31 citations · 217 across the 21 of their papers we have counts for
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A new quasilinear model for turbulent momentum transport in tokamaks with flow shear and plasma shaping
Haomin Sun, Justin Ball, Stephan Brunner +1
In tokamak experiments, sufficiently strong flow shear reduces turbulent transport, thereby improving the prospects for fusion power plants. It is therefore of great im…
Ultra Long Turbulent Eddies, Magnetic Topology, and the Triggering of Internal Transport Barriers in Tokamaks
A. Volčokas, J. Ball, S. Brunner
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…
Local gyrokinetic simulations of tokamaks with non-uniform magnetic shear
Justin Ball, Stephan Brunner
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…
Three-Dimensional Inhomogeneity of Electron-Temperature-Gradient Turbulence in the Edge of Tokamak Plasmas
J. F. Parisi, F. I. Parra, C. M. Roach +15
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-dimension…
Effect of collisions on non-adiabatic electron dynamics in ITG-driven microturbulence
Ajay C. J., Stephan Brunner, Justin 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…
Development of Advanced Linearized Gyrokinetic Collision Operators Using a Moment Approach
B. J. Frei, J. Ball, A. C. D. Hoffmann +3
The derivation and numerical implementation of a linearized version of the gyrokinetic (GK) Coulomb collision operator (Jorge R. et al., J. Plasma Phys. 85, 905850604 (2019)) and o…
A non-twisting flux tube for local gyrokinetic simulations
Justin Ball, Stephan Brunner
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/…
How eigenmode self-interaction affects zonal flows and convergence of tokamak core turbulence with toroidal system size
Ajay C. J., Stephan Brunner, Ben McMillan +3
Self-interaction is the process by which a microturbulence eigenmode that is extended along the direction parallel to the magnetic field interacts with itself non-linearly. This ef…
Toroidal and slab ETG instability dominance in the linear spectrum of JET-ILW pedestals
Jason F. Parisi, Felix I. Parra, Colin M. Roach +9
Local linear gyrokinetic simulations show that electron temperature gradient (ETG) instabilities are the fastest growing modes for in the steep gradient regio…
Eliminating turbulent self-interaction through the parallel boundary condition in local gyrokinetic simulations
Justin Ball, Stephan Brunner, Ajay C. J
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 conditio…
The effect of background flow shear on gyrokinetic turbulence in the cold ion limit
Justin Ball, Stephan Brunner, Ben F. McMillan
The cold ion limit of the local gyrokinetic model is rigorously taken to produce a nonlinear system of fluid equations that includes background flow shear. No fluid closure is requ…
Optimized up-down asymmetry to drive fast intrinsic rotation in tokamaks
Justin Ball, Felix I. Parra, Matt Landreman +1
Breaking the up-down symmetry of the tokamak poloidal cross-section can significantly increase the spontaneous rotation due to turbulent momentum transport. In this work, we optimi…
Turbulent momentum transport due to the beating between different tokamak flux surface shaping effects
Justin Ball, Felix I. Parra
Introducing up-down asymmetry into the tokamak magnetic equilibria appears to be a feasible method to drive fast intrinsic toroidal rotation in future large devices. In this paper…
Up-down asymmetric tokamaks
Justin Ball
Bulk toroidal rotation has proven capable of stabilising both dangerous MHD modes and turbulence. In this thesis, we explore a method to drive rotation in large tokamaks: up-down a…
Effect of the Shafranov shift and the gradient of on intrinsic momentum transport in up-down asymmetric tokamaks
Justin Ball, Felix I. Parra, Jungpyo Lee +1
Tokamaks with up-down asymmetric poloidal cross-sections spontaneously rotate due to turbulent transport of momentum. In this work, we investigate the effect of the Shafranov shift…
Scaling of up-down asymmetric turbulent momentum flux with poloidal shaping mode number in tokamaks
Justin Ball, Felix I. Parra
Breaking the up-down symmetry of tokamaks removes a constraint limiting intrinsic momentum transport, and hence toroidal rotation, to be small. Using gyrokinetic theory, we study t…
Poloidal tilting symmetry of high order tokamak flux surface shaping in gyrokinetics
Justin Ball, Felix I. Parra, Michael Barnes
A poloidal tilting symmetry of the local nonlinear gyrokinetic model is demonstrated analytically and verified numerically. This symmetry shows that poloidally rotating all th…
Radial penetration of flux surface shaping in tokamaks
Justin Ball, Felix I. Parra
Using analytic calculations, the effects of the edge flux surface shape and the toroidal current profile on the penetration of flux surface shaping are investigated in a tokamak. I…
Intrinsic momentum transport in up-down asymmetric tokamaks
Justin Ball, Felix I. Parra, Michael Barnes +4
Recent work demonstrated that breaking the up-down symmetry of tokamak flux surfaces removes a constraint that limits intrinsic momentum transport, and hence toroidal rotation, to…
Conditions for up-down asymmetry in the core of tokamak equilibria
Paulo Rodrigues, Nuno F. Loureiro, Justin Ball +1
A local magnetic equilibrium solution is sought around the magnetic axis in order to identify the key parameters defining the magnetic-surface's up-down asymmetry in the core of to…