Self-consistent plasma-neutrals fluid modeling of edge and scrape-off layer turbulence in diverted tokamaks
Konrad Eder, A. Stegmeir, W. Zholobenko, Jan Pfennig, D. Brida, G. Grenfell, F. Jenko, the ASDEX Upgrade Team
Abstract
Abstract We report on developments in the edge and scrape-off layer turbulence code GRILLIX to self-consistently simulate plasma turbulence coupled to a fluid neutral gas model. The neutrals model is extended from a single fluid moment (neutrals density) to three moments, describing additionally the dynamics of neutrals parallel momentum and neutrals pressure. GRILLIX employs the flux-coordinate-independent (FCI) approach, wherein the mesh is neither conformal to the wall nor the magnetic field. A new flux evaluation method consistent with FCI allows for implementing plasma recycling at the boundaries that preserves particles to high precision. The improved plasma-neutrals model is applied to simulate an ASDEX Upgrade attached L-mode discharge. Diffusion and viscosity of neutrals parallel momentum introduce a loss channel for ion parallel momentum. This increases the plasma-neutrals interaction time, which is expected to facilitate detachment. Evolution of neutrals pressure leads to a smoother neutrals distribution. Through the charge-exchange coupling, fluctuation amplitudes of ion temperature filaments in the divertor region are reduced. When additionally applying self-consistent recycling boundary conditions, neutrals density and ionization rates at the strike-lines further increase, which impacts the heat load distribution on the target plates.