Description
Following the thermal quench (TQ), increased plasma resistivity is responsible for the plasma current decay, which then generates intense toroidal electric fields capable of accelerating electrons to relativistic energies [1]. These runaway electron (RE) populations, retaining a substantial fraction of the pre-disruption current, can inflict severe localized damage on the first wall. To assess beam termination and wall interaction, prior JOREK simulations had been conducted to evaluate the performance of the upper limiter (UL) and guide potential design refinements for DEMO [2].
For the new DEMO large aspect ratio (LAR) design, in this work, the non-linear MHD code JOREK [3,4] is coupled with CARIDDI to investigate the RE dynamics during a mitigated disruption. The simulation performed are free boundary, and the coupling with the CARIDDI code allows for accurate representation of 3D conductive structures [5].
Preliminary studies demonstrate the capability of the JOREK–CARIDDI model to capture both the plasma motion and the RE formation during disruption scenarios. Axisymmetric simulations of the vertical plasma motion and RE generation show a strong avalanche gain that limits the sensitivity to the seed amplitude and the impurity density. Complementary 3D analyses will characterize thermal load distributions on the plasma facing component, during cold vertical displacement events (VDEs), supported by test-particle tracking to evaluate RE-induced heat fluxes and limiter resilience, coupling with damage assessment tools (e.g., MEMOS and MEMENTO) [6].
References
[1] B. Breizman et al, Nucl. Fusion 59 083001 (2019)
[2] F. Vannini et al, Nucl. Fusion 65 046006 (2025)
[3] M. Hoelzl et al, Nucl. Fusion 64 112016 (2024)
[4] V. Bandaru et al, Phys. Rev. E 99(6) 063317 (2019)
[5] N. Isernia et al, Phys. Plasmas 30, 113901 (2023)
[6] S. Ratynskaia et al, Plasma Phys. Control. Fusion in press (2026)