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IDO Takeshi Last modified date:2020.07.02



Graduate School


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Homepage
https://kyushu-u.pure.elsevier.com/en/persons/takeshi-ido
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https://www.triam.kyushu-u.ac.jp/QUEST_HP/indexen.html
Phone
092-583-7695
Fax
092-573-6899
Academic Degree
Ph.D.
Field of Specialization
Plasma Physics
Research
Research Interests
  • Investigation of the physical mechanism of the electric potential profiles in the magnetically confined plasmas
    keyword : Magnetically confined plasma, electric potential profile, Heavy Ion Beam Probe
    2004.04.
  • Development of Heavy Ion Beam Probe on the Large Helical Device
    keyword : Heavy Ion Beam Probe (HIBP), Electric Potential Measurement
    2000.04.
  • Development of Heavy Ion Beam Probe on JFT-2M tokamak
    keyword : Heavy Ion Beam Probe (HIBP)
    1997.10~2004.03.
  • Investigation of spatio-temporal evolution of electric potential in JFT-2Mトカマク
    keyword : magnetically confined plasma, L-H transition, electric field, turbulence, turubulent transport, Heavy Ion Beam Probe (HIBP)
    1999.04~2006.03.
Academic Activities
Reports
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Papers
1. T. Ido, Y. Miura, K. Hoshino, K. Kamiya, Y. Hamada, A. Nishizawa, Y. Kawasumi, H. Ogawa, Y. Nagashima, K. Shinohara, Y. Kusama, JFT-2M group, Observation of the interaction between the geodesic acoustic mode and ambient fluctuation in the JFT-2M tokamak, Nuclear Fusion, 10.1088/0029-5515/46/5/003, 46, 5, 512, 2006.03, [URL], The electrostatic and density fluctuation are measured simultaneously with a heavy ion beam probe. The electrostatic fluctuation with the geodesic acoustic mode (GAM) frequency is observed in L-mode plasmas and not in H-mode plasmas. The poloidal and radial structure is consistent with the GAM. So the fluctuation is concluded to be the GAM. The amplitude of the GAM changes in the radial direction; it is small near the separatrix, has a maximum at 3 cm inside the separatrix and decreases again to 5 cm inside the separatrix. The GAM and the temporal behaviour of the ambient density fluctuation show a significant coherence, and the phase of modulation of the ambient density fluctuation tends to delay the potential oscillation of the GAM. It is clearly verified that the GAM affects ambient fluctuation and also the local particle transport through modulation of the amplitude of the ambient fluctuation..
2. T Ido, Y Miura, K Kamiya, Y Hamada, K Hoshino, A Fujisawa, K Itoh, S-I Itoh, A Nishizawa, H Ogawa, Y Kusama and JFT-2M group, Geodesic–acoustic-mode in JFT-2M tokamak plasmas, Plasma Physics and Controlled Fusion, 10.1088/0741-3335/48/4/S04, 48, S41, 2006.03, [URL], The characteristics of geodesic–acoustic-mode (GAM) are investigated through direct and simultaneous measurement of electrostatic and density fluctuations with a heavy ion beam probe. The amplitude of the GAM changes in relation to the radial position; it is small near the separatrix, reaches a local maximum at 3 cm inside the separatrix and then decreases again to 5 cm inside the separatrix. The frequency is constant in the range, though the predicted GAM frequency varies according to the temperature gradient. The correlation length is about 6 cm and comparable to the structure of the amplitude of the GAM. The results indicate the GAM has a radial structure which reflects the local condition at about 3 m inside the separatrix. The phase relation between the GAM oscillation indicates that the GAM is a radial propagating wave.
The interaction between the GAM and the ambient density fluctuation is shown by the high coherence between the GAM oscillation and the temporal behaviour of the ambient density fluctuation. Moreover, the phase relation between the electric field fluctuation of the GAM (E˜r,GAM) and the amplitude of the density fluctuation indicates that the modulation of the ambient density fluctuation delays the E˜r,GAM. The causality between the GAM and the modulation of the density fluctuation is revealed..
3. Takeshi IDO, Akihiro SHIMIZU, Masaki NISHIURA, Shinji KATO, Haruhisa NAKANO, Akimitsu NISHIZAWA, Yasuji HAMADA, Mitsuhiro YOKOTA, Kiwamu TSUKADA, Hideki OGAWA, Tomoyuki INOUE, Katsumi IDA, Mikiro YOSHINUMA, Sadayoshi MURAKAMI, Kenji TANAKA, Kazumichi NARIHARA, Ichihiro YAMADA, Kazuo KAWAHATA, Naoki TAMURA and the LHD Experimental Group, Electrostatic Potential Measurement by Using 6-MeV Heavy Ion Beam Probe on LHD, Plasma and Fusion Research, 10.1585/pfr.3.031, 3, 031, 2008.04, [URL], A heavy ion beam probe (HIBP) using a 3 MV tandem accelerator was installed in Large Helical Device (LHD). It is designed to measure the electrostatic potential in the core region directly. It is calibrated and can be used to measure the electrostatic potential profiles in LHD plasmas. The radial electric field (Er) obtained from the potential profiles measured using the HIBP agrees with that measured by charge exchange spectroscopy (CXS). Er predicted by the neoclassical theory is also compared to that measured using the HIBP, and is in good agreement with the experimental results in the core region..
4. T. Ido, K. Kamiya, Y. Miura, Y. Hamada, A. Nishizawa, and Y. Kawasumi, Observation of the Fast Potential Change at L-H Transition by a Heavy-Ion-Beam Probe on JFT-2M, Physical Review Letters, 10.1103/PhysRevLett.88.055006 , 88, 5, 055006, 2002.01, [URL], The fast potential change near the separatrix is measured directly at the L-H transition by a heavy-ion-beam probe. The potential changes with two different time scales at the L-H transition triggered by a sawtooth crash: it drops at first with the time scale of 10 100 ms just after the arrival of the heat pulse due to the sawtooth crash. Then, it decreases again at a few 100 ms after the first drop at a time scale of about 200 ms..
5. T. Ido, K. Itoh, M. Osakabe, M. Lesur, A. Shimizu, K. Ogawa, K. Toi, M. Nishiura, S. Kato, M. Sasaki, K. Ida, S. Inagaki, S.-I. Itoh, the LHD Experiment Group, Strong Destabilization of Stable Modes with a Half-Frequency Associated with Chirping Geodesic Acoustic Modes in the Large Helical Device, Physical Review Letters, 10.1103/PhysRevLett.116.015002, 116, 015002, 2016.01, Abrupt and strong excitation of a mode has been observed when the frequency of a chirping energetic-particle driven geodesic acoustic mode (EGAM) reaches twice the geodesic acoustic mode (GAM) frequency. The frequency of the secondary mode is the GAM frequency, which is a half-frequency of the primary EGAM. Based on the analysis of spatial structures, the secondary mode is identified as a GAM. The phase relation between the secondary mode and the primary EGAM is locked, and the evolution of the growth rate of the secondary mode indicates nonlinear excitation. The results suggest that the primary mode (EGAM) contributes to nonlinear destabilization of a subcritical mode..
6. T. Ido, K. Itoh, M. Lesur, M. Osakabe, A. Shimizu, K. Ogawa, M. Nishiura, I. Yamada, R. Yasuhara, Y. Kosuga, M. Sasaki, K. Ida, S. Inagaki, S.-I. Itoh and the LHD Experiment Group, Observation of subcritical geodesic acoustic mode excitation in the large helical device, Nuclear Fusion, 10.1088/1741-4326/aa665a, 57, 072009 , 2017.04, The abrupt and strong excitation of the geodesic acoustic mode (GAM) has been found in the
large helical device (LHD), when the frequency of a chirping energetic particle-driven GAM
(EGAM) approaches twice that of the GAM frequency. The temporal evolution of the phase
relation between the abrupt GAM and the chirping EGAM is common in all events. The result
indicates a coupling between the GAM and the EGAM. In addition, the nonlinear evolution
of the growth rate of the GAM is observed, and there is a threshold in the amplitude of the
GAM for the appearance of nonlinear behavior. A threshold in the amplitude of the EGAM for
the abrupt excitation of the GAM is also observed. According to one theory (Lesur et al 2016
Phys. Rev. Lett. 116 015003, Itoh et al 2016 Plasma Phys. Rep. 42 418) the observed abrupt
phenomenon can be interpreted as the excitation of the subcritical instability of the GAM. The excitation of a subcritical instability requires a trigger and a seed with sufficient amplitude. The observed threshold in the amplitude of the GAM seems to correspond with the threshold in the seed, and the threshold in the amplitude of the EGAM seems to correspond with the threshold in the magnitude of the trigger. Thus, the observed threshold supports the interpretation that the abrupt phenomenon is the excitation of a subcritical instability of the GAM..
Presentations
1. Takeshi Ido, Akihiro Shimizu, Masaki Osakabe, Kimitaka Itoh, Maxime Lesur, Kunihiro Ogawa, Hao Wang, Makoto Sasaki, Yusuke Kosuga, Shigeru Inagaki, Sanae.–I. Itoh, and the LHD Experiment Group , Nonlinear wave-particle interaction in magnetized high temperature plasmas confined in Large Helical Device, 3rd Asia-Pacific Conference on Plasma Physics, 2019.11, Wave-particle interactions are ubiquitous in plasmas, and they are observed as interesting phenomena. In this presentation, observed subcritical instability driven by nonlinear wave-particle interaction in magnetized plasmas will be shown.
In magnetized high temperature plasmas confined in the Large Helical Device (LHD), it is observed that an instability named geodesic acoustic mode(GAM) is excited abruptly by energetic particles existing through the inverse Landau damping. The frequency of this instability usually increases with the time scale of a few milliseconds, and the temporal evolution of the frequency reflects the evolution of the velocity distribution which is a result of wave-particle interaction.
When the frequency of the GAM reaches twice the ordinary GAM frequency and the amplitude of the GAM exceeds a threshold, another GAM is abruptly excited with the shorter time scale of 1 ms or less. The phase relation between the originally-existing GAM, hereinafter referred to as the primary mode, and the abruptly excited GAM, hereinafter referred to as the secondary mode, is locked, and the evolution of the growth rate of the secondary mode indicates nonlinear excitation. These behaviors can be interpreted as the excitation of the subcritical instability of the secondary mode through nonlinear wave-particle interaction triggered by the primary mode. Abrupt excitation phenomena have been wildly observed in laboratory plasmas (e.g. sawtooth oscillation and disruption) and astro-plasmas(e.g. solar flare), and subcritical instabilities are one of the working hypotheses of the onset of abrupt phenomena. The finding of the abrupt excitation of the GAM and the understanding of the phenomena as the subcritical instability demonstrate an experimental path to the understanding of the physical mechanism of the onset of the abrupt phenomena.
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Membership in Academic Society
  • The Japan Society of Plasma Science and Nuclear Fusion
  • The Physical Society of Japan