Christian Theiler awarded EUROfusion grant

Christian Theiler (credit: EPFL)

Christian Theiler (credit: EPFL)

Professor Christian Theiler at the Swiss Plasma Center (EPFL) has been awarded an “Enabling Research Grant” from the EUROfusion Consortium to lead a collaborative research project in the physics of tokamaks.

The Enabling Research Grant is described as “a key ingredient of the EUROfusion Consortium activities as it provides a special path to bring new ideas and techniques into the programme in ways not easily achieved within the strongly goal-oriented main Work Packages.” The €600,000grant was awarded after a call and selection by EUROfusion for project proposals in magnetic confinement fusion.

Christian Theiler, an Assistant Professor with the Swiss Plasma Center at EPFL, will lead a collaborative research project with an international team of 21 researchers from the EPFL, the French Atomic and Alternative Energy Commission (CEA), the Culham Centre for Fusion Energy (CCFE), the Technical University of Denmark, the Italian National Agency for New Technologies, Energy and Sustainable Economic Development (ENEA), and the Max Plank Institute for Plasma Physics (IPP) in Garching.

The project is titled “Towards a first-principles understanding of fluctuations and flows in the X-point region of tokamaks”, and will run for two years. “We aim to validate five leading plasma turbulence codes against well-diagnosed experiments in the challenging but highly relevant ‘X-point geometry’ of tokamak fusion devices,” explains Theiler. “It will result in an important step forward in the understanding of X-point physics, in the predictive capabilities of tokamak boundary modelling, and in establishing these codes as standard tools in the main EUROfusion work packages.”

Project description

Modern tokamaks use a so-called magnetic X-point to separate the confined plasma from the region of the plasma which is in contact with the surrounding wall structure. The plasma dynamics in the region of this X-point is governed by a complex interplay of turbulence, particle drifts, sources, and sinks. Treating these processes theoretically is highly challenging and experimental insight is hampered by limited diagnostic access.

The global, three-dimensional edge plasma turbulence codes GBS, GRILLIX, STORM, TOKAM3X, and FELTOR will first be validated in real-size simulations against an X-point configuration in the basic toroidal device TORPEX.

Being simpler and hence computationally much less expansive to simulate than a tokamak and allowing for full access with probes, TORPEX is ideally suited for this important validation step.

The funded project will then use these codes to perform reduced-size simulations of X-point geometries in the TCV tokamak and qualitatively compare parameter dependencies of turbulence and background drifts observed in simulations and experiments.

This comparison will strongly benefit from the extensive set of X-point diagnostics on TCV, in particular a unique reciprocating probe array, which is currently being commissioned and which will provide two-dimensional measurements of key time-averaged and fluctuation quantities at and around the X-point.

In the final part of this project, the codes will be validated quantitatively using real-size TCV simulations and the work will be extended to plasmas in the MAST-U spherical tokamak.