Modeling of neutral transport in linear divertor plasma using first flight collision probability method

A hybrid model of diffusion and first flight collision probability (FFCP) for two-dimensional (2-D) neutral transport has been developed to analyze neutral behavior in linear gas divertors. In the model, the axial transport of the neutrals is described by the diffusion approximation, while the FFCP model is applied to the radial neutral transport. The model is applied to the analysis of PISCES-A experiments for the model validation. Calculated density profiles of atomic and molecular hydrogen are qualitatively in good agreement with the experimental results. The molecular density sharply decreases near the ionization region where the electron density profile has the maximum. This sharp decrease in the molecular density leads to the atomic density peak. In addition, a sensitivity study of the wall reflection condition suggests that the wall recombination of atoms and the reemission as molecules are important processes to interpret the experimental results.