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Laurent Villard

Cette personne a quitté l’EPFL

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Publications associées (137)

Page 2 sur 7

Non-Linear Gyrokinetic Simulations of Microturbulence in TCV Electron Internal Transport Barriers

Stephan Brunner, Olivier Sauter, Laurent Villard, Emiliano Fable

Using the local (flux-tube) version of the Eulerian code GENE (Jenko et al 2000 Phys. Plasmas 7 1904), gyrokinetic simulations of microturbulence were carried out considering parameters relevant to electron-internal transport barriers (e-ITBs) in the TCV t ...

IOP Publishing2011

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

Study of fast-ion-driven toroidal Alfvén eigenmodes impacting on the global confinement in TCV L-mode plasmas

Stephan Brunner, Laurent Villard, Stefano Coda, Javier García Hernández, Aylwin Iantchenko, Justin Richard Ball, Matteo Vallar, Umesh Kumar, Oleg Krutkin, Luke Simons, Jesús Poley Sanjuán, Samuele Mazzi, Baruch Rofman

Following recent observations of unstable Toroidal Alfven Eigenmodes (TAEs) in a counter-current Neutral Beam Injection (NBI) scenario developed in TCV, an in-depth analysis of the impact of such modes on the global confinement and performance is carried o ...

2023

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

Effects of plasma current on nonlinear interactions of ITG turbulence, zonal flows and geodesic acoustic modes

Olivier Sauter, Trach-Minh Tran, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Paolo Angelino

The mutual interactions of ion temperature gradient (ITG) driven modes, zonal flows and geodesic acoustic modes (GAM) in tokamak plasmas are investigated using a global nonlinear gyrokinetic formulation with totally unconstrained evolution of temperature g ...

Institute of Physics2006

Parallel filtering in global gyrokinetic simulations

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

In this work, a Fourier solver [B.F. McMillan, S. Jolliet, A. Bottino, P. Angelino, T.M. Tran, L Villard, Comp. Phys. Commun. 181 (2010) 7151 is implemented in the global Eulerian gyrokinetic code GT5D [Y. Idomura, H. Urano, N. Aiba, S. Tokuda, Nucl. Fusio ...

Elsevier2012

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

Gyrokinetic flux-driven simulations in mixed TEM/ITG regime using a delta-f PIC scheme with evolving background

Stephan Brunner, Laurent Villard, Moahan Murugappan, Giovanni Di Giannatale

In the context of global gyrokinetic simulations of turbulence using a particle-in-cell framework, verifying the delta-f assumption with a fixed background distribution becomes challenging when determining quasi-steady state profiles corresponding to given ...

American Institute of Physics (AIP)2024

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

Laurent Villard

A new conservative gyrokinetic full-f Vlasov code is developed using a finite difference operator which conserves both the L1 and L2 norms. The growth of numerical oscillations is suppressed by conserving the L2 norm, and the code is numerically stable and ...

2007

An arbitrary wavelength solver for global gyrokinetic simulations. Application to the study of fine radial structures on microturbulence due to non-adiabatic passing electron dynamics

Stephan Brunner, Trach-Minh Tran, Laurent Villard, Ben McMillan, Julien Stanislas Pierre Dominski, Gabriele Merlo

The influence of the fine layers of the non-adiabatic passing electron response on electrostatic turbulent transport, previously studied systematically in flux tube geometry [Dominski et al., Phys. Plasmas 22, 062303 (2015)], is pursued in global geometry ...

Amer Inst Physics2017

Gyrokinetic investigation of Alfven instabilities in the presence of turbulence

Laurent Villard, Alberto Bottino

The nonlinear dynamics of beta-induced Alfven eigenmodes (BAEs) driven by energetic particles (EPs) in the presence of ion-temperature-gradient turbulence is investigated, by means of selfconsistent global gyrokinetic simulations and analytical theory. A t ...

2021

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

Modelling of advanced three-ion ICRF heating and fast ion generation scheme for tokamaks and stellarators

Wilfred Anthony Cooper, Laurent Villard, Jonathan Graves, David Pfefferlé, Jonathan Marc Philippe Faustin, Samuel Lanthaler

Absorption of ion-cyclotron range of frequencies waves at the fundamental resonance is an efficient source of plasma heating and fast ion generation in tokamaks and stellarators. This heating method is planned to be exploited as a fast ion source in the We ...

2017

Nonlinear interaction of Alfvénic instabilities and turbulence via the modification of the equilibrium profiles

Laurent Villard, Alberto Bottino

Nonlinear simulations of Alfvén modes (AMs) driven by energetic particles (EPs) in the presence of turbulence are performed with the gyrokinetic particle-in-cell code ORB5. The AMs carry a heat flux, and consequently they nonlinearly modify the plasma temp ...

Cambridge University Press2023

The negative triangularity tokamak: stability limits and prospects as a fusion energy system

Ambrogio Fasoli, Olivier Sauter, Laurent Villard, Andrei Martynov, Yu Wu

The paper discusses edge stability, beta limits and power handling issues for negative triangularity tokamaks. The edge magnetohydrodynamic stability is the most crucial item for power handling. For the case of negative triangularity the edge stability pic ...

IOP Publishing Ltd2015

Padé approximation of the adiabatic electron contribution to the gyrokinetic quasi-neutrality equation in the ORB5 code

Stephan Brunner, Laurent Villard, Ben McMillan, Emmanuel Lanti, Julien Stanislas Pierre Dominski

This work aims at completing the implementation of a solver for the quasineutrality equation using a PadÃ© approximation in the global gyrokinetic code ORB5. Initially [Dominski, Ph.D. thesis, 2016], the Pade approximation was only implemented for the kine ...

2016

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

Global gyrokinetic stability of collisionless microtearing modes in large aspect ratio tokamaks

Stephan Brunner, Laurent Villard

Linear full radius gyrokinetic calculations show the existence of unstable microtearing modes (MTMs) in purely collisionless, high temperature, large aspect ratio tokamak plasmas. The present study takes into account fully gyrokinetic highly passing ions a ...

Amer Inst Physics2014

A portable platform for accelerated PIC codes and its application to GPUs using OpenACC

Stephan Brunner, Trach-Minh Tran, Laurent Villard, Emmanuel Lanti, Claudio Gheller

We present a portable platform, called PIC_ENGINE, for accelerating Particle-In-Cell (PIC) codes on heterogeneous many-core architectures such as Graphic Processing Units (GPUs). The aim of this development is efficient simulations on future exascale syste ...

Elsevier Science Bv2016

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