The role of gas injection and magnetic perturbations in Runaway Electron experiments at COMPASS tokamak*

Since 2014 the COMPASS tokamak has been contributing to the Runaway Electron (RE) research programme coordinated by the EUROfusion consortium, which is focused on methods of RE mitigation linked to potential threat of the wall damage in tokamaks due to RE beams. The recent experimental campaigns at COMPASS were dedicated to experiments with Massive Gas Injection / gas puff and with the Resonant Magnetic Perturbation fields which are relatively strong in COMPASS, B_RMP / B_T ~ 1%. For the decay studies, scenario with zero loop voltage was implemented. The results enhanced understanding of the role of the B_T, the injected gas amount or the RE seed. Experiments with RMP confirmed that the best RE mitigation is associated to strong resonant component with core kink response.