Relativistic Electron Beam Slicing by Wakefiled in Plasmas
  A method of slicing of high-energy electron beams following their interaction with the transverse component of the wakefield left in a plasma behind a high intensity ultra short laser pulse is proposed. The transverse component of the wakefield focuses a portion of the electron bunch, which experiences betatron oscillations. The length of the focused part of the electron bunch can be made substantially less than the wakefield wavelength. 
S. V. Bulanov, T. Tajima, G. Mourou