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Reseacher Profiling Tool Kyushu University Pure
Field of Specialization
Research InterestsMembership in Academic Society
- 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)
|Conway, G.D., Smolyakov, A.I., Ido, T., Geodesic acoustic modes in magnetic confinement devices, Nuclear Fusion, https://doi.org/10.1088/1741-4326/ac0dd1, 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..
|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..
|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..
|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..
|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..
|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..
|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..
- The Japan Society of Plasma Science and Nuclear Fusion
- The Physical Society of Japan