Model for the X-point radiator height and its energetic coupling to the plasma edge

The physics governing the height of the X-point radiator (XPR) and the influence of the related radiation losses on the edge temperature profiles is studied with a reduced power balance model, which is an extension of a model developed to study XPR access. For ASDEX Upgrade parameters with a heating power of 10 MW, the model reproduces that the X-point radiator can be moved from the X-point up to 14 cm into the confined plasma, dissipating up to 70% of the heating power. The key parameter is the neutral density in the X-point region. A reduction of the edge kinetic pressure gradient of about 50% is found which could explain the suppression of edge localized modes observed in experiment. The calculated edge temperature response is consistent with experimental data.