Transport analysis and modelling of high radiation and high density plasmas at ASDEX Upgrade

Future fusion reactors will require high divertor and core radiation by impurity seeding to limit divertor heat loads. In addition, high core densities are required to maximize the fusion power. A well established technique to reduce heat loads on divertor target plates is to insert low and medium Z impurities in the plasma to convert the heat flux into radiation [1]. Radiative cooling by nitrogen have been extensively investigated at ASDEX Upgrade (AUG). Thereby, a confinement increase due to the presence of N has been discovered [2] [3]. The analysis of the transport properties and the radiative power of H-modes under such conditions is presented. Results from the transport analyses taking into account the spatial radiation distribution are reported in [4]. To provide a reliable radiation profile for transport calculations, a non-coronal radiation model using atomic data and experimental profiles was developed and compared to bolometric measurements. A detailed description of the theoretical background and model development can be found in reference [4] as well. The model takes into account that the edge region of H-mode plasmas is modulated by edge-localized modes (ELMs) which lead to a loss of energy and particles from the confined plasma. In the present contribution the modeling results of the evolution of impurities and radiation at the plasma edge, including ELMs, are presented.