Electron Injection into Plasma Wakefields by Colliding Laser Pulses

An injector and accelerator is analyzed that uses three collinear laser pulses in a plasma: an intense pump pulse, which generates a large wake field $(\ensuremath{\ge}20\mathrm{GV}/\mathrm{m})$, and two counterpropagating injection pulses. When the injection pulses collide, a slow phase velocity beat wave is generated that injects electrons into the fast wake field for acceleration. Particle tracking simulations in 1D with injection pulse intensities near ${10}^{17}\mathrm{W}/\mathrm{cm}{}^{2}$ indicate the production of relativistic electrons with bunch durations as short as 3 fs, energy spreads as small as 0.3%, and densities as high as ${10}^{18}\mathrm{cm}{}^{\ensuremath{-}3}$.