Filled With Plasma Coupled Cavity Traveling Wave Tubes Nonlinear Beam-wave Interaction

In the case of the plasma-filling, the frequency bandwidth, the overall efficiency and the gain can be improved significantly, and meanwhile the guiding magnetic fields can be reduced or eliminated. At present this kind of tubes includes mainly the plasma-filled BOWs, PASPOTRON, the plasma-filled TWT and so on, and a new subject, the plasma microwave electronics, was developed and became an active research area with special theory research approach and experimental technique.In this dissertation, it's studied that the 1-D beam-wave interaction characteristics of the hybrid wave in the plasma-filled coupled-cavity traveling-wave tube.Using the waveguide exciting model, neglecting the electron velocity spread , the transverse motion of electrons and theory of relativity, the one-dimensional model of plasma-filled TWT with an coupled-cavity slow-wave structure and finite guiding magnetic field is founded and analyzed, self-consistent working equations of nonlinear beam-wave interaction is obtained, that present a basical theory for analyzing plasma-filled TWT.Using method of the four-rank Rung-kutta, the large signal characteristic analysis code was compiled by Matlab. It's shown that over a 20% bandwidth the efficiency can exceed 40%, which is lager than the efficiency of its vacuum counterpart. What's more, the depression coefficients is studied in the dissertation. When the space charge is taken into account, the efficiency and the gain is increase dramatically and the saturation length is shortened.The dispersion characteristic and mode distribution in the vacuum coupled-cavity TWT is studied in the PIC software MAGIC. The impact on the dispersion, made by parameters of the structure, is presented minutely, and the distribution of electromagnetic field inπ,3π2, 2πmode are shown, what is more, the dispersion when filling the plasma is analyzed, and the experiment is done about the impact, that the different density of plasma brings to the dispersion character. According to the experiment results, when the plasma density increases to a large scale, the cavity mode and the plasma mode couple with each other, the resonance points fill the whole frequency spectrum, and there is not forbidden region, the bandwidth is improved significantly.