Abstract: Apparatus and method for generating high intensity electrostatic fields for accelerating an electron beam. At least one thin dielectric film is charged on opposite faces thereof with charges of a like polarity. A near-relativistic beam is directed at the charged dielectric film in an area where the electrostatic field created by the surface charges is the greatest. The near relativistic electron beam is radially accelerated by the electrostatic field, generating free electron laser radiation. Electrostatic fields of different polarities or directions are utilized to accelerate the near relativistic electron beam in opposite directions. The radiation generated from each electrostatic field beam interaction is cumulative. Means are provided for charging the dielectric films with the surface charge of the same polarity to generate each electrostatic field.