Research On The Characteristic Of The Disk-loaded Waveguide, Rib-loaded Disk-loaded Waveguide And Helix Slow-wave Structures

The fast development of modern electronic warfare, broadband high power array radar system, high power jammer and microwave directional power weapon impose high demand on high power microwave resource. With such features as high power, broadband, multi-mode, etc., Traveling Wave Tubes (TWT) plays an important role in the high power microwave amplifiers. Since the slow-wave system is the core of beam-wave interaction in TWT, the function and performance of it directly determines the capability of the TWT.The author of this thesis fulfills a comprehensive analysis in the high-frequency properties of the slow-wave system of the TWT (with helix as an example) and the slow-wave system of the relativistic TWT (with disk-loaded waveguide as an example) by such methods as theoretical analysis, computer simulation and experiment. In addition, a new kind of rib-loaded disk-loaded waveguide is put forward along with a thorough analysis of the influence on the characteristics of the disk-loaded waveguide by the plasma injection. Furthermore, the nonlinear characteristics of the relativistic TWT are also touched upon; on the other hand, some experiments have been carried out on the dispersion characteristics of the disk-loaded waveguide. All in all, the innovative theoretic methods and computer simulation methods adopted on the study of the slow-wave structure of the TWT and relativistic TWT provide theoretical support for the design of the slow-wave structure of the TWT.The main achievements and innovations of the thesis can be concluded as follows:Although the symmetry TM01 mode is the main mode, research about the asymmetry mode of disk-loaded waveguide is necessary. Considering the asymmetry mode, the general dispersion equations and interaction impedance expressions of disk-loaded waveguide are obtained through strict field theory. Based on these, the practical disk-loaded waveguides are designed, which can be used in relativistic TWT.Based on the Maxwell equations, the basic equation of the slow-wave structure filled with plasma in the finite magnetic field is deduced. The dispersion equation and interaction impedance of the disk-loaded waveguide filled with plasma are studied in the strong longitudinal magnetic field for the first time, which proves that the frequency of the TM01 mode upshifts and interaction impedance increases as the density of the plasma increases. When a periodic structure is loaded with plasma, the spectrum of the TG modes (Trivelpiece-Gould modes) will become abundant. As the plasma density increases to a large scale, it also can be found that the TM01 mode of the disk-loaded waveguide overlaps the TG mode. These two modes couple with each other and form the new hybrid modes G1, G2.The author improves the method to calculate the axial periodic waveguide by expanding the slow-wave structure's boundary function in Fourier series, which can be adopted in not only the axial periodic waveguide but also the azimuthal periodic waveguide. Furthermore, the general dispersion equations, which can be used to analyze the axial and azimuthal periodic waveguide, are deduced in the thesis.A new rib-loaded disk-loaded waveguide is presented in the thesis, together with the analysis into the dispersion characteristics and interaction impedance. The loading of rib can improve the bandwidth of the disk-loaded waveguide, which can be applied to the relativistic TWT in the future.Taking the radial thickness of the helix into account, the finite size vane model for the vane-loaded helical slow-wave structures (SWS) is suggested in the thesis for the first time. The expressions of dispersion properties, interaction impedance and attenuation constant of this model are derived, by which two vane-loaded helical slow-wave structures of the traveling-wave tube (TWT) are calculated. It is interesting to find that the center angle (2θ)of the vanes has optimal value when phase velocity is minimum by the theoretical analysis.With the consideration of the radial thickness of the helix, the tap...