Abstract
a versatile gas injection system and an absolute calibrated spectroscopic observation system with more than 200 lines-of-sight have been installed in two divertor locations in the Wendelstein 7-X stellarator. This powerful setup enables among other measurements to infer Te and ne in the divertor region by means of line-ratio spectroscopy on thermal helium. This is a robust and routinely used diagnostic at W7-X and this work describes its main characteristics and shows some examples of Te and ne profiles. In particular it is shown that the inclusion of high Rydberg states in the helium collisional-radiative model is necessary to obtain a realistic estimate of Te. The applicability of the diagnostic is currently being extended towards the low Te and high ne conditions occurring during detachment by means of line-ratio spectroscopy on neon. Initial Te, ne profiles obtained with a neon-beam are here presented.
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