ROMBUNNO.S7‐3 (WEB ONLY)  2018  [Not refereed][Not invited]
  
• Fundamental studies on switching arcs -Experimental and numerical approaches

  Yasunori Tanaka, Tomoyuki Nakano, Sun Hao, Kentaro Tomita, Yuki Inada, Akiko Kumada, Kunihiko Hidaka, Takayasu Fujino, Katsumi Suzuki, Takeshi Shinkai  ICEPE-ST 2017 - 4th International Conference on Electric Power Equipment- Switching Technology  2017--  1  -10  2017/12/12  [Not refereed][Not invited]
   

  Both experimental and numerical approaches have been done on switching arc plasmas for fundamental studies. In the experimental approaches, power-semiconductor switching has been used to control intentional current injections and voltage applications to switching arcs with a high accuracy in time. The systematic experiments provided the interruption probability property for different gas kinds and gas flow rates, as well as the dielectric recovery properties between the electrodes. Time evolutions in electron density were derived by Laser Thomson Scattering (LTS) and Shack-Hartmann (SH) method for different gases. On the other hand, for this nozzle space, numerical models were developed to simulate arc dynamic behaviors with and without local thermodynamic equilibrium (LTE) assumptions for different gases. It was found that the time evolution in electron density derived by the chemically non-equilibrium model is in good agreement with the experimental results by LTS.
• Fundamental study on re-ignition process for CO2-blast arcs in a model circuit breaker using synthetic tests highly controlled by power semiconductors

  Tomoyuki Nakano, Yu Tabata, Yasunori Tanaka, Yoshihiko Uesugi, Tatsuo Ishijima, Kentaro Tomita, Yuki Inada, Katsumi Suzuki, Takeshi Shinkai  ICEPE-ST 2017 - 4th International Conference on Electric Power Equipment- Switching Technology  2017--  263  -267  2017/12/12  [Not refereed][Not invited]
   

  This paper reports fundamental measurement results on re-ignition process in synthetic tests for CO2 arcs in a gas blast nozzle. The synthetic test system used comprises a DC current source for an arc ignition, a half cycle AC current source, a DC current source for artificial current zero point and an impulse-like voltage source for application of quasi-transient recovery voltage (quasi-TRV). The electric current and voltage were switched by power-semiconductor-switches to guarantee high time-accuracy of the arc current injection and voltage application. After current zero point, quasi-TRV with a peak of 7.5 kV was applied between the electrodes with a precise specified delay time td to judge arc re-ignition. The results indicated that td = 25 μs involves 60% probability of arc re-ignition. The re-ignition was inferred to originate in thermal mode from joule heating by a small current injection to the residual arc during the quasi-TRV application.
• パワー半導体スイッチを利用した合成試験によるCO₂ガスのアーク消弧能力評価 (放電 静止器 開閉保護 合同研究会 アークプラズマ・電気接点とその応用)

  中野 智之, 田畑 裕, 田中 康規, 上杉 喜彦, 石島 達夫, 富田 健太郎, 稲田 優貴, 鈴木 克巳, 新海 健  電気学会研究会資料. ED = The papers of technical meeting on electrical discharges, IEE Japan  2017-  (68)  11  -16  2017/07/19
• Measurements of Electron Density and Electron Temperature of Atmospheric Pressure Plasmas Using Thomson Scattering

  富田 健太郎, 内野 喜一郎  プラズマ・核融合学会誌 = Journal of plasma and fusion research  93-  (5)  232  -235  2017/05
• 磁気リコネクション実験

  坂和洋一, 下河原浩志, KUMAR Rajesh, 松尾一輝, 佐野孝好, 藤岡慎介, 乗松孝好, 森田太智, 板谷佑太朗, 富田健太郎, 築山晶一, 深田来夢, 内野喜一郎, 松清修一, 香月のどか, 星野真弘, 山崎了, 正治圭崇, 冨田沙羅, 冨谷聡志, 小林瑛史, 野上雅弘, 遠田裕史, 宮田親, 木坂将大, 田中周太, 小沼杏奈, 米田仁紀, 森高外征雄, 高嶺愛子, KOENIG Michel, ALBERTAZZI Bruno, MICHEL Thibault, RIGON Gabriel, CASNER Alexis, MICHAUT Claire, BARROSO Patrice  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2016-  20‐21  2017/03  [Not refereed][Not invited]
  
• 磁化プラズマ中を伝播する低マッハ数の無衝突衝撃波の生成実験

  山崎了, 正治圭崇, 冨谷聡志, 遠田裕史, 宮田親, 大平豊, 冨田沙羅, 小林瑛史, 野上雅弘, 木坂将大, 坂和洋一, 佐野孝好, KUMAR Rajesh, 下河原浩志, 松清修一, 森田太智, 富田健太郎, 香月のどか, 小沼杏奈, 米田仁紀, 田中周太, 大西直文, 石井彩子, 蔵満康浩, 梅田隆行, 高部英明, 星野真弘, 森高外征雄, 高峰愛子, 寺木悠人, 井上剛志  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2016-  9‐10  2017/03  [Not refereed][Not invited]
  
• プラズマ衝撃波のマルチスケール構造の精密測定

  松清修一, 香月のどか, 坂和洋一, 佐野孝好, 下河原浩志, KUMAR Rajesh, 富田健太郎, 森田太智, 山崎了, 正治圭崇, 冨谷聡志, 遠田裕史, 宮田親, 冨田沙羅, 小林瑛史, 野上雅弘, 木坂将大, 森高外征雄, 蔵満康浩, 羽田亨  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2016-  14‐15  2017/03  [Not refereed][Not invited]
  
• Non-equilibrium studies in switching arc plasmas in Japan

  Y. Tanaka, K. Tomita, Y. Inada, A. Kumada, K. Hidaka, T. Fujino, K. Suzuki, T. Shinkaig  22nd Symposium on Physics of Switching Arc  2017--  225  -233  2017  [Not refereed][Not invited]
   

  This paper briefly introduce research work examples of non-equilibrium studies in switching arcs. In understanding arc behavior, one often assumes local thermodynamic equilibrium (LTE) condition in the arc plasma. However, actual arc plasmas are not completely and not always in LTE state because of strong temperature change temporally and spatially, and high electric field application etc. Recently, we have a collaboration work in numerical simulations and experimental approaches for decaying arcs without LTE assumption. First, our numerical model is presented for decaying arcs without chemical equilibrium assumption. Secondly, two experimental methods are introduced for measuring electron density in decaying arcs without LTE assumption: Laser Thomson Scattering method and the Schack-Hartmann method. Finally, comparison results is shown between the LTE simulation, the chemically non-equilibrium simulation, and the above experimental measurements.
• 高出力レーザーを用いたプラズマ中衝撃波における磁場増幅モデル実験とその解析 II

  下河原浩志, 坂和洋一, RAJESH Kumar, 森田太智, 富田健太郎, 松清修一, 山崎了, 蔵満康浩, 佐野孝好, 大西直文, 水田晃, 高部英明, 森高外征雄  日本物理学会講演概要集(CD-ROM)  71-  (2)  ROMBUNNO.16aKC‐4  -704  2016/09/23  [Not refereed][Not invited]
   

  我々は、高出力レーザーを用いた宇宙プラズマ現象の模擬実験を行う事で、宇宙空間での計測の難しい微視的な物理を明らかにすることを目的として研究を行っている。宇宙空間において超新星残骸(SNR)などで観測される無衝突衝撃波は宇宙線加速や磁場増幅に重要な役割を果たすことが、天体観測から明らかになっている。SNRでの磁場増幅機構の1つとして、非一様な媒質中に無衝突衝撃波が伝搬し、励起されたリヒトマイヤー・メシュコフ不安定性（RMI）による磁場増幅が、理論研究やシミュレーションから示されている。今回は、RMIのモデル実験を行い、プラズマの温度・密度の時間発展の解析を進めた。

• 流動型液体電極を有する大気圧プラズマの特性評価と金属電極放電との比較

  白井直機, 白井直機, 占部継一郎, 富田健太郎, 秋山毅志, 村上朝之  応用物理学会秋季学術講演会講演予稿集(CD-ROM)  77th-  ROMBUNNO.16p‐P2‐4  2016/09/01  [Not refereed][Not invited]
  
• Arc Re-ignition Processes by Application of Quasi-Transient Recovery Voltage in Different Gas Flow in a Nozzle

  中野 智之, 村井 康佑, 田中 康規, 上杉 喜彦, 石島 達夫, 白石 竜郎, 清水 陽大, 富田 健太郎, 鈴木 克巳, 新海 健  電気学会研究会資料. SP = The papers of technical meeting on switching and protecting engineering, IEE Japan  2016-  (1)  89  -94  2016/06/13
• 大型レーザー生成プラズマ中衝撃波における磁場増幅のモデル実験

  下河原浩志, 坂和洋一, 原由紀子, KUMAR Rajesh, 森田太智, 富田健太郎, 松清修一, 山崎了, 蔵満康浩, 森高外征雄, 佐野孝好, 大西直文, 水田晃, 高部英明  日本物理学会講演概要集(CD-ROM)  71-  (1)  ROMBUNNO.22AAE‐12  -976  2016/03/22  [Not refereed][Not invited]
  
• プラズマ衝撃波のマルチスケール構造の精密測定

  松清修一, 潮崎幸太, 香月のどか, 椎葉星哉, 坂和洋一, 佐野孝好, 原由希子, 下河原浩志, 富田健太郎, 森田太智, 山崎了, 蔵満康浩, 森高外征雄, 高部英明, 羽田亨  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2015-  22  -23  2016/03  [Not refereed][Not invited]
  
• 無衝突衝撃波研究のための新規協同トムソン散乱システムの開発

  富田健太郎, 坂和洋一, 蔵満康浩, 佐藤祐太, 原由希子, 森田太智, 松清修一, 高部英明  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2015-  16  -17  2016/03  [Not refereed][Not invited]
  
• 磁化プラズマ中を伝播する低マッハ数の無衝突衝撃波の生成実験

  山崎了, 正治圭崇, 冨谷聡志, 冨田沙羅, 大平豊, 坂和洋一, 佐野孝好, 原由希子, 下河原浩志, 松清修一, 森田太智, 富田健太郎, 米田仁紀, 蔵満康浩, 森高外征雄, 大西直文, 石井彩子, 梅田隆行, 高部英明, 田中周太, 寺木悠人, 井上剛志  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2015-  26  -27  2016/03  [Not refereed][Not invited]
  
• 超音速対向プラズマ流による無衝突衝撃波の生成

  坂和洋一, 原由希子, 下河原浩志, KUMAR Rajesh, 佐野孝好, 藤岡慎介, 乗松孝好, 森田太智, 齋藤直哉, 川島諒祐, 枝本雅史, 三浦智之, 板谷佑太朗, 富田健太郎, 佐藤裕太, 川原拓也, BOLOUKI Nima, 内野喜一郎, 松清修一, 潮崎幸太, 椎葉星哉, 香月のどか, 蔵満康浩, 森高外征雄, PENG Cheng‐Wei, HUANG Tzu‐Yao, CHEN Chia‐Heng, 山崎了, 正治圭崇, 冨田沙羅, 冨谷聡志, 大平豊, 前田はるか, 田中周太, 寺木悠人, 小沼杏奈, 米田仁紀, KOENIG Michel, ALBERTAZZI Bruno, FALIZE Emeric  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2015-  20  -21  2016/03  [Not refereed][Not invited]
  
• 磁化プラズマ中を伝播する無衝突衝撃波の生成実験:2015年度の実験結果

  山崎了, 正治圭崇, 冨谷聡志, 冨田沙羅, 大平豊, 坂和洋一, 佐野孝好, 原由希子, 下河原浩志, 松清修一, 森田太智, 富田健太郎, 高部英明, 米田仁紀, 田中周太, 寺木悠人  日本天文学会年会講演予稿集  2016-  273  2016/02/20  [Not refereed][Not invited]
  
• The LTE Thermofluid Simulation of Decaying Arcs in Various Gas Flow in a Nozzle Space and Experimental Study

  村井 康佑, 中野 智之, 田中 康規, 上杉 喜彦, 石島 達夫, 白石 竜朗, 清水 陽大, 富田 健太郎, 鈴木 克巳, 藤野 貴康  電気学会研究会資料. SA  2015-  (56)  31  -36  2015/07/08
• Numerical Simulations of Arc Properties in a Nozzle using Various Alternative Gases

  垂石 早紀, 矢田部 優樹, 藤野 貴康, 田中 康規, 富田 健太郎, 鈴木 克己  電気学会研究会資料. SA  2015-  (56)  25  -30  2015/07/08
• Fundamental Evaluation on Current Interruption Ability of Various Gases using quasi-TRV Application Controlled by Power Semiconductors

  中野 智之, 田中 康規, 上杉 喜彦, 石島 達夫, 白石 竜郎, 清水 陽大, 富田 健太郎, 鈴木 克己  電気学会研究会資料. SA  2015-  (56)  79  -84  2015/07/08
• 大型レーザーによって生成された無衝突衝撃波の協同トムソン散乱計測

  原由希子, 坂和洋一, 富田健太郎, 佐藤裕太, 西川和孝, 森田太智, 佐野孝好, 高部英明  日本物理学会講演概要集(CD-ROM)  70-  (1)  ROMBUNNO.23PBH-5  -892  2015/03/24  [Not refereed][Not invited]
  
• 激光XII号レーザーを用いたEUV‐BEUV光源プラズマデータベースの構築

  大橋隼人, 藤岡慎介, 松隈啓, 吉田健祐, 細田達矢, 東口武史, 笹沼淳史, 原広行, 富田健太郎, 佐藤祐太, 江島丈雄, 鈴木千尋, 砂原淳, 錦野将元  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2014-  11  -12  2015/03  [Not refereed][Not invited]
  
• 磁化プラズマ中を伝播する低マッハ数の無衝突衝撃波の生成実験

  山崎了, 正治圭崇, 河村有志郎, 冨田沙羅, 大平豊, 坂和洋一, 高部英明, 佐野孝好, 森高外征雄, 原由希子, 近藤さらな, 松清修一, 森田太智, 富田健太郎, 米田仁紀, 長嶺和慶, 蔵満康浩, 大西直文, 梅田隆行  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2014-  21  -22  2015/03  [Not refereed][Not invited]
  
• 協同的トムソン散乱法による無衝突衝撃波の研究

  富田健太郎, 坂和洋一, 蔵満康浩, 西川和孝, 佐藤祐太, 原由希子, 森田太智, 松清修一, 中野谷賢, 藤野亮佑, 内野喜一郎, 高部英明  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2014-  41  -42  2015/03  [Not refereed][Not invited]
  
• レーザー生成プラズマと外部磁場を用いた磁場リコネクションの研究

  森高外征雄, 坂和洋一, 佐野孝好, 原由希子, 近藤さらな, 蔵満康浩, 森田太智, 松清修一, 富田健太郎, 藤野亮佑, 山崎了, 正治圭崇, 冨田沙羅, 河村有志郎, CROWSTON R, 長嶺和慶, 米田仁紀, 高部英明  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2014-  37  -38  2015/03  [Not refereed][Not invited]
  
• 超音速対向プラズマ流による無衝突衝撃波の生成

  坂和洋一, 原由希子, 近藤さらな, 森田太智, 蔵満康浩, 佐野孝好, 森高外征雄, 西川和孝, 佐藤裕太, 富田健太郎, 内野喜一郎, 中野谷賢, 藤野亮佑, 久保聡一朗, 松清修一, 齋藤直哉, 正治圭崇, 河村有志郎, 冨田沙羅, 山崎了, 長峰和慶, 米田仁紀, 大西直文, ZHU Baojun, LI Yanfei, LI Yutong, PEI Xiaoxing, WEI Huigang, ZHONG J, CHU Hsu‐Hsin, CROWSTON R, WOOSLEY N, KOENIG M, BARROSO Patrice, MICHAUT C, ZHANG Z, 乗松孝好, 高部英明  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2014-  39  -40  2015/03  [Not refereed][Not invited]
  
• Laboratory astrophysics experiments using large-scale laser systems: Collisionless shock generation

  坂和洋一, PARK H.-S., GREGORI G., SPITKOVSKY A., FIUZA F., HUNTINGTON C., ROSS J. S., RYUTOV D. D., POLLOCK B. B., REMINGTON B., WEBER S. V., TURNBULL D. P., MEINECKE J., LEVY M. C., ZYLSTRA A. B., LI C. K., RINDERKNECHT H., ZYLSTRA A., PETRASSO R., KUGLAND N. L., DRAKE R. P., KURANZ C., FROULA D. H., REGAN S., ROSENBERG M., LAMB D., TZEFERACOS P., WOOLSEY N., KOENIG M., 原由希子, 下河原浩志, 森田太智, 富田健太郎, 松清修一, 山崎了, 蔵満康浩, 森高外征雄, 加藤恒彦, 佐野孝好, 高部英明  プラズマ・核融合学会年会(Web)  32nd-  2015
• 協同的トムソン散乱法を用いたSF₆ガス吹付けアークの減衰過程研究 (放電 静止器 開閉保護合同研究会・アークプラズマ・電気接点とその応用)

  富田 健太郎, 清水 陽大, 内野 喜一郎, 中野 智之, 田中 康規, 鈴木 克己, 飯島 崇文, 内井 敏之, 新海 健  電気学会研究会資料. SA  2014-  (45)  7  -11  2014/06/09
• A Fundamental Investigation on a Decaying Gas-Blast Arcs in a Nozzle using Power Semiconductors

  田中 康規, 中野 智之, 石島 達夫, 上杉 喜彦, 清水 陽大, 富田 健太郎, 内野 喜一郎, 鈴木 克巳, 飯島 崇文, 新海 健  電気学会研究会資料. SA  2014-  (45)  1  -6  2014/06/09
• 高出力レーザー生成無衝突衝撃波のトムソン散乱計測

  坂和洋一, 山浦裕太, 森田太智, 石川大志, 和田垣智也, 佐野孝好, 森高外征雄, ZHANG Z, 佐藤裕太, 下田諒, 富田健太郎, 内野喜一郎, 諌山翔伍, 藤野亮佑, 大山達也, 原田大輔, 松清修一, 長峰和慶, 米田仁紀, 大西直文, 水田晃, YUAN D., LI Y, ZHANG K, ZHONG J, CROWSTON R, WOOLSEY N, PELKA A, KOENIG M, YURCHAK R, MICHAUT C, BARROSO P, 蔵満康浩, 高部英明  日本物理学会講演概要集  69-  (1)  272  -272  2014/03/05  [Not refereed][Not invited]
  
• 球対称プラズマを用いたBEUV光源データベースの構築

  吉田健祐, 藤岡慎介, 東口武史, 鵜篭照之, 田中のぞみ, 川崎将人, 鈴木悠平, 大橋隼人, 鈴木千尋, 富田健太郎, 廣瀬僚一, 江島丈雄, 錦野将元, SCALLY Enda, O’SULLIVAN Gerard, 西村博明, 疇地宏  応用物理学会春季学術講演会講演予稿集(CD-ROM)  61st-  ROMBUNNO.18P-F1-12  2014/03/03  [Not refereed][Not invited]
  
• 激光XII号レーザーを用いたEUV‐BEUV光源プラズマデータベースの構築

  東口武史, 藤岡慎介, 鵜篭輝之, 吉田健祐, 田中のぞみ, 鈴木悠平, 川崎将人, 大橋隼人, 江島丈雄, 廣瀬僚一, 鈴木千尋, 富田健太郎, 砂原淳, 錦野将元  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2013-  47  -48  2014/03  [Not refereed][Not invited]
  
• 協同的トムソン散乱法による無衝突衝撃波の研究

  富田健太郎, 坂和洋一, 蔵満康浩, 森田太智, 下田諒  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2013-  9  -10  2014/03  [Not refereed][Not invited]
  
• レーザー生成プラズマと外部磁場を用いた磁気リコネクションの研究

  森高外征雄, 坂和洋一, 蔵満康浩, 森田太智, 石川大志, 山浦佑太, 富田健太郎, 佐野孝好, 和田垣智也, 松清修一, 山崎了, 星野真弘, 高部英明  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2013-  29  -30  2014/03  [Not refereed][Not invited]
  
• レーザー生成プラズマ中における磁場の計測

  森田太智, 坂和洋一, 坂和洋一, 石川大志, 山浦祐太, 佐野孝好, 森高外征雄, 富田健太郎, 下田諒, 佐藤裕太, 松清修一, 諌山翔伍, 原田大輔, 大山達也, 藤野亮佑, 蔵満康浩, 米田仁紀, 長嶺和慶, KOENIG Michel, YURCHAK Roman, MICHAUT Claire, WOOLSEY Nigel, CROWSTON Robert, PELKA Alexander, LI Yutong, YUAN Dawei, YIN Chuanlei, ZHONG Jiayong, ZHANG Kai, 高部英明, 高部英明  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2013-  23  -24  2014/03  [Not refereed][Not invited]
  
• 超音速対向プラズマ流による無衝突衝撃波の生成

  坂和洋一, 森田太智, 山浦裕太, 石川大志, 和田垣智也, 蔵満康浩, 佐野孝好, 森高外征雄, 下田諒, 佐藤裕太, 富田健太郎, 内野喜一郎, 諌山翔伍, 藤野亮佑, 大山達也, 原田大輔, 松清修一, 長峰和慶, 米田仁紀, 大西直文, 水田晃, ZHANG Z, 乗松孝好, YIN C, YUAN D., LI Y, ZHANG K, ZHONG J, CROWSTON R, WOOLSEY N, PELKA A, YURCHAK R, KOENIG M, BOUDENNE J, MICHAUT C, 高部英明  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2013-  27  -28  2014/03  [Not refereed][Not invited]
  
• 大型レーザーを用いた無衝突衝撃波生成実験

  坂和洋一, 蔵満康浩, 森田太智, 富田健太郎, 高部英明  レーザー学会研究会報告  456th-  31  -37  2014/01/08  [Not refereed][Not invited]
  
• 球対称プラズマを用いたBEUV光源データベースの構築

  吉田健祐, 藤岡慎介, 東口武史, 鵜篭照之, 田中のぞみ, 川崎将人, 鈴木悠平, 鈴木千尋, 富田健太郎, 廣瀬僚一, 江島丈雄, 大橋隼人, 錦野将元, SCALLY Enda, O’SULLIVAN Gerard, 西村博明, 疇地宏  レーザー学会研究会報告  450th-  19  -24  2013/10/22  [Not refereed][Not invited]
  
• Diagnostics of High-Z Light Source Plasmas

  TOMITA Kentaro, UCHINO Kiichiro  プラズマ・核融合学会誌  89-  (10)  664  -668  2013/10  

  多価電離プラズマ光源の一つである,レーザー生成方式極端紫外(EUV)光源プラズマのための,協同的トムソン散乱計測システムの開発を行っている.システム構築のために,まずはレーザー生成炭素プラズマのイオン項スペクトルを計測することで,その電子密度,電子温度,イオン温度,平均イオン価数の局所値を求めた.計測用レーザーにはNd:YAGレーザー第2高調波(波長532nm)を使用した.この時,イオン項のスペクトル幅は0.3nm程度と予想される.イオン項スペクトル計測のために,高い波長分解能と迷光除去性能を有する,差分散型トリプル分光器を作製した.本計測システムを用いて,EUV光源プラズマと同様の電子密度(10^<24>-10^<25>m^<-3>),電子温度(30-50eV)の炭素プラズマに対して,トムソン散乱計測が可能なことを示した.炭素プラズマの計測結果を基に,実際のEUV光源で使用されるスズプラズマのための新たな分光器の開発を行っている.
• Collective Thomson scattering measurements of Laser-produced Sn plasmas for EUV light sources

  SHIMODA Ryo, NISHIKAWA Kazutaka, TOMITA Kentaro, UCHINO Kiichiro  電気学会研究会資料. PST, プラズマ研究会  2013-  (104)  21  -24  2013/09/05
• 球対称BEUV放射プラズマの電子密度計測

  鵜篭照之, 藤岡慎介, 吉田健祐, 田中のぞみ, 西村博明, 東口武史, 鈴木悠平, 川崎将人, 江島丈雄, 廣瀬僚一, 富田健太郎, 鈴木千尋, 大橋隼人, 錦野将元, 疇地宏  応用物理学会秋季学術講演会講演予稿集(CD-ROM)  74th-  ROMBUNNO.18P-A13-12  2013/08/31  [Not refereed][Not invited]
  
• 球対称ガドリニウムプラズマからのB‐EUV放射特性とスペクトル特性

  吉田健祐, 藤岡慎介, 東口武史, 鵜篭照之, 田中のぞみ, 川崎将人, 鈴木悠平, 鈴木千尋, 富田健太郎, 廣瀬僚一, 江島丈雄, 大橋隼人, 錦野将元, 西村博明, 疇地宏  応用物理学会秋季学術講演会講演予稿集(CD-ROM)  74th-  ROMBUNNO.18P-A13-13  2013/08/31  [Not refereed][Not invited]
  
• Results of laser experiments for collisionless shocks

  Sakawa Y., Kuramitsu Y., Morita T., Yamaura Y., Ishikawa T., Sano Y., Moritaka T., Inoue K., Shimoda R., Tomita K., Uchino K., Nagamine K., Yoneda H., Matsukiyo S., Onishi N., Mizuta A., Norimatsu T., Nishida A., Kodama, Yuan D., Li Y., Zhang K., Wang F., Zhong J., Crowston R., Woolsey N., Doyle H., Gregori G., Pelka A., Koenig M., Boudenne J., Michaut C., Spitkovsky A., Kugland N.L., Ross J.S., Park H.-S., Remington B., Takabe H.  Meeting abstracts of the Physical Society of Japan  68-  (2)  202  -202  2013/08/26
• 無衝突衝撃波のレーザー模擬実験の成果

  坂和洋一, 蔵満康浩, 森田太智, 山浦裕太, 石川大志, 佐野孝好, 森高外征雄, 井上和哉, 下田諒, 富田健太郎, 内野喜一郎, 長峰和慶, 米田仁紀, 松清修一, 大西直文, 水田晃, 乗松孝好, 西田明憲, 兒玉了祐, YUAN D., LI Y, ZHANG K, WANG F, ZHONG J, CROWSTON R, WOOLSEY N, DOYLE H, GREGORI G, PELKA A, KOENIG M, BOUDENNE J, MICHAUT C, SPITKOVSKY A, KUGLAND N.L, ROSS J.S, PARK H.‐S, REMINGTON B, 高部英明  日本物理学会講演概要集  68-  (2)  121  2013/08/26  [Not refereed][Not invited]
  
• 高出力レーザー生成プラズマ及び衝撃波のターゲット材質依存性について

  山浦佑太, 坂和洋一, 蔵満康浩, 森田太智, 石川大志, 森高外征雄, 佐野孝好, 下田亮, 富田健太郎, 内野喜一郎, 松清修一, 水田晃, 大西直文, CROWSTON R, WOOLSEY N, DOYLE H, GREGORI G, RAVASIO A, PELKA A, KOENIG M, MICHAUT C, YUAN D., LI Y, ZHANG K, ZHONG J, WANG F, 高部英明  日本物理学会講演概要集  68-  (2)  211  -211  2013/08/26  [Not refereed][Not invited]
  
• 高出力レーザーを用いたプラズマジェットのコリメーション現象の研究

  石川大志, 坂和洋一, 蔵満康浩, 森田太智, 山浦祐太, 森高外征雄, 佐藤孝好, 下田亮, 富田健太郎, 内野喜一郎, 松清修一, 水田晃, 大西直文, CROWSTON R, WOOLSEY N, DOYLC H, GREGORI G, RAVASIO A, PELKA A, KOENIG M, MICHAUT C, YUAN D., LI Y, ZHANG K, ZHONG J, WANG F, 高部英明  日本物理学会講演概要集  68-  (2)  211  -211  2013/08/26  [Not refereed][Not invited]
  
• Observation of Dynamic Behavior of Ar/SF_6 Gas-Blast Arc Confined by a Nozzle under Free Recovery Condition using a High Speed Video Camera

  TANAKA Yasunori, KAMIMAE Ryo, ISHIJIMA Tatsuo, UESUGI Yoshihiko, TOMITA Kentaro, UCHINO Kiichiro, SUZUKI Katsumi, IIJIMA Takanori, SHINKAI Takeshi  電気学会研究会資料. ED, 放電研究会  2013-  (64)  23  -28  2013/06/24
• Measurements of Electron Density and Electron Temperature in a Decay Process of Ar/SF_6 Gas-Blasted Arc Confined by a Nozzle by Using Collective Thomson Scattering

  TOMITA Kentaro, GOJIMA Daisuke, NAGAI Kazuhiko, UCHINO Kiichiro, KAMIMAE Ryo, TANAKA Yasunori, SUZUKI Katsumi  電気学会研究会資料. ED, 放電研究会  2013-  (64)  47  -51  2013/06/24
• 29pEA-1 Experimental study on high Mach number collisionless shocks

  Kuramitsu Y., Sakawa Y., Morita T., Moritaka T., Sano T., Tomita K., Uchino K., Matsukiyo S., Mizuta A., Ohnishi N., Takabe H.  Meeting abstracts of the Physical Society of Japan  68-  (1)  307  -307  2013/03/26
• 29pEA-2 Thomson scattering measurement of collisionless shocks

  Sakawa Y., Kuramitsu Y., Morita T., Yamaura Y., Ishikawa T., Tomita K., Inoue K., Shimoda R., Uchino K., Moritaka T., Sano T., Takabe H.  Meeting abstracts of the Physical Society of Japan  68-  (1)  307  -307  2013/03/26
• 高マッハ数無衝突衝撃波の実験的研究

  蔵満康浩, 坂和洋一, 森田太智, 森高外征雄, 佐野孝好, 富田健太郎, 内野喜一郎, 松清修一, 水田晃, 大西直文, 高部英明  日本物理学会講演概要集  68-  (1)  307  2013/03/05  [Not refereed][Not invited]
  
• 無衝突衝撃波のトムソン散乱計測

  坂和洋一, 蔵満康浩, 森田太智, 山浦佑太, 石川大志, 富田健太郎, 井上和哉, 下田諒, 内野喜一郎, 森高外征雄, 佐野孝好, 高部英明  日本物理学会講演概要集  68-  (1)  307  2013/03/05  [Not refereed][Not invited]
  
• 協同的トムソン散乱法による無衝突衝撃波の研究

  富田健太郎, 坂和洋一, 蔵満康浩, 森田太智, 井上和哉, 井手張良, 坪内邦男  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2012-  11  -12  2013/03  [Not refereed][Not invited]
  
• 高出力レーザーによって生成された高速対向プラズマ流による無衝突衝撃波の生成

  坂和洋一, 蔵満康浩, 森田太智, 山浦裕太, 石川大志, 佐野孝好, 森高外征雄, 井上和哉, 下田諒, 富田健太郎, 内野喜一郎, 長峰和慶, 米田仁紀, 松清修一, 大西直文, 水田晃, 乗松孝好, 西田明憲, 兒玉了祐, YUAN D., LI Y, ZHANG K, WANG F, ZHONG J, CROWSTON R, WOOSLEY N, DOYLE H, GREGORI G, PELKA A, KOENIG M, BOUDENNE J, MICHAUT C, 高部英明  大阪大学レーザーエネルギー学研究センター共同利用・共同研究成果報告書  2012-  24  -25  2013/03  [Not refereed][Not invited]
  
• Measurements of electron density and electron temperature of arc discharge plasmas containing metallic vapors using laser thomson scattering

  Kentaro Tomita, Shinya Yoshitake, Kiichiro Uchino, Daigo Takenaka, Hiroaki Toda, Masayuki Hikita, Katsumi Suzuki  IEEJ Transactions on Fundamentals and Materials  133-  (9)  458  -464  2013  [Not refereed][Not invited]
   

  Laser Thomson scattering (LTS) has been applied to arc discharges generated in the atmospheric air to measure electron density (ne) and electron temperature (Te). As electrode materials, tungsten and tungsten-copper (30%) were used. The electrode gap was 0.8 mm and its diameter was 1 mm. The applied voltage was 6 kV, the peak current was 600 A and the decay time of the voltage and the current was 25 μs. Spatiotemporal evolutions of ne and Te were measured at 10 μs, 30 μs and 50 μs after the discharge initiation. At these times, obtained values of n e and Te were estimated to be in the ranges of (0.8 -2.0)×1023 m-3 and 1.0 -2.2 eV, respectively. These values were consistent with those evaluated from Saha's thermodynamic equation at 1 atm. It was also found that the decay of the arc discharge produced using the tungsten-copper electrodes was much faster than that produced using the tungsten electrodes. © 2013 The Institute of Electrical Engineers of Japan.
• 電子の運動論効果による磁気リコネクション

  蔵満康浩, 坂和洋一, 森田太智, 森高外征雄, 富田健太郎, 内野喜一郎, 星野真弘, 高部英明  日本物理学会講演概要集  67-  (2)  206  2012/08/24  [Not refereed][Not invited]
  
• Studies of Arc Discharges in Gas Circuit Breakers using Collective Thomson Scattering

  TOMITA Kentaro, GOJIMA Daisuke, UCHINO Kiichiro, HIKITA Masayuki, TAKENAKA Daigo, TODA Hiroaki, SUZUKI Katsumi, UCHII Toshiyuki  電気学会研究会資料. SA, 静止器研究会  2012-  (54)  53  -58  2012/06/25
• 26pYC-9 High Mach-number shock-shock interaction in laser-produced plaamas

  Morita Taichi, Nihida Akinori, Norimatsu Takayoshi, Tomita Kentaro, Uchino Kiichiro, Namiki Tomonori, Yoneda Hitoki, Takabe Hideaki, Sakawa Youichi, Kuramitsu Yasuhiro, Ide Takao, Nishio Kento, Kuwada Misa, Ide Harunaga, Tsubouchi Kunio, Shimazaki Seiichi  Meeting Abstracts of the Physical Society of Japan  67-  (0)  276  -276  2012  [Not refereed][Not invited]
  
• Thomson Scattering Measurements of Arc Discharge Plasmas Containing Metallic Vapor

  TAKENAKA Daigo, HIKITA Masayuki, YOSHITAKE Shinya, TOMITA Kentarou, UCHINO Kiichirou, TODA Hiroaki, SUZUKI Katsumi  電気学会研究会資料. SP, 開閉保護研究会  2011-  (19)  173  -177  2011/11/10
• Collective Thomson Scattering Diagnostics of Laser Produced Plasmas

  TOMITA K., UCHINO K.  レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  418-  51  -54  2011/09/12
• Measurements of electron density and electron temperature of arc discharges containing metallic vapors using Thomson scattering

  TAKENAKA Daigo, TODA Hiroaki, HIKITA Masayuki, YOSHITAKE Shinya, TOMITA Kentarou, UCHINO Kiichirou, SUZUKI Katsumi  電気学会研究会資料. ED, 放電研究会  2011-  (55)  19  -23  2011/07/04
• Thomson scattering diagnostics of micro-plasmas for plasma display panel

  Kiichiro Uchino, Yasushi Sonoda, Kentaro Tomita  Proceedings of International Meeting on Information Display  275  -276  2010/12/01  [Not refereed][Not invited]
   

  Laser Thomson scattering (LTS) has been applied to diagnostics of PDP micro-plasmas and revealed electron density ne to be of the order of 1019-1020 m-3 and electron temperature T e to be around 1-2 eV. Furthermore, ne and Te spatial profiles and their temporal changes have been successfully measured and their features have been discussed in connection with the striation phenomenon. In order to assist the development of PDP with high efficiency, LTS is tried to apply to study the structure of PDP discharges with narrow electrodes. Also, the streamer discharges which might give ultimate high efficiency are being examined.
• Thomson Scattering Diagnostics of Discharge Plasmas

  Kiichiro Uchino, Kentaro Tomita  Industrial Plasma Technology: Applications from Environmental to Energy Technologies  385  -397  2010/10/07  [Not refereed][Not invited]
  
• Measurement of Electron Temperature and Electronic Density of the Atmosphere Arc with Collective Thomson Scattering Measuring System

  TAKENAKA Daigo, TODA Hiroaki, HIKITA Masayuki, SUZUKI Katsumi, TOMITA Kentarou, UCHINO Kiichirou  電気学会研究会資料. ED, 放電研究会  2010-  (34)  15  -18  2010/06/28
• Thomson scattering diagnostics of high pressure plasmas and plasma disturbances by lasers

  Kentaro Tomita, Safwat Hassaballa, Kiichiro Uchino  IEEJ Transactions on Fundamentals and Materials  130-  (12)  8  -1104  2010  [Not refereed][Not invited]
   

  Laser Thomson scattering (LTS) has been developed to diagnose high pressure plasmas such as a discharge plasma produced in the plasma display panel (PDP) and a laser produced plasma for the extreme ultra-violet light source. In the LTS diagnostics of the high pressure plasmas, plasma disturbances caused by lasers have to be paid much attention. For the case of PDP plasmas, the multi-photon absorption ionization of Xe atoms at the ground state and the meta-stable states can be the obstacle for the diagnostics. This was shown to be solved by using an infrared laser as a light source of LTS and adjusting the laser power density to be in the linear signal range. For the case of the laser produced plasma, electron heating by absorbing energy of the diagnostic laser beam can be a problem. In order to know the phenomenon quantitatively, increases of electron temperature were measured as a function of the laser energy. Measured results were compared with calculations based on the model taking account of the energy absorption by the process of inverse bremsstrahlung and the heat diffusion to the volume surrounding the laser beam during the laser pulse. Both results agreed well if the electron heating is less than a few tens of percent of the electron temperature. This shows that the model can quantitatively evaluate the electron heating. © 2010 The Institute of Electrical Engineers of Japan.
• Thomson Scattering with Measuring the Conductance Decaying Process System of Arc Plasma in Gas Circuit Breaker

  TAKENAKA Daigo, HARADA Katuhiko, OHTSUKA Shinya, HIKITA Masayuki, TODA Hiroaki, IKEDA Hisatoshi, SUZUKI Katsumi, UCHINO Kiichirou, TOMITA Kentarou  電気学会研究会資料. ED, 放電研究会  2009-  (152)  19  -23  2009/11/19
• Dependence of electron temperature and number density on magnetic field strength in an ion thruster by laser Thomson scattering

  江崎 徹, 小谷優介, 鶴哲平, 山本直嗣, 中島秀紀, 富田健太郎, 山崎尚人, 内野喜一郎  プラズマ応用科学  17-  (1)  21  -26  2009  [Not refereed][Not invited]
  
• Plasma property measurement in a miniature microwave discharge ion thruster by laser Thomson scattering

  Naoji Yamamoto, Shmya Kondo, Teppei Tsuru, Hideki Nakashima, Amane Majima, Naoto Yamasaki, Kentaro Tomita, Knchiro Uchino  44th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit  2008/12/01  [Not refereed][Not invited]
   

  For understanding the mechanism of plasma production and loss in a miniature microwave discharge ion thruster, plasma parameters, electron number density and electron energy distribution function, in a miniature microwave discharge ion thruster were successfully measured by means of laser Thomson scattering. A photon counting method and a double monochromator were used against small Thomson scattering signal and strong stray laser light. The result shows an electron energy distribution function is Maxwellian, since the scattered spectrum can be fitted by Gaussian at the temperature of 1.5 eV. An electron number density is 2.3 × 1018m-3The measured electron number density and electron temperature values were found to be reasonable compared with estimation deduced form extracted ion beam current. © 2008 by the American Institute of Aeronautics and Astronautics, Inc.
• Diagnostics of PDP Micro-discharge Plasmas Using Infrared Laser Thomson Scattering

  SONODA Yasushi, AKUNE Akihiko, TOMITA Kentaro, SAFWAT Hassaballa, UCHINO Kiichiro, ISHII Keiji, HIRANO Yoshikuni, MURAKAMI Yukio  IEICE technical report  107-  (453)  117  -120  2008/01/17  

  In order to avoid laser perturbations for Xe containing discharges, the laser Thomson scattering (LTS) system having an infrared laser at a wavelength of 1064nm as a light source has been developed. The basic behavior of electrons in the Ne/Xe discharges was investigated by using the infrared LTS system. Furthermore, it was demonstrated that the measurement of the electron energy distribution function was possible up to the electron energy corresponding to the excitation energy of the Xe atom.
• Diagnostics of PDP micro-discharge plasmas using infrared laser Thomson scattering

  園田 靖, 阿久根 明彦, 富田 健太郎  ITE technical report  32-  (4)  117  -120  2008/01
• Diagnostics of PDP micro-discharge plasmas using infrared laser thomson scattering system

  Y. Sonoda, A. Akune, K. Tomita, S. Hassaballa, K. Uchino, K. Ishii, Y. Hirano, Y. Murakami  IDW '07 - Proceedings of the 14th International Display Workshops  2-  861  -864  2007/12/01  [Not refereed][Not invited]
   

  In order to avoid laser perturbations for Xe containing discharges, the laser Thomson scattering (LTS) system having an infrared laser at a wavelength of 1064 nm as a light source has been developed. The basic behavior of electrons in the Ne/Xe discharges was investigated by using the infrared LTS system. Furthermore, it was demonstrated that the measurement of the electron energy distribution function was possible up to the electron energy corresponding to the excitation energy of the Xe atom.
• Laser Scattering Diagnostics of Discharge Plasmas

  UCHINO K., TOMITA K., SONODA Y.  レーザー学会研究会報告 = Reports on the Topical meeting of the Laser Society of Japan  365-  43  -47  2007/09/14
• Characterization of Z-pinch plasmas for EUV light sources

  S. Katsuki, H. Imamura, S. Akiyoshi, T. Namihira, T. Sakugawa, H. Akiyama, K. Tomita, K. Uchino  Digest of Technical Papers-IEEE International Pulsed Power Conference  864  -867  2007  [Not refereed][Not invited]
   

  This paper describes the characterization of Z-pinch xenon plasmas for EUV sources. The plasmas were driven by a 15 J pulsed power generator, which delivers pulsed currents (35 kA, 120 ns) to the short circuit load. We have developed a time-resolved interferogram and a Thomson scattering system to characterize the Z-pinch plasmas. The interferogram using a pulsed Nd:YAG laser (532 nm, 7 ns) shows the temporal development of the radial profile of electron density. The electron density in the core plasma during pinch phase was 1.2 × 1019 cm-3. Preliminary result of the Thomson scattering measurement shows the electron temperature and density at the decay phase of the pinch process were 5.5 eV and 3 × 1017 cm -3, respectively. © 2005 IEEE.

Presentations

• Observation of two-dimensional plasma flows toward higher temperature regions in laser produced tin plasmas for extreme ultraviolet (EUV) light sources  [Invited]

  Kentaro Tomita, Yiming Pan, Atsushi Sunahara, Katsunobu Nishihara

  14th International Symposium on Advanced Plasma Science and its Applications for Nitrides and Nanomaterials (ISPlasma2022)  2022/03
• Thomson scattering studies of atmospheric-air streamer discharges and Extreme-ultraviolet (EUV) light sources  [Invited]

  Kentaro Tomita

  The 39th Symposium on Plasma Processing (SPP-39)  2022/01
• Recent progress of laser Thomson scattering studies for industrial plasmas -Measurements of EEDF of air-streamer discharge and 2D velocity field in laser produced EUV sources-  [Invited]

  Kentaro Tomita

  The 12th Asia-Pacific International Symposium on the Basics and Applications of Plasma Technology (APSPT-12)  2021/12
• Recent Studies of Industrial Plasmas using Laser Scattering  [Invited]

  Kentaro Tomita

  日本物理学会 2021年秋季大会  2021/09
• Thomson scattering diagnostics of EUV source plasmas and EUV induced hydrogen plasmas  [Invited]

  Kentaro Tomita

  EUV source workshop2020  2020/11
• Thomson scattering diagnostics of a streamer discharge in atmospheric-pressure air and laser-produced plasmas for light sources  [Invited]

  Kentaro Tomita

  Gaseous Electronics Conference (GEC)  2020/10
• Observation of the whole Thomson scattering spectrum of laser produced plasma for EUV and soft X-ray light sources  [Invited]

  K. Tomita, F. Ito, J. Hotta, K. Uchino

  The 19th LASER AIDED PLASMA DIAGNOSTICS 2019  2019/09
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• [プラズマエレクトロニクス賞受賞記念講演] 極端紫外および軟X線光源用多価電離プラズマの協同的トムソン散乱計測 - 点光源を空間分解計測する -  [Invited]

  Kentaro Tomita

  応用物理学会、2018年9月19日、名古屋国際会議場、愛知  2019/03
• レーザープラズマX線源のプラズマパラメータ計測  [Invited]

  Kentaro Tomita

  物理学会年次大会、領域2シンポジウム、レーザープラズマX線源の物理と応用、九州大学、福岡、2019年、3月15日  2019/03
• In-situ plasma diagnostics using optically-trapped fine particles  [Invited]

  Kentaro Tomita

  International symposium on Frontier of Nano-Materials Based on Advanced Plasma Technologies, MRS-J,Annual meeting, C3-I18-005, 18th, Nov., Kitakyushu, Fukuoka, Japan  2018/12
• optical diagnostics of nano-second pulsed discharges produced in atmosphere  [Invited]

  Kentaro Tomita

  Lecture at the Department of Materials Sciend and Engineering, Feng Chia University, Taiwan, Nov. 17th, 2018, Taichung, Taiwan  2018/11
• Two-dimensional Profiles of Electron Density and Temperature in Laser-produced Sn Plasmas for Extreme-ultraviolet (EUV) light sources  [Invited]

  Kentaro Tomita

  2nd Asia-Pacific Conference on Plasma Physics, Nov. 14th,11.2018, Kanazawa, Japan  2018/11
• Studies of EUV light source plasmas using laser Thomson scattering  [Invited]

  Kentaro Tomita

  Plasma Engineering Forum of MRS-T, Nov. 17th, 2018, Taichung, Taiwan  2018/11
• Introduction to plasma diagnostics”,  [Invited]

  Kentaro Tomita

  Workshop for the Applications of Plasma Technology, Ming Chi University of Technology, New Taipei City, Taiwan, 29th Oct. 2018.  2018/10
• 先端計測で明らかとなったEUV露光光源用プラズマの詳細構造 - 中空様密度構造が実現する4%変換効率 -  [Invited]

  Kentaro Tomita

  日本学術振興会第153委員会研究会 テーマ：『高密度プラズマの計測技術 〜高密度プラズマの物理現象の見える化技術〜』, 2018年1月18日  2018/01
• Diagnostics of extreme-ultraviolet (EUV) light source plasmas for next generation semiconductor lithography  [Invited]

  Kentaro Tomita

  International Symposium in 27th Annual Meeting of MRS-J, Yokohama, Japan, 2017.12  2017/12
• Two-dimensional electron density and temperature profiles of EUV light sources with 4.0% CE  [Invited]

  Kentaro Tomita

  International workshop on EUV and Soft X-ray sources (2017 source workshop), Dublin, Ireland, 2017.11  2017/11
• Two-dimensional profiles of electron density and temperature of laser-produced tin microplasmas for extreme-ultraviolet lithography light sources  [Invited]

  Kentaro Tomita

  International Workshop on Microplasmas (IWM2017), Garmisch-Partenkirchen, Germany, 2017.6  2017/06
• レーザー計測で切り拓く実験室宇宙物理研究  [Invited]

  Kentaro Tomita

  レーザー学会学術講演会第37回年次大会, 徳島, 2017年1月9日  2017/01
• Collective Thomson scattering diagnostics for industrial plasmas  [Invited]

  Kentaro Tomita

  Joint 13th Asia Pacific Physics Conference and 22nd Australian Institute of Physics Congress (APPC-AIP), Brisbane, Australia, 2016.12  2016/12
• Correlation of Fundamental Plasma Parameters with EUV Emission Profiles of Laser-produced Sn Plasmas for EUV Lithography Light Sources  [Invited]

  Kentaro Tomita

  International Workshop on EUV and Soft X-Ray Sources (2016 Source Workshop), Amsterdam, The Netherlands, 2016.11  2016/11
• プラズマ診断・計測  [Invited]

  Kentaro Tomita

  第10回プラズマエレクトロニクスインキュベーションホール、2016年8月31日、国立中央青少年交流の家、静岡県  2016/08
• Diagnostics of laser-produced EUV light source plasmas using collective Thomson scattering  [Invited]

  Kentaro Tomita

  The 13th Asia-Pacific Conference on Plasma Science and Technology (APCPST), Shanghai, China, 2016.5  2016/05
• 高気圧プラズマへのトムソン散乱法の適用とレーザー擾乱の検討  [Invited]

  Kentaro Tomita

  日本物理学会第71回年次大会（2016年）, 領域2シンポジウム「プラズマ診断のための能動的光計測の新展開」, 宮城, 2016年3月  2016/03
• 協同的トムソン散乱によるレーザー生成EUV光源プラズマの電子密度・電子温度・イオン価数計測  [Invited]

  Kentaro Tomita

  第36回レーザー学会年次大会, 愛知, 2016.1  2016/01
• Studies of Laser-produced Tin plasmas for EUV Light Sources using Collective Thomson Scattering  [Invited]

  Kentaro Tomita

  2015 International workshop on EUV and Soft X-ray sources, Dublin, Ireland, 2015.11  2015/11
• Collective Thomson scattering diagnostics of laser-produced plasmas with moderate temperature  [Invited]

  Kentaro Tomita

  17th International Symposium on Laser-Aided Plasma Diagnostics, Sapporo, Hokkaido, Japan, 2015.10  2015/10
• Thomson scattering diagnostics of atmospheric pressure plasmas - Pulsed filament discharges and plasma jets -  [Invited]

  Kentaro Tomita

  68th GEC / ICRP-9, Honolulu, Hawaii, USA, 2015.10  2015/10
• 激光 XII 号レーザーへの協同トムソン散乱法の適用  [Invited]

  Kentaro Tomita

  レーザー研シンポジウム2015−平成26年度共同研究成果報告会−, 大阪大学吹田キャンパス銀杏会館、2015.4.8-9  2015/03
• 高気圧プラズマのレーザー散乱計測  [Invited]

  Kentaro Tomita

  静電気学会計測研究委員会、広島国際大学 呉キャンパス 1号館3階1305教室、2014年9月9日  2014/09
• 協同的トムソン散乱法による大気圧減衰アークの電子密度・電子温度測定  [Invited]

  Kentaro Tomita

  電気学会北陸支部シンポジウム, 石川, 2013.3.6.  2013/03
• Thomson scattering diagnostics of atmospheric pressure plasmas generated with ionic liquid electrode  [Invited]

  Kentaro Tomita

  The 6th International Conference on Plasma Nano Technology and Science, Gifu, Japan, 2013.2  2013/02
• トムソン散乱法を用いた大気圧フィラメント放電の研究  [Invited]

  Kentaro Tomita

  応用物理学会第11回プラズマエレクトロニクス新領域研究会「光・レーザーによるプラズマ計測の最前線」, 大分, 2012.11  2012/11
• 協同的トムソン散乱によるレーザー生成EUVプラズマ診断  [Invited]

  Kentaro Tomita

  レーザー学会専門委員会「レーザー駆動XUV〜X線の産業応用専門委員会」, 東京, 2012.6.20.  2012/06
• レーザー散乱法を用いたプラズマ計測  [Invited]

  Kentaro Tomita

  第8回日本真空学会スパッタリングおよびプラズマプロセスに関する技術交流会, 東京, 2011.12  2011/12
• Thomson scattering diagnostics of a pulsed discharge produced at around atmospheric pressure  [Invited]

  Kentaro Tomita

  15th International symposium of laser-aided plasma diagnostics, Jeju, Korea, 2011.10  2011/10
• Studies of Pulsed Filament Discharges Produced in Near-Atmospheric Pressure Using Laser Thomson Scattering  [Invited]

  Kentaro Tomita

  the 12th international workshop on advanced plasma precessing and diagnostics, Fukuoka, Japan, 2011.1  2011/01
• 「プラズマエレクトロニクスへの要望と期待 ?若手研究者からの声?」第6回プラズマ応用技術の将来ビジョン研究会「プラズマエレクトロニクスの将来研究」  [Invited]

  Kentaro Tomita

  応用物理学会プラズマエレクトロニクス分科会, 東京, 2006.2.6.  2006/02

Research Projects

• 大気圧直流グロー放電生成時に観測される発光の自己組織化メカニズムの解明

  日本学術振興会：科学研究費助成事業

  Date (from‐to) : 2023/04 -2027/03 

  Author : 白井 直機, 佐々木 浩一, 富田 健太郎
• Collisionless shock generation and particle acceleration using power laser

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2022/04 -2026/03 

  Author : 坂和 洋一, 松清 修一, 森田 太智, 富田 健太郎, Morace Alessio, 竹崎 太智, 福田 祐仁, 山崎 了
• Mechanism elucidation of spatio-temporal structure formation of sheath fluctuation using optically trapped fine particles in plasmas

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2020/04 -2024/03 

  Author : 白谷 正治, 小林 達哉, 布村 正太, 石川 健治, 鎌滝 晋礼, 富田 健太郎

   

  シース電場の時空間構造揺らぎ形成機構の解明とこの電場揺らぎとエッチング形状揺らぎの関係解明を目的とする本研究では、4年間の研究期間において次の2項目について明らかにする。1)光捕捉微粒子を用いた低侵襲・超高感度電場計測法によるシース電場の時空間揺らぎ計測・解析(1-3年目)。2)高アスペクト比構造を用いた入射イオンの振る舞い解析(3-4年目)。2年目（2021年度）は、3次元計測用プラズマ装置の製作を行うとともに、電場計測の定量評価に最も重要である、電場較正を行い、光線光学モデルによる力の計算のとのずれは約3%であり高い精度でレーザー光による力が計算できることが確認できた。次にレーザーパワーをパラメータとして光捕捉微粒子を電極に対して水平方向に100μmごとに移動したところ、微粒子の電極に対して垂直方向（z方向）の位置は、バルクプラズマ方向へ移動した。またレーザーパワーを増加させるとレーザーの垂直方向の力の増加により微粒子のz方向の位置がバルクプラズマ側へシフトし光捕捉力の増加により微粒子が光捕捉から離脱するまでに水平移動させることができる距離が増加した。 また、力のつり合いから、各微粒子位置における垂直方向と水平方向の電場強度EzとErを評価し、zr平面における電場ベクトルの空間分布を評価することに成功した。 次に、プラズマ中光捕捉微粒子の位置揺動からプラズマ電場揺動を求めた。電場強度、電場揺動はプラズマ中の位置に強く依存し、水平方向の電場強度が強くなる位置では,水平方向の電場揺動が大きくなる傾向にあることを明らかにした。
• 協同的トムソン散乱法を用いた多価電離プラズマ生成条件と放射スペクトルの関係解明

  日本学術振興会：科学研究費助成事業 基盤研究(B)

  Date (from‐to) : 2020/04 -2023/03 

  Author : 富田 健太郎

   

  本申請に至るまでの事前の研究活動により、光源用多価電離プラズマ、特に波長13.5nmを利用する極端紫外光源用プラズマについては、プラズマ状態と光出力が定量的に関連付けられる可能性が見いだされた。ただし計測結果はわずか数例の実験条件しかない（液滴スズドロップレット装置を用いたプラズマ生成に、共同研究先企業の装置が必要だったため、限られたマシンタイムでの計測であった）。 このような背景のもと、本研究の目的は、様々なプラズマ生成条件にて、微小（1mm以下）・短命（30ns以下）な光源プラズマの物理パラメータ（電子密度や電子温度）の時間及び空間分解計測を行い、プラズマ生成条件と光出力の定量的な関連付けを可能とすること、と位置付けた。計測手法として協同的トムソン散乱法（主としてイオン項スペクトルの計測）を用いる。本研究の学術的独自性・創造性は、計算・シミュレーションを用いず、実験のみで光源プラズマの物理解明に必要な物理量（ne, Te, Ti, Z）の詳細な空間分布・時間変化を明らかにする点である。 本申請の2年目（2021年度）は、プラズマを生成するための固体ターゲット種を様々に変更し（C, Al）、レーザーパワー密度依存性（10^9-10^11W/cm^2）など、種々の実験条件でトムソン散乱計測を行うことを計画した。トムソン散乱計測では、予定していた炭素、アルミに加え、銅及びスズターゲットでプラズマを生成した。炭素ターゲットについては、電子密度・電子温度に加え、プラズマの流れ（ドリフト速度）の時間・空間変化を、計測した。これらの結果を、1次元アブレーションモデルと比較した。対象とするレーザーパワー密度において、レーザー照射中のプラズマ挙動が得られたのは本研究が初めてであり、モデルと実験の比較が初めて可能となった。現在、結果を論文として投稿する準備を行っている。
• Proposal of Laser-Detonated Shock Tube and Improvement of Heating Prediction Accuracy of Atmospheric Entry Capsule with Precursor Radiation

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2019/04 -2022/03 

  Author : 葛山 浩, 富田 健太郎

   

  本研究では、「①超高速突入環境を模擬できるレーザー爆轟式の革新的衝撃波管、②レーザートムソン散乱（LTS）法による先行電子の高精度計測」を提案し、その実用性・性能を評価することを目的としている。本年度（R2年度）は、昨年度（R1年度）末に納入されたTEA-CO2パルスレーザーを用いて、レーザー爆轟波の駆動およびLTS計測を実施する予定であったが、納品直後にパルスレーザーに不具合が発生したため、本年度（R2年度）6月からレーザーはメーカー（海外）に引き取られ、修理及び調整を行っている。コロナ禍の影響もあり、メーカーとのやり取りに非常に時間を要しているが、ようやく返却の目途が見え、現在、次年度（R3年度）7月の再納入を目指してメーカーと調整中である。一方で、爆轟波駆動系、LTS計測系、および同時に実施する自発光・分光計測系の構築はほぼ完了しており、レーザー返却後にすぐに実験ができる状態にある。このように、本年度もレーザー爆轟波の駆動試験は実施できなかったが、爆轟波のLTS計測では非定常計測（一発撮り）が必要となるため、アーク風洞において、LTS計測の一発撮りの試験を行い、計測ノウハウの蓄積を行った。結果は良好であり、密度10^19 m^-3および温度5,000 K程度のアークプラズマ電子を一発撮りすることに成功しており、同様の物理量を持つレーザー爆轟波の先行電子を確実に捕捉できることが示唆された。また、レーザー爆轟波の数値解析において、レーザーカットオフ現象と計算格子依存性を調べ、本実験をシミュレートする際に必要となる格子解像度を明らかにし、次年度の実験を検証するうえで、重要な知見を得た。
• Understanding of anomalous transport in Hall thrusters

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)

  Date (from‐to) : 2018/04 -2022/03 

  Author : Yamamoto Naoji

   

  To understand anomalous electron transport in a Hall thruster, plasma turbulence inside the acceleration channel was observed using a E-band microwave interferometer. The dependence of the amplitude of the turbulence on magnetic flux density, and the relations between the turbulence and other plasma perturbations and between the turbulence and the discharge current, were investigated through power spectral density and bi-coherence analysis. The turbulence has a positive relation to the discharge current, leads to anomalous electron transport inside the acceleration channel, and is coupled with ionization instability. Low frequency perturbations (several hundred Hertz) were observed; this low frequency perturbation could be a key to suppressing plasma turbulence. In addition, we showed usefulness of the short pulse width laser (picosecond laser) diagnostics for the measurement inside the Hall thrusters.
• High-power laser experiment of magnetized collisionless shocks

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research

  Date (from‐to) : 2018/04 -2021/03 

  Author : Yamazaki Ryo

   

  Using GXII high-power lasers in Osaka university, we generated shock waves in laboratory that are physically identical to supernova blast waves propagating into interstellar medium. In our experiment, we imposed external magnetic field with strength of about 5T, and at the same time we directly derived local plasma density and temperatures via collective Thomson scattering measurement. We firstly obtained upstream plasma at rest that is uniform and completely magnetized. Our experimental platform will help us to simply compare the experimental data with theoretical arguments of shock physics and cosmic-ray acceleration.
• Laboratory astrophysics experiments using large-scale high-intensity laser systems

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)

  Date (from‐to) : 2015/04 -2019/03 

  Author : Sakawa Youichi

   

  As generation mechanisms of high-energy charged particles or cosmic rays coming from space, acceleration by collisionless shocks, magnetic reconnection, and wakefield acceleration are strong candidates. We studied collisionless shock generation in external magnetic fields and self-generated magnetic fields by lasers, plasma-driven magnetic reconnection, and incoherent wakefield acceleration using high-power and high-intensity lasers. In the experiments, the element physics of time-evolution of collisionless shock generation and dynamics of plasmas in magnetic reconnection, etc., were clarified. In the future, it is expected that the physics of particle acceleration and the origin of cosmic rays will be approached in laser experiments.
• Development of a New Technology for Controlling the Deceleration Starting Altitude of Magnetohydrodynamic Aerobraking

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2015/04 -2018/03 

  Author : Katsurayama Hiroshi, Yamamoto Naoji, Tomita Kentaro

   

  To clarify the mechanism of the electromagnetic force generation on the magnetohydrodynamic braking in rarefied atmospheres, we conducted an arc wind tunnel experiment and its numerical simulation. Our previous analytical study has predicted that an insulating boundary in a flow is necessary to activate magnetohydrodynamic braking in a rarefied flow. To validate this analytical prediction, we investigated the dependency of the total drag on the insulating boundary location by varying the arc plume boundary location. As a result, the measured and computed total drags increase by applying the magnetic field. The computation is consistent with the analytical prediction because the total drag increases by moving the insulating boundary to the test model. However, the measured electromagnetic drag increase is insensitive to the insulating boundary location because the flow is denser than expected.
• development of ionic charge, electron density, and electron temperature measurement system for soft-X ray light sources

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (A)

  Date (from‐to) : 2015/04 -2018/03 

  Author : Tomita Kentaro

   

  Soft X-ray light source have been used for various applications, such as extreme-ultraviolet(EUV) light sources (wavelength 13.5 nm) for next-generation semiconductor lithography system and water-window light sources (wavelength 2.3-4.4 nm), Laser-produced plasma is an attractive candidate for the Sof X-ray light source, because the plasma can be easily produced by table-top laser system. In order to optimize the plasma as the soft-X-ray light sources, to measure and control fundamental plasma parameters, such as averaged ionic charge state (Z), electron density (ne), and electron temperature (Te) are prerequisite. We have developed a new measurement system to obtain these plasma parameters. In our system, both ion and electron feature spectra of collective Thomson scattering have been observed simultaneously. From these spectra, it is possible to determine Z, ne, and Te.
• Collisionless shock generation using large-scale laser systems

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2012/04 -2015/03 

  Author : SAKAWA Youichi, YONEDA Hitoki, TAKABE Hideaki, MORITAKA Toseo, TOMITA Kentaro, MORITA Taichi

   

  Collisionless shock experiments were conducted using supersonic counter-stream plasmas with parallel double-plane (DP) target. On Gekko XII HIPER laser experiment, collective Thomson scattering ion-term measurement was conducted. Electron and ion temperatures, flow velocity, electron density were measured for counter-streaming plasmas and shock, and their temporal-evolution was investigated. On OMEGA laser (USA) experiment, Weibel filaments were observed by D-3He fusion produced proton radiography. On the NIF laser (USA) experiment, DD neutrons/proton and strong x-ray emission from the hot plasmas in the middle of the two planes are observed with CD DP target. These results indicate that neutrons are produced in a shock-heated hot plasma.
• 協同的トムソン散乱法による無衝突衝撃波の研究

  大阪大学レーザーエネルギー学研究センター：大阪大学レーザーエネルギー学研究センター共同利用・共同研究

  Date (from‐to) : 2012/04 -2015/03 

  Author : 富田健太郎
• 次世代直流・交流電力システムを視野に入れたSF6・代替ガスアーク遮断現象の高精度実験および高精度数値解析 －未知なるアークプラズマ現象解明への挑戦－

  パワーアカデミー：パワーアカデミー研究助成，特別推進研究

  Date (from‐to) : 2013/12 -2014/11 

  Author : 田中康規
• ナノ界面近傍における電子状態の診断

  日本学術振興会：科学研究費助成事業 新学術領域研究(研究領域提案型)

  Date (from‐to) : 2012/04 -2014/03 

  Author : 富田 健太郎

   

  気相であるプラズマと電極等の固相間の界面は、プラズマプロセスに直接的に関わると考えられるため、これまで様々な研究が行われてきた。本研究では、低圧プロセスプラズマと、液面と接する大気圧プラズマを対象に、プラズマの電子状態診断を行った。 大気圧プラズマは、近年では固体ではなく、液体と接した状態に注目が集まっている。これは、大気圧プラズマの医療やバイオ応用を考えた時、液体とプラズマの接触が避けられないからである。しかし、液体とプラズマが接することで、プラズマの基礎物理量（電子密度や電子温度）がどのように影響を受けるかは、まだ明らかになっていない。 このような背景のもと、液体と接する大気圧プラズマ中の電子密度・電子温度を、レーザートムソン散乱法を用いて測定した。トムソン散乱法を用いたのは、液体を含まない大気圧プラズマの診断手法として、高い信頼性を有しているからである。一方、大気圧程度に密度の高いガス中に計測用レーザーを入射すると、母ガスを多光子電離してしまい、計測が不正確になる恐れがある。本研究ではそのような擾乱に配慮し、十分にレーザーパワー密度が低い領域で、計測を行った。十分に低いパワー密度では、その反面、得られるトムソン散乱光強度が微弱となり、レーザー1000ショット程度の積算計測が必須となる。そのような計測が実現できるナノ秒パルス放電と、蒸気圧が極めて低い液体材料（イオン液体）を併用することで、安定した放電生成環境の元、液体電極使用による放電状況の変化を定量的に把握した。 低圧プロセスプラズマについては、数Torrオーダーのプローブ計測が困難となる圧力のプラズマについて、トムソン散乱法が適用可能な領域を明らかにした。
• 高効率かつ低コストな次世代リソグラフィー光源開発のための評価技術の確立

  JST：JST研究成果最適展開支援プログラムA-STEP・FSステージ探索タイプ

  Date (from‐to) : 2012/12 -2013/11 

  Author : 富田健太郎
• SF6ガスに代わる遮断ガス模索のためのアーク放電特性の研究

  パワーアカデミー：パワーアカデミー研究助成・萌芽研究

  Date (from‐to) : 2012/12 -2013/11 

  Author : 富田健太郎
• Studies of arc discharges for gas circuit breakers

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

  Date (from‐to) : 2011 -2013 

  Author : TOMITA KENTARO

   

  Gas circuit breakers (GCBs) are one of the most important components for high voltage power system. For high voltage circuit breaker rated at more than 72 kV, high-pressure SF6 gas is commonly used as arc quenching medium. However, SF6 has very high global warming potential. It has thus been desired to search for alternative gases for SF6. For effective searching and/or development of such alternative gases, diagnostics of arc discharges generated inside GCBs are essentially crucial. Especially, precise measurements of electron density in a decaying arc discharge in transient state are indispensable. In order to measure electron density in arcs, in this study, laser Thomson scattering has been applied to arcs generated with several types of gases and polymer materials, which are used around electrodes. As a result of the measurement, clear differences of spatiotemporal evolutions were found for arcs generated with different conditions.
• Studies on the efficient emission mechanism of plasma display panels

  Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

  Date (from‐to) : 2009 -2011 

  Author : UCHINO Kiichiro, TOMITA Kentaro

   

  Recently, there are some reports that show the high efficacy in the ultraviolet generation form the plasma display panels(PDP). One of the factors allowing such high efficacy is the pulse width to be very short. However, the mechanism how the short pulsed discharges are related with the high efficacy is not clear. This study aims to clarify the mechanism based on the measurements of basic parameters such as electron density and electron temperature of short pulsed discharges. Measurements were performed for the dielectric discharge simulating the PDP discharge and a capacity coupled discharge(CCD). It was confirmed that the short pulsed discharges for both realized improvements in the ultraviolet generation, ant possible causes for that are discussed.
• 高効率かつ長寿命LED照明開発のための高精度リアルタイム温度計測システムの開発

  JST：JST研究成果最適展開支援プログラムA-STEP，FSステージ探索タイプ

  Date (from‐to) : 2009/08 -2010/03 

  Author : 富田健太郎