Research On High Frequency Field Of Coaxial Corrugated Resonator

Gyrotron is a kind of important high power and high frequency microwave apparatus. Since it displays a lot special properties under development, it has attracted people’s extensive attention. It has been applied in the corperation project of the field energy in the world, such as: electron cyclotron resonance heating of plamas in the thermonuclear fusion, instability and diagnosis of plasma; microwave communication in the field military and astronavigation; material processing in the industry; biomedicine in THz science and technology. And it is developing toward the direction of higher frequency and higher power end to end. This requires gyrotron operating mode from low order to high order, which gives rise to mode dense to increase, and then, intensifies mode competition and riase ohmic losse of the gyrotron. To slove thses problem, people have worked out coaxial gyrotron on the basis of cylindrical gyrotron. A representative is coaxial gyrotron with 170 GHz 、 1WM, which has made in Russis and German,respectively. To improve further their traits, the inner corrugated coaxial resonator has been introduced, and a lot of improtrant results have been obtained. Hence, we shall research coaxial resonator along longitudinal corrugation on the inner and outer conductor in the dissertation.At the present, there are two methods setting up eigenequation of coaxial corrugated resonator: one is rigorus field match ?RFM?; the other is surface impendence method ?SIM?. As the eigenequation of coaxial corrugatd resonator derived by SIM is simpler than by RFM, hence eigenequation of coaxial resonator with inner-outer corrugation is obtained by SIM. And then, the influence of corrugation parameters of on eigenvalue is researched. According to theory of equivalent waveguide, the trait of select mode is researched on the coaxial resonator with inner-outer corrugation.When the operating frequency of gyrotron increases from low frequency to high frequency, ohmic losse on the wall of gyrotron raises greatly. But, it must be confined in the region23~ 4 KW / cm in practicial application. Therefore, ohmic loss and ohmic quality factor are investigated and mathematical formulas are obtained. By meams of above formulas, the influence of gyrotron corrugation parameter on ohmic loss and ohmic quality factor is studied. Results show that ohmic losses concentrate on the corrugated bottom of the resonator; the maxmum of ohmic losses appear in the regionof most strong field in the resonator. In addtion, the relation between eigenvalue and ohmic loss and ohmic quality is studied, too.Since the research on eigenmode benefits the calculation of interaction between electronic beam and electromagnetic field, the first-order transmission line equation with free source for coaxial resonator with inner-outer corrugation is derived by Maxwell differential equations and transmission theory; mode coupling coefficients are obtained by coupling wave principle; wave function expressions of the resonator are gained by Helmholz differential equations. By means of numerical method, eigenmode is studied, and eigenfrequency and diffractive quality factor are obtained. In addition,the influence of resonator corrugation parameter on eigenfrequency and diffractive quality factor is investigated, and their important relationships are found.On the basis of eigenmode analysis, we research further interaction between electronic beam and electromagnet field. Hence, the first-order transmission line equation with source for coaxial resonator with inner-outer corrugation is derived by Maxwell’s equations with source and transmission theory; the electronic kinetic equation of coaxial gyrotron with longlitudinal inner-outer corrugation is derived from Lorentz force equation in the guide center coordinate system. And meantime, coupling coefficient between electronic beam and electromagnet field as well as the expression of starting courrent of corrugated gyrotron are got.The beam-wave interaction is most important research on gyrotron. Therefore,according to the first-order transmission line equations and the electronic kinetic equations as well as their boundary conditions, the codes of the beam-wave interaction are finished by Matlab language. And then, the beam-wave interaction of the coaxial inner corrugated gyrotrons with 170 GHz 、2.2MW 、34,19 TE and 165 GHz 、1.5MW 、31,17 TE are investigated, and the effect of corrugation and operating parameters on corrugated gyrotron is investigated. Results fit up well above reference. A gyrotron with170 GHz 、 2MW 、34,19 TE is desigened and its output power and beam-wave efficient are calculated. The effects of operating and structure parameters the gyrotron on beam-wave interaction are studied. These workes will help us to further study the other gyrotron with coaxial inner-outer corrugation.