Stochastic Electron Acceleration in Laser-plasma Interactions

Book excerpt: The generation of energetic electron beams in the interaction of an intense laser pulse with plasma is of great interest for many different applications and different mechanisms of electron acceleration have been proposed and studied analytically, numerically, and experimentally over many years. However, due to the multidimensional spatio-temporal characteristics of the electromagnetic (EM) fields and strong nonlinearity of relativistic electron dynamics, the analytic investigations of the mechanism of electron acceleration in the earlier studies are quite limited and thus more profound analysis is needed. This dissertation work is devoted to the analytic investigation of the electron dynamics in the fields of lasers and quasi-static EM fields by employing a novel Hamiltonian, which, by finding proper canonical variables, is time-independent when an appropriately selected perturbation is absent. Such characteristics of the new Hamiltonian can significantly simplify the analysis of electron dynamics. Three different configurations of laser waves and quasi-static EM fields will be considered: counter-propagating laser waves, laser radiation with quasi-static EM fields that can confine the electron motions (e.g., EM fields in the ion channels), and single laser wave but with spatially periodic quasi-static EM fields (e.g., EM fields in electric and magnetic undulators), where the Hamiltonian, canonical variables and choice of perturbations are different for these cases. The mechanism of the electron acceleration will be examined, paying attention to the stochastic acceleration, where the physics underlying the stochastic electron motion is revealed and the maximum electron energies in all cases are obtained.