Spatiotemporal analysis of the runaway distribution function from synchrotron images in an ASDEX Upgrade disruption
Journal article, 2021

Synchrotron radiation images from runaway electrons (REs) in an ASDEX Upgrade discharge disrupted by argon injection are analysed using the synchrotron diagnostic tool Soft and coupled fluid-kinetic simulations. We show that the evolution of the runaway distribution is well described by an initial hot-tail seed population, which is accelerated to energies between 25-50 MeV during the current quench, together with an avalanche runaway tail which has an exponentially decreasing energy spectrum. We find that, although the avalanche component carries the vast majority of the current, it is the high-energy seed remnant that dominates synchrotron emission. With insights from the fluid-kinetic simulations, an analytic model for the evolution of the runaway seed component is developed and used to reconstruct the radial density profile of the RE beam. The analysis shows that the observed change of the synchrotron pattern from circular to crescent shape is caused by a rapid redistribution of the radial profile of the runaway density.

runaway electrons

fusion plasma

Author

Mathias Hoppe

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

Linnea Hesslow

Chalmers, Physics, Subatomic and Plasma Physics

Ola Embréus

Chalmers, Physics, Subatomic and Plasma Physics

Lucas Unnerfelt

Chalmers, Physics, Subatomic and Plasma Physics

Gergely Papp

Max Planck Society

Istvan Pusztai

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

Tünde Fülöp

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

Olle Lexell

Chalmers, Physics, Subatomic and Plasma Physics

T. Lunt

Max Planck Society

E. Macusova

Czech Academy of Sciences

P. McCarthy

University College Cork

G Pautasso

Max Planck Society

G.I. Pokol

Budapest University of Technology and Economics

Gábor Pór

Budapest University of Technology and Economics

Pontus Svensson

Chalmers, Physics, Subatomic, High Energy and Plasma Physics

Journal of Plasma Physics

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

Vol. 87 1 855870102

Subject Categories

Accelerator Physics and Instrumentation

Astronomy, Astrophysics and Cosmology

Fusion, Plasma and Space Physics

DOI

10.1017/S002237782000152X

More information

Latest update

2/8/2021 8