ENHANCEMENT OF COHERENT EMISSION BY ENERGY-PHASE CORRELATION IN A BUNCHED ELECTRON-BEAM

A radio-frequency (rf) modulated electron beam passing through a magne tic undulator emits coherent radiation at harmonics of the rf with a p hase which depends an the electron drift velocity. Treating the bunche s as ensembles of electrons, each with its energy and phase, the radia ted field is calculated as a sum over the particle distribution in the phase space. At long wavelengths a proper correlation between the ene rgy and phase distributions of the electrons in the bunch can be explo ited to lock the radiated field in phase, resulting in a significant e nhancement of the coherent emission.