Investigation Of Radial Three Cavity Transit Time Oscillator

Compare to numbers of high power microwave (HPM) sources, the transit time oscillators have the special merits, such as, simple structure, high efficiency and so on. These characters make the transit time oscillators been given most attention by the studies. But usually, the traditional axial transit time oscillators have a character of high impedance which restricts the output wave power seriously. And so under the uptrend of lower impedance, high efficiency and high power, how to improving the impedance merit and obtain higher power become the keystone of the transit time oscillators.By the base of the three-cavity transit time oscillator, and considering the merits of the radial structure such as the small space charge offect and big space charge restricting current, A new kind of low impedance HPM oscillator named radial three-cavity transit time oscillator is brought forward. Through the PIC simulation, the oscillator gives an output wave of 7.4GW, and the impedance 7.5 Q, and the efficiency 27.4%. In order to improve the highest power capacity, and depress the difficulty of the cure, the side-appending configuration is also brought forward with an efficiency of 33.3% by the PIC simulation. And through the 3D theoretic analysis, an improved side-appending configuration is brought forward, and the efficiency enhanced to 47.4%. In this dissertation, we will comprehensively study the radial three-cavity transit time oscillator by the theoretic analysis and the PIC simulation. Main jobs and contribution done by this dissertation are as follows:First, the structures of the radial three-cavity transit time oscillators, including the foil structure, the side-appending structure, and the advanced side-appending structure are brought forward.Second, the Floquet theory is firstly applied to the radial structure by an approximate method. And under the theory, the high-frequency merits of the cavities including the foil structure and the appending structure are analyzed, and the dispersive equations are obtained. For illustration, the dispersive equations of the foil structure are solved by the numerical method, and errors are analyzed, and the applicable additions are given.Third,1-D theory is applied to explain the process of the co-action of the beam and the cavity, and the applicable additions are given.Forth, A 3-D theory is constructed. Using the 3-D theory, full analysis to the radial three-cavity transit time oscillator has been done. The volts of the beam, the modulation coefficient, the length of the cavity in the radial and the beam location, are analyzed how to infecting the co-action efficiency. And also the electrons tracks are given. Through the theory, we know that, the advanced side-appending structure indeed has a higher efficiency (higher than 50% by theory).Fifth, comprehensive simulations have been done to the radial three-cavity transit time oscillator, and the infections of the beam parameters and the cavity parameters to the efficiency have been analyzed. And some valuable results to the experiments are obtained.