Computer simulations of cathodeless, high-brightness electron-beam production by multiple laser beams in plasmas

The use of two crossed laser pulses in a plasma for the cathodeless production of high-current low-emittance electron beams [D. Umstadter, J. K. Kim, and E. Dodd, Phys. Rev. Lett. 76, 2073 (1996)] is examined with fully relativistic, two-and-a-half-dimensional particle-in-cell simulations. Estimates for the number of injected particles, their energy spread, and their emittance are given as functions of the amplitude and timing of the injection pulse relative to the drive pulse of the laser wake field accelerator. The physical mechanism of the trapping of particles is examined based on single particle phase space trajectories in the simulations and numerical calculations.