Magneto-Fluid Dynamics Seminar

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A new gyrokinetic moment-based method for the simulation of the plasma boundary of fusion devices

Speaker: Baptiste Frei, Ecole Polytechnique Fédérale de Lausanne, Switzerland

Location: Warren Weaver Hall 905

Date: Tuesday, October 19, 2021, 11 a.m.

Synopsis:

Understanding the turbulent dynamics of the plasma in the boundary of fusion devices is of
crucial importance on the way to fusion energy and a critical issue to make reliable predictions of
the performances of future experiments, such as ITER. Analytical progress and numerical
simulations of the plasma boundary are made particularly challenging because of the multiscale
and multiphysics nature of this region, and the wide range of the values of the plasma
collisionality. In fact, while gyrokinetic simulations are successfully applied to determine the
turbulent plasma dynamics in the collisionless regime of the core and fluid simulations are used
to study the dynamics of collisional plasmas of the SOL, it is challenging to represent both
collisional regimes at the same time, as required for proper simulations of the plasma boundary.

In this presentation, a novel moment-based method is described to approach the modelling of the
plasma boundary at arbitrary collisionality [1], bridging the gap between gyrokinetic and fluid
simulations. A suitable velocity-space polynomial decomposition of the gyrocenter distribution
allows us to develop the gyrokinetic Boltzmann equation onto a set of fluid-like equations that
retain collisional effects described by the full gyrokinetic Coulomb collision operator [2,3]. We
discuss and illustrate the analytical and numerical capabilities of the moment-based method by
considering different parameter regimes relevant for edge and SOL modelling. The first
numerical implementation of a linearized gyrokinetic Coulomb collision operator using the
moment approach [3] allows us to explore the collisional effects on drift-wave type instabilities,
demonstrating the numerical efficiency of the method in particular as the collisionality increases.
The first nonlinear simulations of the moment-based method are shown.

 

[1] Frei B. J. et al., J. Plasma Physics 82 (2020) 905860205
[2] Jorge R. et al., J. Plasma Physics 85 (2019) 905850604
[3] Frei B. J. et al., J. Plasma Physics 87 (2021) 905870501