Parameter dependences of runaway electron dynamics on ASDEX Upgrade and TCV

The institutes collaborating within the EUROfusion consortium are executing a coordinated research program to better understand disruption-generated runaway electron (RE) generation, control and mitigation. The generation and subsequent suppression of REs on both ASDEX Upgrade (AUG) and TCV is achieved using massive gas injection (MGI) of neon or argon [PAPP IAEA 2016, Pautasso PPCF 2017].
Plasma shaping scans on TCV showed that control of a generated RE beam is possible up to an elongation of k ~ 1.5, and that intermediate elongations (k ~ 1.3) seem to be the most favorable for RE generation. Injecting D2 pellets into a RE beam on AUG lead to a decreased RE dissipation, probably explained by the flushing out of argon. The impact of ITER-relevant dueterium-argon mixture injections will also be discussed. The scaling of the runaway current on plasma- and MGI parameters is analysed using 1D disruption-runaway simulations [Papp NF 2013]. The subsequent dissipation of the RE current scales well with the amount and atomic number of the gas injected. RE dissipation on these two machines is well described by state-of-the-art full-f kinetic models [Hesslow PPCF 2018], which were run for the complete duration of the thermal & current quench for the first time.