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Laurent Villard

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Publications associées (144)

Gyrokinetic particle-in-cell simulations of electromagnetic turbulence in the presence of fast particles and global modes

Laurent Villard, Emmanuel Lanti

Global simulations of electromagnetic turbulence in circular-flux-surface tokamak and ASDEX-Upgrade geometry, tearing instabilities and their combination with the electromagnetic turbulence, nonlinear Alfvenic modes in the presence of fast particles and th ...

2022

EUROfusion-theory and advanced simulation coordination (E-TASC): programme and the role of high performance computing

Laurent Villard, Jonathan Graves, Eric Serre

This paper is a written summary of an overview oral presentation given at the 1st Spanish Fusion High Performance Computer (HPC) Workshop that took place on the 27 November 2020 as an online event. Given that over the next few years ITER24 will move to its ...

2022

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

Stephan Brunner, Laurent Villard, Stefano Coda

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 ...

2021

An optimisation of allreduce communication in message-passing systems

Laurent Villard, Emmanuel Lanti, Noé Thomas Elie Ohana

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 ...

2021

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

Implementation of energy transfer technique in ORB5 to study collisionless wave-particle interactions in phase-space

Laurent Villard, Alberto Bottino, Emmanuel Lanti, Noé Thomas Elie Ohana, Emanuele Poli

A new diagnostic has been developed to investigate the wave-particle interaction in the phase-space in gyrokinetic particle-in-cell codes. Keeping information about energy transfer terms in the velocity space, the technique has been implemented and tested ...

2021

Nonlocal effects in negative triangularity TCV plasmas

Stephan Brunner, Olivier Sauter, Laurent Villard, Stefano Coda, Zhouji Huang, Gabriele Merlo, Claudio Marini

Global gradient driven gyrokinetic simulations performed with the Gyrokinetic Electromagnetic Numerical Experiment (GENE) code are used to investigate Tokamak a configuration variable (TCV) plasmas with negative triangularity. Considering limited L-mode pl ...

2021

Moment approach of the multi-species non-linear Coulomb collision operator adapted to particle-in-cell codes

Stephan Brunner, Laurent Villard, Emmanuel Lanti, Noé Thomas Elie Ohana, Moahan Murugappan, Claudio Gheller

In this article an approximated version of the multi-species, non-linear Coulomb collision operator is derived via the use of a truncated moment expansion of the distribution function to compute the Rosenbluth potentials. The evolution of the distribution ...

2021

Gyrokinetic simulations on many- and multi-core architectures with the global electromagnetic Particle-In-Cell Code ORB5

Stephan Brunner, Laurent Villard, Emmanuel Lanti, Noé Thomas Elie Ohana, Claudio Gheller

Gyrokinetic codes in plasma physics need outstanding computational resources to solve increasingly complex problems, requiring the effective exploitation of cutting-edge HPC architectures. This paper focuses on the enabling of ORB5, a state-of-the-art, fir ...

2021

Numerics and computation in gyrokinetic simulations of electromagnetic turbulence with global particle-in-cell codes

Laurent Villard, Alberto Bottino, Emmanuel Lanti

Electromagnetic turbulence is addressed in tokamak and stellarator plasmas with the global gyrokinetic particle-in-cell codes ORB5 (E Lanti et al, Comp. Phys. Comm., 251, 107072 (2020)) and EUTERPE (V Kornilov et al, Phys. Plasmas, 11, 3196 (2004)). The la ...

2021

Nonlinear dynamics of energetic-particle driven geodesic acoustic modes in ASDEX Upgrade

Laurent Villard, Alberto Bottino, Emmanuel Lanti, Noé Thomas Elie Ohana, Emanuele Poli

Turbulence in tokamaks generates radially sheared zonal flows. Their oscillatory counterparts, geodesic acoustic modes (GAMs), appear due to the action of the magnetic field curvature. The GAMs can be driven unstable by an anisotropic energetic particle (E ...

AMER INST PHYSICS2020

Modeling ICRH and ICRH-NBI Synergy in High Power JET Scenarios Using European Transport Simulator (ETS)

Olivier Sauter, Laurent Villard

The European Integrated Modelling effort (EU-IM) provides the European Transport Simulator (ETS) [1] which was designed to simulate arbitrary tokamak plasma discharges. Two new 1D Fokker-Planck solvers have recently been implemented within ETS: StixRedist ...

AMER INST PHYSICS2020

Nonlinear gyrokinetic PIC simulations in stellarators with the code EUTERPE

Eduardo Sanchez, Laurent Villard, Alberto Bottino

In this work, the first nonlinear particle-in-cell simulations carried out in a stellarator with the global gyrokinetic code EUTERPE using adiabatic electrons and realistic plasma parameters are reported. Several studies are conducted with the aim of enabl ...

Cambridge University Press2020

Finite beta effects on short wavelength ion temperature gradient modes

Laurent Villard

The electromagnetic effect is studied on the short wavelength branch of the ion temperature gradient mode in the linear regime for the first time using a global gyrokinetic model. The short wavelength ion temperature gradient mode growth rate is found to b ...

2020

Global turbulence features across marginality and non-local pedestal-core interactions

Stephan Brunner, Olivier Sauter, Laurent Villard, Alberto Bottino, Ben McMillan, Emmanuel Lanti, Noé Thomas Elie Ohana

Spatially non-local aspects of turbulent transport in tokamak plasmas are examined with global gyrokinetic simulations using the ORB5 code. Inspired by very accurate measurements in the TCV tokamak in L-mode, we initialise plasma profiles with constant log ...

2019

First principles gyrokinetic analysis of electromagnetic plasma instabilities

Stephan Brunner, Laurent Villard, Alberto Bottino, Emmanuel Lanti, Noé Thomas Elie Ohana

A two-fold analysis of electromagnetic core tokamak instabilities in the framework of the gyrokinetic theory is presented. First principle theoretical foundations of the gyrokinetic theory are used to explain and justify the numerical results obtained with ...

2019

L-mode-edge negative triangularity tokamak reactor

Olivier Sauter, Laurent Villard, Dafa Chen, Antoine Pierre Emmanuel Alexis Merle, Matteo Fontana

The negative triangularity tokamak (NTT) is a unique reactor concept based on 'power-handling-first' philosophy with the heat exhaust problem as the leading concern. The present paper exposes a reactor concept using L-mode edge based on NTT configuration, ...

IOP Publishing Ltd2019

Orb5: A global electromagnetic gyrokinetic code using the PIC approach in toroidal geometry

Stephan Brunner, Laurent Villard, Alberto Bottino, Sébastien Jolliet, Paolo Angelino, Thibaut Vernay, Ben McMillan, Emmanuel Lanti, Julien Stanislas Pierre Dominski, Noé Thomas Elie Ohana, Aaron Lewis Scheinberg, Claudio Gheller

This paper presents the current state of the global gyrokinetic code Orb5 as an update of the previous reference (Jolliet et al., 2007). The Orb5 code solves the electromagnetic Vlasov–Maxwell system of equations using a PIC scheme and also includes collis ...

2019

MHD Stability and Energy Principle for Two-Dimensional Equilibria without Assumption of Nested Magnetic Surfaces

Laurent Villard, Andrei Martynov

Abandoning the assumption of nested magnetic surfaces in tokamak plasma expands the field of research and opens up new approaches for both theoretical and experimental plasma physics. The computer code KINX for calculations of the ideal MHD stability was d ...

PLEIADES PUBLISHING INC2019

Pullback Scheme Implementation in ORB5

Stephan Brunner, Laurent Villard, Alberto Bottino, Emmanuel Lanti, Noé Thomas Elie Ohana

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 ...

Elsevier2019

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