Spectroscopic analysis of tokamak edge plasmas

The most intense deuterium and impurity line spectra, measured in the edge plasma of the Tore-Supra Tokamak operated with the Ergodic Divertor, are analyzed in detail by comparison with theoretical profiles. Line profiles are calculated using a lineshape code which includes all level splitting and line broadening mechanisms (Zeeman, Fine structure, Doppler and Stark effects). Deuterium Balmer-alpha line spectra are fitted by considering three neutral populations with different temperatures characteristic of the main recycling mechanisms of the plasma ions (Molecular dissociation, reflection, and Charge exchange). Based on a least square fit method, a statistical study of symmetric spectra (sigma components with equal intensities) has revealed a partial thermalization mechanism of recycled deuterium. Asymmetric spectra (sigma components with different intensities), observed in some discharges after wall conditioning with long helium glow discharges, are modelled by assuming a partial thermalization of neut...