Combination of micro–macro and spatially hybrid fluid‐kinetic approach for hydrogenic plasma edge neutrals

Abstract

AbstractA new hybrid fluid‐kinetic approach for the hydrogenic neutrals (atoms and molecules) in the plasma edge is presented. The hybrid approach combines a fully kinetic model for the atoms in the low‐collisional regions near the vessel wall, and for the molecules in the whole plasma edge domain, with a micro–macro approach for atoms originating from recycling at the divertor targets, volumetric recombination, and dissociation of molecules. With the micro–macro approach, the originally scattering‐dominated collision term due to charge‐exchange collisions in the kinetic equation is transformed to an absorption‐dominated term, while a large part of the neutral population is treated through a fluid approach. For JET L‐mode plasmas, the premature termination of Monte Carlo particle trajectories in the hybrid approach leads to a reduction of the CPU time by approximately a factor 3 for a high‐recycling case and by approximately a factor 11 for a partially detached case compared with a simulation with fully kinetic neutrals and the same amount of particles. For coupled fluid plasma – hybrid neutral simulations – the hybrid approach predicts the plasma divertor target profiles with a maximum hybrid‐kinetic discrepancy of approximately 30%.