Physics of Laser-Wakefield Accelerators (LWFA)

Intense ultrashort laser pulses propagating through an underdense plasma are able to drive relativistic plasma waves, creating accelerating structures with extreme gradients. These structures represent a new type of compact sources for generating ultrarelativistic, ultrashort electron beams. This chapter covers the theoretical background behind the process of LWFA. Starting from the basic description of electromagnetic waves and their interaction with particles, the main aspects of the LWFA are presented. These include the excitation of plasma waves, description of the acceleration phase and injection mechanisms. These considerations are concluded by a discussion of the fundamental limits on the energy gain and scaling laws.