Publications by Stephan Brunner

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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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

Gyrokinetic simulations are extensively used as a tool to describe various phenomena in magnetically confined plasmas. Among others, turbulent transport induced by drift-wave type instabilities such as Ion Temperature Gradient (ITG), Trapped Electron Mode (TEM) and Electron Temperature Gradient (ETG) plays a central role in fusion research. While the ITG mode in first approximations can be modeled using a reduced adiabatic electron model, the TEM and ETG modes require a kinetic description. The global delta

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 ...

Kinetic theory is used to develop equations describing dynamics of small-amplitude electromagnetic perturbations in toroidal axisymmetric plasmas. The closed Vlasov-Maxwell equations are first solved for a hot stationary plasma using the expansion in the small parameter epsilon(e) = rho/L, where rho is the Larmor radius and L a characteristic length scale of the stationary state. The ordering and additional assumptions are specified so as to obtain the well-known Grad-Shafranov equation. The dielectric tens

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 ...

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 ...

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 ...

Proper comparison of simulated turbulent fluctuations with experimental observations is neces- sary for code validation, and for establishing a link between experimental fluctuation measure- ments and the underlying physics. In this contribution we report on the progress of modelling localised measurements of turbulent electron density fluctuations, obtained with the tangential phase contrast imaging (TPCI) diagnostic installed on the TCV tokamak. The modelling is done in two steps. First, nonlinear flux-tu

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 ...

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 ...

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 ...

Machine-scale instabilities in fusion devices are commonly described using magnetohydrodynamics (MHD), however kinetic effects can significantly affect MHD instabilities through kinetic compression and wave-particle interaction. We propose a new code that solves the drift-kinetic-MHD equations using a spectral method, formulated using a Case-Van Kampen approach (N. G. Van Kampen, Physica 21 , 949 (1955)). The eigenvectors of the standardised eigenvalue problem are composed of the perpendicular MHD-like disp

Stephan Brunner

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Full-field drift Hamiltonian particle orbits in 3D geometry

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

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

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

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

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

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

Gyrokinetic simulations of turbulent transport: size scaling and chaotic behaviour

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

An improved hybrid electron model for global gyrokinetic simulations using the ORB5 PIC code

Neoclassical equilibria as starting point for global gyrokinetic microturbulence simulations

Dielectric Tensor Operator of Hot Plasmas in Toroidal Axisymmetrical Systems

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

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

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

Modelling of turbulent fluctuations measured in the TCV tokamak with gyrokinetic simulations and a synthetic phase contrast imaging diagnostic

A non-twisting flux tube for local gyrokinetic simulations

Integrated modelling of Ion Cyclotron Resonant Heating in toroidal system

Nonlinear quasisteady state benchmark of global gyrokinetic codes

Study of kinetic effects on MHD instabilities in cylindrical geometry using a spectral hybrid kinetic-MHD code