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Jonathan Graves

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Publications associées (326)

Simulation of bootstrap current in 2D and 3D ideal magnetic fields in tokamaks

Wilfred Anthony Cooper, Olivier Sauter, Jonathan Graves, Michael Pedro, Madhusudan Raghunathan

We aim to simulate the bootstrap current for a MAST-like spherical tokamak using two approaches for magnetic equilibria including externally caused 3D effects such as resonant magnetic perturbations (RMPs), the effect of toroidal ripple, and intrinsic 3D e ...

Iop Publishing Ltd2016

Hybrid guiding-centre/full-orbit simulations in non-axisymmetric magnetic geometry exploiting general criterion for guiding-centre accuracy

Wilfred Anthony Cooper, Jonathan Graves, David Pfefferlé

To identify under what conditions guiding-centre or full-orbit tracing should be used, an estimation of the spatial variation of the magnetic field is proposed, not only taking into account gradient and curvature terms but also parallel currents and the lo ...

Iop Publishing Ltd2015

Overview of MAST results

Wilfred Anthony Cooper, Ricardo Pérez Suárez, Jan Horacek, Jonathan Graves, Mario Ludovico Podesta, Ben McMillan, Otto Asunta

The Mega Ampere Spherical Tokamak (MAST) programme is strongly focused on addressing key physics issues in preparation for operation of ITER as well as providing solutions for DEMO design choices. In this regard, MAST has provided key results in understand ...

Iop Publishing Ltd2015

Extended MHD simulations of infernal mode dynamics and coupling to tearing modes

Wilfred Anthony Cooper, Jonathan Graves, Federico David Halpern, Daniele Brunetti

A numerical study of pressure driven magnetohydrodynamic (MHD) instabilities in a low-shear tight aspect ratio configuration is presented. When the magnetic shear is sufficiently small over an extended region in the core, enhanced instability occurs due to ...

Iop Publishing Ltd2015

The merits of ion cyclotron heating schemes for sawtooth control in tokamak plasmas

Jonathan Graves, Jonathan Marc Philippe Faustin

JET experiments have compared the efficacy of low-and high field side ion cyclotron resonance heating (ICRH) as an actuator to deliberately minimise the sawtooth period. It is found that low-field side ICRH with low minority concentration is optimal for sa ...

Cambridge University Press2015

A 3D MHD equilibrium description of nonlinearly saturated ideal external kink/peeling structures in tokamaks

Wilfred Anthony Cooper, Basil Duval, Olivier Sauter, Trach-Minh Tran, Holger Reimerdes, Laurie Porte, Jonathan Graves

Novel free boundary magnetohydrodynamic equilibrium states with spontaneous three-dimensional (3-D) deformations of the plasmaâ vacuum interface are computed. The structures obtained look like saturated ideal external kink/peeling modes. Large edge pre ...

Cambridge University Press2015

Suprathermal electron dynamics and MHD instabilities in a tokamak

Stefano Coda, Jonathan Graves, Josef Kamleitner, Joan Decker

The dynamics of suprathermal electrons in the presence of magnetohydrodynamics (MHD) activity and the excitation of MHD modes by suprathermal electrons are studied experimentally to improve the understanding of the interaction of fast particles with MHD in ...

2015

ELM frequency feedback control on JET

Jonathan Graves

This paper describes the first development and implementation of a closed loop edge localized mode (ELM) frequency controller using gas injection as the actuator. The controller has been extensively used in recent experiments on JET and it has proved to wo ...

IOP Publishing Ltd2015

Free boundary equilibrium in 3D tokamaks with toroidal rotation

Wilfred Anthony Cooper, Olivier Sauter, Minh Tâm Tran, Jonathan Graves, David Pfefferlé, Daniele Brunetti, Jonathan Marc Philippe Faustin, Madhusudan Raghunathan

The three-dimensional VMEC equilibrium solver has been adapted to numerically investigate the approximate toroidal rotation model we have derived. We concentrate our applications on the simulation of JET snakes and MAST long-lived modes under free boundary ...

IOP Publishing Ltd2015

NBI fast ion confinement in the helical core of MAST hybrid-like plasmas

Wilfred Anthony Cooper, Jonathan Graves, David Pfefferlé, Cyril Misev

Energetic ions are found to be transported strongly from the core of MAST hybrid-like plasmas during long-lived mode (LLM) magnetohydrodynamic activity. The resulting impact on the neutral beam ion deposition and concurrent current drive is modelled usin ...

IOP Publishing Ltd2014

Non-perturbative modelling of energetic particle effects on resistive wall mode: Anisotropy and finite orbit width

Jonathan Graves

A non-perturbative magnetohydrodynamic-kinetic hybrid formulation is developed and implemented into the MARS-K code [Liu et al. , Phys. Plasmas 15 , 112503 (2008)] that takes into account the anisotropy and asymmetry [Graves et al. ,Nature Commun. 3 , 624 ...

American Institute of Physics (AIP)2014

VENUS-LEVIS and its spline-Fourier interpolation of 3D toroidal magnetic field representation for guiding-centre and full-orbit simulations of charged energetic particles

Wilfred Anthony Cooper, Jonathan Graves, David Pfefferlé, Cyril Misev

Curvilinear guiding-centre drift and full-orbit equations of motion are presented as implemented in the code{VENUS-LEVIS} code. A dedicated interpolation scheme based on Fourier reconstruction in the toroidal and poloidal direction and cubic spline in the ...

Elsevier2014

Impact of RMP magnetic field simulation models on fast ion losses

Wilfred Anthony Cooper, Jonathan Graves, David Pfefferlé, Cyril Misev

Two opposing approaches to include resonant magnetic perturbations (RMPs) in fast ion simulations are compared, one where the vacuum field caused by the RMP current coils is added to the axisymmetric MHD equilibrium, the other where the MHD equilibrium inc ...

International Atomic Energy Agency2014

Three-dimensional distortions of the tokamak plasma boundary: boundary displacements in the presence of saturated MHD instabilities

Wilfred Anthony Cooper, Jonathan Graves, Daniele Brunetti

The three-dimensional plasma boundary displacement induced by long-lasting core magnetohydrodynamic (MHD) instabilities has been measured in JET, MAST and NSTX. Only saturated instabilities are considered here since transient rapidly growing modes which de ...

IOP Publishing Ltd2014

Self-consistent Simulations of ICRH with the Background Equilibrium in Tokamaks and Stellarators

Wilfred Anthony Cooper, Martin Jucker, Jonathan Graves

The SCENIC code package has been developed to integrate self-consistently an anisotropic pressure magnetohydrodynamic equilibrium state with power absorption from Ion Cyclotron Resonance Heating and with a guiding center particle distribution function for ...

American Nuclear Society2014

Sawtooth Control in JET with ITER relevant low field side resonance ICRH and ITER like wall

Jonathan Graves, Jonathan Marc Philippe Faustin

New experiments at JET with the ITER-like wall show for the first time that ITER-relevant low field side resonance first harmonic ion cyclotron resonance heating (ICRH) can be used to control sawteeth that have been initially lengthened by fast particles. ...

IOP2014

Fast growing resistive two fluid instabilities in hybrid-like tokamak configuration

Wilfred Anthony Cooper, Jonathan Graves, Daniele Brunetti

An analytic derivation of the dispersion relation for resistive instabilities in a low-shear tokamak configuration is presented. The resistive infernal mode model (Charlton et al 1989 Phys. Fluids B 1 798) is generalized to include plasma diamagnetism, sub ...

Institute of Physics2014

Ideal saturated MHD helical structures in axisymmetric hybrid plasmas

Wilfred Anthony Cooper, Jonathan Graves, Daniele Brunetti

Kinked saturated m = 1 helical structures are frequently observed in tokamak hybrid plasmas and in reversed field pinches (RFP). These modes occur when an extremum in the safety factor is close to, but necessarily resonant with, a low order rational (typic ...

International Atomic Energy Agency2014

Analysis of global hydromagnetic instabilities driven by strongly sheared toroidal flows in tokamak plasmas

Jonathan Graves

Recent numerical calculations have shown that while strong toroidal rotation can increase the external kink limit of tokamak plasmas, the associated rotation shear can drive a Kelvin-Helmholtz like global instability in the plasma, if the rotation frequenc ...

Iop Publishing Ltd2013

Power requirements for electron cyclotron current drive and ion cyclotron resonance heating for sawtooth control in ITER

Timothy Goodman, Olivier Sauter, Stefano Coda, Martin Jucker, Jonathan Graves, Costanza Zucca, Otto Asunta

13 MW of electron cyclotron current drive (ECCD) power deposited inside the q = 1 surface is likely to reduce the sawtooth period in ITER baseline scenario below the level empirically predicted to trigger neoclassical tearing modes (NTMs). However, since t ...

IOP Publishing Ltd2013

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