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Jonathan Graves

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Publications associées (326)

Toroidal drift precession and wave - particle interaction in shaped tokamaks with infinite beta and neoclassical equilibrium effects

Jonathan Graves

The drift kinetic equation is analysed for linear instabilities that are sensitive to the toroidal drift motion of long-mean free path particle populations. The interaction Lagrangian is resolved, and the toroidal drift precession evaluated for realistic t ...

IOP2013

Magnetohydrodynamic helical structures in nominally axisymmetric low-shear tokamak plasmas

Wilfred Anthony Cooper, Antoine Pochelon, Olivier Sauter, Holger Reimerdes, Jonathan Graves, Federico David Halpern, Daniele Brunetti

The primary goal of hybrid scenarios in tokamaks is to enable high performance operation with large plasma currents whilst avoiding MHD instabilities. However, if a local minimum in the safety factor is allowed to approach unity, the energy required to ove ...

Iop Publishing Ltd2013

Bifurcated Helical Core Equilibrium States in Tokamaks

Wilfred Anthony Cooper, Basil Duval, Antoine Pochelon, Olivier Sauter, Trach-Minh Tran, Holger Reimerdes, Stefano Coda, Jonathan Graves, Benoît Labit, David Pfefferlé, Federico David Halpern, Daniele Brunetti

Tokamaks with weak to moderate reversed central shear in which the minimum inverse rotational transform (safety factor) qmin is in the neighbourhood of unity can trigger bifurcated magnetohydrodynamic equilibrium states, one of which is similar to a satura ...

IOP Publishing Ltd2013

Fast seeding of NTMs by sawtooth crashes in TCV and their preemption using ECRH

Basil Duval, Timothy Goodman, Antoine Pochelon, Olivier Sauter, Holger Reimerdes, Jonathan Graves, Duccio Testa

Many tokamaks have observed that sawteeth of sufficient duration may trigger neoclassical tearing modes (NTMs) that lead to plasma performance degradation. In this paper, TCV's ability to accurately control the period of individual sawteeth is exploited, u ...

IOP Publishing Ltd2013

Exploitation of a general-coordinate guiding centre code for the redistribution of fast ions in deformed hybrid tokamak equilibria

Wilfred Anthony Cooper, Jonathan Graves, David Pfefferlé

Self-consistent fast ion distributions are usually obtained using a code that solves the guiding-centre equations, with an appropriate fast ion source (e.g. NBI pinis) and sink (e.g. collision operators). Straight field-line coordinate systems, such as Boo ...

Iop Publishing Ltd2012

Bifurcated Helical Core Equilibrium States in Tokamaks

Wilfred Anthony Cooper, Basil Duval, Antoine Pochelon, Olivier Sauter, Holger Reimerdes, Stefano Coda, Jonathan Rossel, Jonathan Graves, Benoît Labit, David Pfefferlé, Mattia Albergante, Federico David Halpern, Daniele Brunetti

Tokamaks with weak to moderate reversed central shear in which the minimum rotational transform

q_{min}

is in the neighbourhood of unity can trigger bifurcated MagnetoHydrodynamic (MHD) equilibrium states, one of which is similar to a saturated ideal ...

2012

Control of magnetohydrodynamic stability by phase space engineering of energetic ions in tokamak plasmas

Stefano Coda, Martin Jucker, Jonathan Graves, Mattia Albergante

Nature Research2012

Kinetic damping of resistive wall modes in ITER

Martin Jucker, Jonathan Graves, Otto Asunta

American Institute of Physics2012

Full-field drift Hamiltonian particle orbits in 3D geometry

Stephan Brunner, Wilfred Anthony Cooper, Jonathan Graves

A Hamiltonian/Lagrangian theory to describe guiding centre orbit drift motion which is canonical in the Boozer coordinate frame has been extended to include full electromagnetic perturbed fields in anisotropic pressure 3D equilibria with nested magnetic fl ...

IOP2011

Full-field drift Hamiltonian particle orbits in axisymmetric tokamak geometry

Wilfred Anthony Cooper, Jonathan Graves

A Hamiltonian/Lagrangian theory to describe guiding center orbit drift motion that is canonical in Boozer magnetic coordinates is developed to include full electrostatic and electromagnetic perturbed fields in axisymmetric tokamak geometry. Furthermore, th ...

American Institute of Physics (AIP)2011

MHD equilibrium and stability of tokamaks and RFP systems with 3D helical cores

Wilfred Anthony Cooper, Olivier Sauter, Jonathan Graves

Bifurcated magnetohydrodynamic (MHD) equilibrium states are computed for ITER hybrid scenario and RFX-mod SHAx configurations with very flat or reversed core magnetic shear conditions. In the ITER studies, the minimum inverse rotational transform qmin is n ...

IOP Publishing2011

Ion cyclotron resonance heating with consistent finite orbit widths and anisotropic equilibria

Wilfred Anthony Cooper, Martin Jucker, Jonathan Graves

Minority ion cyclotron resonance heating is studied using the self-consistent numerical model SCENIC. This model includes 3D geometries with full shaping and anisotropic pressure effects, warm contributions to the dielectric tensor and full orbit effects. ...

Institute of Physics2011

Macroscopic Stability of High Beta MAST plasmas

Wilfred Anthony Cooper, Jonathan Graves

The high-beta capability of the spherical tokamak, coupled with a suite of world-leading diagnostics on MAST, has facilitated significant improvements in the understanding of performance-limiting core instabilities in high performance plasmas. For instance ...

IOP Publishing Ltd2011

Helical core tokamak MHD equilibrium states

Wilfred Anthony Cooper, Basil Duval, Antoine Pochelon, Olivier Sauter, Holger Reimerdes, Stefano Coda, Jonathan Rossel, Jonathan Graves, Benoît Labit, Mattia Albergante

Bifurcated magnetohydrodynamic tokamak equilibrium states with axisymmetric or helical core structure are computed. When a peaked pressure profile is chosen, the helical core structures appear like the {em snakes} that are observed in the JET tokamak. They ...

Caroline Wilkinson2011

Numerical modelling of electromagnetic turbulent transport of energetic ions in burning plasmas

Wilfred Anthony Cooper, Ambrogio Fasoli, Martin Jucker, Jonathan Graves, Xavier Lapillonne, Mattia Albergante

We investigate the redistribution of the neutral beam driven current in the presence of small scale turbulence in the ITER steady-state scenario. Gyrokinetic simulations show that anomalous transport of beam ions can be larger than collisional estimates. T ...

Institute of Physics2011

Integrated modelling of Ion Cyclotron Resonant Heating in toroidal system

Stephan Brunner, Wilfred Anthony Cooper, Nicolas Mellet, Martin Jucker, Jonathan Graves

An integrated model capable of self-consistent Ion Cyclotron Resonant Heating (ICRH) simulations has been developed. This model includes both full shaping and pressure effects, warm contributions to the dielectric tensor, pressure anisotropy and finite orb ...

Elsevier B.V2011

Recent Advances in Sawtooth Control

Olivier Sauter, Stefano Coda, Jonathan Graves, James Paley

Important advances have been made recently in the invention and application of experimental methods to control the sawtooth instability in tokamak plasmas. The primary means of control involves the application of either ion cyclotron resonance heating (ICR ...

American Nuclear Society2011

Sawtooth control in ITER using ion cyclotron resonance heating

Olivier Sauter, Martin Jucker, Jonathan Graves, Otto Asunta

Numerical modelling of the effects of ion cyclotron resonance heating (ICRH) on the stability of the internal kink mode suggests that ICRH should be considered as an essential sawtooth control tool in ITER. Sawtooth control using ICRH is achieved by direct ...

2011

The effects of sheared toroidal rotation on stability limits in tokamak plasmas

Jonathan Graves

Sheared toroidal rotation is found to increase the ideal external kink stability limit, thought to be the ultimate performance limit in fusion tokamaks. However, at rotation speeds approaching a significant fraction of the Alfv´en speed, the toroidal rotat ...

2011

Helical ITER hybrid scenario equilibria

Wilfred Anthony Cooper, Olivier Sauter, Jonathan Graves

Numerical computations of ITER equilibria in the hybrid scenario using a three-dimensional (3D) magnetohydrodynamic equilibrium code with nested magnetic flux surfaces demonstrate the formation of internal 3D helical cores similar to saturated ideal intern ...

IOP2011

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