Reduced kinetic modelling of shattered pellet injection in ASDEX Upgrade

TL;DR

This paper demonstrates that reduced kinetic modelling effectively captures key experimental trends of shattered pellet injection in ASDEX Upgrade, aiding disruption mitigation understanding for future tokamaks like ITER.

Contribution

It introduces a simplified kinetic model that reproduces major experimental observations of SPI in ASDEX Upgrade, including energy radiation and runaway electron suppression.

Findings

Model reproduces dependence of radiated energy on neon content

Simulations match observed lack of runaway electrons with neon

Fragmentation variability impacts disruption dynamics at intermediate neon levels

Abstract

Plasma-terminating disruptions represent a critical outstanding issue for reactor-relevant tokamaks. ITER will use shattered pellet injection (SPI) as its disruption mitigation system to reduce heat loads, vessel forces, and to suppress the formation of runaway electrons. In this paper we demonstrate that reduced kinetic modelling of SPI is capable of capturing the major experimental trends in ASDEX Upgrade SPI experiments, such as dependence of the radiated energy fraction on neon content, or the current quench dynamics. Simulations are also consistent with the experimental observation of no runaway electron generation with neon and mixed deuterium-neon pellet composition. We also show that statistical variations in the fragmentation process only have a notable impact on disruption dynamics at intermediate neon doping, as was observed in experiments.