Justin Richard Ball

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Reducing transport via extreme flux-surface triangularity

Stefano Coda, Justin Richard Ball

Based on a gyrokinetic analysis of and extrapolation from TCV discharges with large negative and positive triangularity delta, the potential of extreme | delta | in reducing turbulent transport is assessed. Linearly, both positive and negative delta can ex ...

IOP Publishing Ltd2024

Negative triangularity scenarios: from TCV and AUG experiments to DTT predictions

Olivier Sauter, Stefano Coda, Justin Richard Ball, Matteo Vallar, Filippo Bagnato

Experiments, gyrokinetic simulations and transport predictions were performed to investigate if a negative triangularity (NT) L-mode option for the Divertor Tokamak Test (DTT) full-power scenario would perform similarly to the positive triangularity (PT) H ...

IOP Publishing Ltd2024

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

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

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

Analysis of edge transport in L-mode negative triangularity TCV discharges

Justin Richard Ball, Sophie Danielle Angelica Gorno

One of the major problems for future tokamak devices are ELMs (Edge Localized Modes) as they can lead to large, uncontrolled heat fluxes at the machine targets. For this reason, different techniques and alternative magnetic configurations are under study t ...

Elsevier2023

Ultra long turbulent eddies, magnetic topology, and the triggering of internal transport barriers in tokamaks

Stephan Brunner, Justin Richard Ball, Arnas Volcokas

Local nonlinear gyrokinetic simulations of tokamak plasmas demonstrate that turbulent eddies can extend along magnetic field lines for hundreds of poloidal turns when the magnetic shear is very small. By accurately modeling different field line topologies ...

IOP Publishing Ltd2023

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

Study of fast-ion-driven toroidal Alfvén eigenmodes impacting on the global confinement in TCV L-mode plasmas

Stefano Coda, Laurent Villard, Stephan Brunner, Justin Richard Ball, Oleg Krutkin, Luke Simons, Umesh Kumar, Baruch Rofman, Jesús Poley Sanjuán, Javier García Hernández

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

Three-dimensional inhomogeneity of electron-temperature-gradient turbulence in the edge of tokamak plasmas

Justin Richard Ball

Nonlinear multiscale gyrokinetic simulations of a Joint European Torus edge pedestal are used to show that electron-temperature-gradient (ETG) turbulence has a rich three-dimensional structure, varying strongly according to the local magnetic-field configu ...

IOP Publishing Ltd2022

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

Development of advanced linearized gyrokinetic collision operators using a moment approach

Paolo Ricci, Justin Richard Ball, Louis Nicolas Stenger, Rogério Manuel Cabete De Jesus Jorge, Baptiste Jimmy Frei, Antoine Cyril David Hoffmann

The derivation and numerical implementation of a linearized version of the gyrokinetic (GK) Coulomb collision operator (Jorge et al., J. Plasma Phys., vol. 85, 2019, 905850604) and of the widely used linearized GK Sugama collision operator (Sugama et al., ...

Cambridge University Press2021

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