• G. Dattoli, A. Renieri
  ENEA C.R. Frascati, Frascati (Roma)
• P.L. Ottaviani, S. Pagnutti
  ENEA-Bologna, Bologna

The theory of pulse propagation of low gain Free Electron Laser oscillators is extended to the high gain regime. The physics underlying the relevant phenomenology is discussed and it is shown that the system dynamics, from small signal to saturation, can be reproduced using simple scaling formulae. The inclusion of non linear harmonic generation is considered too, the performances of a source operating in the extreme UV is considered and compared with those operating in the SASE configuration.