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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.
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
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.
