Publications by Justin Richard Ball

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Specific energy (i.e. energy per unit mass) is one of the most fundamental and consequential properties of a fuel source. In this work, a systematic study of measured fusion cross-sections is performed to determine which reactions are potentially feasible ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

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 ...

In this work, we highlight an issue that may reduce the accuracy of many local nonlinear gyrokinetic simulations – turbulent self-interaction through the parallel boundary condition. Given a sufficiently long parallel correlation length, individual turbule ...

Self-interaction is the process by which a microinstability eigenmode that is extended along the direction parallel to the magnetic field interacts non-linearly with itself. This effect is particularly significant in gyrokinetic simulations accounting for ...

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., ...

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 ...

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 ...

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 ...

Local linear gyrokinetic simulations show that electron temperature gradient (ETG) instabilities are the fastest growing modes for ky rho i greater than or similar to 0.1

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 ...

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 ...

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 ...

Justin Richard Ball

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Maximizing specific energy by breeding deuterium

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

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

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

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

A non-twisting flux tube for local gyrokinetic simulations

Reducing transport via extreme flux-surface triangularity

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

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

Eliminating turbulent self-interaction through the parallel boundary condition in local gyrokinetic simulations

How eigenmode self-interaction affects zonal flows and convergence of tokamak core turbulence with toroidal system size

Development of advanced linearized gyrokinetic collision operators using a moment approach

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

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

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

Toroidal and slab ETG instability dominance in the linear spectrum of JET-ILW pedestals

Local gyrokinetic simulations of tokamaks with non-uniform magnetic shear

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

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