A pellet launcher tool optimized for the control of edge localized modes in ASDEX Upgrade H-mode plasmas

A main challenge for fusion research oriented pellet launcher systems is the control of the plasma edge region, especially of the possibly dangerous edge localized modes (ELMs) observed in high performance H-mode plasmas. In order to improve the experimental data base required for extrapolation, a novel cryogenic multi-pellet injection system was developed for ASDEX Upgrade, which is entirely dedicated to control and mitigation of type-I ELMs. Based on the blower gun principle, it is capable of combining high repetition rates up to 143 Hz and low pellet sizes and velocities. Expected benefits are an enhanced tokamak operational area and the option for more sophisticated experiments investigating the underlying physical mechanisms. This paper reports on design criteria, construction, extensive laboratory tests and first injection into ASDEX Upgrade plasmas.