ANALYSIS OF FEL RADIATION IN PULSED RAMAN REGIME

A direct numerical analysis, based on the Lienard-Wiechert potentials, is performed in the present paper, aiming to describe the relativisti c interaction of the electrons composing a high-intensity beam (in Ram an regime) both with each other and with the fields of an FEL structur e and of an external resonant travelling electromagnetic wave. The dif ferent accelerations, due to the various forces acting on the charged particles, are seen to give different contributions to the total radia tion field, which are separately considered here. The angular and freq uency distributions of the obtained radiation are compared with the an alytic ones deduced in the particular case of a single charge launched along the FEL structure. The interference effect between the fields o f many bunches is seen to cause the shrinkage of the resulting radiati on beam.