Theoretical investigation of two-frequency generation mechanism in vircator

At present, the virtual cathode systems (vircators) are used for generation of powerful emission. One of peculiarities of the magneto-insulated diode vircator is the generation possibility on the two frequencies. In particular, it can be used for plasma heating of fusion plasmas. In present paper the two-frequency generation mechanism for increasing of emission efficiency and realizing of the emission parameters operating is investigated. The problem has been investigated by means analytical and numerical methods. It has been shown that two-frequency generation regime is conditioned by two virtual cathodes forming. In result, the nonsymmetrical potential well is formed in which the flow electrons are captured. It has obtained that the depth of the potential well and emission power are considerably higher for the foil system in comparison with foilless system. The dependencies of frequency spectrum and efficiency on system geometry and external magnetic field have been determined. It has been shown that the frequency spectrum and emission power do not depend on drift tube length if it exceeds the Debye radius calculated with taking into account the reduction coefficient. The influence of transverse impulse and velocity spread on efficiency are studied. Comparison of theoretical results with experiments is carried out