The physics of the laser-plasma accelerators: Challenges and limits

To meet the challenge of future accelerators based on the laserplasma techniques new experimental schemes have to be investigated and a strategy on the laser technology to get ultra-high peak power as well as very high average power formulated. Top-level laser requirements for potential laser-based accelerator applications will be needed and the major limits to the electron energy gain have to be overcome, including laser pulse diffraction, electron dephasing and laser pulse energy depletion. A viable alternative to the multi-stage acceleration scheme could be a greater control of the laser pulse evolution in the underdense plasma that could inhibit filamentation and other detrimental instabilities as Raman and self-phase modulation enabling the full exploitation of the laser guiding over several Rayleigh lengths. A brief overview will be given of those aspects of laser plasma acceleration leading to a completely new generation of compact sources of energetic particles. In particular, a simplified introduction to the field of electron laser wakefield acceleration will be first given and some recent experiments reported.