Wide-bandwidth high-power traveling wave tube amplifiers: Comparison of dielectric and periodic slow-wave structures

At present, many various kinds of high-power microwave sources driven by relativistic high-current electron beams have already been developed and are under development and investigations. There is, however, a class of devices which remains practically unexplored. Those are wide-bandwidth amplifiers capable of hundreds MW power level and, at the same time, allowing frequency tuning over a range of up to an octave. Recently, it has been shown that rather wide (40–50%) −3 dB bandwidth can be achieved in the dielectric Cherenkov maser (DCM) amplifier [1]. As it is a smooth slow-wave structure, a dielectric-lined waveguide does not have stopbands, and a liner of a small to moderate dielectric constant may provide it with rather weak dispersion over a very wide frequency range at relativistic values of phase velocities. A DCM is a good candidate for a high-power wide-bandwidth amplifier, however, presence of a dielectric causes significant problems connected with charging a surface, RF breakdown along it, etc. This is a serious drawback of DCMs.