Effects of magnetic perturbations and radiation on the runaway avalanche
Artikel i vetenskaplig tidskrift, 2021

The electron runaway phenomenon in plasmas depends sensitively on the momentum- space dynamics. However, efficient simulation of the global evolution of systems involving runaway electrons typically requires a reduced fluid description. This is needed, for example, in the design of essential runaway mitigation methods for tokamaks. In this paper, we present a method to include the effect of momentum-dependent spatial transport in the runaway avalanche growth rate. We quantify the reduction of the growth rate in the presence of electron diffusion in stochastic magnetic fields and show that the spatial transport can raise the effective critical electric field. Using a perturbative approach, we derive a set of equations that allows treatment of the effect of spatial transport on runaway dynamics in the presence of radial variation in plasma parameters. This is then used to demonstrate the effect of spatial transport in current quench simulations for ITER-like plasmas with massive material injection. We find that in scenarios with sufficiently slow current quench, owing to moderate impurity and deuterium injection, the presence of magnetic perturbations reduces the final runaway current considerably. Perturbations localised at the edge are not effective in suppressing the runaways, unless the runaway generation is off-axis, in which case they may lead to formation of strong current sheets at the interface of the confined and perturbed regions.

fusion plasma

runaway electrons

Författare

Pontus Svensson

Chalmers, Fysik, Subatomär, högenergi- och plasmafysik

Ola Embréus

Chalmers, Fysik, Subatomär, högenergi- och plasmafysik

Sarah Newton

Culham Lab

Konsta Särkimäki

Chalmers, Fysik, Subatomär, högenergi- och plasmafysik

Oskar Vallhagen

Chalmers, Fysik, Subatomär, högenergi- och plasmafysik

Tünde Fülöp

Chalmers, Fysik, Subatomär, högenergi- och plasmafysik

Journal of Plasma Physics

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

Vol. 87 2 905870207

Ämneskategorier

Annan fysik

Fusion, plasma och rymdfysik

Den kondenserade materiens fysik

DOI

10.1017/S0022377820001592

Mer information

Senast uppdaterat

2021-03-26