Publications de Jonathan Graves

Schemes for Generating Deeply Trapped Fast Ions Via Ion-cyclotron-resonance Heating in Wendelstein 7-x

Wendelstein 7-X (W7-X) is a large, superconducting, optimized stellarator being operated in Greifswald, Germany. One of the original optimization criteria (Grieger et al 1992 Phys. Fluids B: Plasma Physics 4 2081) is good fast-ion confinement, mainly at in ...

IOP Publishing Ltd2025

Interplay of plasma resistivity and rotation on β limits in free boundary diverted tokamaks

Jonathan Graves

A plasma resistivity-β driving mechanism aimed at explaining the appearance of long wavelength global instabilities in free boundary high-β tokamak plasmas with a divertor is presented. These perturbations resemble very closely the resistive wall mode phen ...

2024

Direct prediction of saturated neoclassical tearing modes in slab using an equilibrium approach

Jonathan Graves, Joaquim Loizu Cisquella

We demonstrate for the first time that the nonlinear saturation of neoclassical tearing modes (NTMs) can be found directly using a variational principle based on Taylor relaxation, without needing to simulate the intermediate, resistivity-dependent dynamic ...

IOP Publishing2024

News and announcements from the Editor-in-Chief for 2024

Jonathan Graves

2024

Occam's razor on the mechanism of resistive-wall-mode-induced beta limits in diverted tokamaks

Jonathan Graves, Daniele Brunetti

External kink modes, believed to be the drive of the 0-limiting resistive wall mode, are strongly stabilized by the presence of a separatrix. We thus propose a novel mechanism explaining the appearance of long-wavelength global instabilities in free bounda ...

2023

Numerical tools for burning plasmas

Laurent Villard, Alberto Bottino, Jonathan Graves, Ben McMillan, Emmanuel Lanti, Emanuele Poli, Xiao Wang, Baruch Rofman

The software stack under development within a European coordinated effort on tools for burning plasma modelling is presented. The project is organised as a Task (TSVV Task 10) under the new E-TASC initiative (Litaudon et al 2022 Plasma Phys. Control. Fusio ...

IOP Publishing Ltd2023

Equilibrium β-limits dependence on bootstrap current in classical stellarators

Jonathan Graves, Joaquim Loizu Cisquella, Antoine Baillod

While it is important to design stellarators with high magnetohydrodynamic stability β-limit, it is also crucial to ensure that good magnetic surfaces exist in a large range of β values. As β increases, pressure-driven currents perturb the vacuum magnetic ...

Cambridge University Press2023

Exact expression for the hot plasma conductivity kernel in configuration space

Jonathan Graves, Mike Machielsen

Electromagnetic perturbations of a magnetized plasma cause induced charges and currents, collectively known as the plasma response. In the frequency domain, this response is a non-local functional of the electric field. The associated integral kernel, know ...

2023

Fast ion generation by combined RF-NBI heating in W7-X

Jonathan Graves, Mike Machielsen

Good fast ion confinement in quasi-isodynamic stellarators still has to be demonstrated experimentally. In the absence of fusion alphas, auxiliary heating systems can be used to generate fast ions. For this purpose, W7-X has neutral beam injection and its ...

Cambridge University Press2023

EUROfusion-theory and advanced simulation coordination (E-TASC): programme and the role of high performance computing

Laurent Villard, Jonathan Graves, Eric Serre

This paper is a written summary of an overview oral presentation given at the 1st Spanish Fusion High Performance Computer (HPC) Workshop that took place on the 27 November 2020 as an online event. Given that over the next few years ITER24 will move to its ...

2022

Understanding JET-C quiescent phases with edge harmonic magnetohydrodynamic activity and comparison with behaviour under ITER-like wall conditioning

Wilfred Anthony Cooper, Jonathan Graves, Daniele Brunetti, Andreas Kleiner, Alberto Mariani, Guillermo Bustos Ramirez

An analysis of edge localised mode-free (quiescent) H-mode discharges exhibiting edge harmonic magnetoydrodynamic activity in the JET-carbon wall machine is presented. It is observed that the otherwise quiescent pulses with multiple-n harmonic oscillations ...

IOP Publishing Ltd2022

Experimental confirmation of efficient island divertor operation and successful neoclassical transport optimization in Wendelstein 7-X

Gregory Vogel, Eduardo Sanchez, Frank Rüdiger Wagner, Alberto Bottino, Hartmut Zohm, Jonathan Graves, Thomas Binderup Jensen, Michel Haas, Emiliano Fable, Joaquim Loizu Cisquella, Attila Bencze, Xiaoxue Han, Adnan Ali, Jieping Zhu, Jonathan Marc Philippe Faustin, Antoine Baillod, Konstantinos Avramidis, Nicola Vianello, Sheng Xu, Mike Machielsen, Ajay Kumar, Hui Wang, Shuai Liu

We present recent highlights from the most recent operation phases of Wendelstein 7-X, the most advanced stellarator in the world. Stable detachment with good particle exhaust, low impurity content, and energy confinement times exceeding 100 ms, have been ...

IOP Publishing Ltd2022

Overview of the TCV tokamak experimental programme

Patrick Blanchard, Stephan Brunner, Stefano Alberti, Basil Duval, Ambrogio Fasoli, Timothy Goodman, Xavier Llobet, Yves Martin, Jean-Marc Moret, Olivier Sauter, Henri Weisen, Ivo Furno, Holger Reimerdes, Jean-Philippe Hogge, Jan Horacek, Alexander Karpushov, Laurie Porte, Yanis Andrebe, Jonathan Graves, Duccio Testa, Benoît Labit, Joaquim Loizu Cisquella, Paolo Ricci, Christian Gabriel Theiler, Federico Alberto Alfredo Felici, Miguel Filipe Silva Füglister, Antoine Pierre Emmanuel Alexis Merle, Oulfa Chellaï, Curdin Tobias Wüthrich, Joan Decker, Cedric Kar-Wai Tsui, Pedro Andres Molina Cabrera, Matteo Fontana, Umar Sheikh, Cristian Galperti, Marcelo Baquero Ruiz, Dahye Choi, Aylwin Iantchenko, Mengdi Kong, Roberto Maurizio, Francesco Carpanese, , , , , , , , , , , , , , , , , , , , , , ,

Verification and validation of linear gyrokinetic and kinetic-MHD simulations for internal kink instability in DIII-D tokamak

Jonathan Graves

Verification and linear validation of the internal kink instability in tokamak have been performed for both gyrokinetic (GTC) and kinetic-MHD codes (GAM-solver, M3D-C1-K, NOVA, XTOR-K). Using realistic magnetic geometry and plasma profiles from the same eq ...

IOP Publishing Ltd2022

Pressure driven long wavelength MHD instabilities in an axisymmetric toroidal resistive plasma

Jonathan Graves

A general set of equations that govern global resistive interchange, resistive internal kink and resistive infernal modes in a toroidal axisymmetric equilibrium are systematically derived in detail. Tractable equations are developed such that resistive eff ...

2022

Heavy impurity transport in tokamaks subject to plasma rotation, NTV and the influence of saturated ideal MHD perturbations

Jonathan Graves, Eduardo José Lascas Neto, Cristian Sommariva

Strongly peaked tungsten accumulation is a common feature of high performance plasma scenarios in JET with the ITER-like wall, particularly during MHD activity induced by m/n = 1/1 continuous modes. This study investigates the effect of 1/1 long living int ...

2022

Finite magnetic well effects on resistive and drift-resistive ballooning modes in a shaped tokamak

Jonathan Graves

The impact of plasma shaping through magnetic well modifications on the stability of resistive ballooning modes (RBMs) in tokamaks is analysed, also including finite diamagnetic flows. Various limiting cases of the dispersion relation, obtained by matching ...

IOP Publishing Ltd2022

Modeling of saturated external MHD instabilities in tokamaks: A comparison of 3D free boundary equilibria and nonlinear stability calculations

Jonathan Graves

3D free boundary equilibrium computations have recently been used to model external kinks and edge harmonic oscillations (EHOs), comparing with linear MHD stability codes, and nonlinear analytic theory [Kleiner et al., Phys. Plasma Controlled Fusion 61, 08 ...

2022

Stellarator optimization for nested magnetic surfaces at finite β and toroidal current

Jonathan Graves, Joaquim Loizu Cisquella, Antoine Baillod

Good magnetic surfaces, as opposed to magnetic islands and chaotic field lines, are generally desirable for stellarators. In previous work, Landreman et al. [Phys. of Plasmas 28, 092505 (2021)] showed that equilibria computed by the Stepped-Pressure Equili ...

American Institute of Physics (AIP)2022

Overview of JET results for optimising ITER operation

Patrick Blanchard, Ambrogio Fasoli, Olivier Sauter, Henri Weisen, Jonathan Graves, Duccio Testa, Federico Alberto Alfredo Felici, Matteo Fontana, Umar Sheikh, Paulo Giovane Paschoali Pereira Puglia, Eduardo José Lascas Neto, Cristian Sommariva, Davide Galassi, Mike Machielsen, Alessandro Pau, Gino Marceca

The JET 2019-2020 scientific and technological programme exploited the results of years of concerted scientific and engineering work, including the ITER-like wall (ILW: Be wall and W divertor) installed in 2010, improved diagnostic capabilities now fully a ...

IOP Publishing Ltd2022