Comparison of impurity transport model with measurements of He-like spectra of argon at the tokamak TEXTOR

The measured Kα spectra of He-like argon were used to determine the densities of H-, He- and Li-like argon ions in ohmically heated plasmas in the tokamak TEXTOR. The obtained ratio of the densities for the Li- and He-like ions shows a significant deviation from coronal equilibrium. In order to interpret these results numerical modelling of the impurity transport was performed by the code RITM with neoclassical and anomalous contributions to the transport coefficients. The measurements show that the transport in the plasma core is much higher than that predicted from the model and has a strong correlation with the line averaged density. This paper also demonstrates the unique ability of the He-like spectra to separate the transport properties and the charge-exchange processes in the plasma.