Transient effects, modulation, and energy transfer in the interaction between electrons and a spatially nonuniform electromagnetic field

A technique for the density and velocity modulation of an electron beam in a microwave device is considered. A theoretical study shows that, in the presence of sharp jumps in the HF-field distribution, transient effects lead to the modulation of a rectilinear electron field in velocity and density. Jumps in the field distribution can be produced in open resonators with additional mirrors in grid gaps; these systems can be used to transform the beam into a sequence of bunches and to produce intense coherent emission from the charged particles. The characteristic geometric parameter defining the degree of bunching and energy transfer is the electron transit distance over time.