Abstract: Electron acceleration from the interaction of an intense short-pulse laser with low density plasma is considered. The relation between direct electron acceleration within the laser pulse and that in the wake is investigated analytically. The magnitude and location of the ponderomotive-force-caused charge separation field with respect to that of the pulse determine the relative effectiveness of the two acceleration mechanisms. It is shown that there is an optimum condition for acceleration in the wake. Electron acceleration within the pulse dominates as the pulse becomes sufficiently short, and the latter directly drives and even traps the electrons. The latter can reach ultrahigh energies and can be extracted by impinging the pulse on a solid target. (C) 2003 American Institute of Physics.

Abstract: The propagation of a short laser beam in plasma is investigated analytically Relativistic ponderomotive force and space charge effects are included, and an equation describing the evolution of the laser spot size is derived. It is shown that self-consistent electron cavitation can lead to self channelling and thus long-distance self-focusing of the laser. The condition for the latter to occur is given.