Exact solutions are obtained for the monodimensional and higher dimens
ional Free Electron Laser high-gain equations. These equations, which
belong to the class of integrodifferential Volterra equations are trea
ted within the context of a perturbative approach, yielding suitable c
losed-form expressions for the relevant solutions. The proposed method
allows to obtain a unified analytical formalism for the full FEL dyna
mics. Numerical results are given for the one-dimensional case where a
suitable expression has been derived for the solution in terms of eas
ily computable functions. Copyright (C) 1996 Elsevier Science Ltd.