Energy Transfer from Electron Beam to Electromagnetic Wave having Envelope with Phase Inversion

Abstract

Generation of electromagnetic (EM) waves in microwave vacuum electron devices takes place due to fundamental phenomena known as instabilities of electron beams (EB) with respect to EM fields. One of the most popular instability is related to Cherenkov type interaction that takes place when EB moves along a wave propagation direction with initial velocity slightly higher than the wave phase velocity. Such instability is exploited in TWT, Carsinotron and BWO tubes. The basic physical principles of energy exchange are well studied. Similar (but not completely the same) mechanism takes place in diffraction radiation generator (DRG) and orotron where kinetic energy of electrons is transferred to EM field of open resonator (OR) with periodic structure. In these devices energy exchange and self-oscillations may be formally described in terms of interaction of EB with synchronous spatial harmonic of EM field of OR, which is mathematically a travelling wave. However, because of rather different physical nature of the EM fields excited in OR (or any other resonators) one may face qualitatively different picture of EB energy transfer to EM field. In the paper such unusual phenomena are considered theoretically. The results obtained have been approved experimentally for DRG.