Details of the Researcher

PHOTO

Hiroyuki Takahashi
Section
Graduate School of Engineering
Job title
Senior Assistant Professor
Degree

  • 博士（工学）（東北大学）

  • 修士（工学）（東北大学）

e-Rad No.
30768982

Research History 3

  • 2023/01 - Present
    東北大学大学院 工学研究科 量子エネルギー工学専攻 講師

  • 2015/07 - Present
    東北大学大学院工学研究科　助教

  • 2015/04 - 2015/07
    東北大学大学院工学研究科　日本学術振興会特別研究員(PD)

Education 1

  • Tohoku University　Graduate School, Division of Engineering　量子エネルギー工学専攻

    - 2015/03

Committee Memberships 2

  • プラズマ・核融合学会　プラズマ・核融合学会誌編集委員

    2022/07 - 2024/06

  • 日本物理学会 領域2　領域運営委員

    2018/10 - 2020/09

Professional Memberships 2

  • The Japan Society of Plasma Science and Nuclear Fusion Research

  • The Physical Society of Japan

Research Interests 1

  • magnetically confined fusion, divertor, plasma

Research Areas 1

  • Energy / Nuclear fusion /

Awards 2

  1. プラズマ・核融合学会 第39回年会 若手学会発表賞 正会員部門

    2022/11　プラズマ・核融合学会　円形アパチャーを有したRetarding field analyzer を用いた平行および垂直方向イオン温度の同時推定

  2. 第14回核融合エネルギー連合講演会 Best Audience Award

    2022/07　核融合エネルギー連合講演会

Papers 37

  1. Estimation of Ion Density of Helium Plasma using Collisional-Radiative Models in Linear Plasma Device NUMBER Peer-reviewed

    Koki SATO, Atsushi OKAMOTO, Takaaki FUJITA, Yuichi KAWACHI, Mimami SUGIMOTO, Muneo KOIKE, Yuto YAMADA, Kota TAKEDA, Kazuhiro TORII, Hiroyuki TAKAHASHI

    Plasma and Fusion Research　20　n/a-n/a　2025/06/17

    Publisher: Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.20.1201031 　

    eISSN： 1880-6821

  2. Contribution of Hydrogen Molecular Activated Recombination to Plasma Particle Loss in DT-ALPHA Peer-reviewed

    Keigo YOSHIMURA, Hiroyuki TAKAHASHI, Ryota NISHIMURA, Tomoya HARA, Shigetaka KAGAYA, Tetsutarou OISHI, Akinobu MATSUYAMA, Kenji TOBITA

    Plasma and Fusion Research　20　n/a-n/a　2025/02/21

    Publisher: Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.20.1401015 　

    eISSN： 1880-6821

  3. Evaluation of Spatial Profile of Local Emissions from W17+–W23+ Unresolved Transition Array Spectra Peer-reviewed

    Ryota Nishimura, Tetsutarou Oishi, Izumi Murakami, Daiji Kato, Hiroyuki A. Sakaue, Hayato Ohashi, Shivam Gupta, Chihiro Suzuki, Motoshi Goto, Yasuko Kawamoto, Tomoko Kawate, Hiroyuki Takahashi, Kenji Tobita

    Atoms　13　(2)　21-21　2025/02/18

    Publisher: MDPI AG

    DOI： 10.3390/atoms13020021 　

    eISSN： 2218-2004

    More details Close

    Tungsten (W) spectroscopy has attracted significant attention because W is one of the major impurities in ITER and future DEMO reactors. W22+–W33+ spectra at 15–45 Å have been useful for impurity diagnostics. Unresolved Transition Array (UTA) spectra around 200 Å, which contain W17+–W23+, have potential for diagnostics tungsten ions in even lower charge states. Because multiple charge states overlap with very similar wavelengths, it is challenging to evaluate impurity spatial profiles from UTA spectra around 200 Å. In this study, we conducted tungsten pellet injection experiments in Large Helical Device (LHD) and attempted to evaluate the spatial profiles of UTA spectra around 200 Å, observed at 0.3–0.8 keV of central electron temperature. The results indicated that tungsten ions around W20+ were locally profiled in a radial region, reff = 0.38 m, where the local electron temperature decreases by 30% to 40% with respect to more central and outer temperatures. These results suggested that the UTA spectrum around 200 Å would be useful for diagnostics of tungsten impurities in lower charge states than the charge states contained in UTA spectra around 15–45 Å.

  4. EUV Spectra of W<sup>13+</sup> Ions in the Large Helical Device: Recent Progress in Observation of Tungsten Ions in Low to Intermediate Charge State Range for Fusion Plasma Diagnostics Peer-reviewed

    Tetsutarou OISHI, Ryota NISHIMURA, Izumi MURAKAMI, Daiji KATO, Hiroyuki A. SAKAUE, Motoshi GOTO, Yasuko KAWAMOTO, Tomoko KAWATE, Nobuyuki NAKAMURA, Hiroyuki TAKAHASHI, Kenji TOBITA

    Plasma and Fusion Research　20　2402009-2402009　2025/01/22

    Publisher: Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.20.2402009 　

    eISSN： 1880-6821

  5. Investigation of Tungsten Unresolved Transition Array Spectrum around 300Å for Fusion Plasma Diagnostics Peer-reviewed

    Ryota NISHIMURA, Tetsutarou OISHI, Izumi MURAKAMI, Daiji KATO, Hiroyuki A. SAKAUE, Gupta SHIVAM, Hayato OHASHI, Motoshi GOTO, Yasuko KAWAMOTO, Tomoko KAWATE, Chihiro SUZUKI, Hiroyuki TAKAHASHI, Kenji TOBITA

    Plasma and Fusion Research　20　2402005-2402005　2025/01/22

    Publisher: Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.20.2402005 　

    eISSN： 1880-6821

  6. Collisional-Radiative modeling of unresolved transition array spectra near 200\AA from W17+-W25+ emissions for diagnostics of ITER edge plasma Peer-reviewed

    R. Nishimura, T. Oishi, I. Murakami, D. Kato, H.A. Sakaue, S. Gupta, H. Ohashi, M. Goto, Y. Kawamoto, T. Kawate, H. Takahashi, K. Tobita

    Nuclear Materials and Energy　101740-101740　2024/09

    Publisher: Elsevier BV

    DOI： 10.1016/j.nme.2024.101740 　

    ISSN： 2352-1791

  7. Observation of tungsten emission spectra up to W46+ ions in the Large Helical Device and contribution to the study of high-Z impurity transport in fusion plasmas

    Tetsutarou Oishi, Shigeru Morita, Daiji Kato, Izumi Murakami, Hiroyuki A. Sakaue, Motoshi Goto, Yasuko Kawamoto, Tomoko Kawate, Ryota Nishimura, Hiroyuki Takahashi, Kenji Tobita

    Nuclear Fusion　64　(10)　106011-106011　2024/08/20

    Publisher: IOP Publishing

    DOI： 10.1088/1741-4326/ad6c5d 　

    ISSN： 0029-5515

    eISSN： 1741-4326

    More details Close

    Abstract Spectroscopic studies of emissions released from tungsten ions combined with a pellet injection technique have been conducted in Large Helical Device for contribution to the tungsten transport study in tungsten divertor fusion devices and for expansion of the experimental database of tungsten line emissions. The spectral intensities of W5+, W24+–W28+, W37+, W38+, W41+–W43+, W45+, and W46+ emission lines were measured simultaneously over a wide wavelength range from x-ray to visible. Time evolutions of the various tungsten line spectra indicate that the tungsten confinement time depends on the electron density of the plasma and is long in high density plasmas, on the order of seconds, and short in low density plasmas, on the order of sub-seconds. When the confinement time was long, the tungsten ions remained in the plasma until the end of the discharge, changing their dominant charge with the change in electron temperature. When the confinement time was short, the tungsten ions rapidly decreased in all charge states and disappeared. Space-resolved EUV and visible spectroscopy measurements have revealed that tungsten ions stayed in the core region of the plasma with changing their dominant charge state depending on the electron temperature in the discharges with the long confinement time. Detailed analysis of soft x-ray emission suggested that the confinement time increases with density and becomes saturated when the central electron density exceeds 2 × 1013 cm−3.

  8. Observation and Identification of W<sup>19+</sup>-W<sup>23+</sup> Spectra in the EUV Wavelength Region in the Vicinity of 200Å

    Ryota NISHIMURA, Tetsutarou OISHI, Izumi MURAKAMI, Daiji KATO, Hiroyuki A SAKAUE, Shivam GUPTA, Hayato OHASHI, Motoshi GOTO, Yasuko KAWAMOTO, Tomoko KAWATE, Hiroyuki TAKAHASHI, Kenji TOBITA

    Plasma and Fusion Research　19　1402022-1402022　2024/07/09

    Publisher: Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.19.1402022 　

    eISSN： 1880-6821

  9. Systematic numerical analysis of ECCD exploring injection conditions with high CD efficiency and current profile controllability in JA DEMO Peer-reviewed

    Tomohiro Seino, Kota Yanagihara, Hiroyuki Takahashi, Kenji Tobita, Kazunobu Nagasaki, Atsushi Fukuyama, Akinobu Matsuyama, Tetsutarou Oishi, Takashi Maekawa

    Fusion Engineering and Design　203　114460-114460　2024/06

    Publisher: Elsevier BV

    DOI： 10.1016/j.fusengdes.2024.114460 　

    ISSN： 0920-3796

  10. Determination of Parallel and Perpendicular Ion Temperatures Based on Selective Ion Transmission in a Retarding Field Analyzer Peer-reviewed

    Shigetaka KAGAYA, Hiroyuki TAKAHASHI, Tomohiro SEINO, Keigo YOSHIMURA, Ryota NISHIMURA, Akihiro KANNO, Yusaku TAKAHASHI, Tomoya HARA, Tetsutarou OISHI, Akinobu MATSUYAMA, Kenji TOBITA

    Plasma and Fusion Research　19　1201021-1-1201021-3　2024/05

    DOI： 10.1585/pfr.19.1201021 　

  11. Spatial Distribution Analyses of Axially Long Plasmas under a Multi-Cusp Magnetic Field Using a Kinetic Particle Simulation Code KEIO-MARC

    Ryota Nishimura, Tomohiro Seino, Keigo Yoshimura, Hiroyuki Takahashi, Akinobu Matsuyama, Kazuo Hoshino, Tetsutarou Oishi, Kenji Tobita

    Plasma　7　(1)　64-75　2024/01/22

    Publisher: MDPI AG

    DOI： 10.3390/plasma7010005 　

    eISSN： 2571-6182

    More details Close

    To realize the development of a long plasma source with a uniform electron density distribution in the axial direction, the spatial distribution of plasma under a multi-cusp magnetic field was analyzed using a KEIO-MARC code. Considering a cylindrical plasma source with an axial length of 3000 mm and a cross-sectional diameter of 100 mm, in which the filament electrode was the electron source, the electron density distribution was calculated using the residual magnetic flux density, Bres, and the number of permanent magnets installed at different locations surrounding the device, Nmag, as design parameters. The results show that both Bres and Nmag improved the uniformity of the electron density distribution in the axial direction. The maximum axial electron density decreased with increasing Nmag and increased with increasing Bres. These trends can be explained by considering the nature of the multi-cusp field, where particles are mainly confined to the field-free region (FFR) near the center of the plasma column, and the loss of particles due to radial particle transport. The use of multiple filaments at intervals shorter than the plasma decay length dramatically improved axial uniformity. To further improve axial uniformity, the filament length and FFR must be properly set so that electrons are emitted inside the FFR.

  12. Impact of selective ion transmission on measurement by retarding field analyzer Peer-reviewed

    H. Takahashi, T. Seino, R. Nishimura, K. Yoshimura, A. Kanno, T. Hara, Y. Takahashi, S. Kagaya, A. Matsuyama, Y. Hayashi, K. Tobita

    Physics of Plasmas　30　(5)　2023/05/01

    Publisher: AIP Publishing

    DOI： 10.1063/5.0144798 　

    ISSN： 1070-664X

    eISSN： 1089-7674

    More details Close

    The impact of selective ion transmission on the use of retarding field analyzers (RFAs), which is attributed to the ion Larmor motion, was investigated. Depending on the ion Larmor radius and ion guiding center position, selective transmission limits the parallel and perpendicular ion velocities inside the RFA volume. The velocity limitation flattens I–V curve, leading to an overestimation of the parallel ion temperature. However, the overestimation can be reduced to an acceptable level using the slope in a large grid potential region. The influence of selective transmission depends on both parallel and perpendicular ion temperatures. This nature likely allows the simultaneous determination of two ion temperatures by the best fit of the experimental data, even from a single I–V curve. Applicability of this method was investigated using a radio frequency plasma.

  13. Observation of Electron Density Rollover in Hydrogen Plasma Produced with DT-ALPHA Device Peer-reviewed

    Keigo YOSHIMURA, Hiroyuki TAKAHASHI, Tomohiro SEINO, Kaoru KUSABIRAKI, Yuki SAKATA, Ryota NISHIMURA, Akinobu MATSUYAMA, Kenji TOBITA

    Plasma and Fusion Research　17　1201082-1201082　2022/06/22

    Publisher: Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.17.1201082 　

    eISSN： 1880-6821

  14. On electron temperature rise in divertor relevant recombining plasma along magnetic field line Peer-reviewed

    H. Takahashi, M. N. Winarto, A. Okamoto, P. Boonyarittipong, T. Seino, K. Kusabiraki, Y. Sakata, K. Yoshimura, R. Nishimura, S. Kitajima, A. Matsuyama, K. Tobita

    Physics of Plasmas　29　(3)　032508-032508　2022/03

    Publisher: AIP Publishing

    DOI： 10.1063/5.0073896 　

    ISSN： 1070-664X

    eISSN： 1089-7674

  15. Development of an ion beam measurement instrument for divertor simulation experiments in radio-frequency plasma Peer-reviewed

    Hiroyuki Takahashi, Atsushi Okamoto, Sumio Kitajima, Kenji Tobita

    AIP Advances　10　(8)　085018-085018　2020/08/01

    Publisher: AIP Publishing

    DOI： 10.1063/5.0009321 　

    eISSN： 2158-3226

  16. Dependence of Plasma Parameters in Hydrogen Discharges on Magnetic Field Configuration and Neutral Pressure in the DT-ALPHA Device Peer-reviewed

    Tomohiro SEINO, Hiroyuki TAKAHASHI, Peerapat BOONYARITTIPONG, Takeshi SAIKYO, Kenta OGASAWARA, Atsushi OKAMOTO, Sumio KITAJIMA, Kenji TOBITA

    Plasma and Fusion Research　15　(0)　1201056-1-1201056-3　2020/08

    Publisher: Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.15.1201056 　

    eISSN： 1880-6821

  17. Influence of the formation of a bi-Maxwellian distribution on volumetric recombining plasma spectroscopy Peer-reviewed

    H. Takahashi, A. Okamoto, P. Boonyarittipong, T. Saikyo, K. Ogasawara, T. Seino, K. Tobita, S. Kitajima

    Physics of Plasmas　26　(3)　033506-1-033506-8　2019/03/01

    DOI： 10.1063/1.5078580 　

    ISSN： 1070-664X

    eISSN： 1089-7674

  18. Validation of ion temperature measurement using an ion sensitive probe technique in finite boundary RF plasma Peer-reviewed

    H. Takahashi, K. Ogasawara, P. Boonyarittipong, T. Saikyo, T. Seino, S. Kitajima, A. Okamoto, K. Tobita

    Physics of Plasmas　26　(2)　022511-1-022511-6　2019/02/01

    DOI： 10.1063/1.5083214 　

    ISSN： 1070-664X

    eISSN： 1089-7674

  19. High-Density Plasma Production in Converging Field Following a Magnetic Beach Plasma Source Peer-reviewed

    Atsushi OKAMOTO, Ryosuke OCHIAI, Katsuya SATOU, Hiroki HACHIKUBO, Minami SUGIMOTO, Takaaki FUJITA, Hiroyuki TAKAHASHI

    Plasma and Fusion Research　14　2401005-1-2401005-4　2019/01

    DOI： 10.1585/pfr.14.2401005 　

  20. Development of ion sensitive probe and its application to RF plasma device DT-ALPHA Peer-reviewed

    Takahiko Kobayashi, Hiroyuki Takahashi, Sumio Kitajima, Atsushi Okamoto, Kenji Tobita, Peerapat Boonyarittipong, Takeshi Saikyo, Yusuke Ishikawa, Kenta Ogasawara, Hidetoshi Hashizume

    Plasma and Fusion Research　13　3401090-1-3401090-7　2018

    DOI： 10.1585/PFR.13.3401090 　

    eISSN： 1880-6821

  21. Divertor plasma simulation experiment using hydrogen ionizing plasma and helium ion beam in an RF plasma source DT-ALPHA Peer-reviewed

    Hiroyuki Takahashi, Takahiko Kobayashi, Peerapat Boonyarittipong, Takeshi Saikyo, Yusuke Ishikawa, Kenta Ogasawara, Atsushi Okamoto, Kenji Tobita, Sumio Kitajima, Hidetoshi Hashizume

    Plasma and Fusion Research　13　3401053　2018

    DOI： 10.1585/PFR.13.3401053 　

    eISSN： 1880-6821

  22. Development of a high energy hydrogen beam injection system for divertor plasma simulation experiments on the DT-ALPHA device Peer-reviewed

    Peerapat Boonyarittipong, Hiroyuki Takahashi, Sumio Kitajima, Atsushi Okamoto, Kenji Tobita, Takahiko Kobayashi, Takeshi Saikyo, Yusuke Ishikawa, Kenta Ogasawara, Hidetoshi Hashizume

    Plasma and Fusion Research　13　3402102-1-3402102-5　2018

    DOI： 10.1585/PFR.13.3402102 　

    eISSN： 1880-6821

  23. Influence of electron energy distribution on helium recombining plasma diagnostics using line emissions Peer-reviewed

    H. Takahashi, A. Okamoto, S. Kitajimal, T. Kobayashi, P. Boonyarittipong, T. Miura, D. Nakamura, J. Kon, T. Saikyo, Y. Tanaka, M. Goto

    CONTRIBUTIONS TO PLASMA PHYSICS　57　(8)　322-328　2017/09

    DOI： 10.1002/ctpp.201700014 　

    ISSN： 0863-1042

    eISSN： 1521-3986

  24. Experimental study of the volumetric recombination under energetic ion flow using a radio-frequency plasma source Peer-reviewed

    H. Takahashi, A. Okamoto, D. Nakamura, T. Miura, P. Boonyarittipong, S. Kitajima

    PHYSICS OF PLASMAS　23　(11)　112510-1-112510-7　2016/11

    DOI： 10.1063/1.4968239 　

    ISSN： 1070-664X

    eISSN： 1089-7674

  25. Helium volumetric recombining plasma formation for energetic ion injection in radio-frequency plasma device DT-ALPHA Peer-reviewed

    Hiroyuki Takahashi, Atsushi Okamoto, Takatsugu Miura, Daiki Nakamura, Peerapat Boonyarittipong, Shuhei Sekita, Sumio Kitajima

    Plasma and Fusion Research　11　(1)　2402059-1-2402059-6　2016

    Publisher: Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.11.2402059 　

    ISSN： 1880-6821

  26. ENERGETIC HELIUM ION INJECTION INTO HELIUM RECOMBINING PLASMA IN RADIO-FREQUENCY PLASMA SOURCE Peer-reviewed

    H. Takahashi, A. Okamoto, T. Takahashi, S. Kitajima

    FUSION SCIENCE AND TECHNOLOGY　68　(1)　190-195　2015/07

    DOI： 10.13182/FST14-910 　

    ISSN： 1536-1055

    eISSN： 1943-7641

  27. Effect of Energetic Ion on Spatial Distribution of Recombining Plasma Peer-reviewed

    A. Okamoto, A. Daibo, S. Kitajima, T. Kumagai, H. Takahashi, T. Takahashi, S. Tsubota

    JPS Conf. Proc　1　015010-1-015010-4　2014/03

    DOI： 10.7566/JPSCP.1.015010 　

  28. Ion flow measurement using a directional Langmuir probe in the radio frequency plasma source DT-ALPHA Peer-reviewed

    Takahiro Kumagai, Atsushi Okamoto, Hiroyuki Takahashi, Akira Daibo, Takuya Takahashi, Shimpei Tsubota, Sumio Kitajima

    JPS Conf. Proc.　1　015043-1-015043-5　2014/03

    DOI： 10.7566/JPSCP.1.015043 　

  29. Development of ion source for simulation of edge localized mode in divertor plasma Peer-reviewed

    A. Daibo, A. Okamoto, H. Takahashi, T. Kumagai, T. Takahashi, S. Tsubota, S. Kitajima

    REVIEW OF SCIENTIFIC INSTRUMENTS　85　(2)　02B307-1-02B307-3　2014/02

    DOI： 10.1063/1.4826099 　

    ISSN： 0034-6748

    eISSN： 1089-7623

  30. Electron energy distribution in a divertor simulating device with an RF source Peer-reviewed

    Hiroyuki Takahashi, Atsushi Okamoto, Takahiro Kumagai, Akira Daibo, Takuya Takahashi, Shimpei Tsubota Sumio Kitajima

    Plasma and Fusion Research　9　(2)　3401065-1-3401065-4　2014

    Publisher: Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.9.3401065 　

    ISSN： 1880-6821

  31. LINE SPECTRA OBSERVATION OF THE RYDBERG HELIUM ATOMS DUE TO VOLUMETRIC RECOMBINATION IN THE RF PLASMA SOURCE DT-ALPHA Peer-reviewed

    H. Takahashi, A. Okamoto, Y. Kawamura, T. Kumagai, A. Daibo, S. Kitajima

    FUSION SCIENCE AND TECHNOLOGY　63　(1T)　404-407　2013/05

    DOI： 10.13182/FST13-A16969 　

    ISSN： 1536-1055

    eISSN： 1943-7641

  32. Development of Multi-Port Imaging System for Divertor Simulating Linear Device Peer-reviewed

    A. Okamoto, Y. Kawamura, H. Takahashi, T. Kumagai, A. Daibo, S. Kitajima

    Fusion Science and Technology　63　(1T)　205-208　2013/05

    DOI： 10.13182/FST13-A16906 　

  33. Steady-state recombining plasma in a radio-frequency plasma device for divertor-detachment study Peer-reviewed

    Atsushi Okamoto, Hiroyuki Takahashi, Yusuke Kawamura, Akira Daibo, Takahiro Kumagai, Sumio Kitajima, Mamiko Sasao

    Plasma and Fusion Research　7　(1)　2401018-1-2401018-4　2012

    DOI： 10.1585/pfr.7.2401018 　

    ISSN： 1880-6821

  34. Charge exchange momentum transfer due to ion beam injection in partially ionized plasmas Peer-reviewed

    Atsushi Okamoto, Hiroyuki Takahashi, Sumio Kitajima, Mamiko Sasao

    Plasma and Fusion Research　6　(2011)　1201153-1-1201153-2　2011

    DOI： 10.1585/pfr.6.1201153 　

    ISSN： 1880-6821

  35. Charge-Exchanged Beam Measurement by Using a Grid-Biased Faraday Cup Peer-reviewed

    Atsushi OKAMOTO, Takehiro ISONO, Tsuguhiro NISHIUCHI, Hiroyuki TAKAHASHI, Sumio KITAJIMA, Mamiko SASAO

    Plasma and Fusion Research　5　S2088-1-S2088-4　2010/12/10

    Publisher: The Japan Society of Plasma Science and Nuclear Fusion Research

    DOI： 10.1585/pfr.5.S2088 　

    ISSN： 1880-6821

    More details Close

    A method for neutral beam measurement by using a Faraday cup is proposed in this paper. The method enables us to detect neutral beams by controlling secondary electrons by using a biasing grid in front of the Faraday cup. A procedure is also proposed for in situ determination of the secondary electron emission coefficient of the Faraday cup. Experimental results show that appropriate emission coefficients are determined for helium beams with energies of 2-10 keV. The neutral flux charge-exchanged from a helium ion beam passing through a helium gas is also measured. Saturation of the neutral flux is observed above the pressure expected from the solution of a rate equation. The method is promising for neutral beam measurement, especially for small current-neutral beams.

  36. High density helicon source for beam attenuating target Peer-reviewed

    A. Okamoto, T. Isono, T. Nishiuchi, H. Takahashi, S. Kitajima, M. Sasao

    J. Plasma Fusion Res. SERIES　9　428-431　2010/08/13

  37. Fine-structure characteristics in the emittance images of a strongly focusing He+ beam Peer-reviewed

    M. Sasao, T. Kobuchi, M. Kisaki, H. Takahashi, A. Okamoto, S. Kitajima, O. Kaneko, K. Tsumori, K. Shinto, M. Wada

    Review of Scientific Instruments　81　(2)　2010

    DOI： 10.1063/1.3277211 　

    ISSN： 0034-6748

Show all ︎Show first 5

Misc. 4

  1. Measurement of the electron temperature and density profile under neutral density controlling in the radio-frequency plasma source DT-ALPHA

    Takahashi H., Okamoto A., Daibo A., Kumagai T., Takahashi T., Tsubota S., Kitajima S.

    Meeting abstracts of the Physical Society of Japan　68　(2)　207-207　2013/08/26

    Publisher: The Physical Society of Japan (JPS)

    ISSN： 1342-8349

  2. 26aEF-9 Spatial distribution measurement of helium recombining plasma in the radio-frequency plasma source DT-ALPHA

    Takahashi H., Okamoto A., Kawamura Y., Kumagai T., Daibo A., Takahashi T., Kitajima S.

    Meeting abstracts of the Physical Society of Japan　68　(1)　262-262　2013/03/26

    Publisher: The Physical Society of Japan (JPS)

    ISSN： 1342-8349

  3. 20pFA-5 Spectra observation from highly excited helium atoms in the radio-frequency plasma device DT-ALPHA

    Takahashi H., Okamoto A., Kawamura Y., Kumagai T., Daibo A., Takahashi T., Sasao M., Kitajima S.

    Meeting abstracts of the Physical Society of Japan　67　(2)　214-214　2012/08/24

    Publisher: The Physical Society of Japan (JPS)

    ISSN： 1342-8349

  4. 24aYE-8 Plasma response against controlled neutral particle density in the linear radio-frequency plasma device DT-ALPHA

    Takahashi H., Okamoto A., Kawamura Y., Kumagai T., Daibo A., Sasao M., Kitajima S.

    Meeting abstracts of the Physical Society of Japan　67　(1)　250-250　2012/03/05

    Publisher: The Physical Society of Japan (JPS)

    ISSN： 1342-8349

Presentations 44

  1. Progresses of divertor plasma research in RF plasma device DT-ALPHA Invited

    H. Takahashi, K. Yoshimura, R. Nishimura, S. Kagaya, S. Otsuka, R. Taho, T. Oishi, K. Tobita

    AAPPS-DPP2024　2024/11/04

  2. Collisional-radiative model analysis of nitrogen seeded divertor plasma of LHD

    Hiroyuki Takahashi, Felix Reimold, Frederik Henke, Masahiro Kobayashi, Kiyofumi Mukai, Satoshi Togo, Gakushi Kawamura, he LHD experiment group

    24th International Stellarator Heliotron Workshop　2024/09/11

  3. Evaluation of proton density ratio in a bucket-type ion source based on kinetic code plasma simulation and rate equation for hydrogen ions

    H. Takahashi, R. Nishimura, T. Seino, K. Yoshimura, A. Kanno, T. Hara, Y. Takahashi, T. Oishi, A. Matsuyama, K. Tobita, K. Hoshino

    Global Plasma Forum in Aomori　2023/10/17

  4. KEIO-MARCコードに基づくマルチカスプ型磁場配位イオン源における水素イオン比向上方法の検討

    高橋宏幸, 西村涼汰, 清野智大, Boonyarittipong Peerapa, 吉村渓冴, 菅野耀広, 原智也, 高橋優作, 大石鉄太郎, 松山顕之, 飛田健次, 星野一生

    日本物理学会 第78回年次大会　2023/09/17

  5. Determination of Ion Temperature Parallel and Perpendicular to Magnetic field by Retarding Field Analyzer Based on Selective Ion Transmission

    13th International Conference on Open Magnetic Systems for Plasma Confinement,　2023/08/21

  6. 円形アパチャーを有したRetarding field analyzer を用いた平行および垂直方向イオン温度の同時推定

    高橋宏幸, 清野智大, 西村涼汰, 吉村渓冴, 菅野耀広, 原智也, 髙橋優作, 松山顕之, 飛田健次

    第39回 プラズマ・核融合学会年会　2022/11/23

  7. 磁力線に対して垂直方向の速度成分を持つイオンの混入が Retarding field analyzer を用いた平行方向イオン温度計測に及ぼす影響の検証

    高橋宏幸, 清野智大, 吉村渓冴, 西村涼汰, 菅野耀広, 原智也, 高橋優作, 松山顕之, 飛田健次

    日本物理学会 2022年秋季大会　2022/09/14

  8. 高周波プラズマ源DT-ALPHAにおける水素原子線および分子線分光を組み合わせた水素原子密度の評価

    高橋宏幸, 草開薫, 清野智大, 坂田裕紀, Muhammad Naufal Winarto, 吉村渓冴, 西村涼汰, Boonyarittipong Peerapat, 飛田健次, 松山顕之, 岡本敦

    日本物理学会 第77会年次大会　2022/03/16

  9. Observation of Electron Temperature Rise in Divertor Relevant Recombining Plasma along Magnetic Field Line

    H. Takahashi, M. N. Winarto, P. Boonyarittipong, T. Seino, K. Kusabiraki, Y. Sakata, K. Yoshimura, R. Nishimura, A. Okamotoa, A. Matsuyamab, S. Kitajima, K. Tobita

    The 30th International Toki Conference on Plasma and Fusion Research　2021/11/17

  10. DT-ALPHA における中性粒子圧力制御性の改善と圧力制御下の水素原子線計測

    吉村渓冴, 高橋宏幸, Boonyarittipong Peerapat, 清野智大, 草開薫, 坂田裕紀, Muhammad Naufal Winarto, 西村涼汰, 北島純男, 飛田健次, 松山顕之, 岡本敦

    日本物理学会 2021年秋期大会　2021/09/22

  11. DT-ALPHAにおけるヘリウム再結合プラズマの空間分布計測

    高橋宏幸, Muhammad Naufal Winarto, Boonyarittipong Peerapat, 清野智大, 草開薫, 坂田裕紀, 吉村渓冴, 北島純男, 岡本敦, 飛田健次

    日本物理学会 第76回年次大会　2021/03

  12. 動的なプラズマ-気相境界における衝突・輻射物理と粒子輸送

    高橋宏幸

    日本物理学会 第76回年次大会　2021/03

  13. プラズマ-気相境界の動的振る舞いと衝突・輻射物理

    高橋宏幸

    日本物理学会 第75回年次大会　2020/03

  14. DT-ALPHA におけるダイバータ模擬プラズマ中の軸方向イオン温度計測

    高橋宏幸, 小笠原健太, Boonyarittipong Peerapat, 西京毅, 清野智大, 草開薫A, 坂田裕紀A, Muhammad Naufal WinartoA, 北島純男, 岡本敦, 飛田健次

    日本物理学会 第75回年次大会　2020/03

  15. 高周波放電装置を用いたダイバータプラズマ中の電子・イオン・中性粒子間 エネルギーバランス研究

    髙橋 宏幸

    第36回 プラズマ・核融合学会年会　2019/11/29

  16. Application of an RF plasma source for divertor plasma study and its recent results International-presentation Invited

    TAKAHASHI Hiroyuki

    3rd Asia-Pacific Conference on Plasma Physics　2019/11/04

  17. DT-ALPHA装置を用いた非磁化プラズマに対するIon Sensitive Probe 計測適用の検証

    髙橋 宏幸

    日本物理学会2019年秋季大会　2019/09/10

  18. ダイバータ模擬プラズマ中における中性粒子密度制御下の電子・イオン・中性粒子間エネルギー輸送評価

    髙橋 宏幸

    日本物理学会第74回年次大会　2019/03/14

  19. DT-ALPHAを用いた体積再結合進展過程における電子・イオン・中性粒子間エネルギーフロー調査

    髙橋 宏幸

    第35回プラズマ・核融合学会年次大会　2018/12/03

  20. Investigation of energy flow in a divertor-simulating plasma produced in the radio-frequency plasma source DT-ALPHA

    H. Takahashi

    2018/09/09

  21. Ion temperature measurement of divertor-simulating plasma aiming for detached divertor formation study International-presentation

    髙橋 宏幸

    12th International Conference on Open Magnetic Systems for Plasma Confinement　2018/08/27

  22. Measurement of ion temperature by ion sensitive probe in radio-frequency plasma source DT-ALPHA

    Takahash Hiroyuki

    2018/03/22

  23. Divetor plasma simulating experiment using hydrogen ionizing plasma and helium ion beam in an RF plasma source DT-ALPHA International-presentation

    髙橋 宏幸

    25th International Toki Conference　2017/12/05

  24. Divertor plasma simulating experiment in radio-frequency plasma source DT-ALPHA

    TAKAHASHI Hiroyuki

    2017/11/20

  25. Recent progress of energetic ion beam injection experiment in a radio-frequency plasma source

    TAKAHASHI Hiroyuki

    6th International Workshop on Plasma Material Interaction Facilities for Fusion Research　2017/11/01

  26. Experimental study of influence of the electron energy distribution on spectroscopic measurement of helium volumetric recombining plasma

    H. Takahashi

    2017/03/17

  27. Energetic ion beam injection into volumetric recombining plasma for divertor plasma simulation in linear plasma source

    TAKAHASHI Hiroyuki

    2016/11/29

  28. Influence of the electron energy distribution on low electron temperature and high electron density plasma diagnostics using line emission intensity

    TAKAHASHI Hiroyuki

    2016/09/13

  29. Experimental study of the volumetric recombination under energetic ion flow using a radio-frequency plasma source International-presentation

    髙橋 宏幸

    22nd International conference on Plasma Surface Interactions　2016/05/30

  30. Investigation of the excited Helium atom behavior coexisting with energetic ions in the divertor plasma simulating device DT-ALPHA

    TAKAHASHI Hiroyuki

    2016/03/16

  31. Helium volumetric recombining plasma formation for energetic ion injection in a radio-frequency plasma device DT-ALPHA International-presentation

    髙橋 宏幸

    25th International Toki Conference　2015/11/03

  32. Helium volumetric recombining plasma with controlled helium ion flux in the radio-frequency plasma source DT-ALPHA

    TAKAHASHI Hiroyuki

    2015/09/16

  33. Influence of energetic helium ion to helium volumetric recombination in the radio-frequency plasma source DT-ALPHA

    TAKAHASHI Hiroyuki

    2015/03/21

  34. Helium Volumetric Recombining Plasma with Pulsed High Energy Ion Flux in the Radio-frequency Plasma Source DT-ALPHA

    TAKAHASHI Hiroyuki

    2014/11/18

  35. 10th International Conference on Open Magnetic Systems for Plasma Confinement International-presentation

    髙橋 宏幸

    Development of the divertor simulating experiment by energetic ion beam injection into helium recombining plasma　2014/08/26

  36. イオンビーム源を用いたELM存在下のダイバータプラズマ模擬の基礎研究

    髙橋 宏幸

    日本物理学会第69回年次大会　2014/03/27

  37. Electron energy distribution in a divertor simulating device with an an RF source International-presentation

    髙橋 宏幸

    23rd International Toki Conference　2013/11/18

  38. Measurement of the electron temperature and density profile under neutral density controlling in the radio-frequency plasma source DT-ALPHA

    TAKAHASHI Hiroyuki

    2013/09/25

  39. Helium recombining plasma production for divertor plasma study in RF plasma source DT-ALPHA International-presentation

    髙橋 宏幸

    Asia Pacific Plasma Conference　2013/06/14

  40. Spatial distribution measurement of helium recombining plasma in the radio-frequency plasma source DT-ALPHA

    TAKAHASHI Hiroyuki

    2013/03/26

  41. Spectra observation from highly excited helium atoms in the radio-frequency plasma device DT-ALPHA

    TAKAHASHI Hiroyuki

    2012/09/18

  42. Development of Volumetric Recombining Plasma using a Radio-Frequency Plasma Device for Study of Transient Behavior in Divertor Plasma International-presentation

    髙橋 宏幸

    20th International Conference on Plasma Surface Interactions　2012/05/20

  43. Plasma response against controlled neutral particle density in the linear radio-frequency plasma device DT-ALPHA

    TAKAHASHI Hiroyuki

    2012/03/24

  44. Steady State Production of Recombining Plasma in DT-ALPHA

    TAKAHASHI Hiroyuki

    2011/11/22

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Research Projects 10

  1. 励起分子から始まるプラズマ消滅特性の解明とダイバータ熱制御シナリオ高度化への挑戦

    高橋 宏幸

    Offer Organization: 日本学術振興会

    System: 科学研究費助成事業

    Category: 基盤研究(B)

    Institution: 東北大学

    2024/04/01 - 2028/03/31

  2. Global Development of Toroidal Plasma Peripheral Radiative Cooling Method Using Magnetic Field Topology and Generalization of its Stabilization Mechanism

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Fund for the Promotion of Joint International Research (Fostering Joint International Research (B))

    Institution: National Institute for Fusion Science

    2022/10/07 - 2027/03/31

  3. Rlation between spatial profile of a disappearing plasma and deformation of electron energy distribution

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Research (Exploratory)

    Category: Grant-in-Aid for Challenging Research (Exploratory)

    Institution: Tohoku University

    2022/06 - 2024/03

  4. Structural formation and non-steady state dynamics of detached divertor explored in a laboratory plasma

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Tohoku University

    2020/04 - 2024/03

  5. Volumetric recombination in anisotropic non-equilibrium real plasma

    Okamoto Atsushi

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (B)

    Institution: Nagoya University

    2019/04/01 - 2023/03/31

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    Objective of the research is clarifying volumetric recombination processes in anisotropic non-equilibrium plasma. We successfully induced the volumetric recombination process in an electron cyclotron plasma. A calculation method for neutral particle pressure distribution was proposed. A laser Thomson scattering measurement system was developed. A collisional radiative model for anisotropic non-equilibrium plasma was developed.

  6. Impact of ion heating such as alpha particle channeling on fusion reactor design space

    Tobita Kenji

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (C)

    2017/04/01 - 2021/03/31

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    In the plasma condition with ion temperature higher than electron temperature, which could be realized as a result of alpha channeling, the operation space (plasma temperature and density space) and the design space (plasma major radius and minor radius space) of fusion reactor were investigated on the basis of fusion reactor system analysis. It was concluded that, in such a higher ion temperature condition, the design space is expanded, especially in a compact reactor regime, as a result of reduced plasma requirements such as energy confinement time.

  7. Production and extinction processes of hydrogen particles caused by energetic hydrogen ion impact for improvement of divertor heat load prediction

    Takahashi Hiroyuki

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for Young Scientists (B)

    Category: Grant-in-Aid for Young Scientists (B)

    Institution: Tohoku University

    2017/04 - 2021/03

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    In magnetically confined fusion reactors, energetic ions are periodically exhausted from confinement region and transported into divertor region. Detached divertor is sustained by plasma volumetric recombination. So there is a concern that reaction rate of volumetric recombination is decreased by periodic energetic ion inflow. But such study has not been conducted enthusiastically. We performed ion beam injection experiments using the DT-ALPHA device and an ion beam generator to simulate transient divertor plasma behavior. It was confirmed that energetic ions could change production and extinction rates of excited hydrogen atoms and molecules. In addition, we developed electron and ion diagnostic techniques. It was demonstrated that the Boltzmann plot method considerably underestimates both electron temperature and electron density when it is utilized for non-Maxwellian plasma diagnostics. This results in overestimation of volumetric recombination rate in divertor plasma.

  8. Energetic ion induced excitation dynamics of hydrogen molecule in divertor plasma

    Okamoto Atsushi, TAKAHASHI HIROYUKI

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (C)

    2014/04/01 - 2017/03/31

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    Plasma, the ionized state of gas, suffers from recombination, reverse process of ionization, in the divertor region of magnetically confined fusion devices. Effect of energetic ion flowing into the divertor region on the recombination processes is investigated. Combining a plasma experimental device and a ion beam injector, we have developed a divertor plasma simulating environment, which enables us to control experimental condition more precisely and more easily than actual fusion devices. We have found population density of excited states, which is an indicator of the recombining processes, decreases when the energetic ion density increases experimentally for the first time. A model we have developed by including the effect of energetic ion on production-annihilation processes of excited state qualitatively agree with the experiment.

  9. Basic research for advanced helical systems by a spatial axis stellarator

    KITAJIMA Sumio, OKAMOTO Atsushi, TANIIKE Akira, ISOBE Mitsutaka, TAKAHASHI Hiromi, TAKAHASHI Hiroyuki

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research

    Category: Grant-in-Aid for Scientific Research (A)

    Institution: Tohoku University

    2012/10/31 - 2016/03/31

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    We surveyed the condition for high beta plasma production by an electrode biasing in the spatial axis stellarator (Tohoku University Heliac). We can obtained transition conditions for the improved confinement mode in helical systems and we can successfully summarize the dependence between configuration of magnetic fields and the poloidal viscosity at a local maximum in Tohoku University Heliac and domestic helical systems. And we also proposed the evaluation method for the confinement performance of high energy particles (alpha particle) in advanced small helical devices and surveyed the condition for high energy particle injection by the hydrogen storage electrode. The experimental result suggests that hydrogen ions were accelerated by the hydrogen storage electrode biasing.

  10. Study of the interaction between energetic particle flux and bulk plasma aiming for improved heat controllability of divertor

    Offer Organization: Japan Society for the Promotion of Science

    System: Grants-in-Aid for Scientific Research Grant-in-Aid for JSPS Fellows

    Category: Grant-in-Aid for JSPS Fellows

    Institution: Tohoku University

    2014/04 - 2016/03

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Other 2

  1. プラズマ中性化セルの原理検証を目指した無電極高周波プラズマの高密度化

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    これまでのNBI装置の研究開発は主としてビーム源である負イオン源について精力的に行われており、ITERで要求される40 A・1 MeVの大電流・高エネルギーのビーム生成が実現しつつある。一方で原型炉を見据えた場合、大電流かつ高エネルギービームの生成に加えて高い電力効率を持つNBIシステムが求められる。ビームの中性化効率はNBIシステム全体の効率に大きく関わるため、新規手法を開発することでNBIシステムの高効率化が期待できる。その有力な候補の１つがプラズマ中性化セルである。本研究はDT-ALPHA装置を用いてその原理検証実験を行うものであり、核融合炉の実現に向けて大きな貢献があると考えられる。

  2. 高周波放電装置を用いたプラズマ中性化セルの原理検証

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    核融合炉では電力効率が50%を超える高効率の中性粒子ビーム入射(NBI)システムが求められる。イオン源から引き出されたビームの中性化効率はNBI加熱の総合的な効率に大きく影響することから、従来よりも高効率の中性化手法の確立が求められる。本研究では電極を持たない高周波放電装置を用いたプラズマ中性化セルの原理検証を行う事を目的としている。