Research On High Frequency Characteristics Of Radial Relativistic Klystron Buncher Cavity

In recent years, the development of relativistic klystron is no longer blind pursuit of high power, but rather focus on higher output power and moderate size of the device.However, the axial devices generally either high efficiency but also high impedance or low impedance but the efficiency is low, and most of them has complex focusing system. And this problems cause axial relativistic klystron severely in developing high-power microwave device miniaturization and high efficiency of restriction.Since the radial device has advantages of smaller space charge effect, the bigger space limit current, low impedance, which will help improve the power and efficiency of the device, and to contribute to the achievement the miniaturization of the device, etc. which makes the radial device become one of important development direction of high power microwave devices. This thesis designed a resonator as a middle cavity of radial relativistic,and analyed its high-frequency characteristics. Finally proposes a method of suppressing high-order mode oscillation using a magnetic coupling.First, the paper describes the significance of the radial relativistic klystron, and outlined its development status, and then the electron beam movement in high frequency structures were described in detail.Secondly, the main radial klystron devices found through research is the RKO. And the high frequency structure of mostly RKO are coaxial resonator structure with grids. It is satisfied the needs of the klystron. But there is grid will affect the life of the device and makes the device more complicated. Therefore,the author removed the grid when she designed the RKA middle cavity,so as to form a new type of resonator cavity which named grooved resonator. The author divided its structure into three standard cavity.And using boundary-field matching method to solve the resonant frequency and field distribution.Finally the author simulation TM011 model and she found its radial electric field was fully compliance with the field distribution needs of the radial device.At last, in analyzing grooved resonator frequency characteristics we found that TM011 mode and other high-order mode frequency interval is small. It’s easy to produce high-order mode oscillation. In this paper,by the field distribution of grooved cavity,we proposed using a magnetic coupling to reduce the high-order mode Q value method to increase the high-order mode start-up current.The simulation found that the addition of magnetic coupling ring lead to the closest Q value of TM011, TM111 and TM211 mode becomes the 764.7,92.5 and 92.8.So the start-up current of TM111 and TM211 modes will be close to 8 times of TM011 mode. They are difficult to start-up.And ultimately achieve the purpose of suppressing the high-order mode oscillation.