Research and development on the technologies for transport and application of “Giga-watts-class short-pulse microwave"

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New type of high power microwave sources, HPM, are recently proposed by Russian theorist and developed by us. This type of HPM is characterized by a strong sharp pulse. The oscillator of HPM is operated in superradiative regime, “SR" In the SR regime, energy flows from electron beam to HPM in one direction, and is not reversed. The HPM has strong electric field, though the total joule per one pulse is low. The peak power of HPM is a few Mega-watts to a few Giga-watts, which is about thousands times larger than the constant wave type oscillators. It can induce breakdown in the gas in free space, and produces plasma. The application is not only for radar (radio detection and ranging), for example, diagnostic in large and high temperature plasma. HPM will realize other unique methods to basic plasma science. It can be applied to plasma production in free space, study on non-linear phenomena, ablation on dielectric surface, etc. In this research, we studied the generation that includes SR, and the transport for these applications.Backward wave oscillator, BWO, is one of the most powerful microwave source for Giga-watts. Powerful BWO is already developed for HPM of 5 GHz by us. This time, the power became much higher. BWO for higher frequency, 10 GHz, is newly developed to achieve higher power density in free space.A quasi-optical antenna, called “Vlasov antenna", is studied intensively in this research. It makes possible launching HPM from waveguides to free space. Several antenna designs are tested and its conversion efficiency is investigated at the wavelength 6 cm, i. e. 5 GHz. The wavelength is not short compared to the diameter of wave guide. The conversion efficiency can be improved by increasing the diameter of the final waveguide. It changes from 15% to 75% in the experiment.