Design of VUV/XUV Spectrometers for Impurity Studies on W7-X

Introduction and Overview. The content and transport of impurities is a key issue for the performance and optimisation of fusion plasmas, in particular with respect to confinement and stationarity. Impurities are either released to the plasma via the plasma-wall contact (Be, B, C, O, Si, metals), or produced by the fusion reaction (He ash) or added artificially (He, N, Ne, Ar) to modify the plasma radiation properties (radiation cooling). The most fundamenta