Linac-based free electron lasers and e-beam energy modulation

We discuss the effect of the energy modulation over the macropulse of an e- beam driving a free electron lasers oscillator. It is shown that this modul ation produces an efficient cavity depletion and provides an output optical beam, chopped at the same frequency of the beam energy modulation. The adv antages offered by this method are discussed, with particular reference to the case of intracavity harmonic generation. The effective realization of a n electron beam energy modulating device is finally discussed. (C) 1999 Ame rican Institute of Physics. [S0034-6748(99)01302-7].