Feasibility of line-ratio spectroscopy on helium and neon as edge diagnostic tool for Wendelstein 7-X.

A beam emission spectroscopy system on thermal helium (He) and neon (Ne) has been set up at Wendelstein 7-X to measure edge electron temperature and density profiles utilizing the line-ratio technique or its extension by the analysis of absolutely calibrated line emissions. The setup for a first systematic test of these techniques of quantitative atomic spectroscopy in the limiter startup phase (OP1.1) is reported together with first measured profiles. This setup and the first results are an important test for developing the technique for the upcoming high density, low temperature island divertor regime.