Publications de Laurent Villard

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The spectrum of n = 0 Alfven modes is calculated analytically and numerically in cylindrical and toroidal geometries. It includes global Alfven eigenmodes (GAEs) and surface modes (SMs) of the fast magnetoacoustic wave. These modes are not induced by toroidicity. The n = 0 GAEs owe their existence to shear. The frequency spacing between different radial and poloidal modes and the correlation of eigenfrequencies with changes in the edge density are examined and found to be in complete agreement with experime

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 ...

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 ...

The abstract goes here.

In this Letter, it is shown that global, nonlinear, particle-in-cell (PIC) simulations of electron temperature driven turbulence recover the same level of transport as flux-tube codes when the level of statistical noise, associated with the PIC discretizat ...

Stability limits against external kink modes driven by large current density and pressure gradient values in the pedestal region are investigated for tokamak plasmas with separatrix. Stability diagrams for modes with different toroidal wave numbers under v ...

Collective communication, namely the pattern allreduce in message-passing systems, is optimised based on measurements at the installation time of the library. The algorithms used are set up in an initialisation phase of the communication, as so-called pers ...

The Eulerian gyrokinetic turbulence code GENE has recently been extended to a full torus code. Moreover, it now provides Krook-type sources for gradient-driven simulations where the profiles are maintained on average as well as localized heat sources for a ...

The pullback scheme is implemented in the global gyrokinetic particle-in-cell code ORB5 (Jolliet et al., 2007[1]) to mitigate the cancellation problem in electromagnetic simulations. The equations and the discretisation used by the code are described. Nume ...

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 ...

A quasilinear operator for wave-particle interactions in the electron cyclotron range is derived using the cold plasma dispersion relation. The finite width of the beam implies a broadening of the resonance layer in the velocity space which allows the use ...

Laurent Villard

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Gyrokinetic simulations of shaping effects on turbulent heat and particle transport observed on the TCV tokamak

Alfven frequency modes and global Alfven eigenmodes

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

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

3D warm effects for low-frequency wave propagation in magnetically confined plasmas

First Measurement of the Damping Rate of High-n Toroidal Alfvén Eigenmodes in JET Tokamak Plasmas

Reversed current density in tokamaks - equilibrium and stability issues

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

Gyrokinetic simulations of microturbulence in tokamak plasmas presenting an electron internal transport barrier, and development of a global version of the GENE code

Reversed current density in tokamaks - equilibrium and stability issues

Nonlinear low noise particle-in-cell simulations of electron temperature gradient driven turbulence

Edge kink/ballooning mode stability in tokamaks with separatrix

An optimisation of allreduce communication in message-passing systems

Flux- and gradient-driven global gyrokinetic simulation of tokamak turbulence

Pullback Scheme Implementation in ORB5

Three-dimensional warm plasma simulations for low-frequency waves

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

Quasilinear treatment of wave-particle interactions in the electron cyclotron range and its implementation in a gyrokinetic code

Gyrokinetic particle simulations of ITG modes and zonal flows with canonical and local equilibrium distributions

Benchmark of a semi-Lagrangian and a Lagrangian code for gyrokinetic simulations