Publications de Mike Machielsen

Measurements of radial neutral density profiles from Balmer-α emission in Wendelstein 7-X

Joaquim Loizu Cisquella, Mike Machielsen

Radial neutral density profiles are estimated from measurements of passive Hα emission in the Wendelstein 7-X stellarator. To parametrize the generally three-dimensional distribution with a low number of degrees of freedom, the neutral density is reduced t ...

2025

A control oriented strategy of disruption prediction to avoid the configuration collapse of tokamak reactors

Olivier Sauter, Ambrogio Fasoli, Duccio Testa, Patrick Blanchard, Alessandro Pau, Federico Alberto Alfredo Felici, Cristian Sommariva, Umar Sheikh, Henri Weisen, Davide Galassi

The objective of thermonuclear fusion consists of producing electricity from the coalescence of light nuclei in high temperature plasmas. The most promising route to fusion envisages the confinement of such plasmas with magnetic fields, whose most studied ...

Nature Research2024

Overview of the first Wendelstein 7-X long pulse campaign with fully water-cooled plasma facing components

Joaquim Loizu Cisquella, Mike Machielsen

After a long device enhancement phase, scientific operation resumed in 2022. The main new device components are the water cooling of all plasma facing components and the new water-cooled high heat flux divertor units. Water cooling allowed for the first lo ...

IOP Publishing Ltd2024

Fast ion generation with ICRF waves and beams in the Wendelstein 7-X stellarator

Mike Machielsen

The largest operating stellarator, Wendelstein 7-X, is of the quasi-isodynamic type. For this design to scale up to a fusion reactor, several criteria must be met, one of them being good fast ion confinement. The latter still has to be tested experimentall ...

EPFL2023

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

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

Jieping Zhu, Jonathan Graves, Joaquim Loizu Cisquella, Eduardo Sanchez, Antoine Baillod, Mike Machielsen, Xiaoxue Han, Nicola Vianello, Jonathan Marc Philippe Faustin, Alberto Bottino

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 JET results for optimising ITER operation

Olivier Sauter, Ambrogio Fasoli, Jonathan Graves, Duccio Testa, Patrick Blanchard, Alessandro Pau, Federico Alberto Alfredo Felici, Cristian Sommariva, Umar Sheikh, Henri Weisen

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

ICRF modelling in 2D and 3D magnetic configurations using a hot plasma model

Wilfred Anthony Cooper, Jonathan Graves, Mike Machielsen

The generation of energetic trapped ions is important for experiments investigating their confinement in 3D magnetic fields, for plasma heating, for studies into unwanted drive of instabilities, and improved transport regimes. An effective way to generate ...

2021

Validation of the BEAMS3D neutral beam deposition model on Wendelstein 7-X

Jonathan Graves, David Pfefferlé, Mike Machielsen, Adnan Ali, Yu Gao

The neutral beam deposition model in the BEAMS3D code is validated against neutral beam attenuation data from Wendelstein 7-X (W7-X). A set of experimental discharges where the neutral beam injection system of W7-X was utilized were reconstructed. These di ...

IOP Publishing Ltd2020