Gyrokinetic calculation of plasma transport with a material boundary

Both the radially outer wall and the limiter are investigated as material boundary conditions for electrostatic gyrokinetic full particle distribution simulation for axisymmetric tokamaks. Emphasis is put on conditions keeping the simulation stable with least effect on the plasma turbulent structures. Introduction While the gyrokinetic formalism and its implementation in numerical procedures are presently well studied up to widely accepted accuracy and ordering, even in so called full f distribution calculation, progress is still required in adapting such tools to the plasma-wall interface. The latter introduces the complexity by neutrals, atomic physics, sheaths, and recycling among others, which recently have been dealt with some success with a higher dimensional particle-in-cell approach for the scrape-off plasma region [1]. In numerical gyrokinetic implementation, numerical stability issues arise due to the imposed boundary conditions on the distribution function and electrostatic potential. In the present work, the introduction of the plasma-material interface in the tokamak scrape-off-layer region to the gyrokinetic solution is investigated both by the physics and numerical viewpoint. The full f global electrostatic gyrokinetic code Elmfire [2] for tokamaks is applied in such studies, and physical and numerical issues relevant for the interface implementation are discussed and formulated. A metallic wall in its simplest geometry is set as the outer boundary of the calculation region and the solutions are investigated with respect to the plasma density and electrostatic potential from the plasma to the wall. As a further complication, a toroidal limiter as an extension of the wall and defining the separatrix is set as the boundary. Numerical stability issues of the solution are investigated as well as the effect of the limiter configuration on the Bohm condition of the plasma along the open field lines. 40 EPS Conference on Plasma Physics P1.109