S. Brunner
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View article: Gyrokinetic simulations of the core turbulence in the reference JT-60SA scenario
Gyrokinetic simulations of the core turbulence in the reference JT-60SA scenario Open
Linear and nonlinear local gyrokinetic simulations of the high power high current JT-60SA scenario are presented, based on inputs from predictive transport modelling. Carbon impurities and fast ions are included in the simulations as well …
View article: Collisional effects on positive and negative triangularity through local and global temperature gradient-driven and flux-driven gyrokinetic simulations
Collisional effects on positive and negative triangularity through local and global temperature gradient-driven and flux-driven gyrokinetic simulations Open
In this work, we explore the effects of collisions on turbulent transport, focusing on two different TCV magnetic equilibria featuring positive and negative triangularity. The investigation is conducted using gyrokinetic modeling. Both gra…
View article: Global electromagnetic gyrokinetic simulations of internal transport barriers in reversed-shear tokamaks
Global electromagnetic gyrokinetic simulations of internal transport barriers in reversed-shear tokamaks Open
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 …
View article: Reducing turbulent transport in tokamaks by combining intrinsic rotation and the low momentum diffusivity regime
Reducing turbulent transport in tokamaks by combining intrinsic rotation and the low momentum diffusivity regime Open
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 M…
View article: A quasilinear model for momentum transport including rotation and electron-scale turbulence
A quasilinear model for momentum transport including rotation and electron-scale turbulence Open
In a previous paper, a new gyrokinetic quasilinear model was proposed to study turbulent momentum transport in tokamaks with up-down asymmetric plasma shaping and toroidal flow shear [H. Sun et al., Nuclear Fusion 64, 036026 (2024)]. In th…
View article: Intrinsic momentum transport driven by almost-rational surfaces in tokamak plasmas
Intrinsic momentum transport driven by almost-rational surfaces in tokamak plasmas Open
We demonstrate that a symmetry of the local gyrokinetic model is broken when the safety factor q is almost (but not exactly) a rational number and magnetic shear is $\hat{s} \approx 0$. Tokamaks with such a q profile will spontaneously rot…
View article: Turbulence-Generated Stepped Safety Factor Profiles in Tokamaks with Low Magnetic Shear
Turbulence-Generated Stepped Safety Factor Profiles in Tokamaks with Low Magnetic Shear Open
Nonlinear local and global gyrokinetic simulations of tokamak plasmas demonstrate that turbulence-generated currents flatten the safety factor profile near low-order rational surfaces when magnetic shear is low, even when the plasma $β$ is…
View article: Modelling of ETG turbulent transport in the TCV pedestal
Modelling of ETG turbulent transport in the TCV pedestal Open
Results of the first gyrokinetic simulations of the TCV pedestal are presented. Two discharges at varying levels of gas puffing are considered as input parameters for the local GENE simulations. Linear and nonlinear simulations are carried…
View article: Particle-in-cell methods in edge plasma physics: the PICLS code
Particle-in-cell methods in edge plasma physics: the PICLS code Open
Over the past decades, multiple gyrokinetic codes have shown to be able to simulate turbulence and associated transport in the core of Tokamak devices. However, their application to the edge and scrape-off layer (SOL) region presents signi…
View article: Global electromagnetic gyrokinetic simulations of internal transport\n barriers in reversed-shear tokamaks
Global electromagnetic gyrokinetic simulations of internal transport\n barriers in reversed-shear tokamaks Open
This work aims at improving our understanding of the conditions enabling the\ndevelopment of an Internal transport barriers (ITB), using a more comprehensive\nphysical model, including low-$\\beta$ electromagnetic flux-driven simulations.\…
View article: Particle-in-cell methods in edge plasma physics: the PICLS code
Particle-in-cell methods in edge plasma physics: the PICLS code Open
Over the past decades, multiple gyrokinetic codes have shown to be able to simulate turbulence and associated transport in the core of Tokamak devices. However, their application to the edge and scrape-off layer (SOL) region presents signi…
View article: Turbulence-Induced Safety Factor Profile Flattening at Rational Surfaces in Tokamaks with Low Magnetic Shear
Turbulence-Induced Safety Factor Profile Flattening at Rational Surfaces in Tokamaks with Low Magnetic Shear Open
In this paper, we investigate the effects of ion-scale turbulence-generated currents on the local safety factor profile under conditions of low magnetic shear and proximity to rational surfaces, relevant to Internal Transport Barrier (ITB)…
View article: Effects of Kinetic Ballooning Modes on the electron distribution function in the core of high-performance tokamak plasmas
Effects of Kinetic Ballooning Modes on the electron distribution function in the core of high-performance tokamak plasmas Open
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 Scatteri…
View article: On the importance of slow ions in the kinetic Bohm criterion
On the importance of slow ions in the kinetic Bohm criterion Open
Between a plasma and a solid target lies a positively charged sheath of several Debye lengths $\lambda _{D}$ width, typically much smaller than the characteristic length scale $L$ of the main plasma. This scale separation implies that the …
View article: Numerical study of turbulent eddy self-interaction in tokamaks with low magnetic shear. Part I: Linear simulations
Numerical study of turbulent eddy self-interaction in tokamaks with low magnetic shear. Part I: Linear simulations Open
This study examines the impact of low and zero magnetic shear, along with rational values of safety factor, on linear mode behavior in tokamak plasmas. We focus on how magnetic field line topology and parallel domain length influence linea…
View article: Numerical study of turbulent eddy self-interaction in tokamaks with low magnetic shear. Part II: Nonlinear simulations
Numerical study of turbulent eddy self-interaction in tokamaks with low magnetic shear. Part II: Nonlinear simulations Open
Using local nonlinear gyrokinetic simulations and building up on linear results from a companion paper (Volčokas 2024 Submitted for publication), we demonstrate that turbulent eddies can extend along magnetic field lines for hundreds of po…
View article: Gyrokinetic flux-driven simulations in mixed TEM/ITG regime using a delta-f PIC scheme with evolving background
Gyrokinetic flux-driven simulations in mixed TEM/ITG regime using a delta-f PIC scheme with evolving background Open
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 corre…
View article: Reducing turbulent transport in tokamaks by combining intrinsic rotation and the low momentum diffusivity regime
Reducing turbulent transport in tokamaks by combining intrinsic rotation and the low momentum diffusivity regime Open
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 M…
View article: Physics of the low momentum diffusivity regime in tokamaks and its experimental applicability
Physics of the low momentum diffusivity regime in tokamaks and its experimental applicability Open
Strong $E\times B$ plasma flow shear is beneficial for reducing turbulent transport. However, traditional methods of driving flow shear do not scale well to large devices such as future fusion power plants. In this paper, we use a large nu…
View article: Sheath constraints on turbulent magnetised plasmas
Sheath constraints on turbulent magnetised plasmas Open
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) …
View article: System size scaling of triangularity effects on global temperature gradient-driven gyrokinetic simulations
System size scaling of triangularity effects on global temperature gradient-driven gyrokinetic simulations Open
In this work, we explore the triangularity effects on turbulent transport employing global gyrokinetic simulations performed with the ORB5 code. Numerous experiments on the Tokamak á Configuration Variable (TCV) and, more recently, on the …
View article: Gyrokinetic flux-driven simulations in mixed TEM/ITG regime using a delta-f PIC scheme with evolving background
Gyrokinetic flux-driven simulations in mixed TEM/ITG regime using a delta-f PIC scheme with evolving background Open
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 corre…
View article: On the importance of slow ions in the kinetic Bohm criterion
On the importance of slow ions in the kinetic Bohm criterion Open
Between a plasma and a solid target lies a positively charged sheath of several Debye lengths $λ_{\rm D}$ in width, typically much smaller than the characteristic length scale $L$ of the main plasma. This scale separation implies that the …
View article: Self-interaction of turbulent eddies in tokamaks with low magnetic shear
Self-interaction of turbulent eddies in tokamaks with low magnetic shear Open
Using local nonlinear gyrokinetic simulations, we demonstrate that turbulent eddies can extend along magnetic field lines for hundreds of poloidal turns in tokamaks with weak or zero magnetic shear $\hat{s}$. We observe that this parallel …
View article: Verification of the Fourier-enhanced 3D finite element Poisson solver of the gyrokinetic full-f code PICLS
Verification of the Fourier-enhanced 3D finite element Poisson solver of the gyrokinetic full-f code PICLS Open
View article: A new quasilinear model for turbulent momentum transport in tokamaks with flow shear and plasma shaping
A new quasilinear model for turbulent momentum transport in tokamaks with flow shear and plasma shaping Open
In tokamak experiments, sufficiently strong E × B flow shear reduces turbulent transport, thereby improving the prospects for fusion power plants. It is therefore of great importance to efficiently explore parameter space to find where str…
View article: Sheath constraints on turbulent magnetised plasmas
Sheath constraints on turbulent magnetised plasmas Open
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) …
View article: Validation of short-pulse reflectometry turbulence measurements with a synthetic diagnostic
Validation of short-pulse reflectometry turbulence measurements with a synthetic diagnostic Open
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…
View article: Gyrokinetic turbulence modeling of a high performance scenario in JT-60SA
Gyrokinetic turbulence modeling of a high performance scenario in JT-60SA Open
Local gyrokinetic simulations are used to model turbulent transport for the first time in a representative high-performance plasma discharge projected for the new JT-60SA tokamak. The discharge features a double-null separatrix, 41 MW of c…
View article: A new quasilinear model for turbulent momentum transport in tokamaks with flow shear and plasma shaping
A new quasilinear model for turbulent momentum transport in tokamaks with flow shear and plasma shaping Open
In tokamak experiments, sufficiently strong $E\times B$ flow shear reduces turbulent transport, thereby improving the prospects for fusion power plants. It is therefore of great importance to efficiently explore parameter space to find whe…