ELM-averaged power exhaust on JET

This paper describes experiments performed on JET over the past two years dedicated to characterizing ELM-averaged power exhaust (based on time-averaged divertor power deposition profiles), with an emphasis on unfuelled, Type-I ELMy H-mode. Radial energy transport in the scrape-off layer (SOL) is found to behave differently in the ion and electron channels: the former is dominated by (neo-)classical ion conduction, i.e. by diffusion of heat due to ion-ion collisions, while the latter appears to be governed by turbulent convection, most likely driven by MHD interchange and/or drift-Alfven instabilities. Comparison of forward and reversed field experiments indicates that classical drifts can explain the observed in-out poloidal asymmetry in the heat loads deposited on the divertor. Whereas the role of ELMs needs further characterization, a coherent picture of ELM-averaged power exhaust can be formed by considering the role of collisional heat diffusion in the highly dissipative SOL turbulence.