Research On Optical System Of Electron Gun For Long Transmission Distance

The electron gun is used to produce electron beam that meets certain requirements,and the focusing and deflection systems can be used to focus and deflect electron beam.The well-designed electron gun optical system can provide an electron beam with a certain amount of energy,a small divergence and a required transmission distance.This kind of electron beam has important application in the research of new type terahertz radiation source and the melting of metal materials.The research on the electron gun system has important scientific and engineering value.In this paper,the optical systems of the miniaturized electron gun and the high power electron gun are studied.The miniaturized electron gun is used as the energy source to produce the terahertz radiation.Because our experimental environment is in high vacuum system and the position of the nano structure and the electron gun is relatively far away,it is vital to enhance the steady transmission distance of the electron beam.The main research contents and conclusions about the miniaturized electron gun system are as follows: According to the performance parameters of the electron beam,the initial structure of the electron gun is modeled by using CST software.On the basis of the initial model,the structure of gun area is optimized.The parameters of gun structure are given after optimization.Magic software is used to simulate the optimized gun area.The focusing system is simulated and the dimensions of the two stage focusing coil is determined.The deflection system is simulated.The deflection system adopts two pairs of coil structure.In the simulation,the relationship between the theoretical deflection position and the simulated deflection position is given.The simulation results can be accurately estimated by theoretical calculation results.The final simulation structure of gun system is given,and the machining drawings of the gun system are drawn according to the simulation structure.The high power electron gun system is mainly used for smelting metal.The working voltage is 75 kV and the rated current is 4A.In practical use,the high power electron gun is used to melt material in the crucible.In order to use safely,the gun and the crucible are not in a same vacuum system.The control system is needed to guide electron beam to the crucible to complete melting.Therefore,it is highly required for a long steady transmission distance.The main work and results are as follows: The structure design of optical system is presented.The gun's emitting surface is made of a bulk cathode with a through hole at the center of it.The coil structure wrapped with slotted iron is used as the focusing system.The structure optimization of the gun area is carried out and we obtain the conclusions that the position of the cathode,the focusing electrode's angle have significant impact on the transmission trajectory.The focusing coil wrapped with iron has also been optimized.We determine the structure of the gun system finally.The electron beam produced by the optimized system spread little and the transmission distance is far enough.