Review of the high-power vacuum tube microwave sources based on Cherenkov radiation

Abstract

Since the first vacuum tube (X-ray tube) was invented by Wilhelm Röntgen in Germany, after more than one hundred years of development, the average power density of the vacuum tube microwave source has reached the order of 108 [MW][GHz]2. In the high-power microwave field, the vacuum devices are still the mainstream microwave sources for applications such as scientific instruments, communications, radars, magnetic confinement fusion heating, microwave weapons, etc. The principles of microwave generation by vacuum tube microwave sources include Cherenkov or Smith-Purcell radiation, transition radiation, and Bremsstrahlung. In this paper, the vacuum tube microwave sources based on Cherenkov radiation were reviewed. Among them, the multi-wave Cherenkov generators can produce 15 GW output power in X-band. Cherenkov radiation vacuum tubes that can achieve continuous-wave operation include Traveling Wave Tubes and Magnetrons, with output power up to 1MW. Cherenkov radiation vacuum tubes that can generate frequencies of the order of 100 GHz and above include Traveling Wave Tubes, Backward Wave Oscillators, Magnetrons, Surface Wave Oscillators, Orotrons, etc.

Two-Color TeraHertz Radiation by a Multi-Pass FEL Oscillator

“…Traditional microwave sources in the THz region, like backward wave oscillators, orotrons, vircators, and klinotrons suffer from simple physical scaling problems, metallic wall losses, the need for higher static magnetic, electric fields, and electron current densities with increasing frequency, and have already achieved saturation in their developments. A summary of these sources and their main properties can be found in [1]. Other sources, like IMPATT-diodes, are low-cost, reliable, and compact, but characterized by moderately efficient mW power levels.…”