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Stephan Brunner

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Related publications (128)

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Vlasov simulations of electron-ion collision effects on damping of electron plasma waves

Stephan Brunner, Trach-Minh Tran

Collisional effects can play an essential role in the dynamics of plasma waves by setting a minimum damping rate and by interfering with wave-particle resonances. Kinetic simulations of the effects of electron-ion pitch angle scattering on Electron Plasma ...

Amer Inst Physics2016

Two-dimensional Vlasov simulation of electron plasma wave trapping, wavefront bowing, self-focusing, and sideloss

Stephan Brunner

Two-dimensional Vlasov simulations of nonlinear electron plasma waves are presented, in which the interplay of linear and nonlinear kinetic effects is evident. The plasma wave is created with an external traveling wave potential with a transverse envelope ...

American Institute of Physics (AIP)2011

Sheath constraints on turbulent magnetised plasmas

Stephan Brunner, Alessandro Geraldini

A solid target in contact with a plasma charges (negatively) to reflect the more mobile species (electrons) and thus keep the bulk plasma quasineutral. To shield the bulk plasma from the charged target, there is an oppositely (positively) charged sheath wi ...

2024

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

How non-adiabatic passing electron layers of linear microinstabilities affect turbulent transport

Stephan Brunner, Laurent Villard, Julien Stanislas Pierre Dominski

The response of passing electrons in ion temperature gradient and trapped electron mode microturbulence regimes is investigated in tokamak geometry making use of the flux-tube version of the gyrokinetic code GENE. Results are obtained using two different e ...

Amer Inst Physics2015

Investigating profile stiffness and critical gradients in shaped TCV discharges using local gyrokinetic simulations of turbulent transport

Stephan Brunner, Olivier Sauter, Laurent Villard, Yann Camenen, Alessandro Marinoni, Gabriele Merlo

The experimental observation made on the TCV tokamak of a significant confinement improvement in plasmas with negative triangularity (delta < 0) compared to those with standard positive triangularity has been interpreted in terms of different degrees of pr ...

Iop Publishing Ltd2015

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

On the non-stiffness of edge transport in L-mode tokamak plasmas

Stephan Brunner, Roland Behn, Basil Duval, Timothy Goodman, Olivier Sauter, Stefano Coda, Alexander Karpushov, Yann Camenen, Lucia Isabel Federspiel, Doohyun Kim, Gabriele Merlo, Antoine Pierre Emmanuel Alexis Merle

Transport analyses using first-principle turbulence codes and 11/2-D transport codes usually study radial transport properties between the tokamak plasma magnetic axis and a normalized minor radius around 0.8. In this region, heat transport shows significa ...

Amer Inst Physics2014

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

Kinetic Simulations of the Self-Focusing and Dissipation of Finite-Width Electron Plasma Waves

Stephan Brunner

Two-dimensional simulations, both Vlasov and particle-in-cell, are presented that show the evolution of the field and electron distribution of finite-width, nonlinear electron plasma waves. The intrinsically intertwined effects of self-focusing and dissipa ...

Amer Physical Soc2013

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

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

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

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

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

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

Investigation of the role of electron temperature gradient modes in electron heat transport in TCV plasmas

Stephan Brunner, Olivier Sauter, Alexander Karpushov, Laurie Porte, Claudio Marini, Alberto Mariani

Electron-scale micro-turbulence driven by the electron temperature gradient (ETG) instability has recently been shown to impact the electron heat transport in tokamaks. Given the relevance of these mechanisms for ITER scenarios, a new study has been carrie ...

IOP Publishing Ltd2019

Nonlinear Effects in Fluctuation Short Pulse Reflectometry

Stephan Brunner, Stefano Coda, Oleg Krutkin

The fluctuation short pulse reflectometry diagnostic is simulated with the full-wave CUWA code for ad-hoc turbulence and simplified geometry. The nonlinear effects on the measurements are investigated while accounting for the plasma curvature, probing angl ...

IOP Publishing Ltd2025