Linear Electron Beam Coaxial Quasi-optical Cavity To Motivate The Study Of The Short Millimeter Wave

The cylindrical quasi-optical systems have been presented in this paper in order to obtain high-frequency and high-power output of the millimeter wave radiation. The research of the interaction, radiation mechanism of the system have been done to explore the method to achieve higher-frequency and higher-power output.A series of coaxial interaction structures are presented, which are based on conventional coaxial conductor. Changing and engraving the inside conductor surface with periodic grooves becomes cylindrical gratings and changing the shape of the outer conductor with spherical surface forms a curved mirror. Then this structure after being changed is known as the closed coaxial quasi-optical cavity. The top part of cavity is removed to form open coaxial quasi-optical cavity. A special field distribution exists in such interaction systems, with a strong field region near the grating surface. And it is conducive to improve the efficiency of interaction. Because changing the shape of cross sections of cylindrical gratings can alter the distribution of high-frequency field and strengthen the intensity of electromagnetic wave in the interaction area. Three shapes of cylindrical grating section are discussed, including the inverted trapezoidal cross-section, rectangular and trapezoidal cross-section. The interaction between the electron beam and electromagnetic wave and the output characteristics in these structures are analyzed under different parameters by the particle simulation software MAGIC.The inverted-curved-mirror coaxial quasi-optical cavities are analyzed and simulated. In this kind of structures the inner surface of the outer conductor of coaxial conductor becomes cylindrical gratings and the outer surface of the inner conductor of coaxial conductor forms inverted curved mirrors. And in the same way, removing the top part of cavity forms open inverted-curved-mirror coaxial quasi-optical cavity. The software MAGIC is also used to simulate the interaction in these structures. By comparing the simulation results of the open inverted-curved-mirror coaxial quasi-optical cavities and the open coaxial quasi-optical cavities before under the same simulation parameters, it is proved that the former structure can obtain 158.46GHz electromagnetic radiation and the output power up to 578MW; but the latter structure can only get 76.6GHz electromagnetic radiation and 25MW output power, when the electron beam voltage is 0.5MV, the current is 3000A. Therefore, the inverted open coaxial quasi-optical cavity structure could be a potential high-frequency system of short-millimeter-wave radiation and even THz band radiation.