Abstract
In the dissertation, theoretical study and experimental investigation of a novel scheme for efficient interaction between a linear electron beam and an electromagnetic wave in a complex extended interaction structure were reported. The structure of the complex extended interaction consists of a high R/Q, five-gap, coupled-cavity resonator which incorporates a coaxial section of a half wavelength placed between the first and second cavity. And the length from the first cavity gap to the second cavity gap is equal to a quarter reduced plasma wavelength and functions as the drift section. In the coaxial section, beam and wave propagate in separate channels. The first cavity, strongly coupled to the other cavities through the wave channel of the coaxial section, serves as a buncher cavity. An inner channel goes through the center conductor of the coaxial section provides both a cutoff section for waves and a drift space for ballistic bunching of electrons, an effect that is shown to significantly enhance the interaction efficiency. Oscillation power of 2.15 kW at 16.55 GHz was demonstrated with an interaction efficiency of 30%. The total efficiency was further increased to 41% by incorporation of a two-stage depressed collector.