L-mode Radiative Plasma Edge Studies for Model Validation in ASDEX Upgrade and JET
The presently favoured option for reactor power handling combines metallic plasma-facing components and impurity seeding to achieve highly radiative scrape-off layer and divertor plasmas. It is uncertain whether tolerable divertor power loads will be obtained in this scenario, necessitating the development of predictivemodelling tools. L-mode experiments with N2 seeding have been conducted at both ASDEX Upgrade and JET for benchmarking the critically important impurity radiation models in edge fluid codes. In both machines, a roll-over in ion fluxes and a reduction in target power load is observed first in the inner divertor. The outer divertor evolves from low-recycling to conduction-limited conditions once a reduction of inner target particle load is observed. First comparisons between SOLPS5.0 simulations and N2 seeded experiment support the observed in-out asymmetry in the effect of seeding.