Atomic And Molecular Deuterium Edge Density Evaluation From Spectral Analysis Of The D Alpha Line Shape

A method for molecular and atomic deuterium density evaluation, based on the analysis of the Dalpha spectral line shape coupled to a collisional radiative model, is presented. It is illustrated by its application to the plasma edge in the ergodic divertor configuration of the tokamak Tore Supra. An important molecular density (n(D2) > 10(18) m(-3), 1 cm radially away from the neutralizer plate), of the same order as the total atomic density n(D) (n(D)/n(D2) similar to 1.4), is found for the entire range of edge electron temperatures (10eV < T-e < 40eV). The density ratio of D atoms created by charge exchange or reflection of deuterons on the neutralizer plate and D atoms coming from D-2 dissociation is approximately constant for electron temperatures larger than 20eV (similar to0.9). A reasonable agreement is found with the results of the multi-one-dimensional code EDCOLL and the three-dimensional Monte Carlo code BBQ. The influence of the electron temperature and density distributions along the spectroscopic line of sight on the measurements is discussed in the frame of simulations with the numerical code EDCOLL.