Publications by Justin Richard Ball

A Quasilinear Model for Momentum Transport Including Rotation and Electron-scale Turbulence

Stephan Brunner, Haomin Sun, Justin Richard Ball

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 (Sun et al 2024 Nuclear Fusion 64 036026). In this work, we start by appl ...

IOP Publishing Ltd2025

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

Stephan Brunner, Justin Richard Ball, Arnas Volcokas

This study examines the impact of low and zero magnetic shear, along with rational values ofsafety factor, on linear mode behavior in tokamak plasmas. We focus on how magnetic field linetopology and parallel domain length influence linear mode structures a ...

IOP Publishing Ltd2025

Electromagnetic instability and turbulence in plasmas with positive and negative triangularity

Olivier Sauter, Justin Richard Ball, Reinart Andreas J. Coosemans, Matteo Vallar

While a number of studies exist comparing positive triangularity (PT) and negative triangularity (NT) δ, the nature of how the normalized electron pressure β affects microinstabilities and turbulence in fusion devices with substantial δ has not been studie ...

AIP Publishing2025

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

Laurent Villard, Stephan Brunner, Justin Richard Ball, Moahan Murugappan, Giovanni Di Giannatale, Arnas Volcokas

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 ...

2025

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

Stephan Brunner, Haomin Sun, Justin Richard Ball

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 ...

IOP Publishing Ltd2025

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

Study of impurity C transport and plasma rotation in negative triangularity on the TCV tokamak

Olivier Sauter, Basil Duval, Stefano Coda, Benoît Labit, Alessandro Pau, Laurie Porte, Alexander Karpushov, Antoine Pierre Emmanuel Alexis Merle, Justin Richard Ball, Dmytry Mykytchuk

Carbon impurity transport is studied in the TCV tokamak using a charge exchange recombination diagnostic. TCVs flexible shaping capabilities were exploited to extend previous impurity transport studies to negative triangularity (delta < 0). A practical way ...

Iop Publishing Ltd2024

A new quasilinear model for turbulent momentum transport in tokamaks with flow shear and plasma shaping

Stephan Brunner, Haomin Sun, Justin Richard Ball, Arnas Volcokas

In tokamak experiments, sufficiently strong E x 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 strong plasma flow c ...

IOP Publishing Ltd2024

Experiments and gyrokinetic simulations of TCV plasmas with negative triangularity in view of DTT operations

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

Negative triangularity (NT) scenarios in TCV have been compared to positive triangularity (PT) scenarios using the same plasma shapes foreseen for divertor tokamak test tokamak operations. The experiments provided a NT/PT L-mode pair and a PT H-mode with d ...

Iop Publishing Ltd2024

Physical insights from the aspect ratio dependence of turbulence in negative triangularity plasmas

Stefano Coda, Justin Richard Ball

In this work, we study the impact of aspect ratio A = R 0 / r (the ratio of major radius R 0 to minor radius r) on the confinement benefits of negative triangularity (NT) plasma shaping. We use high-fidelity flux tube gyrokinetic GENE simulations and consi ...

Iop Publishing Ltd2024