First Results from the Soft X-ray Pulse Height Analysis System on Wendelstein 7-X Stellarator.

Abstract The paper presents experimental results obtained during the first operational phase (called OP1.1) of the Wendelstein 7-X stellarator (W7-X). One of W7-X diagnostics that delivers information about plasma impurities and was commissioned during the OP1.1, is the Pulse Height Analysis (PHA) system which provides soft X-ray spectra of highly ionized impurity species over a very broad energy range with energy resolution not worse than 200 eV and with temporal resolution of 100 ms. The line-of-sight integrated spectra, collected by a Silicon Drift Detector in the energy range between 0.9 and 10 keV, have been analyzed for various experimental conditions and are discussed with respect to results from other diagnostics. In this work, injected impurities (argon and neon) as well as intrinsic impurities (sulphur and chlorine) have been identified. Spectral lines corresponding to heavier impurities have not been observed. [ABSTRACT FROM AUTHOR]