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Jolliet, S.; McMillan, B. F.*; Villard, L.*; Vernay, T.*; Angelino, P.*; Tran, T. M.*; Brunner, S.*; Bottino, A.*; 井戸村 泰宏
Journal of Computational Physics, 231(3), p.745 - 758, 2012/02
被引用回数：13 パーセンタイル：60.98(Computer Science, Interdisciplinary Applications)In this work, a Fourier solver is implemented in the global Eulerian gyrokinetic code GT5D and in the global Particle-In-Cell code ORB5 in order to reduce the memory of the matrix associated with the field equation. This scheme is verified with linear and nonlinear simulations of turbulence. It is demonstrated that the straight-field-line angle is the coordinate that optimizes the Fourier solver, that both linear and nonlinear turbulent states are unaffected by the parallel filtering, and that the 
spectrum is independent of plasma size at fixed normalized poloidal wave number.
Labit, B.*; Pochelon, A.*; Rancic, M.*; Piras, F.*; Bencze, A.*; Bottino, A.*; Brunner, S.*; Camenen, Y.*; Chattopadhyay, P. K.*; Coda, S.*; et al.
Proceedings of 23rd IAEA Fusion Energy Conference (FEC 2010) (CD-ROM), 8 Pages, 2011/03
We present recent results on turbulence measurements in TCV L-mode plasmas. The transport reduction at negative triangularity (compared to positive triangularity) is reflected in the reduction of the temperature fluctuation level, in the low frequency part of the spectrum (30-150 kHz), measured by correlation ECE in the outer equatorial plane. The TEM induced transport computed from nonlinear gyrokinetic simulations is shown to decrease with decreasing triangularity and increasing collisionality. First results of an experimental scenario to reach the H-mode regime at negative triangularity in TCV are presented. Then, we report on an innovative divertor magnetic configuration: the snowflake (SF) divertor as opposed to the classical single-null (SN) divertor. For ELMy SF plasmas, the strike-point properties (density, temperature, fluctuation level,...) are studied with Langmuir probes (LPs) and compared with those of a SN configuration obtained within the same discharge.
Villard, L.*; Bottino, A.*; Brunner, S.*; Casati, A.*; Chowdhury, J.*; Dannert, T.*; Ganesh, R.*; Garbet, X.*; G
rler, T.*; Grandgirard, V.*; et al.
Plasma Physics and Controlled Fusion, 52(12), p.124038_1 - 124038_18, 2010/11
被引用回数：18 パーセンタイル：56.51(Physics, Fluids & Plasmas)This paper presents some of the main recent advances in gyrokinetic theory and computing of turbulence. A past controversy regarding the finite size (finite 
) effect in ITG turbulence has now been resolved. Now, both Eulerian and Lagrangian global codes are shown to agree and to converge to the flux-tube result in the 
0 limit. It is found, however, that an appropriate treatment of geometrical terms is necessary. Turbulent processes are characterized by a chaotic behavior, often accompanied by bursts and avalanches. Performing ensemble averages of statistically independent simulations, starting from different initial conditions, is presented as a way to assess the intrinsic variability of turbulent fluxes and obtain reliable estimates of the standard deviation.
McMillan, B. F.*; Lapillonne, X.*; Brunner, S.*; Villard, L.*; Jolliet, S.; Bottino, A.*; Grler, T.*; Jenko, F.*
Physical Review Letters, 105(15), p.155001_1 - 155001_4, 2010/10
被引用回数：100 パーセンタイル：93.39(Physics, Multidisciplinary)The scaling of turbulence-driven heat transport with system size in magnetically confined plasmas is re-examined using first-principles based numerical simulations. Two very different numerical methods are applied to this problem, in order to resolve a long-standing quantitative disagreement, which may have arisen due to inconsistencies in the geometrical approximation. System size effects are further explored by modifying the width of the strong gradient region at fixed system size. The finite width of the strong gradient region in gyroradius units, rather than the finite overall system size, is found to induce the diffusivity reduction seen in global gyrokinetic simulations.
Bottino, A.*; Scott, B. D.*; Brunner, S.*; McMillan, B. F.*; Tran, T. M.*; Vernay, T.*; Villard, L.*; Jolliet, S.; Hatzky, R.*; Peeters, A. G.*
IEEE Transactions on Plasma Science, 38(9), p.2129 - 2135, 2010/09
被引用回数：26 パーセンタイル：69.51(Physics, Fluids & Plasmas)The particle-in-cell code ORB5 is a global gyrokinetic turbulence simulation code in tokamak geometry. It solves the gyrokinetic equation in the whole plasma core, including the magnetic axis. A field-aligned filtering procedure and sophisticated noise/control and heating operators allow for accurate simulations. Recently, the code ORB5 has been extended to include self-consistent perpendicular magnetic field perturbations. The inclusion of magnetic perturbations allows for a comprehensive study of finite 
effects on microinstability. In this paper, we present the first linear and nonlinear code results concerning electromagnetic effects on tokamak microinstabilities.
Bottino, A.*; Angelino, P.*; Allfrey, S. J.*; Brunner, S.*; Hatzky, R.*; 井戸村 泰宏; Jolliet, S.*; Sauter, O.*; Tran, T. M.*; Villard, L.*
Theory of Fusion Plasmas, ISPP21, p.75 - 86, 2004/00
非線形静電的グローバルPICコードORB5は実MHD平衡において、断熱的電子応答を仮定してジャイロ運動論的Vlasov-Poisson系を解析する。最適化粒子配分法と適応幅ジャイロ平均アルゴリズムの実装により、現バージョンのコードは非常に優れて粒子・エネルギー保存特性を有する。この基本的な保存特性は数値シミュレーションの質を測る量として重要である。論文ではExB帯状流と平行速度非線形性を含めた静電的無衝突微視的不安定性のシミュレーション結果をCHEASEコードから得られた実MHD並行配位において初めて示す。
Vernay, T.*; Brunner, S.*; Villard, L.*; Jolliet, S.; McMillan, B. F.*; Lapillonne, X.*
no journal, ,
In this work, a Lorentz collision operator using a random walk over the pitch angle, as well as a full, linearized self-collision operator including a random walk in velocity space and a background reaction acting on the weights, are implemented in a simple 1D Particle-In-Cell (PIC) code simulating Langmuir waves with a 2 weights scheme. The crucial conservation properties of the discretized collision operators are explained. In a second step, the implementations of the 2 weights scheme and such operators in the global gyrokinetic PIC code ORB5 are presented. Some results concerning the effects of collisions on micro-instabilities and neoclassical transport are studied.
菊池 満; Fasoli, A.*; 滝塚 知典*; Diamond, P.*; Medvedev, S.*; Duan, X.*; 図子 秀樹*; 古川 勝*; 岸本 泰明*; Wu, Y.*; et al.
no journal, ,
トカマクにおける標準的なD型Hモードプラズマシナリオは熱粒子制御の観点からは課題を含んでいる。革新的なトカマク配位として負三角度の可能性が菊池等によって議論されている。CRPP-EPFLによる負三角度プラズマの実験と理論研究で閉じ込め改善が報告されており、負三角度配位はSOL流速の低減が示唆される。近年のタイプII ELMやグラッシーELMの理論研究によると第2安定化領域へのアクセスを閉じることと運動論的効果が小ELMの達成に重要であることがわかってきた。Medvedevによると負三角度では第2安定化領域への窓が閉じることが分かっている。講演では、これらを含む最近の理解進展をまとめる。
井戸村 泰宏; 松岡 清吉; 伊奈 拓也; Garbet, X.*; Brunner, S.*; Villard, L.*; 河合 智賀*
no journal, ,
本講演では、平成26年度-28年度に実施したGT5DISOプロジェクトの研究成果を概説する。本プロジェクトではジャイロ運動論的トロイダル5次元full-fオイラーコードGT5Dを用いて乱流輸送の同位体効果を研究してきた。平成26年度には、断熱応答電子のイオン温度勾配駆動(ITG)乱流には同位体効果が見られず、運動論的捕捉電子が駆動する捕捉電子モード(TEM)がこの問題において重要となることを示した。平成27年度には、GT5Dにおいて新たなハイブリッド運動論的電子モデルを開発し、ITG-TEM乱流計算の精度検証を実施した。平成28年度には、TEM乱流が粒子と運動量の輸送において重要な役割を果たす電子変調加熱実験に対する運動論的電子モデルの実証研究を実施した。最後に、ITG-TEM乱流計算の同位体スキャンを実施し、水素プラズマと重水素プラズマで閉じ込め特性が異なる傾向を確認した。
