Evolution of a high-density electron beam in the field of a super-intense laser pulse

Abstract

The evolution of a high-density electron beam in the field of a super-intense laser pulse is considered. The one-dimensional (1D) theory for the description of interaction, taking into account the space-charge forces of the beam, is developed, and exact solutions for the equations of motion of the electrons are found. It was shown that the length of the high-density electron beam increases slowly in time after initial compression of the beam by the laser pulse as opposed to the low-density electron beam case, where the length is constant on average. Also, for the high-density electron beam, the sharp peak frozen into the density distribution can appear in addition to a microbunching, which is characteristic for a low-density electron beam in a super-intense laser field. Characteristic parameters for the evolution of the electron beam are calculated by an example of a step-like envelope of the laser pulse. Comparison with 1D particle-in-cell simulations shows adequacy of the derived theory. The considered issue is very important for a special two-pulse realization of a Thomson scattering scheme, where one high-intensity laser pulse is used for acceleration, compression and microbunching of the electron beam, and the other probe counter-streaming laser pulse is used for scattering with frequency up-shifting and amplitude enhancement.