Impact of large type I ELMs on plasma radiation in JET

• Large type I ELMs with losses over 0.72MJ show enhanced radiation losses associated with an ablation of the redeposited carbon layer in the inner divertor. • Surface (layer) temperatures do not exceed ∼ 2000°C at inner target. The surface temperature is too low for bulk carbon ablation but provokes ablation of the deposited layers. • Large ELMs are often compound (Type I ELM followed by Type III ELMs). • A significant part (up to 80%) of the plasma energy degradation during the compound phase is exhausted by radiation. The degradation of confinement during the compound phase is accompanied by a collapse in pedestal density. • The "compound" phase indicates an increased plasma contamination, which otherwise does not lead to a radiative collapse of the plasma. • ELM-induced radiation is always higher at the inner than at the outer divertor: approximately a linear increase in asymmetry up to ΔW_ELM ∼ 0.6 MJ then a decrease for higher ΔW_ELM. • During the ELMs, the radiation is mostly located in the divertor region. • Giant ELMs drive the divertor into detachment after the ELM crash. Divertor detachment remains during the entire compound phase. • Larger ELMs deposit more energy on limiters. No energy is deposited in compound phases.