| The electromagnetic radiation sources, especially the terahertz (THz) radiation sources, become the most important and attractive project in modern science and technology. This dissertation presents a special kind of three-mirror quasi-optical cavity which lies between the traditional microwave resonator and the optical resonant cavity. Theoretical and experimental studies on this cavity have been carried out together with the computer simulation by the PIC (Particle In Cell) code MAGIC. A very good agreement has been achieved among them, and it demonstrates that this cavity is tunable and capable for high-power at frequency ranging from millimeter waves to THz. Three kinds of possible applications of this cavity in the electromagnetic radiation sources have been given. The works done in this dissertation which bring forth new ideas are achieved and listed as the following:1. From the concept of the formation of the three-mirror quasi-optical cavity, the theoretical study of this cavity has been carried out in detail and achieved good agreement with the simulation and the experimental results. Utilizing the computersimulation, the process from the commonly optical cavity to the three-mirror quasi-optical cavity has been demonstrated visually. Theoretical study, computer simulation and experimental verification show that this cavity is tunable and capable for high power at frequency ranging from millimeter waves to THz.2. Based on the field distribution of the three-mirror quasi-optical cavity, a new kind of coaxial vircator with a three-mirror quasi-optical resonant cavity is proposed and studied. This oscillator combines the merit of the coaxial vircator and the vircator with quasi-optical resonator. The PIC simulation shows great potential of this new kind of oscillator.3. Theoretical study and computer simulation of a THz Vavilov-Cherenkov radiation (VCR) in the three-mirror quasi-optical cavity are presented. It may greatly increase the output power and improve the coherence of the radiation through collectiong the emission of the radiation in the entire solid angle of the radiatin direction at a resonant mode of the cavity. Under coherent conditions the VCR of electron bunches excites one of the resonant modes in the cavity. PIC simulation shows for 4.41 dielectric permittivity and 180kV electron beam, the coherent VCR at 0.8THz was obtained.4. Through the beam wave interaction anlysis of the electron beam and the metal grating, the optimized grating parameter and operation point have been carried out. The relation between the the surface wave above the grating and the Smith-Purcell radiation (SPR) has been indentified. Base on this study, a new kind of model has been proposed. This model can combines the power generated by the two electron beams efficiently, which shows its great potential to develop a compact, powerful and coherent THz radiation source working in room tempreature. Theoretical study and computer simulation show the system can work in two kinds of modes by adjust the working parameters. Primary consideration and experimental designs of this system have been carried out.
|
PDF Full Text Request