Generation of Mega-Electron-Volt Electron Beams

this paper we present our studies on the MeV electron emission driven by an ultrafast intense laser pulse in a regime in which the laser pulse's longitudinal spatial extent is close to or shorter than both the focal spot size and the plasma oscillation wavelength. A beam of MeV electrons is generated, and the electron emission is discovered to be strongly correlated to relativistic filamentation of the laser pulse in underdense plasmas. A new net-energy-gain mechanism is proposed for interpreting the origin of the MeV electrons through the laser intensity decrease that is due to relativ- 132 J. Opt. Soc. Am. B / Vol. 20, No. 1 / January 2003 Wang et al. 0740-3224/2003/010132-06$15.00 2003 Optical Society of America istic filamentation and beam breakup. These results suggest an approach for generating a beam of MeV electrons at a kilohertz (kHz) repetition rate with a compact kHz laser syste