Electron Trapping in Self-Modulated Laser Wakefields by Raman Backscatter

Simultaneous measurements of high energy electrons and plasma-wave characteristics have been conducted in a self-modulated laser-wakefield accelerator. Approximately ${10}^{8}$ electrons were accelerated from the background plasma to energies greater than 1 MeV with a peak energy of approximately 30 MeV. A strong correlation between the plasma-wave amplitude and electron production was measured with no evidence of wave breaking. Simulations indicate plasma electrons are trapped by the low-phase-velocity beat waves produced by backward Raman scattering.