Radiative L-mode Edge Plasma Regimes in JET and ASDEX Upgrade

Low-Z impurities must be seeded into the edge plasmas of future high-power full-metal devices like ITER and DEMO in order to dissipate the exhaust power through radiation. Extensive studies have been performed in ASDEX Upgrade and JET to understand the effects of N-seeding on the divertor and scrape-off layer plasmas of full-metal tokamaks of different size and different geometry of the W divertor. The radiation patterns and divertor regimes change substantially in L-mode discharges for various levels of seeding and fuelling, and distinct transitions between the different radiative regimes are observed. In this contribution, conditions for these radiative regimes are described with the help of 2D simulations and the physics behind existing scaling laws for power exhaust are discussed.