Ultra-high gradient acceleration of electrons by laser wakefield plasma waves

Abstract

Summary form only given, as follows. Short, intense laser pulses can be produced by table top laser systems utilizing the chirped-pulse-amplification (CPA) technique to have femto-second pulse lengths and terawatt power levels. These laser pulses have very good beam qualities which allow them to be focused to intensities in excess of 10/sup 18/ W/cm/sup 2/. At such intensities, the wiggling motion caused by the laser field of the electrons in a plasma reaches relativistic velocities. The electrons can experience a tremendous ponderomotive force from the radiation pressure and be expelled from the vicinity of the laser pulse. When the intense laser pulse propagates through a plasma with the appropriate density, the expelled electrons can resonantly excite a large amplitude plasma wave in the wake of the laser pulse, the laser wakefield accelerator (LWFA). This wakefield plasma wave has phase velocity close to the speed of light and longitudinal electric field strength of tens of GV/m. Self-trapped plasma electrons or externally injected electrons can be accelerated by the wakefield to multi-MeV energies in distances of mm's. The LWFA mechanism and other laser driven plasma acceleration schemes will be reviewed. Recent experimental results of electron acceleration to 100 MeV, efforts to extend acceleration distances to beyond Rayleigh diffraction lengths, and the laser ionization and ponderomotive acceleration (LIPA) electron injection scheme will be presented.