Spectral line shape modeling for the calculation of radiation transport in divertors

Radiation transport in divertor plasmas is strongly coupled to the spectral profiles of absorption and emission of the hydrogen isotopes. As a consequence an accurate description of spectral line shapes is required in order to understand the ionization equilibrium in edge plasmas. The Ly_α line gives the main contribution to reabsorption. In this work, we present a line shape model which is appropriate to describe the Ly_α line in typical divertor conditions expected in tokamaks like JET, Alcator or ITER. Our results are based on an analytical calculation, which predicts the structure and broadening of the line due to combination of fine structure, Zeeman, Stark, and Doppler effects. The model is also applied to D_α line shape and predicts that the contribution of fine structure can be significant.