Section: New Results

Kinetic modeling and simulation of edge tokamak plasmas and plasma-wall interactions

Participants : Sever Hirstoaga, David Coulette, Giovanni Manfredi.

We performed a full parallelization (over species and using 4D domain decomposition) of the 1D3V Multi-species Vlasov-Poisson finite-volumes code. The 4D code was then used to perform, by means of parametric studies, an analysis of the structure of the multi-scale boundary layer (the so-called Debye sheath and various pre-sheaths) for a magnetized-plasma in contact with an absorbing wall. This study allowed us to show, notably, that when the strong confining magnetic field is close to grazing incidence with respect to the absorbing surface, the boundary layer extends further into the plasma and as a result the magnitude of the electric field is lessened.

A second study was devoted to the dynamics of the propagation of the so-called "ELMs" (Edge-Localized-Modes) at the edge of Tokamak devices. The 1D1V collisionless model used in previous studies was extended by coupling a 1D1V kinetic model for the fast parallel propagation of the plasma disturbance along magnetic field lines with a fluid model in the directions perpendicular to the magnetic field. The coupling occurs by means of collision operators allowing for energy transfer between the parallel and perpendicular degrees of freedom. The initial asymptotic preserving scheme was extended to allow for adaptive time-stepping due to the introduction of the fluid transport equation. Using simulation results for various realistic collision rates we showed that collisional isotropization of the electronic population have a significant impact on the heat flux impacting the devices wall. The results were presented to the magnetic fusion community at the EPS conference in Leuven [9].