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Idomura, Yasuhiro
Europhysics Conference Abstracts (Internet), 45A, 4 Pages, 2021/06
This work presents the impacts of the hydrogen isotope mass and the normalized plasma size on confinement of hydrogen (H) and deuterium (D) plasmas dominated by ion temperature gradient driven turbulence. Numerical experiments of H and D plasmas with ion and electron heating conditions were conducted using the Gyrokinetic Toroidal 5D full- f Eulerian code GT5D. The energy confinement time in the ion heated numerical experiments was almost independent of isotope mass, and the energy confinement was determined mainly by the normalized plasma size or the plasma size divided by the ion gyro radius, indicating an impact of non-local transport. On the other hand, the electron heated numerical experiments showed a clear isotope mass dependency. In addition to the plasma size effect, the isotope mass dependency of the collisional energy transfer from electrons to ions changes the ion heat flux and the turbulence intensity, leading to the degradation of confinement in H plasmas. These results qualitatively agree with the hydrogen isotope scaling in experiments.
Asahi, Yuichi*; Grandgirard, V.*; Idomura, Yasuhiro; Garbet, X.*; Latu, G.*; Sarazin, Y.*; Dif-Pradalier, G.*; Donnel, P.*; Ehrlacher, C.*
Physics of Plasmas, 24(10), p.102515_1 - 102515_17, 2017/10
Times Cited Count：7 Percentile：37.55(Physics, Fluids & Plasmas)Two full-F global gyrokinetic codes are benchmarked to compute flux-driven ion temperature gradient turbulence in tokamak plasmas. For this purpose, the Semi-Lagrangian code GYSELA and the Eulerian code GT5D are employed, which solve the full-F gyrokinetic equation with a realistic fixed flux condition. Using the appropriate settings for the boundary and initial conditions, flux-driven ITG turbulence simulations are carried out. The avalanche-like transport is assessed with a focus on spatio-temporal properties. A statistical analysis is performed to discuss this self-organized criticality (SOC) like behaviors, where we found 
spectra and a transition to 
spectra at high-frequency side in both codes. Based on these benchmarks, it is verified that the SOC-like behavior is robust and not dependent on numerics.
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.
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.
Villard, L.*; Angelino, P.*; Bottino, A.*; Allfrey, S. J.*; Hatzky, R.*; Idomura, Yasuhiro; Sauter, O.*; Tran, T. M.*
Plasma Physics and Controlled Fusion, 46(12B), p.B51 - B62, 2004/12
Times Cited Count：29 Percentile：67.01(Physics, Fluids & Plasmas)This paper reviews the present status of recent first principles based plasma turbulence simulations, and gives quantitative discussions on influences of the v// nonlinearlity and the geometry effects in the gyrokinetic Poisson equaiton, which are ignored in the conventional approximations, on simulations results. Careful treatments of these effects enable turbulence simulations satisfying the conservation of the energy and the particle number. The new simulation disclosed new phenomena, and it is found that (1) turbulence spreading is induced by avalanche like phnemena consisting of bursty heat transport and local flattening of pressure profiles, and (2) nonlinearly driven E
B flows become global shear flows with scale lengths of about 30 ion gyro radii.
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.
Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki
Nuclear Fusion, 43(4), p.234 - 243, 2003/04
Times Cited Count：119 Percentile：94.91(Physics, Fluids & Plasmas)no abstracts in English
Idomura, Yasuhiro
no journal, ,
Decaying turbulence simulations of ion temperature gradient driven (ITG) turbulence with adiabatic electrons and ion temperature gradient driven trapped electron mode (ITG-TEM) turbulence with kinetic electrons are performed using a full-f gyrokinetic code. Nonlinear critical temperature gradients exceeding linear critical temperature gradients are observed in both simulations, and mechanisms to sustain them are investigated. It is found that unlike zonal flows in the ITG turbulence, the ITG-TEM turbulence produces corrugated electron density profiles, which form radial electric fields with strong shear following a force balance relation.
Idomura, Yasuhiro
no journal, ,
We develop a kinetic electron model for electrostatic ion temperature gradient driven trapped electron mode (ITG-TEM) turbulence simulations in the Gyrokinetic Toroidal 5D full-f Eulerian code, GT5D. In the model, a full kinetic electron model is used for computing collisional processes and radial electric fields, while turbulent fluctuations are computed by kinetic response of trapped electrons only in order to avoid a high frequency mode, which appear as the electrostatic limit of kinetic Alfv
n waves. By using this model, we compare full-f gyrokinetic simulations of ITG turbulence with adiabatic and kinetic electron models, and discuss influences of kinetic electrons on ion turbulent transport.
Idomura, Yasuhiro
no journal, ,
To analyze electrostatic turbulence including trapped electron modes (TEMs), a kinetic electron model is developed in the gyrokinetic full-f Eulerian code GT5D. This model computes turbulent fields by assuming kinetic trapped electrons responses and adiabatic passing electrons, and describes collisional processes of the ion-electron system using multi-species Fokker-Planck operator. Linear growth rates of ITG-TEMs and ion-electron neoclassical transport are successfully reproduced, and a nonlinear critical temperature gradient is found by decaying turbulence simulations.
Asahi, Yuichi*; Garbet, X.*; Idomura, Yasuhiro; Grandgirard, V.*; Latu, G.*; Sarazin, Y.*; Dif-Pradalier, G.*; Donnel, P.*; Ehrlacher, C.*; Passeron, Ch.*
no journal, ,
Two global full-f gyrokinetic codes, which have been developed at CEA and JAEA, are benchmarked. Quantitative agreements between two codes are obtained regarding linear processes such as the linear stability of ion temperature gradient driven modes, the linear damping of zonal flows, and the collisional transport. Preliminary benchmarks on nonlinear turbulence simulations show some differences of calculation results, which arise due to differences in calculation models such as boundary conditions and heat source models, and the remaining issues towards quantitative nonlinear benchmarks are clarified.
Idomura, Yasuhiro
no journal, ,
Gyrokinetics gives first principles based descriptions of multi-scale phenomena in fusion plasmas ranging from micro-scale plasma turbulence to macro-scale plasma profiles. The development of supercomputers enabled full-f gyrokinetic simulations, which directly compute the multi-scale problem, which conventional 
f simulation realized low cost simulations by avoiding the multi-scale problem under scale separation between them. Moreover, recent development of a kinetic electron model enabled more realistic numerical experiments including electron turbulence, and experimental observations, in which electron turbulence plays a critical role, have been analyzed. In this invited talk, the progress of full-f gyrokinetic simulations leading to the latest electron turbulence simulation is reviewed.
