Light impurity transport in the TFR tokamak: Comparison of oxygen and carbon line emission with numerical simulations

Abstract

Space- and time-resolved emission studies of oxygen and carbon ions are reported for high-density TFR discharges (n_e (0) ~ 1 – 1.5×10¹⁴ cm⁻³). The experimental data show that ions of low ionization potential (up to O⁵⁺) are very sensitive to local peripheral phenomena. Radial emissivity profiles of the resonance lines of H-like and He-like ions have been used to study the impurity ion transport by comparison with a numerical simulation code, including anomalous diffusion coefficients (of the order of a few thousand cm² s⁻¹). Quantitative comparison (when possible) with the resistive effective charge Z_eff was always satisfactory, whereas in some cases disagreement was found with the bolometric radiated power.