Transport and turbulence with innovative plasma shapes in the TCV tokamak

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

http://www-naweb.iaea.org/napc/physics/FEC/FEC2010/html/node584.htm#113563

System size effects on gyrokinetic turbulence

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

https://doi.org/10.1103/PhysRevLett.105.155001

Gyrokinetic simulations of turbulent transport

Garbet, X.*; Idomura, Yasuhiro; Villard, L.*; Watanabe, Tomohiko*

Nuclear Fusion, 50(4), p.043002_1 - 043002_30, 2010/04

https://doi.org/10.1088/0029-5515/50/4/043002

This overview is an assessment of the gyrokinetic framework and simulations to compute the turbulent transport in fusion plasmas. It covers an introduction to the gyrokinetic theory, the principal numerical techniques which are being used to solve the gyrokinetic equations, fundamentals in gyrokinetic turbulence and the main results which have been brought by simulations with regard to transport in fusion devices and actuation measurements.

New conservative gyrokinetic full- Vlasov code and its comparison to gyrokinetic particle-in-cell code

Idomura, Yasuhiro; Ida, Masato; Tokuda, Shinji; Villard, L.*

Journal of Computational Physics, 226(1), p.244 - 262, 2007/09

https://doi.org/10.1016/j.jcp.2007.04.013

A new conservative gyrokinetic full- Vlasov code is developed using a finite difference operator which conserves both the and norms. The growth of numerical oscillations is suppressed by conserving the norm, and the code is numerically stable and robust in a long time simulation. In the slab ion temperature gradient driven (ITG) turbulence simulation, the energy conservation and the entropy balance relation are confirmed, and solutions are benchmarked against a conventional particle-in-cell (PIC) code. The results show that the exact particle number conservation and the good energy conservation in the conservative Vlasov simulation are advantageous for a long time micro-turbulence simulation. In the comparison, physical and numerical effects of the nonlinearity are clarified for the Vlasov and PIC simulations.

First principles based simulations of instabilities and turbulence

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

https://doi.org/10.1088/0741-3335/46/12B/005

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 EB flows become global shear flows with scale lengths of about 30 ion gyro radii.

A Linear gyrokinetic model in magnetic coordinates

Jolliet, S.*; Angelino, P.*; Bottino, A.*; Idomura, Yasuhiro; Villard, L.*

Theory of Fusion Plasmas, ISPP21, p.345 - 351, 2004/00

Global particle-in-cell (PIC) simulations are a very useful tool for studying the time evolution of turbulence induced by ion-temperature-gradient (ITG) instabilities. Unfortunately, the linear code LORB5 and its non-linear version ORB5 require high computational power. In order to study more sophisticated models, we need to optimize these codes. We will focus on LORB5, which uses a cylindrical grid (r,z) for solving the Vlasov equation and a (s,) grid for the Poisson equation. The approach presented in this work consists of implementing the gyrokinetic model using a single (s,) grid. Here is the straight-field-line poloidal coordinate. A method to avoid the singularity at the magnetic axis is presented, and a benchmark with the CYCLONE case is shown.

Gyrokinetic PIC simulation of trapped electron mode turbulence

Jolliet, S.*; Villard, L.*; Idomura, Yasuhiro; McMillan, B. F.*; Bottino, A.*; Lapillonne, X.*

no journal, , 

no abstracts in English

Collisions in global gyrokinetic particle-in-cell code ORB5

Vernay, T.*; Brunner, S.*; Villard, L.*; Jolliet, S.; McMillan, B. F.*; Lapillonne, X.*

no journal, , 

Progress of understanding negative triangular tokamak configuration

Kikuchi, Mitsuru; Fasoli, A.*; Takizuka, Tomonori*; Diamond, P.*; Medvedev, S.*; Duan, X.*; Zushi, Hideki*; Furukawa, Masaru*; Kishimoto, Yasuaki*; Wu, Y.*; et al.

no journal, , 

Power and particle control is challenging for standard D-shaped H-mode scenario in tokamak. Possibility of negative triangularity as innovative tokamak concept is discussed by Kikuchi et al. Experimental and numerical studies of negative triangular plasma at CRPP-EPFL success-fully demonstrated improved connement and the weakening of the SOL flow acceleration is implied for the negative triangularity. Recent studies on mechanism of type II and grassy ELM show importance of closure of second stability access to achieve small ELM regimes and also kinetic effects. Medvedev showed that closure of second stability also occurs for negative triangularity. But the MHD stability in negative triangularity is a bit more complicated so that closure of second stability does not imply easy access to small ELM regimes. We discuss critical elements behind.