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Stephan Brunner

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Related publications (128)

Page 5 of 7

Finite ballooning angle effects on ion temperature gradient driven mode in gyrokinetic flux tube simulations

Stephan Brunner

This paper presents effects of finite ballooning angles on linear ion temperature gradient (ITG) driven mode and associated heat and momentum flux in Gyrokinetic flux tube simulation GENE. It is found that zero ballooning angle is not always the one at whi ...

Amer Inst Physics2014

The effect of plasma triangularity on turbulent transport:modelling TCV experiments by linear and non linear gyrokinetic simulations

Olivier Sauter, Jonathan Graves, Stefano Coda, Laurent Villard, Antoine Pochelon, Yann Camenen, Stephan Brunner, Alessandro Marinoni

The effect of plasma shape on confinement has been experimentally explored in the TCV tokamak revealing that the core electron heat transport is significantly reduced by a negative triangularity configuration, which could indicate a (partial) stabilization ...

2009

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

Experimental observations of modes with geodesic acoustic character from the core to the edge in the TCV tokamak

Stefano Coda, Laurent Villard, Stephan Brunner, Benoît Labit, Christian Gabriel Theiler, Gabriele Merlo, Zhouji Huang

2018

Validation of short-pulse reflectometry turbulence measurements with a synthetic diagnostic

Stefano Coda, Stephan Brunner, Oleg Krutkin, Samuele Mazzi, Umesh Kumar, Mackenzie Peter-Fulford Van Rossem

Experimental measurements of the turbulence amplitude utilizing a short pulse reflectometry method are presented. Two discharges with shaped plasma possessing opposite signs of triangularity are considered and a higher turbulence amplitude is found in the ...

IOP Publishing Ltd2024

Locality and universality in gyrokinetic turbulence

Laurent Villard, Stephan Brunner

The nature of nonlinear interactions in gyrokinetic (GK) turbulence, driven by the ion-temperature gradient instability, is investigated using direct numerical simulations in toroidal flux tube geometry. To account for the level of separation existing betw ...

American Physical Society2012

The effect of background flow shear on gyrokinetic turbulence in the cold ion limit

Stephan Brunner, Ben McMillan, Justin Richard Ball

2019

Generalized radiation boundary conditions in gyrotron oscillator modeling

Stefano Alberti, Minh Quang Tran, Stephan Brunner, Jean-Philippe Hogge, Jérémy Genoud, Trach-Minh Tran

A numerical procedure to implement a frequency-independent generalized non-reflecting radiation boundary conditions, GNRBC, based on the Laplace Transform, is described in details and tested successfully on a simple 2 frequency test problem. In the case of ...

Springer2015

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

Stefano Coda, Laurent Villard, Stephan Brunner, 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

Complete multi-field characterization of the geodesic acoustic mode in the TCV tokamak

Stefano Coda, Laurent Villard, Stephan Brunner, Laurie Porte, Zhouji Huang, Gabriele Merlo, Julien Stanislas Pierre Dominski, Thibaut Vernay, Cornelis Adrianus de Meijere

The geodesic acoustic mode (GAM) is a coherently oscillating zonal flow that may regulate turbulence in toroidal plasmas. Uniquely, the complete poloidal and toroidal structure of the magnetic component of the turbulence-driven GAM has been mapped in the T ...

Iop Publishing Ltd2014

On the importance of slow ions in the kinetic Bohm criterion

Stephan Brunner, Alessandro Geraldini

Between a plasma and a solid target lies a positively charged sheath of several Debye lengths λD width, typically much smaller than the characteristic length scale L of the main plasma. This scale separation implies that the asymptotic limit ε = λD/L → 0 i ...

Cambridge University Press2024

First principles gyrokinetic analysis of electromagnetic plasma instabilities

Laurent Villard, Stephan Brunner, 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

Numerical study of turbulent eddy self-interaction in tokamaks with low magnetic shear. Part II: Nonlinear simulations

Stephan Brunner, Justin Richard Ball, Arnas Volcokas

Using local nonlinear gyrokinetic simulations and building up on linear results from acompanion paper (Volcokas 2024 Submitted for publication), we demonstrate that turbulenteddies can extend along magnetic field lines for hundreds of poloidal turns in tok ...

IOP Publishing Ltd2025

Convolution and iterative methods applied to low frequency waves in 3D configurations

Laurent Villard, Wilfred Anthony Cooper, Stephan Brunner

Kinetic effects have been implemented in the three-dimensional full-wave code LEMan. These allow modeling Landau damping as well as the Kinetic Alfvén Wave (KAW). Special attention has been taken on the exact computation of the parallel wave vector as it c ...

Elsevier2011

High-Order Accurate Conservative Finite Difference Methods For Vlasov Equations In 2D+2V

Stephan Brunner

This manuscript discusses discretization of the Vlasov-Poisson system in 2D+2V phase space using high-order accurate conservative finite difference algorithms. One challenge confronting direct kinetic simulation is the significant computational cost associ ...

SIAM PUBLICATIONS2019

Mechanism for blob generation in the TORPEX toroidal plasma

Jonathan Graves, Ambrogio Fasoli, Ivo Furno, Benoît Labit, Paolo Ricci, Stephan Brunner, Christian Gabriel Theiler, Mario Ludovico Podesta, Francesca Maria Poli

The mechanism for blob generation is detailed in the toroidal magnetized plasma of the TORPEX device [ Fasoli et al., Phys. Plasmas 13, 055902 (2006) ] using an experimental configuration, which features a plasma region dominated by a coherent wave and a r ...

2008

Longitudinal and Transverse Instability of Ion Acoustic Waves

Stephan Brunner

Ion acoustic waves are found to be susceptible to at least two distinct decay processes. Which process dominates depends on the parameters. In the cases examined, the decay channel where daughter modes propagate parallel to the mother mode is found to domi ...

Amer Physical Soc2017

Gyrokinetic analysis of radial dependence and global effects on the zero particle flux condition in a TCV plasma

Olivier Sauter, Stephan Brunner, Gabriele Merlo, Alberto Mariani

In small-sized tokamaks, finite Larmor radius effects could lead to a significant discrepancy between gyrokinetic local flux-tube results and global ones. This has been highlighted by previous turbulent transport studies as in McMillan et al (2010 Phys. Re ...

IOP2019

The global version of the gyrokinetic turbulence code GENE

Stephan Brunner

The understanding and prediction of transport due to plasma microturbulence is a key open problem in modern plasma physics, and a grand challenge for fusion energy research. Ab initio simulations of such small-scale, low-frequency turbulence are to be base ...

2011

Short wavelength ion temperature gradient turbulence

Laurent Villard, Stephan Brunner

The ion temperature gradient (ITG) mode in the high wavenumber regime (k(y)rho(s) > 1), referred to as short wavelength ion temperature gradient mode (SWITG) is studied using the nonlinear gyrokinetic electromagnetic code GENE. It is shown that, although t ...

American Institute of Physics2012