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Kobayashi, Tatsuya*; Ito, Kimitaka*; Ido, Takeshi*; Kamiya, Kensaku; Ito, Sanae*; Miura, Yukitoshi; Nagashima, Yoshihiko*; Fujisawa, Akihide*; Inagaki, Shigeru*; Ida, Katsumi*; et al.
Scientific Reports (Internet), 6, p.30720_1 - 30720_7, 2016/08
Times Cited Count：13 Percentile：64.24(Multidisciplinary Sciences)In this Letter, we report model verifications for a key physics for the L-H transition. Radial electric field excitation, using discharges having a two-step transition. Examining time derivative of Poissons equation, it is found that the sum of the loss cone loss current and neoclassical bulk viscosity current agrees the experimentally observed current in the order of magnitude at the first transition. Following second transition and an ambipolar condition in the L-mode cannot be explained by the models.
Kada, Wataru*; Kambayashi, Yuya*; Iwamoto, Naoya*; Onoda, Shinobu; Makino, Takahiro; Koka, Masashi; Kamiya, Tomihiro; Hoshino, Norihiro*; Tsuchida, Hidekazu*; Kojima, Kazutoshi*; et al.
Nuclear Instruments and Methods in Physics Research B, 348, p.240 - 245, 2015/04
Times Cited Count：4 Percentile：32.95(Instruments & Instrumentation)Pastuovi
, 
*; Capan, I.*; Cohen, D.*; Forneris, J.*; Iwamoto, Naoya*; Oshima, Takeshi; Siegele, R.*; Hoshino, Norihiro*; Tsuchida, Hidekazu*
Nuclear Instruments and Methods in Physics Research B, 348, p.233 - 239, 2015/04
Times Cited Count：7 Percentile：51.03(Instruments & Instrumentation)Kobayashi, Tatsuya*; Ito, Kimitaka*; Ido, Takeshi*; Kamiya, Kensaku; Ito, Sanae*; Miura, Yukitoshi; Nagashima, Yoshihiko*; Fujisawa, Akihide*; Inagaki, Shigeru*; Ida, Katsumi*; et al.
Nuclear Fusion, 54(7), p.073017_1 - 073017_14, 2014/07
Times Cited Count：27 Percentile：76.96(Physics, Fluids & Plasmas)In the JFT-2M tokamak, limit-cycle oscillation among several variables is observed before L-to-H transition. Spatiotemporal dynamics of the LCO is analyzed in detail. Zonal fows are not seen, and modulation in edge-localized poloidal flow and density gradient is observed. Modulation is also seen in Reynolds stress, caused by that in turbulence intensity and turbulence wavenumber. However, flow acceleration is not able to be explained by the modulation in the Reynolds stress. Rapid inward propagation in density gradient and turbulence packet is also observed. Characteristics of the propagation are veried by means of turbulence spreading theory and diffusion theory.
Makino, Takahiro; Deki, Manato; Iwamoto, Naoya; Onoda, Shinobu; Hoshino, Norihiro*; Tsuchida, Hidekazu*; Hirao, Toshio*; Oshima, Takeshi
IEEE Transactions on Nuclear Science, 60(4), p.2647 - 2650, 2013/08
Times Cited Count：18 Percentile：79.63(Engineering, Electrical & Electronic)Heavy ion induced anomalous charge collection was observed from 4H-SiC Schottky barrier diodes. It is suggested that the incident ion range with suspect to the thickness of the epi-layer of the SBD in key to understanding these observation and the understanding mechanism.
Kobayashi, Tatsuya*; Ito, Kimitaka*; Ido, Takeshi*; Kamiya, Kensaku; Ito, Sanae*; Miura, Yukitoshi; Nagashima, Yoshihiko*; Fujisawa, Akihide*; Inagaki, Shigeru*; Ida, Katsumi*; et al.
Physical Review Letters, 111(3), p.035002_1 - 035002_5, 2013/07
Times Cited Count：95 Percentile：94.27(Physics, Multidisciplinary)In this Letter, we report analyses of spatiotemporal dynamics of turbulence and structure in the limit cycle oscillation that precedes L-to-H transition. Zonal flows are not observed during LCO, and the oscillation is the periodic generations/decays of barrier with edge localized mean flow. Oscillatory Reynolds stress is found too small to accelerate the LCO flow. Changes of the density gradient and turbulence amplitude are found to propagate into the core in a ballistic manner, suggesting a cause of fast change of core transport after H-mode transition.
Kitagaki, Toru; Hoshino, Takanori; Sambommatsu, Yuji; Yano, Kimihiko; Takeuchi, Masayuki; Igarashi, Takeshi*; Suzuki, Tatsuya*
Journal of Radioanalytical and Nuclear Chemistry, 296(2), p.975 - 979, 2013/05
Times Cited Count：4 Percentile：32.32(Chemistry, Analytical)Iwamoto, Naoya; Johnson, B. C.; Hoshino, Norihiro*; Ito, Masahiko*; Tsuchida, Hidekazu*; Kojima, Kazutoshi*; Oshima, Takeshi
Journal of Applied Physics, 113(14), p.143714_1 - 143714_5, 2013/04
Times Cited Count：33 Percentile：77.63(Physics, Applied)Makino, Takahiro; Deki, Manato; Iwamoto, Naoya; Onoda, Shinobu; Hoshino, Norihiro*; Tsuchida, Hidekazu*; Oshima, Takeshi
Proceedings of 10th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-10) (Internet), p.66 - 69, 2012/12
Silicon carbide (SiC) is regarded as a promising candidate for electronic devices requiring high radiation tolerance (rad-hard devices). Some results indicate that SiC has superior radiation tolerance from the point of view of total ionizing dose effects (TIDs). For the development of rad-hard SiC devices, it is necessary to understand the response of their performance when dense charge is generated in them by an incident ion, resulting in single event effects (SEEs). Therefore, we have measured the bias dependence of the collected charge distribution induced by heavy ions in 4H-SiC-schottky barrier diodes (SBDs) fabricated in thick epi-layer to reveal SEE mechanisms. As a result, anomalous collected charge peaks (2nd peaks) induced by the heavy ions were observed for the first time. The new process of the SEB was observed in the case of incident ions on thick epi-layer of SiC-SBDs.
Iwamoto, Naoya; Johnson, B. C.; Oshima, Takeshi; Hoshino, Norihiro*; Ito, Masahiko*; Tsuchida, Hidekazu*
Proceedings of 10th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-10) (Internet), p.62 - 65, 2012/12
Hoshino, Eijiro*; Kobayashi, Daisuke*; Makino, Takahiro; Oshima, Takeshi; Hirose, Kazuyuki*
Proceedings of 10th International Workshop on Radiation Effects on Semiconductor Devices for Space Applications (RASEDA-10) (Internet), p.130 - 133, 2012/12
Single event effects on phase locked loops (PLLs) are experimentally investigated. Test chips of the PLLs are fabricated in a 0.2-
m fully-depleted silicon-on-insulator technology. The PLL architecture is designed in conjunction with hardening techniques such as the triple modular redundancy and a stacked transistor design approach. A heavy-ion beam test confirms that the hardened PLL exhibits higher radiation tolerance than non-hardened one for 7.5-MeV Ne irradiation: The accelerated ions have the linear energy transfer of 7.3 MeV/cm
/mg in Si.
Fujisawa, Akihide*; Ido, Takeshi*; Shimizu, Akihiro*; Okamura, Shoichi*; Matsuoka, Keisuke*; Iguchi, Harukazu*; Hamada, Yasuji*; Nakano, Haruhisa*; Oshima, Shinsuke*; Ito, Kimitaka*; et al.
Nuclear Fusion, 47(10), p.S718 - S726, 2007/10
Times Cited Count：101 Percentile：95.24(Physics, Fluids & Plasmas)Present status of experiments on zonal flows is overviewed. Innovative use of modern diagnostics has revealed the existence of zonal flows, their spatio-temporal characteristics, their relationship with turbulence, and their effects on confinement. Particularly a number of observations have been accumulated on the oscillatory branch of the zonal flow, dubbed as geodesic acoustic modes suggesting necessity of theories to give their proper description. Several new methods have elucidated the zonal flow generation processes from the turbulence. Further investigation of relationship between the zonal flows and confinement is strongly encouraged as cross-device activity.
Nagashima, Yoshihiko*; Ito, Kimitaka*; Ito, Sanae*; Fujisawa, Akihide*; Yagi, Masatoshi*; Hoshino, Katsumichi; Shinohara, Koji; Ejiri, Akira*; Takase, Yuichi*; Ido, Takeshi*; et al.
Plasma Physics and Controlled Fusion, 49(10), p.1611 - 1625, 2007/10
Times Cited Count：45 Percentile：81.37(Physics, Fluids & Plasmas)It was found that the envelope of the ambient density fluctuation of the drift wave turbulence has spectral peaks aroound zonal flow frequencies. A method to detect the zonal flow using this characteristic was considered using the JFT-2M density fluctuation data. There is a possibility that the zonal flow will be able to be detected in the future burning plasmas by using the density fluctuations measured by some density fluctuation measurement by such as the microwave reflectometer and so on.
Hoshino, Katsumichi; Ido, Takeshi*; Nagashima, Yoshihiko*; Shinohara, Koji; Ogawa, Hiroaki; Kamiya, Kensaku; Kawashima, Hisato; Tsuzuki, Kazuhiro*; Kusama, Yoshinori; Oasa, Kazumi; et al.
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 8 Pages, 2007/03
We report on the potential/density fluctuations in the JFT-2M tokamak. We identified a geodesic acoustic mode (GAM) and its electric field structure. The GAM interacts with the background turbulence in consistent with a drift wave - zonal flow theory. The GAM modulates the turbulence, and the suppression depends on the direction and gradient of the flow velocity in consistent with a theory. During the H-mode, the GAM disappears presumably due to the suppression of the turbulence. We analysed the low frequency potential oscillation during the H-mode. A wavelet analysis showed a low frequency characteristic potential fluctuations (several handred kHz), which disappears in the L-mode and at the occurence of ELM. Observed poloidal flow is about 20 times as large as that of the GAM during the H-mode. If the potential has a spatial inhomogineity, there is a possibility that this low frequency fluctuation comes from the EXB flow or the zonal flow.
Fujisawa, Akihide*; Ido, Takeshi*; Shimizu, Akihiro*; Okamura, Shoichi*; Matsuoka, Keisuke*; Hamada, Yasuji*; Hoshino, Katsumichi; Nagashima, Yoshihiko*; Shinohara, Koji; Nakano, Haruhisa*; et al.
Proceedings of 21st IAEA Fusion Energy Conference (FEC 2006) (CD-ROM), 12 Pages, 2007/03
Present status of experiments on zonal flows is overviewed. Innovative use of traditional and modern diagnostics has revealed unambiguously the existense of the zonal flows, their spatio-temporal caracteristics, their relationship with turbulence, and their effects on confinement. Particularly, a number of observations have been accumulated on the oscillatory branch of zonal flows, dubbed geodesic acoustic modes, suggesting necessity of theories to give their proper description. Furthur investigation of relationship between zonal flows and confinement is strongly encouraged as cross-device activity.
Nagashima, Yoshihiko*; Ito, Kimitaka*; Fujisawa, Akihide*; Ito, Sanae*; Yagi, Masatoshi*; Hoshino, Katsumichi; Shinohara, Koji; Ido, Takeshi*; Miura, Yukitoshi; Ejiri, Akira*; et al.
Europhysics Conference Abstracts (CD-ROM), 31F, 4 Pages, 2007/00
The recent results on the identification of the outer most magnetic surface and on the identification of the characteristic of the zonal flow are presented by using the measured data of the zonal flow which is a plasma flow in the tokamak plasma. The positon of the outermost magnetic surface was identified using the characteristic of the oscillating zonal flow called as the geodesic acoutic mode (GAM) that the mode exists only in the closed magnetic surface, and the position of the surface was in agreement with that by the magnetic equilibrium reconstruction. Some coincidence with the drift wave - zonal flow theory was obtained by using the finding that the envelope of the density fluctuation of the background turbulence is modulated by the GAM.
Tsuzuki, Kazuhiro; Kamiya, Kensaku; Shinohara, Koji; Bakhtiari, M.*; Ogawa, Hiroaki; Kurita, Genichi; Takechi, Manabu; Kasai, Satoshi; Sato, Masayasu; Kawashima, Hisato; et al.
Nuclear Fusion, 46(11), p.966 - 971, 2006/11
Times Cited Count：16 Percentile：48.19(Physics, Fluids & Plasmas)no abstracts in English
Ido, Takeshi*; Miura, Yukitoshi; Hoshino, Katsumichi; Kamiya, Kensaku; Hamada, Yasuji*; Nishizawa, Akimitsu*; Kawasumi, Yoshiaki*; Ogawa, Hiroaki; Nagashima, Yoshihiko*; Shinohara, Koji; et al.
Nuclear Fusion, 46(5), p.512 - 520, 2006/05
Times Cited Count：86 Percentile：92.73(Physics, Fluids & Plasmas)The electrostatic fluctuation spectrum and the fluctuation-induced particle flux of the JFT-2M tokamak were estimated using the hevy ion beam probe (HIBP) measurement. A geodesic acoustic mode (GAM) of the frequency about15kHz was identified in the L-mode. The GAM has its peak at about 3cm inside of the separatrix with the electric field of about 1.4kV/m. The estimated turbulent particle flux is found to be intermittent. It is found that the density fluctuation is modulated by the GAM in the wide frequency range and the coherence analysis shows that the flucruation-induced particle flux is partially contributed by the GAM. In the H-mode the GAM disappears and the fluctuation and the flux is much decreased.The mechanism of the large burst-like flux in the L-mode is not understood yet and left as the future problem.
Ido, Takeshi*; Miura, Yukitoshi; Kamiya, Kensaku; Hamada, Yasuji*; Hoshino, Katsumichi; Fujisawa, Akihide*; Ito, Kimitaka*; Ito, Sanae*; Nishizawa, Akimitsu*; Ogawa, Hiroaki; et al.
Plasma Physics and Controlled Fusion, 48(4), p.S41 - S50, 2006/04
Times Cited Count：129 Percentile：96.64(Physics, Fluids & Plasmas)The potential and density fluctuations of Geodesic-Acoustic-Mode (GAM) were investigated through the direct and simultaneous measurement of electrostatic and density fluctuations with a heavy ion beam probe(HIBP). It was found that the amplitude of the fluctuation has a maximum inside of the plasma boundary and that it has an almost constant frequency. It was also found that the mode propagates in the radial direction and that the GAM affects the background turbulence. The influence to the background turbulence was found to be in consistent with a theoretical prediction.
Kasai, Satoshi*; Kamiya, Kensaku; Shinohara, Koji; Kawashima, Hisato; Ogawa, Hiroaki; Uehara, Kazuya; Miura, Yukitoshi; Okano, Fuminori; Suzuki, Sadaaki; Hoshino, Katsumichi; et al.
Fusion Science and Technology, 49(2), p.225 - 240, 2006/02
Times Cited Count：3 Percentile：24.08(Nuclear Science & Technology)The diagnostic system of JFT-2M has consisted of about 30 individual diagnostic instruments,which were used to study the plasma production, control, equilibrium, stability, confinement, plasma heating by NBI and/or RF (LH, ICRF, ECH) and current drive by RF. In these instruments, the motional Stark effect (MSE) polarimeter, charge exchanged recombination spectroscopy (CXRS), heavy-ion beam probe (HIBP), time of flight (TOF) neutral particle analyzer, etc. have contributed to make clear the improved mechanism of confinement such as H-mode and High Recycling Steady (HRS) H-mode, and to search the operational region of these modes.The infrared TV camera system and lost ion probe have played a very important role to investigate the heat load onto the walls due to ripple loss particles and escaping ions from core plasma, respectively.
