Low-Frequency Instabilities of Electron Beams in Weakly Irregular Transportation Channels

Evolution of low-frequency instabilities degrades electron beams in beam transportation channels and, not less importantly, deteriorates the coherence of the output radiation produced by microwave generators based on the use of such beams. These instabilities also determine the beam dynamics, including that associated with transitions of the beams from one stationary state to another. In this work, we use the method of coupled waves to study the stability of stationary states of the beams with high electron densities in weakly irregular vacuum beam transportation channels, specifically, in channels with shallow periodic wall corrugations. It is shown that in this case, the Bursian instability of the absolute type can evolve, which leads to a jump-wise transition of the beam to a state with a lower electron density.