The physics of laser acceleration of particles

In our quest to build higher energy accelerators that are both cheaper and smaller, we search for new paradigms that offer potentially high accelerating gradients. The laser features very prominently in many of these schemes. The proposed use of lasers to accelerate particles to ultra-high energies has been motivated by the very high electric fields associated with focused laser beams. A number of conceptually different schemes have been proposed for this purpose and are under very active investigation. In the last couple of years significant results have been obtained on four of these schemes: the inverse-Cherenkov accelerator, the inverse-free-electron laser accelerator, the laser-plasma beat-wave accelerator, and the self-modulated laser wake-field accelerator. Of these, the first two are an example of what is known as far-field accelerators, that is, the acceleration of charges takes place far away from any solid surfaces. On the other hand, the latter two are an example of acceleration by a space charge wave that is induced by a laser beam in an ionized medium: a plasma