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Kawai, Chika*; Idomura, Yasuhiro; Ogawa, Yuichi*; Yamada, Hiroshi*
Physics of Plasmas, 27(8), p.082302_1 - 082302_11, 2020/08
Times Cited Count：2 Percentile：11.02(Physics, Fluids & Plasmas)Self-organization in the toroidal electron temperature gradient driven (ETG) turbulence is investigated based on a global gyrokinetic model in a weak magnetic shear configuration. Because of global profile effects, toroidal ETG modes with higher toroidal mode number n are excited at the outer magnetic surfaces, leading to strong linear wave dispersion. The resulting anisotropic wave turbulence boundary and the inverse energy cascade generate the self-organization of zonal flows, which is the unique mechanism in the global gyrokinetic model. The self-organization is confirmed both in the decaying turbulence initialized by random noises and in the toroidal ETG turbulence. It is also shown that the self-organization process generates zonal flows and isotropic eddies depending on a criterion parameter, which is determined by the ion to electron temperature ratio and the turbulence intensity.
Ishikawa, Hirotaku*; Kai, Tetsuya; Sato, Hirotaka*; Kamiyama, Takashi*
Journal of Nuclear Science and Technology, 56(2), p.221 - 227, 2019/02
Times Cited Count：4 Percentile：35.14(Nuclear Science & Technology)Oka, Hiroshi; Tanno, Takashi; Otsuka, Satoshi; Yano, Yasuhide; Kaito, Takeji
Nuclear Materials and Energy (Internet), 16, p.230 - 237, 2018/08
Times Cited Count：4 Percentile：33.89(Nuclear Science & Technology)Kawai, Chika*; Idomura, Yasuhiro; Maeyama, Shinya*; Ogawa, Yuichi*
Physics of Plasmas, 24(4), p.042303_1 - 042303_13, 2017/04
Times Cited Count：2 Percentile：9.46(Physics, Fluids & Plasmas)Self-organization in the slab electron temperature gradient driven (ETG) turbulence is investigated based on gyrokinetic simulations and the Hasegawa-Mima (HM) equation. The scale and the anisotropy of self-organized turbulent structures vary depending on the Rhines scale and the characteristic scale given by the adiabatic response term in the HM equation. The former is determined by competition between the linear wave dispersion and the nonlinear turbulent cascade, while the latter is given as the scale, at which the turbulent cascade is impeded. These scales are controlled by plasma parameters such as the density and temperature gradient, and the temperature ratio of ion to electron. It is found that depending on the plasma parameters, the ETG turbulence shows either isotropic turbulence or zonal flows, which give significantly different transport levels. Although the modulational instability excites zonal modes regardless of the plasma parameters, the final turbulent structure is determined by the self-organization process.
Oka, Hiroshi; Tanno, Takashi; Otsuka, Satoshi; Yano, Yasuhide; Uwaba, Tomoyuki; Kaito, Takeji; Onuma, Masato*
Nuclear Materials and Energy (Internet), 9, p.346 - 352, 2016/12
Times Cited Count：22 Percentile：87.41(Nuclear Science & Technology)Idomura, Yasuhiro
Plasma and Fusion Research (Internet), 11, p.2403006_1 - 2403006_5, 2016/02
In this work, we address saturation mechanisms of decaying turbulence induced by the ion temperature gradient driven trapped electron mode. In the simulation, turbulent transport is quenched in the nonlinear quasi-steady phase, where temperature profiles exceeding linear critical temperature gradient parameters are formed. This kind of nonlinear critical temperature gradient is sustained by radial electric fields with strong shear, which is generated by corrugated density profiles. It is found that the density profile structure is related to electrons transport near low order mode rational surfaces, where non-adiabatic response of passing electrons becomes important.
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
Nuclear Fusion, 45(12), p.1571 - 1581, 2005/12
Times Cited Count：42 Percentile：75.95(Physics, Fluids & Plasmas)Using a global gyrokinetic toroidal particle code, the toroidal electron temperature gradient driven (ETG) turbulence is studied in positive and reversed shear tokamaks. In the nolinear turbulent state, the ETG turbulence in the positive and reversed shear configurations show quite different structure formations. In the positive shear configuration, the ETG turbulence is dominated by streamers which have a ballooning type structure, and the electron temperature 
profile is quickly relaxed to the marginally stable state in a turbulent time scale. In the reversed shear configuration, quasi-steady zonal flows are produced in the regative shear region, while the positive shear region is characterized by streamers. Accordingly, the electron thermal diffusivity 
has a gap structure across the 
surface, and the gradinet is sustained above the marginal value for a long time in the quasi-steady phase. The results suggest a stiffness of the profile in positive shear tokamaks, and a possibility of the Te transport barrier in reversed shear tokamaks.
ion beam in a large negative ion sourceHanada, Masaya; Seki, Takayoshi*; Takado, Naoyuki*; Inoue, Takashi; Morishita, Takatoshi; Mizuno, Takatoshi*; Hatayama, Akiyoshi*; Imai, Tsuyoshi*; Kashiwagi, Mieko; Sakamoto, Keishi; et al.
Fusion Engineering and Design, 74(1-4), p.311 - 317, 2005/11
Times Cited Count：7 Percentile：44.05(Nuclear Science & Technology)no abstracts in English
simulations of microturbulenceIdomura, Yasuhiro
Purazuma, Kaku Yugo Gakkai-Shi, 81(8), p.581 - 592, 2005/08
A gyrokinetic particle simulation is a powerful tool in studying tokamak microturbulence. A method, which is a standard method in recent gyrokinetic particle simulations, dramatically improved an efficiency of a particle simulation by reducing a particle noise, and full torus turbulence simulations are enabled. In this paper, the method is reviewed, and issues in full torus gyrokinetic particle simulations are discussed.
Hatae, Takaki; Nakatsuka, Masahiro*; Yoshida, Hidetsugu*
Purazuma, Kaku Yugo Gakkai-Shi, 80(10), p.870 - 882, 2004/10
A high performance phase conjugate mirror by stimulated Brillouin scattering (SBS-PCM) is applied to Thomson scattering diagnostics in JT-60U for the first time. To improve the measurement performance, two developments were performed with SBS-PCM. First, we developed a new optical design to provide a double-pass scattering scheme with SBS-PCM. A laser beam passing through the plasma is reflected by the SBS-PCM, and a reflected beam returned back through the same path as coming one by the phase conjugate effect, and passed through the plasma again. The double path Thomson scattering scheme demonstrated in JT-60U plasma that a factor of 1.6 increase of the scattered light in contrast with single-pass scattering. Second, an improvement of the output power of YAG laser system using the SBS-PCM was performed. As a result, average power was increased over 8 times in contrast with conventional system, and was achieved up to 368 W (7.4 J 
50 Hz). A multi-pass Thomson scattering scheme is also proposed based on the results of double-pass scattering.
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
Journal of Plasma and Fusion Research SERIES, Vol.6, p.17 - 72, 2004/00
A global gyrokinetic toroidal particle code for a 3D nonlinear simulation (GT3D) has been developed for a comprehensive study of the ion and electron anomalous transport arising from the ion temperature gradient driven - trapped electron mode (ITG-TEM) turbulence in tokamak plasmas. In the preliminary linear ITG-TEM calculations, basic properties of ITG-TEM modes are confirmed. Adding trapped electrons not only increases the growth rate of the ITG mode, but also produces another unstable electron mode, the TEM mode, which is unstable even at 
. The dominant mode changes from the ITG mode to the TEM mode depending on 
and 
. In linear benchmark calculations using Cyclone base case parameters, eigenfrequencies obtained from GT3D, GTC(PPPL-UCI) and FULL(PPPL) show reasonable quantitative agreement.
Iwase, Akihiro; Hamatani, Yutaro*; Mukumoto, Yoshinori*; Ishikawa, Norito; Chimi, Yasuhiro; Kambara, Tadashi*; M
ller, C.*; Neumann, R.*; Ono, Fumihisa*
Nuclear Instruments and Methods in Physics Research B, 209(1-4), p.323 - 328, 2003/08
Times Cited Count：21 Percentile：77.73(Instruments & Instrumentation)Fe=Ni Invar alloy is irradiated with GeV Xe and U ions at room temperature. By the irradiation, the Curie temperature of the soecimens increases, which is correlated with the electronic stopping power. This phenomenon can be explained as due to the lattice expansion and/or the local increase in Ni concentration.
Ogawa, Hiroaki*; Kiuchi, Kiyoshi
JAERI-Research 2002-037, 48 Pages, 2002/12
JAERI-Research-2002-037.pdf:2.57MB
The difference in hydrogen permeation among candidate cladding materials such as 25Cr-35Ni stainless steel, Nb liner and reference materials such as 18Cr-8Ni SS, and Zr of Zircaloy base metal were evaluated by low energy plasma permeation simulated to hydrogen excited by heavy neutron irradiation. RF excitation source was arranged for the experimental apparatus in cooperating with temperature and bias control. Comparing with the thermodynamic gas driven permeation (GDP) in the same hydrogen pressure, the hydrogen permeation rate by the plasma driven permeation (PDP) was markedly accelerated at low to medium temperature range. The temperature dependency showed a knick at around 530K due to hydrogen-defect interactions. Comparing with Zr, Nb showed the high hydrogen solubility without the degradation by hydrate formation that is required to a getter material. The difference in PDP among candidates was analyzed with a new dissolution model for hydrogen.
Kiuchi, Kiyoshi; Ioka, Ikuo; Tachibana, Katsumi; Suzuki, Tomio; Fukaya, Kiyoshi*; Inohara, Yasuto*; Kambara, Shozo; Kuroda, Yuji*; Miyamoto, Satoshi*; Ogura, Kazutomo*
JAERI-Research 2002-008, 63 Pages, 2002/03
JAERI-Research-2002-008.pdf:7.85MB
no abstracts in English
Serizawa, Hiroyuki; Arai, Yasuo
Journal of Alloys and Compounds, 312(1-2), p.257 - 264, 2001/00
Times Cited Count：11 Percentile：57.13(Chemistry, Physical)no abstracts in English
Hatae, Takaki; Naito, Osamu
Proceedings of 10th International Symposium on Laser-Aided Plasma Diagnostics, p.160 - 166, 2001/00
In recent strong electron heating experiments in JT-60U, it seems that central 
rises above 
15 keV which is measured by Ruby laser and YAG laser Thomson scattering systems. However, error bars are relatively large and it is difficult to measure the very high beyond 15 keV with high accuracy because the electron temperature region exceeds that of the original design. To improve the measurement performance in very high , we have tried the combination of existing Ruby laser system and YAG laser system. From simulations, it was found that (1) changing the form of the spectrum with the other laser is an effective way for very high measurement, (2) furthermore the combined system in YAG laser scattering is well optimized at 20keV and relative error is reduced significantly compared with original system.
Kojima, Takuji; Sunaga, Hiromi; Tachibana, Hiroyuki; Takizawa, Haruki; Tanaka, Ryuichi
IAEA-TECDOC-156, p.91 - 98, 2000/06
no abstracts in English
Seguchi, Tadao
Radiation Physics and Chemistry, 57, p.367 - 371, 2000/00
Times Cited Count：30 Percentile：85.19(Chemistry, Physical)no abstracts in English
Yoshida, Hidetoshi; Naito, Osamu; ; Kitamura, Shigeru; Hatae, Takaki; Nagashima, Akira
Review of Scientific Instruments, 70(1), p.747 - 750, 1999/01
Times Cited Count：4 Percentile：38.18(Instruments & Instrumentation)no abstracts in English
Yoshida, Hidetoshi; Naito, Osamu; Yamashita, Osamu; Kitamura, Shigeru; ; ; ; ; Hatae, Takaki; Nagashima, Akira; et al.
Review of Scientific Instruments, 70(1), p.751 - 754, 1999/01
Times Cited Count：16 Percentile：69.57(Instruments & Instrumentation)no abstracts in English
