Publications by Stephan Brunner

Related publications (128)

Full-field drift Hamiltonian particle orbits in 3D geometry

Stephan Brunner, Wilfred Anthony Cooper, Jonathan Graves

A Hamiltonian/Lagrangian theory to describe guiding centre orbit drift motion which is canonical in the Boozer coordinate frame has been extended to include full electromagnetic perturbed fields in anisotropic pressure 3D equilibria with nested magnetic fl ...

IOP2011

Effects of Kinetic Ballooning Modes on the electron distribution function in the core of high-performance tokamak plasmas

Stephan Brunner

This article is dedicated to study the physical causes of a long-standing issue experienced in different tokamak devices throughout the last decades: the observed discrepancies between electron cyclotron emission (ECE) and Thomson Scattering (TS) diagnosti ...

IOP Publishing Ltd2025

Turbulence and zonal flow structures in the core and L-mode pedestal of tokamak plasmas

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

Zonal flows (ZF) play a crucial role in regulating ion temperature gradient (ITG) turbulence. In previous global gyrokinetic simulations [1] using the ORB5 code with the adiabatic electron model, it was observed that long-lived ZF structures, leading to a ...

IOP Publishing2014

The competing effects of wave amplitude and collisions on multi-ion species suppression of stimulated Brillouin scattering in inertial confinement fusion Hohlraums

Stephan Brunner

Reduction in stimulated Brillouin scattering (SBS) from National Ignition Facility Hohlraums has been predicted through the use of multi-ion species materials on Hohlraum walls. This approach to controlling SBS is based upon introducing a lighter ion speci ...

2023

Global 'zero particle flux-driven' gyrokinetic analysis of the density profile for a TCV plasma

Stephan Brunner, Olivier Sauter, Gabriele Merlo, Alberto Mariani

The tokamak `a configuration variable (TCV) is a small-sized tokamak, where finite size effects (often called 'rho-star' or 'global' effects) could significantly impact the heat and particle fluxes, leading to discrepancies between gyrokinetic flux-tube re ...

IOP Publishing Ltd2023

Effects of collisionality and T e /T i on fluctuations in positive and negative δ tokamak plasmas

Stephan Brunner, Ambrogio Fasoli, Olivier Sauter, Stefano Coda, Laurie Porte, Gabriele Merlo, Matteo Fontana, Ajay Chandrarajan Jayalekshmi

The effects of negative triangularity () on confinement and fluctuations in plasmas covering a large range of parameters were investigated on the tokamak à configuration variable (TCV). The conditions explored in this paper include discharges where neutral ...

IOP Publishing Ltd2019

Nonlinear kinetic simulation study of the ion-ion streaming instability in single- and multi-ion species plasmas

Stephan Brunner

The nonlinear evolution of the ion-ion streaming instability (IISI) is studied using numerical techniques novel to this problem that afford direct insight into the evolution of the particle distributions of each species. During the linear phase of the inst ...

2021

A phase-contrast-imaging core fluctuation diagnostic and first-principles turbulence modeling for JT-60SA

Stephan Brunner, Stefano Coda, Matthieu Toussaint, Aylwin Iantchenko

A core fluctuation diagnostic based on the phase-contrast imaging (PCI) technique has been designed for the JT-60SA tokamak, with the assistance of a synthetic diagnostic coupled to a gyrokinetic code. Using a tangentially viewing geometry, this system wou ...

IOP Publishing Ltd2021

Gyrokinetic simulations of turbulent transport: size scaling and chaotic behaviour

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

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

Stephan Brunner, Laurent Villard, Moahan Murugappan, Justin Richard Ball, Arnas Volcokas, Philippe Sylvain Stéphane Marie Griveaux, Giovanni Di Giannatale

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

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

Reducing Turbulent Transport in Tokamaks by Combining Intrinsic Rotation and the Low Momentum Diffusivity Regime

Stephan Brunner, Justin Richard Ball, Haomin Sun

Based on the analysis of a large number of high-fidelity nonlinear gyrokinetic simulations, we propose a novel strategy to improve confinement in spherical tokamak plasmas by combining up-down asymmetric flux surface shaping with the Low Momentum Diffusivi ...

IOP Publishing Ltd2025

Effect of collisions on non-adiabatic electron dynamics in ITG-driven microturbulence

Stephan Brunner, Justin Richard Ball

Non-adiabatic electron response leads to significant changes in ion temperature gradient (ITG) eigenmodes, leading, in particular, to fine-structures that are significantly extended along the magnetic field lines at corresponding mode rational surfaces (MR ...

2021

Gyrokinetic simulations of turbulence and zonal flows driven by steep profile gradients using a delta-f approach with an evolving background Maxwellian

Stephan Brunner, Laurent Villard, Alberto Bottino, Ben McMillan, Moahan Murugappan

Long global gyrokinetic turbulence simulations are particularly challenging in situations where the system deviates strongly from its initial state and when fluctuation levels are high, for example, in strong gradient regions. For particle-in-cell simulati ...

2022

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, Peter François Tony Donnel

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

A non-twisting flux tube for local gyrokinetic simulations

Stephan Brunner, Justin Richard Ball

Local gyrokinetic simulations use a field-aligned domain that twists due to the magnetic shear of the background magnetic equilibrium. However, if the magnetic shear is strong and/or the domain is long, the twist can become so extreme that it fails to prop ...

2021

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

Integrated modelling of Ion Cyclotron Resonant Heating in toroidal system

Stephan Brunner, Wilfred Anthony Cooper, Martin Jucker, Jonathan Graves

An integrated model capable of self-consistent Ion Cyclotron Resonant Heating (ICRH) simulations has been developed. This model includes both full shaping and pressure effects, warm contributions to the dielectric tensor, pressure anisotropy and finite orb ...

Elsevier B.V2011

Electron and ion kinetic effects on non-linearly driven electron plasma and ion acoustic waves

Stephan Brunner

Fully non-linear kinetic simulations of electron plasma and ion acoustic waves (IAWs) have been carried out with a new multi-species, parallelized Vlasov code. The numerical implementation of the Vlasov model and the methods used to compute the wave freque ...

Amer Inst Physics2013

Nonlinear quasisteady state benchmark of global gyrokinetic codes

Stephan Brunner, Laurent Villard, 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