Confinement degradation of ELMy H modes at high density and/or radiated power fraction

High density, high radiated power fraction and small ELMs are key elements of the current ITER design. In JET, these conditions are shown to be associated with high ELM frequency, low pedestal pressure and correspondingly reduced global energy confinement time. The article reviews the current understanding of the connections between these parameters and the mechanisms for the saturation of the density with gas Afuelling.