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Laurent Villard

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Publications associées (144)

Global Nonlinear Electromagnetic Simulations of Tokamak Turbulence

Stephan Brunner, Trach-Minh Tran, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Thibaut Vernay, Ben McMillan

The particle-in-cell code ORB5 is a global gyrokinetic turbulence simulation code in tokamak geometry. It has been developed at CRPP, Lausanne, Switzerland, with major contributions from IPP, Garching, Germany, and IPP, Greifswald, Germany, under a long-st ...

Institute of Electrical and Electronics Engineers2010

Tokamak Magnetohydrodynamic Equilibrium States with Axisymmetric Boundary and a 3D Helical Core

Wilfred Anthony Cooper, Antoine Pochelon, Olivier Sauter, Laurent Villard, Jonathan Graves

Magnetohydrodynamic (MHD) equilibrium states with imposed axisymmetric boundary are computed in which a spontaneous bifurcation develops to produce an internal three-dimensional (3D) configuration with a helical structure in addition to the standard axisym ...

American Physical Society2010

System size effects on gyrokinetic turbulence

Laurent Villard, Alberto Bottino, Sébastien Jolliet, Xavier Lapillonne, Ben McMillan

The scaling of turbulence-driven heat transport with system size in magnetically confined plasmas is reexamined using first-principles based numerical simulations. Two very different numerical methods are applied to this problem, in order to resolve a long ...

The American Physical Society2010

Toroidal Universal Drift Instability: A Global Gyrokinetic Study

Stephan Brunner, Laurent Villard

An electron density gradient driven instability identified as the toroidal branch of the universal drift instability is studied using a global gyrokinetic model treating both electrons and ions fully nonadiabatically and valid at all orders in the ratio of ...

American Institute of Physics (AIP)2010

Gyrokinetic simulations of turbulent transport: size scaling and chaotic behaviour

Stephan Brunner, Trach-Minh Tran, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Thibaut Vernay, Xavier Lapillonne, Ben McMillan

Important steps towards the understanding of turbulent transport have been made with the development of the gyrokinetic framework for describing turbulence and with the emergence of numerical codes able to solve the set of gyrokinetic equations. This paper ...

IOP Publishing2010

Gyrokinetic simulations of turbulent transport

Laurent Villard

This overview is an assessment of the gyrokinetic framework and simulations to compute turbulent transport in fusion plasmas. It covers an introduction to the gyrokinetic theory, the principal numerical techniques which are being used to solve the gyrokine ...

IOP Publishing Ltd2010

Nonlinear quasisteady state benchmark of global gyrokinetic codes

Stephan Brunner, Laurent Villard, Xavier Lapillonne, Ben McMillan

Two global gyrokinetic codes are benchmarked against each other by comparing simulation results in the case of ion temperature gradient driven turbulence, in the adiabatic electron response limit The two codes are the Eulerian code GENE and the Lagrangian ...

American Institute of Physics2010

Neoclassical equilibria as starting point for global gyrokinetic microturbulence simulations

Stephan Brunner, Trach-Minh Tran, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Jonathan Graves, Thibaut Vernay, Ben McMillan

The implementation of linearized operators describing inter- and like-species collisions in the global gyrokinetic particle-in-cell code ORB5 [ S. Jolliet, Comput. Phys. Commun. 177, 409 (2007) ] is presented. A neoclassical axisymmetric equilibrium with s ...

American Institute of Physics2010

Global collisional gyrokinetic simulations of ITG microturbulence starting from a neoclassical equilibrium

Stephan Brunner, Olivier Sauter, Trach-Minh Tran, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Thibaut Vernay, Ben McMillan

Linearized operators describing inter-species and like-species collisions have been discretized and implemented in the gyrokinetic Particle-In-Cell (PIC) code ORB5 [S. Jolliet, Comp. Phys. Comm. 177, 409 ( 2007)] based on the delta-f approach. Simulation r ...

Iop Publishing Ltd, Dirac House, Temple Back, Bristol Bs1 6Be, England2010

Comparing magnetic triggering of ELMs in TCV and ASDEX Upgrade

Jonathan Bryan Lister, Yves Martin, Laurent Villard, Sun Hee Kim

Frequency locking of edge localized modes (ELMs) to the vertical plasma movements induced by magnetic perturbations first demonstrated in TCV was successfully repeated in ASDEX Upgrade. However, the ELMs were triggered in ASDEX Upgrade when the plasma was ...

2009

Rapid Fourier space solution of linear partial differential equations in toroidal magnetic confinement geometries

Trach-Minh Tran, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Paolo Angelino, Ben McMillan

Fluctuating quantities in magnetic confinement geometries often inherit a strong anisotropy along the field lines. One technique for describing these structures is the use of a certain set of Fourier components on the tori of nested flux surfaces. We descr ...

Elsevier2009

Clarifications to the limitations of the s-alpha equilibrium model for gyrokinetic computations of turbulence

Stephan Brunner, Laurent Villard, Sébastien Jolliet, Alessandro Marinoni, Xavier Lapillonne

In the context of gyrokinetic flux-tube simulations of microturbulence in magnetized toroidal plasmas, different treatments of the magnetic equilibrium are examined. Considering the Cyclone DIII-D base case parameter set [Dimits et al., Phys. Plasmas 7, 96 ...

American Institute of Physics2009

The effect of plasma triangularity on turbulent transport:modelling TCV experiments by linear and non linear gyrokinetic simulations

Stephan Brunner, Antoine Pochelon, Olivier Sauter, Laurent Villard, Stefano Coda, Yann Camenen, Jonathan Graves, Alessandro Marinoni, Xavier Lapillonne

The effect of plasma shape on confinement has been experimentally explored in the TCV tokamak revealing that the core electron heat transport is significantly reduced by a negative triangularity configuration, which could indicate a (partial) stabilization ...

2009

Avalanche-like bursts in global gyrokinetic simulations

Trach-Minh Tran, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Paolo Angelino, Ben McMillan

Highly variable flux surface averaged heat fluxes are resolved in gyrokinetic simulations of ion temperature gradient (ITG) turbulence, even in large systems. Radially propagating fronts or avalanches are also seen. Their propagation lengths in gyroradii a ...

American Institute of Physics (AIP)2009

The role of plasma elongation on turbulent transport in magnetically confined plasmas

Trach-Minh Tran, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Paolo Angelino, Ben McMillan

The theoretical study of plasma turbulence is of central importance to fusion research. Experimental evidence indicates that the confinement time results mainly from the turbulent transport of energy, the magnitude of which depends on the turbulent state r ...

American Physical Society2009

Quasi-steady and steady states in global gyrokinetic particle-in-cell simulations

Laurent Villard, Alberto Bottino, Sébastien Jolliet, Paolo Angelino, Thibaut Vernay, Ben McMillan

Collisionless delta-f gyrokinetic particle-in-cell simulations suffer from the entropy paradox, in which the entropy grows linearly in time while low-order moments are saturated. As a consequence, these simulations do not reach a steady state and are unsui ...

American Institute of Physics (AIP)2009

A comprehensive gyrokinetic description of global electrostatic microinstabilities in a tokamak

Stephan Brunner, Laurent Villard, Paolo Angelino

It is believed that low frequency microinstabilities such as ion temperature gradient (ITG) driven modes and trapped electron modes (TEMs) are largely responsible for the experimentally observed anomalous transport via the ion and electron channels in a to ...

American Institute of Physics (AIP)2009

Influence of the parallel nonlinearity on zonal flows and heat transport in global gyrokinetic particle-in-cell simulations

Laurent Villard, Alberto Bottino, Sébastien Jolliet, Paolo Angelino, Thibaut Vernay, Ben McMillan

In this paper, the influence of the parallel nonlinearity on zonal flows and heat transport in global particle-in-cell ion-temperature-gradient simulations is studied. Although this term is in theory orders of magnitude smaller than the others, several aut ...

American Institute of Physics (AIP)2009

The role of plasma elongation on the linear damping of zonal flows

Trach-Minh Tran, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Paolo Angelino, Ben McMillan

American Institute of Physics (AIP)2008

Role of nonadiabatic untrapped electrons in global electrostatic ion temperature gradient driven modes in a tokamak

Stephan Brunner, Laurent Villard, Paolo Angelino

In this work, role of nonadiabatic untrapped electrons in the context of a global ion temperature gradient driven mode has been investigated. In past studies, untrapped electrons have been assumed to be able to respond "instantaneously" to a disturbance. I ...

American Institute of Physics2008

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