The lmpact of the New lsland Divertor on the Plasma Performance in the W 7 - AS Stellarator

W7-AS has recently been equipped with ten open divertor modules in order to experimentally evaluate this exhaust concept in view of future application to W7-X. The new divertor enables access to a new NBl-heated, very high density (up to n" = 3.5x1020 m-3) operating regime with promising confinement properties. The energy confinement time increases steeply with density. In contrast, the particle and impurity confinement times decrease with increasing density. This allows full density control and stable quasi steady-state operation also under conditions of partial detachment from the divertor targets. Radiated power fractions are low to moderate in attached regimes and reach up to about gOVo in detachment scenarios. The radiation mainly originates from lower ionization states of carbon and oxygen and stays always peaked at the edge.