Analysis of SOL carbon radiation distributions with changing plasma parameters at W7-X*

The plasma-surface interaction (PSI) on both the divertors of the island divertor at W7-X and on the first wall leads to carbon erosion and carbon as the main plasma impurity. It is of importance to quantify the amount and distribution of carbon in the scrape-off layer (SOL), as an excess of radiating impurities can move the radiation boundary layer inward, and in extreme cases can ultimately lead to radiative collapse of the plasma. This work provides insight into the distribution of carbon in the SOL using a combination of a sophisticated divertor spectroscopy set-up and ORNL Filterscopes viewing the first wall. The C-II (514.5nm) and C-III (465nm) radiation distributions in the SOL will be analyzed as a first attempt to infer a partial carbon particle flux distribution using electron density and temperature measurements provided by the Helium-beam diagnostic. The effects of plasma parameters on the carbon radiation and particle flux distribution and how these distributions are correlated to plasma performance is assessed.