Runaway electron mitigation by applied magnetic perturbations in the ASDEX Upgrade and COMPASS experiments

Runaway electrons (RE) generated during tokamak disruptions represent a severe threat for plasma-facing components in controlled fusion devices and require reliable and efficient mitigation techniques. Dedicated experiments and modeling have been carried out by considering resonant magnetic perturbations (RMP) of different amplitude with toroidal mode number n=1 in ASDEX Upgrade [1] and with n=1 and n=2 in COMPASS. The application of RMPs results in a lower amount and shorter duration of the post-disruption runaway electron current. The efficacy of this technique strongly depends on the upper-to-lower coil phasing i.e on the poloidal spectrum of the perturbations which has been reconstructed including the plasma response by the code MARS-F [2]. Most performant RMPs in RE mitigation partially affect also the electron temperature, the disruption evolution and the associated hard-X-ray spectrum.

[1] M.Gobbin et al, Plasma Phys. Control. Fusion 60 014036 (2018)
[2] Liu Y Q et al, Phys. Plasmas 7 3681(2000)