Kyushu University Academic Staff Educational and Research Activities Database
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IDO Takeshi Last modified date:2023.06.26

Graduate School

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 Reseacher Profiling Tool Kyushu University Pure
Academic Degree
Field of Specialization
Plasma Physics
Research Interests
  • Investigation of the physical mechanism of formation of the electric potential profiles and turbulent transport in the magnetically confined plasmas
    keyword : Magnetically confined plasma, electric potential profile, Heavy Ion Beam Probe, turbulence, nuclear fusion
  • Development of Heavy Ion Beam Probe on the Large Helical Device
    keyword : Heavy Ion Beam Probe (HIBP), Electric Potential Measurement
  • Development of Heavy Ion Beam Probe on JFT-2M tokamak
    keyword : Heavy Ion Beam Probe (HIBP)
  • 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)
Academic Activities
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1. Conway, G.D., Smolyakov, A.I., Ido, T., Geodesic acoustic modes in magnetic confinement devices, Nuclear Fusion,, 62, 1, 013001-1-013001-149, vol.62, No.1, 013001, 2022.01, Geodesic acoustic modes (GAMs) are ubiquitous oscillatory flow phenomena observed in toroidal magnetic confinement fusion plasmas, such as tokamaks and stellarators. They are recognized as the non-stationary branch of the turbulence driven zonal flows which play a critical regulatory role in cross-field turbulent transport. GAMs are supported by the plasma compressibility due to magnetic geodesic curvature—an intrinsic feature of any toroidal confinement device. GAMs impact the plasma confinement via velocity shearing of turbulent eddies, modulation of transport, and by providing additional routes for energy dissipation. GAMs can also be driven by energetic particles (so-called EGAMs) or even pumped by a variety of other mechanisms, both internal and external to the plasma, opening-up possibilities for plasma diagnosis and turbulence control. In recent years there have been major advances in all areas of GAM research: measurements, theory, and numerical simulations. This review assesses the status of these developments and the progress made towards a unified understanding of the GAM behaviour and its role in plasma confinement. The review begins with tutorial-like reviews of the basic concepts and theory, followed by a series of topic orientated sections covering different aspects of the GAM. The approach adopted here is to present and contrast experimental observations alongside the predictions from theory and numerical simulations. The review concludes with a comprehensive summary of the field, highlighting outstanding issues and prospects for future developments..
2. T. Ido, A. Fujisawa, K. Takemura, T.-K. Kobayashi, D. Nishimura, N. Kasuya, A. Fukuyama, C. Moon, K. Yamasaki, S. Inagaki, Y. Nagashima, and T. Yamada, Conceptual design of heavy ion beam probes on the PLATO tokamak, Review of Scientific Instruments , 10.1063/5.0041814, 92, 053553, 2021.05, [URL], Heavy ion beam probe (HIBP) systems have been designed for the new tokamak, PLATO [A. Fujisawa, AIP Conf. Proc. 1993, 020011 (2018)]. The designs have been completed, and the installations are in progress. Two HIBPs are being installed in toroidal sections 180○ apart to investigate long-range correlations in the toroidal direction. Each HIBP consists of an injection beamline and a detection beamline as usual. Yet, one of the HIBPs is equipped with an additional detection beamline; the measurement positions of its two detection beamlines can be placed on almost the same magnetic surface yet at poloidal angles that differ by ∼180○. The use of three detection beamlines allows us to investigate spatial asymmetry and long-range correlations in both the toroidal and poloidal directions, simultaneously. The detected beam intensity is expected to be enough for turbulence measurements in almost the entire plasma region when the electron density is up to 1 × 10^19 m−3 by selecting appropriate ion species for the probe beam. Each detector has three channels 10 mm apart, allowing measurement of local structures of micro-scale turbulence. Therefore, using the HIBPs on the PLATO tokamak will enable both local and global properties of plasma turbulence to be investigated, simultaneously..
3. 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..
4. 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..
5. 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..
6. 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..
7. 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..
1. T. Ido, M. Hasegawa, R. Ikezoe, T. Onchi, K. Hanada, H. Idei, K. Kuroda, Y. Nagashima, Conceptual Design of a Heavy Ion Beam Probe for the QUEST spherical tokamak, 24th Topical Conference on High Temperature Plasma Diagnostics, 2022.05, A heavy ion beam probe (HIBP) has been designed for the QUEST spherical tokamak to measure plasma turbulence and the electric potential profiles. By using a cesium ion beam with the energy of several keV, the observable region covers most of the upper half of the plasma. Although the probe beam is deflected by the poloidal magnetic field produced by plasma current and poloidal coil currents, it can be detected under the plasma current up to 150 kA by modifying the trajectories with two electrostatic sweepers. According to numerical estimation of the detected beam intensity, sufficient signal intensity for measuring plasma turbulence can be obtained over almost the measurable region when the electron density is up to 1×10^19 m^(-3) which is larger than the cut-off density of ECH in QUEST. The performance of the designed HIBP is sufficient for the QUEST project..
2. Takeshi Ido, Dynamics of energetic particle-driven oscillatory zonal flow in toroidal plasmas, 第38回 プラズマ・核融合学会, 2021.11.
3. Takeshi Ido, Akihide Fujisawa, Keiji Takemura, Naohiro Kasuya, Shigeru Inagaki, Atsushi Fukuyama, Yoshihiko Nagashima, Chanho Moon, Kotaro Yamasaki, Takuma Yamada, Yusuke Kosuga, Makoto Sasaki , Design of Heavy Ion Beam Probes on the PLATO tokamak, High-Temperature Plasma Diagnostics Conference, 2020.12, Plasma turbulence plays a decisive role in determining dynamics of plasmas not only in laboratories but also in the space. Especially, recent studies have indicated the importance of not only local but also global properties of the turbulence such as symmetry breaking and multi-scale interaction. In order to explore dynamics of plasmas through measuring plasma turbulence precisely and globally, a new tokamak named Plasma Turbulence Observatory (PLATO) is being constructed in Kyushu University.
One of the key diagnostic systems for the PLATO project is Heavy Ion Beam Probe (HIBP), by which the electric potential, its fluctuations, density fluctuations, and magnetic fluctuations are measured directly and simultaneously without any perturbation to the plasmas. The HIBPs are installed in two toroidal sections to observe long range correlation in the toroidal direction. In addition, two energy analyzers in a poloidal cross section to observe the poloidal asymmetry and the correlation in the poloidal direction. The measurable area covers almost the whole plasma with a circular poloidal cross section and approximately 80 % of a poloidal cross section of the plasma with \kappa of 1.5 and \delta of 0.5, where \kappa is the ellipticity and \delta is the triangularity. The beam energy is 10 – 50 keV for Rubidium (Rb) beam or 50 – 150 keV for Sodium (Na) beam. According to a numerical calculation under the condition in which the central electron density is 1x10^19 (m^-3) and the density profile is parabolic, the detected beam intensity will be sufficient for micro-turbulence measurement in the region from the normalized minor radius(rho) of 0.2 to the plasma edge by Rb beam and in whole measurable region by Na beam. Therefore, we will be able to investigate nature of turbulence through multi-scale and simultaneous measurement.
4. 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..
Membership in Academic Society
  • The Japan Society of Plasma Science and Nuclear Fusion
  • The Physical Society of Japan