Analysis of the impurity content in Wendelstein 7-X using VUV spectroscopic data

Throughout the second operation phase of the stellarator Wendelstein 7-X, the impurity content and their (dynamic) behaviour in various discharge configurations were carefully monitored and investigated. The main diagnostics for the determination of impurity compositions is the VUV spectrometer system HEXOS. As this device is absolutely intensity calibrated, its data is also used, in conjunction with the 1D impurity transport code STRAHL, to derive the individual impurity concentrations. First assessments of the impurity composition and concentrations in Helium and Hydrogen discharges are presented. This comparison might give insight into the general difference in performance in the two gases, and allows for a careful discussion of possible impurity sources during this operation phase.