Type II ELMy H modes on ASDEX Upgrade with good confinement at high density

H modes with good confinement and small ELMs with the characteristics of type II or grassy ELMs have been observed on ASDEX Upgrade. Such an ELM behaviour is essential to minimize erosion of the divertor tiles in any next step device. For the first time, operation with this favourable ELM type could be demonstrated close to the Greenwald density. Even for such high densities, energy confinement times were close to recent H mode scalings. High density even seems to be favourable, since steady state pure type II ELMy H mode phases on ASDEX Upgrade are obtained only above e/GW ⩾ 0.85. Additional requirements are q95 ⩾ 4.2 and an equilibrium close to a double null configuration with an average triangularity δ = 0.40. For these small ELMs magnetic precursors are observed with a frequency of ≈ 30 kHz and dominant mode numbers of toroidally 3 and 4 and poloidally ⩾ 14.