Multi-level model of radiation transport in inhomogeneous plasma

Radiation transport in plasma can be important for a number of problems, for example, first wall-shielding effects or influence of hydrogen isotope radiation on tokamak edge plasma. Existing calculations in the field employ many simplifying assumptions. For example, the model of radiation transport in one of the most used codes, SOLPS, suggests that photoexcitation can be ignored for all transitions, not including the ground level. We develop a collisional radiative model of radiation transport in a multi-level system, fully accounting for all transitions between levels. The role of the Stark effect in line shape is taken into account. The validity of some of the approximations made in SOLPS is analysed for detached divertor plasma in DIII-D-like tokamak geometry. It is shown that total radiation flux is directed away from the divertor target due to nonuniform plasma temperature and density.