Coherent and incoherent electromagnetic radiation emitted from a laser
wakefield accelerator is calculated based on Lienard-Wiechert potentials. It is
found that at wavelengths longer than the bunch length, the radiation is
coherent. The coherent radiation, which typically lies in the infrared range,
shows features that reveal details of the acceleration process and properties
of the electron bunch, such as its duration, charge, energy, and offset with
respect to the wakefield axis. The incoherent range of the spectrum, which
extends to the X-ray frequency range, consists of rather broad peaks, which are
caused by the acceleration.Comment: 14 pages, incl. 6 figures, submitted for publicatio