The synchrotron radiation emitted by runaway electrons in a fusion plasma
provides information regarding the particle momenta and pitch-angles of the
runaway electron population through the strong dependence of the synchrotron
spectrum on these parameters. Information about the runaway density and its
spatial distribution, as well as the time evolution of the above quantities,
can also be deduced. In this paper we present the synchrotron radiation spectra
for typical avalanching runaway electron distributions. Spectra obtained for a
distribution of electrons are compared to the emission of mono-energetic
electrons with a prescribed pitch-angle. We also examine the effects of
magnetic field curvature and analyse the sensitivity of the resulting spectrum
to perturbations to the runaway distribution. The implications for the deduced
runaway electron parameters are discussed. We compare our calculations to
experimental data from DIII-D and estimate the maximum observed runaway energy.Comment: 22 pages, 12 figures; updated author affiliations, fixed typos, added
a sentence at the end of section I
