Influence of massive material injection on avalanche runaway generation during tokamak disruptions
Journal article, 2019

In high-current tokamak devices such as ITER, a runaway avalanche can cause a large amplification of a seed electron population. We show that disruption mitigation by impurity injection may significantly increase the runaway avalanche growth rate in such devices. This effect originates from the increased number of target electrons available for the avalanche process in weakly ionized plasmas, which is only partially compensated by the increased friction force on fast electrons. We derive an expression for the avalanche growth rate in partially ionized plasmas and investigate the effects of impurity injection on the avalanche multiplication factor and on the final runaway current for ITER-like parameters. For impurity densities relevant for disruption mitigation, the maximum amplification of a runaway seed can be increased by tens of orders of magnitude compared to previous predictions. This motivates careful studies to determine the required densities and impurity species to obtain tolerable current quench parameters, as well as more detailed modeling of the runaway dynamics including transport effects.



runaway electron

runaway avalanche


Linnea Hesslow

Chalmers, Physics, Subatomic and Plasma Physics

Ola Embréus

Chalmers, Physics, Subatomic and Plasma Physics

Oskar Vallhagen

Chalmers, Physics, Subatomic and Plasma Physics

Tünde Fülöp

Chalmers, Physics, Subatomic and Plasma Physics

Nuclear Fusion

0029-5515 (ISSN)

Vol. 59 8 084004

Running away and radiating (PLASMA)

European Commission (EC) (EC/H2020/647121), 2015-10-01 -- 2020-09-30.

Runaway electrons in fusion plasmas

Swedish Research Council (VR) (2018-03911), 2018-12-01 -- 2021-12-31.

Subject Categories

Fusion, Plasma and Space Physics



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