Stimulated processes and self-modulation of a short intense laser pulse in the laser wake-field accelerator

Abstract

The basic equations for self-consistent pulse evolution taking into account stimulated Raman backward and near-backward scattering are formulated. These equations are used to study the three-dimensional (3-D) axisymmetrical self-consistent laser pulse evolution analytically and numerically. Special attention is paid to the case of the pulse self-modulation. The spectra and intensity of backscattered radiation are obtained in both the strong and weak coupling limits. A simple criterion to ignore the action of stimulated Raman backscattering on the pulse evolution is derived. The possibility of using a backscattered radiation spectrum for diagnostics of both the laser-pulse and generated wake-field evolution is discussed. Triggering of the laser-pulse self-modulation by the relativistic self-focusing and by a second frequency-shifted weak-intensity laser pulse is discussed. Basing on the obtained results, a new configuration of stimulation and maintaining a strong wake-field excitation is proposed. This configuration makes it possible to obtain acceleration of electrons up to giga-electron-volt energies in the field of the excited plasma wave by using the laser technology that is presently available.