Theory and simulation of quasi-phase matched acceleration of electrons in a corrugated plasma channel

Abstract

A laser pulse propagating in an axially corrugated plasma channel is composed of spatial harmonics whose phase velocities can be subluminal. The phase velocity of a spatial harmonic can be matched to the speed of relativistic electrons, resulting in direct acceleration by the guided laser field and linear energy gain over the interaction length. Here we examine the fully self-consistent interaction of the laser pulse and electron beam using particle-in-cell (PIC) simulations. For low electron beam densities, we find that the ponderomotive force of the laser pulse pushes plasma channel electrons toward the propagation axis, which can deflect the beam electrons. When the beam density is high, the space charge force of the beam drives the channel electrons off axis, providing collimation of the beam. In addition, we consider a ramped density profile for lowering the threshold energy for trapping by a subluminal spatial harmonic. By using a density ramp, the trapping energy for a normalized vector potential of a0 = 0.1 is reduced from a relativistic factor γ0 = 170 to γ0 = 20. © 2012 American Institute of Physics.