Electron Trapping from Interactions between Laser-Driven Relativistic Plasma Waves

Interactions of large-amplitude relativistic plasma waves were investigated experimentally by propagating two synchronized ultraintense femtosecond laser pulses in plasma at oblique crossing angles to each other. The electrostatic and electromagnetic fields of the colliding waves acted to preaccelerate and trap electrons via previously predicted, but untested injection mechanisms of ponderomotive drift and wakewake interference. High-quality energetic electron beams were produced, also revealing valuable new information about plasma-wave dynamics.