Electron cavitation and generation of MeV ions produced by relativistically self-guided laser pulse in He gas jet

Summary form only given. An interaction of ultra-high intensity short laser pulses with underdense plasma is of considerable interest from the standpoint of basic physics and potential application for advanced inertial confinement fusion, X-ray lasers and particle accelerators. The ultra-high electromagnetic fields in the laser focus produce an extremely high pondermotive force that expels free electrons from the laser axis and relativistically modify the electron mass, plasma frequency and the plasma refractive index so that the plasma acts as a positive lens. If the laser pulse duration is long enough, the charge separation produces strong electrostatic field /spl sim/1 GV/cm that can accelerate ions to MeV energies. All these effects lead to a relativistic self-focusing and self-guiding of the laser beam that can further increase the laser intensity and maintain it over distances much longer than a Rayleigh range.