Laser-plasma interaction and future accelerators

In particle accelerators, the resistance to magnetic fields of the inner wall of accelerating cavities imposes an upper limit to the acceleration gradient (about a few tens of 106 V/m). So to get higher energies implies to get a bigger machine. This evolution towards giantism has a limit: the exponential costs. The interaction between laser and plasma can be used to accelerate electrons in different ways, one of the most promising is the channeling acceleration. Electrons riding on a wave at the proper phase can have their energy boosted to relativistic values as a result of the longitudinal electrical field in the wave. A project at the SLAC (Stanford) aims at producing an acceleration gradient of 1 GeV/m in a plasma whose length is 1,4 m. The authors reviews also different experimental results, in one experiment electrons have been accelerated to 200 MeV over a 1 millimeter long distance, that is to say that the average acceleration gradient was 200 GeV/m. (A.C.)