Acceleration concepts based on electromagnetic structures

In the last two decades a variety of novel concepts of electrons acceleration have been suggested and investigated. According to the interaction mechanism, these can be classified into three main groups: inverse radiation processes, space-charge wakes and electromagnetic wakes. In the first case, electrons are injected in structures that in 'normal' situations would generate radiation. Electromagnetic radiation is actually injected into the system and it accelerates a bunch of electrons. In the second case, a space-charge wake is generated in plasma by an intense laser pulse or short bunch of electrons. This space-charge wake may also accelerate a bunch of electrons. In the third case, an intense electron beam (bunch) generates radiation in a structure. This radiation is guided into an acceleration structure. Based on this classification, we shall review the basic concepts behind the first and the third group