Autoresonant cavity acceleration

Summary form only given. The autoresonance effect is of considerable interest for efficiently accelerating electron beams to multi-MeV energies. Under an ideal autoresonant interaction, the resonance condition of the electrons with the wave, /spl omega/=/spl Omega//sub c0///spl gamma/+k/sub z/v/sub z/, is completely maintained because the two terms on the RHS change to compensate one another. It is incorrectly believed that autoresonance cannot occur in a cavity. However, an autoresonant TE/sub 111/ cavity accelerator has been employed to produce MeV-level electron beams in a distance of only one wavelength with a modest RF power of /spl sim/1 MW. An advantage to operating with a cavity accelerator over a traveling-wave accelerator is the enhancement of the fields by a factor /spl radic/Q which Yields much stronger acceleration. In addition, one can choose to be in resonance with either the forward or backward wave. The most attractive case is where the electrons switch from being in resonance with the backward-wave to resonance with the forward-wave as the axial velocity slows. This leads to an energy gain one order of magnitude higher than in the more conventional case of strictly forward-wave resonance.