Fluid and kinetic studies of tokamak disruptions using Bayesian optimization
Journal article, 2024

When simulating runaway electron dynamics in tokamak disruptions, fluid models with lower numerical cost are often preferred to more accurate kinetic models. The aim of this work is to compare fluid and kinetic simulations of a large variety of different disruption scenarios in ITER. We consider both non-activated and activated scenarios; for the latter, we derive and implement kinetic sources for the Compton scattering and tritium beta decay runaway electron generation mechanisms in our simulation tool Dream (Hoppe et al., Comput. Phys. Commun., vol. 268, 2021, 108098). To achieve a diverse set of disruption scenarios, Bayesian optimization is used to explore a range of massive material injection densities for deuterium and neon. The cost function is designed to distinguish between successful and unsuccessful disruption mitigation based on the runaway current, current quench time and transported fraction of the heat loss. In the non-activated scenarios, we find that fluid and kinetic disruption simulations can have significantly different runaway electron dynamics, due to an overestimation of the runaway seed by the fluid model. The primary cause of this is that the fluid hot-tail generation model neglects superthermal electron transport losses during the thermal quench. In the activated scenarios, the fluid and kinetic models give similar predictions, which can be explained by the significant influence of the activated sources on the runaway dynamics and the seed.

fusion plasma

runaway electrons

plasma simulation

Author

Ida Ekmark

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

M. Hoppe

Royal Institute of Technology (KTH)

Tünde-Maria Fülöp

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

Patrik Jansson

Chalmers, Computer Science and Engineering (Chalmers), Functional Programming

Liam Antonsson

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

Oskar Vallhagen

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

Istvan Pusztai

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

Journal of Plasma Physics

0022-3778 (ISSN) 1469-7807 (eISSN)

Vol. 90 3 905900306

Subject Categories

Other Physics Topics

Fusion, Plasma and Space Physics

DOI

10.1017/S0022377824000606

More information

Latest update

8/6/2024 1