Three-dimensional Simulation Of Flat Slow-wave Structure Of The Metal Column

Terahertz (THz) radiation source which based on vacuum electronics, because of its higher power, has wide application in the military and civilian fields.The characteristics of slow-wave structure (SWS) to a large extent determine the performances of vacuum electric device. In order to improve operating frequency, increase efficiency and power, a new type of SWS, Metallic-Pole-Planar SWS, is studied. By employing three-dimensional finite-difference time-domain (3-D FDTD) arithmetic, the dispersive characteristics of the new SWS are calculated. On this basis, Particle-in-cell (PIC) simulation software is used to make a study on the beam-wave interactions and radiation mechanisms of THz wave in two kinds of structures.In this dissertation, we first derived 3-D difference equations of square SWS. 3-D periodic perfectly matched layer (PML) was applied to simulate infinite periodic free-space, calculated the dispersion curve of square SWS by 3-D FDTD procedures, and analyzed how the metal column's height and period influenced the characteristics of dispersion. The results show that the dispersion curve of the structure is greatly similar to the traditional SWS. Then we changed the square SWS to equilateral triangle SWS. Accordingly, the incised Yee's Grid was employed to calculate the inclined periodic boundary, other than the complicated no orthogonal grid. The results show that the operating frequency of changed structure is appreciably higher than that of the square SWS. Finally these two structures'Smith-Purcell radiation characteristics were observed using PIC software in three-dimension. It was found that the characteristics of surface wave of these structures are similar to the traditional SWS. In addition, Smith-Purcell super radiations were observed at the third harmonic and fourth harmonics frequencies of surface waves. The fourth harmonic'intensity is much stronger than the third harmonic's.