At TEXTOR, an X-ray spectrometer in a Johann mount is utilized to measure the X-ray spectra of He-like elements with intermediate Z. Up to now, the spectra of He-like argon have been investigated. The spectra have been modeled with the most recent atomic data using physically relevant parameters only. Good agreement has been found both in modeling the experimental spectra and in the determination of the plasma parameters, such as ion temperature and plasma motion and electron temperature. The deviations between the theoretical and experimental spectra are below 7% for all lines; the precision of the plasma parameters obtained by X-ray spectroscopy agrees with the accuracy of the standard diagnostics at TEXTOR.

In addition, the abundance of Li-/He-like ions, as well as the H-/He-like ions, has been measured. For the higher densities, the abundance approaches the coronal expectation. Larger deviations to the coronal limit have been found with neutral beam injection. The system is now being upgraded for spatial resolution.