The Special Three-mirror Quasi-optical Cavity Gyrotron

Three-mirror quasi-optical cavity, which is a kind of resonant system between ordinary microwave resonant cavity and optical resonant cavity, plays a huge role in developing new electromagnetic sources, especially the terahertz (THZ) radiation sources. The target of this thesis is to explore a new approach to high power and high efficiency gyrotron at THZ wave band. The combination of quasi-optical cavity and instability of ERCM is an important way to realize this aim.The main works of this thesis are listed as following:1. A novel open-resonator—an axisymmetrical three-mirror quasi-optical cavity of oblique rotation is studied, and the particular theoretical results are obtained. Using mathematical method, the field distributions and resonant condition are derived, and the influence of parameters on the field distributions is analyzed. The stored field energy in the cavity is also obtained.2. Based on the linear theory of gyrotron, and using the Laplace transformation and Residue theorem, the kinetic theory of a novel gyrotron with three-mirror quasi-optical cavity, is carried out within the framework of the linearized Vlasov-Maxwell equations. The beam-wave interaction power, frequency shift and starting current have been derived and numerically calculated. The results indicate that this novel gyrotron has high interaction power operating at high cyclotron harmonics and has potential application in THZ band.3. Based on the characteristic of field distribution in three-mirror quasi-optical cavity, a model of three-mirror quasi-optical cavity is designed. And the cavity is simulated in the cold cavity way by using PIC simulation software. The electromagnetic field distributions which carried out by cold cavity test achieve good agreement with the theoretical results4. Using the well designed model of cavity and introducing cyclotron electron beam, the cavity is simulated in the hot cavity way. We get the foundamental cyclotron harmonic at 107.25 GHz, and the power of this quasi-optical cyclotron mode is 47.7KW. And we also get the second cyclotron harmonic at 215.6 GHz. The power of this quasi-optical cyclotron mode is 129.33 KW. The electromagnetic field distributions which carried out by hot cavity test achieve good agreement with results carried out by the cold cavity test. The results indicate that this novel gyrotron really has superiority operating at high cyclotron harmonics and prove the correctness of conclusions from theoretical analysis. Therefore, the PIC simulation shows great potential of this novel three-mirror quasi-optical cavity gyrotron.Hence, this new kind of quasi-optical cavity gyrotron may have potential applications in millimeter and sub-millimeter wave, especially in developing the THZ radiation sources based on the mechanism in elcctron cyclotron maser.