Kinetic modelling of runaway electron generation in argon-induced disruptions in ASDEX Upgrade

Abstract

Massive material injection has been proposed as a way to mitigate the formation of a beam of relativistic runaway electrons that may result from a disruption in tokamak plasmas. In this paper we analyse runaway generation observed in eleven ASDEX Upgrade discharges where disruption was triggered using massive gas injection. We present numerical simulations in scenarios characteristic of on-axis plasma conditions, constrained by experimental observations, using a description of the runaway dynamics with self-consistent electric field and temperature evolution in two-dimensional momentum space and zero-dimensional real space. We describe the evolution of the electron distribution function during the disruption, and show that the runaway seed generation is dominated by hot-tail in all of the simulated discharges. We reproduce the observed dependence of the current dissipation rate on the amount of injected argon during the runaway plateau phase. Our simulations also indicate that above a threshold amount of injected argon, the current density after the current quench depends strongly on the argon densities. This trend is not observed in the experiments, which suggests that effects not captured by 0D kinetic modeling -- such as runaway seed transport -- are also important.

arXiv comment17 pages, 15 figures, published in Journal of Plasma Physics (Invited Contributions from the 18th European Fusion Theory Conference)

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Cited by in corpus (4)

• Spatiotemporal analysis of the runaway distribution function from synchrotron images in an ASDEX Upgrade disruption
• Electron runaway in ASDEX Upgrade experiments of varying core temperature
• Modelling of runaway electron dynamics during argon-induced disruptions in ASDEX Upgrade and JET
• Validity of models for Dreicer generation of runaway electrons in dynamic scenarios