Numerical calculation of the runaway electron distribution function and associated synchrotron emission
Artikel i vetenskaplig tidskrift, 2014

Synchrotron emission from runaway electrons may be used to diagnose plasma conditions during a tokamak disruption, but solving this inverse problem requires rapid simulation of the electron distribution function and associated synchrotron emission as a function of plasma parameters. Here we detail a framework for this forward calculation, beginning with an efficient numerical method for solving the Fokker-Planck equation in the presence of an electric field of arbitrary strength. The approach is continuum (Eulerian), and we employ a relativistic collision operator, valid for arbitrary energies. Both primary and secondary runaway electron generation are included. For cases in which primary generation dominates, a time-independent formulation of the problem is described, requiring only the solution of a single sparse linear system. In the limit of dominant secondary generation, we present the first numerical verification of an analytic model for the distribution function. The numerical electron distribution function in the presence of both primary and secondary generation is then used for calculating the synchrotron emission spectrum of the runaways. It is found that the average synchrotron spectra emitted from realistic distribution functions are not well approximated by the emission of a single electron at the maximum energy. © 2013 Elsevier B.V.

Synchrotron emission

Runaway electrons

Kinetic

Plasma

Fokker-Planck

Relativistic

Författare

M. Landreman

Adam Stahl

Chalmers, Teknisk fysik, Nukleär teknik

Tünde Fülöp

Chalmers, Teknisk fysik, Nukleär teknik

Computer Physics Communications

0010-4655 (ISSN)

Vol. 185 847-855

Styrkeområden

Energi

Fundament

Grundläggande vetenskaper

Ämneskategorier

Fusion, plasma och rymdfysik

DOI

10.1016/j.cpc.2013.12.004