Runaway electron beam formation, vertical motion, termination and wall loads in EU-DEMO

Runaway electron (RE) loads onto material structures are a major concern for future large tokamaks due to the efficient avalanching at high plasma currents. Here, we perform predictive numerical studies using the JOREK code for a plausible plasma configuration in the European DEMO fusion power plant, focusing in this paper on the scenario where the highest multi-ampere RE beam is formed. The work first comprises axisymmetric predictions of RE beam formation in a mitigated scenario and of the simultaneous vertical motion of the beam due to loss of position control. The subsequent RE beam termination triggered by a burst of magnetohydrodynamic (MHD) activity during the course of the vertical motion is then simulated in 3D with the RE fluid self-consistently coupled to the MHD modes. Finally, the resulting deposition pattern of the REs onto wall structures is calculated with a relativistic test particle approach. This way, the suitability of a possible sacrificial limiter concept for the protection of first wall components is assessed.