Item

Abstract

Analysis of Type I ELMs from present experiments shows that ELM energy losses decrease with increasing pedestal plasma collisionality (ν*_ped) and/or increasing τ^Front_║, where (τ_║^Front=2πRq₉₅/c_s,ped) is the typical ion transport time from the pedestal to the divertor target. ν^*_ped and τ^Front_║ are not the only parameters that affect the ELMs, also the edge magnetic shear influences the plasma volume affected by the ELMs. ELM particle losses are influenced by this ELM affected volume and are weakly dependent on other pedestal plasma parameters. `Minimum' Type I ELMs, with energy losses acceptable for ITER, where there is no change in the plasma temperature profile during the ELM, are observed for some conditions in JET and DIII-D. The duration of the divertor ELM power pulse is well correlated with τ^Front_║ and not with the duration of the ELM-associated MHD activity. Similarly, the time scale of ELM particle fluxes is also determined by τ^Front_║. The extrapolation of present experimental results to ITER is summarised.