Channeling of relativistic laser pulses in underdense plasmas and subsequent electron acceleration

¹ Theoretical Physics Institute, University of Alberta, Edmonton T6G 2J1, Alberta, Canada
² Centre de Physique Théorique, CNRS, Ecole Polytechnique, 91128 Palaiseau Cedex, France
³ P. N. Lebedev Physics Institute, Russian Academy of Science, Moscow 119991, Russia
⁴ Department of Physics, University of Ottawa, Ottawa, Ontario, Canada

^a e-mail: pesme@cpht.polytechnique.fr

Published online: 15 November 2013

Abstract

This contribution is concerned with the nonlinear behavior of a relativistic laser pulse focused in an underdense plasma and with the subsequent generation of fast electrons. Specifically, we study the interaction of laser pulses having their intensity Iλ² in the range [10¹⁹, 10²⁰]  W/cm²  μm², focused in a plasma of electron density n₀ such that the ratio n₀/n_c lies in the interval [10⁻³, 2 × 10⁻²], n_c denoting the critical density; the laser pulse power P_L exceeds the critical power for laser channeling P_ch. The laser-plasma interaction in such conditions is investigated by means of 3D Particle in Cell (PIC) simulations. It is observed that the laser front gives rise to the excitation of a surface wave which propagates along the sharp boundaries of the electron free channel created by the laser pulse. The mechanism responsible for the generation of the fast electrons observed in the PIC simulations is then analyzed by means of a test particles code. It is thus found that the fast electrons are generated by the combination of the betatron process and of the acceleration by the surface wave. The maximum electron energy observed in the simulations with Iλ² = 10²⁰  W/cm²  μm² and n₀/n_c = 2 × 10⁻² is 350 MeV.