Study Of Sheet Beam Electron Gun With High Compression Ratio

When the operating frequency of vacuum electron devices increases,for cylindrical electron devices, the device size becomes smaller and the beam tunnel is narrowed, which result in the difficulty of processing. Besides, the beam current is weakened, the losses grow and the input power decreases, This hinders the realization of high frequency vacuum electron devices. As high power millimeter wave devices with high current density and intense beam current, the sheet beam electron devices has been paid more and more attention. The sheet beam electron devices has the following merits: the wide of sheet beam can be extended, the space charge field can be maintained, the input current and power can increase; the sheet beam run In small cross-section devices, so it can work in millimeter wave and terahertz frequency; the sheet beam electron devices have high efficiency; the slow wave structure can be processed, installed and adjusted easily; besides, it has small size and can be modularized, which makes it have a wide range of applications. In this paper, we mainly study the sheet beam electron gun.Based on the Pierce's theory, the structural characteristics and operational principle of the sheet beam electron gun are studied. The initial size of the electron gun is programmed according to the theory. A parabolic curved cathode, a beam focusing electrode (BFE) based on spline interpolation curves and the anode, are proposed to obtain a beam with good quality. The sheet beam electron gun was constructed by using CST and HFSS. The simulation, optimization and the analysis of the electron gun were also carried out.This paper mainly presents the design of two one-directional compression electron guns and two bidirectional compression electron guns. The compression ratio in narrow side is 10:1 and 20:1 respectively. The effects of the electron emission angle,temperature, the distance between the cathode and the anode, the relative position of the cathode and the BFE, and the displacement of the cathode, are analyzed. The results show that the emittance increases linearly with the increased electron emission angle.When the temperature is rising, the emittance increases in broadside and decreases in the narrow side. With the increased distance between the cathode and the anode, the electrons converge quickly at first, and then they diverge. The compression of the electrons is enhanced. At this time, the maximum current density increases and the beam current decreases. When the cathode surface moves outward the BFE,the compression of the electrons becomes weak, the maximum current density decreases and the current rises. When the offset is greater than 0.01mm, the emittance increases obviously in the narrow side and the divergence of the electrons is heavy.