Publications by Laurent Villard

Particle-in-cell methods in edge plasma physics: the PICLS code

Laurent Villard, Stephan Brunner, Giovanni Di Giannatale

Over the past decades, multiple gyrokinetic codes have shown to be able to simulate turbulence and associated transport in the core of Tokamak devices. However, their application to the edge and scrape-off layer (SOL) region presents significant challenges ...

2025

Collisional effects on positive and negative triangularity through local and global temperature gradient-driven and flux-driven gyrokinetic simulations

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

In this work, we explore the effects of collisions on turbulent transport, focusing on two different TCV magnetic equilibria featuring positive and negative triangularity. The investigation is conducted using gyrokinetic modeling. Both gradient-driven and ...

2025

Global electromagnetic gyrokinetic simulations of internal transport barriers in reversed-shear tokamaks

Laurent Villard, Stephan Brunner, Justin Richard Ball, Moahan Murugappan, Giovanni Di Giannatale, Arnas Volcokas

Internal transport barriers (ITB) form through turbulence suppression, often observed when the safety factor profile exhibits an off-axis minimum. This work aims at improving our understanding of the conditions enabling the development of an ITB, using a m ...

2025

Gyrokinetic transport driven by ubiquitous modes in LTX-like tokamak with ‘flat’ temperature

Laurent Villard, Emmanuel Lanti

A global, gyro-kinetic nonlinear study of the ubiquitous mode (UM) for Lithium Tokamak eXperiment (LTX)-like profiles, under flat electron and ion temperature scenarios is conducted using a global gyrokinetic model. Exact MHD equilibria with circular shape ...

2025

Verification of the Picls Electromagnetic Upgrade in Mixed Variables

Laurent Villard

The gyrokinetic particle-in-cell code PICLS is a full-f finite element tool to simulate turbulence in open and closed field lines. During the previous year, the capability of PICLS was extended to encompass electromagnetic effects. Successful tests using t ...

IOP Publishing Ltd2025

Verification of the Fourier-enhanced 3D finite element Poisson solver of the gyrokinetic full-f code PICLS

Laurent Villard, Stephan Brunner, Moahan Murugappan, Alberto Bottino

We introduce and derive the Fourier -enhanced 3D electrostatic field solver of the gyrokinetic full -f PIC code PICLS. The solver makes use of a Fourier representation in one periodic direction of the domain to make the solving of the system easily paralle ...

Elsevier2024

Ion temperature gradient mode mitigation by energetic particles, mediated by forced-driven zonal flows

Laurent Villard, Giovanni Di Giannatale, Baruch Rofman

In this work, we use the global electromagnetic and electrostatic gyro kinetic approaches to investigate the effects of zonal flows forced-driven by Alfvén modes due to their excitation by energetic particles on the dynamics of ITG (ion temperature gradien ...

American Institute of Physics (AIP)2024

Global gyrokinetic study of density gradient driven instability in tokamaks: the ubiquitous mode

Laurent Villard

The ubiquitous mode is investigated in the linear regime for the first time using a global gyrokinetic model. These modes are driven by the density gradient in trapped electron population but with mode frequency in the ion diamagnetic drift direction, in c ...

2024

Magnetic shaping effects on turbulence in ADITYA-U tokamak

Laurent Villard, Emmanuel Lanti

The work reported in this paper addresses two aspects. In the first part, numerical simulations are conducted to examine the impact of magnetic equilibrium shaping (elongation and triangularity), on both conventional Ion Temperature Gradient (ITG) modes an ...

IOP Publishing Ltd2024

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

Laurent Villard, Stephan Brunner, 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