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Stephan Brunner

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Publications associées (134)

A method for density fluctuation measurements using pulse reflectometry

Stephan Brunner, Stefano Coda, Oleg Krutkin

An analytical 1D model based on the WKB approximation is used to study the properties of a short pulse reflectometry diagnostic in a magnetic fusion device. Expressions linking the pulse delay with the parameters of the turbulence near the cut-off layer ar ...

IOP Publishing Ltd2023

A synthetic phase-contrast imaging diagnostic with spatial filtering for gyrokinetic simulations

Stephan Brunner, Stefano Coda, Gabriele Merlo, Aylwin Iantchenko, Justin Richard Ball

A Phase-contrast imaging (PCI) diagnostic provides measurements of line-integrated electron density fluctuations. Localisation along the laser beam path can be achieved with a spatial filter that selects the wave-vector directions of the fluctuations contr ...

2023

Moment-based approach to the flux-tube linear gyrokinetic model

Stephan Brunner, Paolo Ricci

This work reports on the development and numerical implementation of the linear electromagnetic gyrokinetic (GK) model in a tokamak flux-tube geometry using a moment approach based on the expansion of the perturbed distribution function on a velocity-space ...

Cambridge University Press2023

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

Local gyrokinetic simulations of tokamaks with non-uniform magnetic shear

Stephan Brunner, Justin Richard Ball

In this work, we modify the standard flux tube simulation domain to include arbitrary ion gyroradius-scale variation in the radial profile of the safety factor. To determine how to appropriately include such a modification, we add a strong ion gyroradius-s ...

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

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

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

Overview of the TCV tokamak experimental programme

Patrick Blanchard, Stephan Brunner, Stefano Alberti, Basil Duval, Ambrogio Fasoli, Timothy Goodman, Xavier Llobet, Yves Martin, Jean-Marc Moret, Olivier Sauter, Henri Weisen, Ivo Furno, Holger Reimerdes, Jean-Philippe Hogge, Jan Horacek, Alexander Karpushov, Laurie Porte, Yanis Andrebe, Jonathan Graves, Duccio Testa, Benoît Labit, Joaquim Loizu Cisquella, Paolo Ricci, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Miguel Filipe Silva Füglister, Antoine Pierre Emmanuel Alexis Merle, Oulfa Chellaï, Curdin Tobias Wüthrich, Joan Decker, Cedric Kar-Wai Tsui, Pedro Andres Molina Cabrera, Matteo Fontana, Umar Sheikh, Cristian Galperti, Marcelo Baquero Ruiz, Dahye Choi, Aylwin Iantchenko, Mengdi Kong, Roberto Maurizio, Francesco Carpanese, , , , , , , , , , , , , , , , , , , , , , ,

Electron-cyclotron resonance heating and current drive source for flux-driven gyrokinetic simulations of tokamaks

Stephan Brunner, Laurent Villard, Stefano Coda, Joan Decker, Jean Arthur Cazabonne

Electromagnetic waves that resonate with the cyclotron motion of electrons in a magnetized plasma can efficiently transfer their momentum and energy to the plasma. This is routinely used to heat or drive current in tokamak plasmas. The impact of this local ...

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

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

Stephan Brunner, Stefano Coda, Matthieu Toussaint, Aylwin Iantchenko, Kenji Tanaka

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

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

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

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

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

How eigenmode self-interaction affects zonal flows and convergence of tokamak core turbulence with toroidal system size

Stephan Brunner, Julien Stanislas Pierre Dominski, Gabriele Merlo, Ajay Chandrarajan Jayalekshmi, Justin Richard Ball

Self-interaction is the process by which a microinstability eigenmode that is extended along the direction parallel to the magnetic field interacts non-linearly with itself. This effect is particularly significant in gyrokinetic simulations accounting for ...

Cambridge University Press2020

Eliminating turbulent self-interaction through the parallel boundary condition in local gyrokinetic simulations

Stephan Brunner, Ajay Chandrarajan Jayalekshmi, Justin Richard Ball

In this work, we highlight an issue that may reduce the accuracy of many local nonlinear gyrokinetic simulations – turbulent self-interaction through the parallel boundary condition. Given a sufficiently long parallel correlation length, individual turbule ...

Cambridge University Press2020

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Ajay Chandrarajan Jayalekshmi

Mirko Wensing

Lorenzo Stipani

Federico Pesamosca

Olivier Claude Martin Février

Anna Ngoc Minh Trang Vu

Arsène Stéphane Tema Biwole

Lorenzo Martinelli

Jean Arthur Cazabonne

Alessandro Pau

Matteo Vallar

Sophie Danielle Angelica Gorno

The tokamak a configuration variable (TCV) continues to leverage its unique shaping capabilities, flexible heating systems and modern control system to address critical issues in preparation for ITER and a fusion power plant. For the 2019-20 campaign its c ...

IOP Publishing Ltd2022