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Journal Articles

Benchmarking of flux-driven full-F gyrokinetic simulations

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

AA2017-0418.pdf:4.26MB

 Times Cited Count:3 Percentile:23.72(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 $$1/f$$ spectra and a transition to $$1/f^3$$ 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.

Journal Articles

Saturation mechanism of decaying ion temperature gradient driven turbulence with kinetic electrons

Idomura, Yasuhiro

Plasma and Fusion Research (Internet), 11, p.2403006_1 - 2403006_5, 2016/02

BB2015-1300.pdf:0.58MB

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.

Journal Articles

$$delta f$$ simulations of microturbulence

Idomura, 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 $$delta f$$ 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 $$delta f$$ method is reviewed, and issues in full torus gyrokinetic particle simulations are discussed.

Journal Articles

Gyrokinetic simulations of tokamak micro-turbulence including kinetic electron effects

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 $$eta_i = 0$$. The dominant mode changes from the ITG mode to the TEM mode depending on $$k_theta$$ and $$eta_i$$. In linear benchmark calculations using Cyclone base case parameters, eigenfrequencies obtained from GT3D, GTC(PPPL-UCI) and FULL(PPPL) show reasonable quantitative agreement.

Journal Articles

Global gyrokinetic simulation of ion temperature gradient driven turbulence in plasmas using a canonical Maxwellian distribution

Idomura, Yasuhiro; Tokuda, Shinji; Kishimoto, Yasuaki

Nuclear Fusion, 43(4), p.234 - 243, 2003/04

 Times Cited Count:112 Percentile:95.35(Physics, Fluids & Plasmas)

no abstracts in English

Oral presentation

Formations of radial electric fields and critical temperature gradients in ion temperature gradient driven trapped electron mode turbulence

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.

Oral presentation

Full-f gyrokinetic simulation including kinetic electrons

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$'e$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.

Oral presentation

Development of kinetic electron model in full-f gyrokinetic simulation

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.

Oral presentation

Benchmarking of global full-f gyrokinetic codes

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.

Oral presentation

Progress of full-f gyrokinetic simulations including kinetic electrons

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 $$delta$$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.

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