Coherence effects in FEL radiation generated by short electron bunches

In the last few years there has been a growing interest in the study of coherent radiation from short electron bunches. The possibility of realizing compact FEL devices in the far-infrared and millimeter wave regions utilizing small to medium size radio-frequency (RF) accelerators has stimulated a number of theoretical and experimental investigations to clarify basic physics issues in this process. nt emission experiments will be reviewed in this paper. Measurements on the temporal and spectral characteristics of the coherent emission from a single bunch and on the coherence between consecutive bunches will be presented along with an analysis of the influence of coherence on the dynamics of the laser.