Abstract: An electron beam tube such as a klystron includes a penultimate resonant cavity (22) located before the output cavity (14). The penultimate resonant cavity (22) is arranged to be inductively coupled, being resonant at a frequency which is slightly greater than a harmonic frequency. This provides increased sharpening of bunches of electrons arriving at the output cavity (14) giving increased efficiency at the output.

Abstract: A standing wave accelerator structure that has both inline coupling cavities and side coupling cavities combined into one structure. Additionally, the invention uses a prebunching (re-entrant) cavity, excited electrically or magnetically, through apertures between a first accelerating cavity and the prebunching cavity.

Abstract: The interaction structure with integral coupling and bunching section and method of use of the present invention produces backward wave oscillations in an RF structure which combines ballistic bunching and extended beam-wave interaction in a complex resonator assembly. The complex extended interaction structure includes a five-gap electromagnetically-coupled cavity structure with a coaxial section inserted between the first and second cavities. The first cavity serves as a buncher cavity while the four subsequent cavities serve as energy cavities. In the coaxial section, beam and wave propagate in separate channels. The field in the buncher cavity is coupled to the four subsequent energy extraction cavities through the wave channel between the inner and outer conductors of the coaxial section, while the electron beam drifts along a cylindrical channel cut through the inner conductor of the coaxial section.