Design And Applied Research Of Cold Cathode Electron Gun

Carbon nanotubes as field emission cathode with a quick start,working at room temperature,high current density and many other advantages have broad application prospects in the cold cathode electron gun and its components.Based on carbon nanotubes as cathode,the key problems in the design process of cold cathode electron gun are studied and tested,and the cold cathode electron gun for the microwave tube is designed and researched preliminarily.Firstly,field emission performance of carbon nanotubes with bipolar structure is studied.The maximum emission current is 34mA,corresponding to the current density is 4.3A/cm2 and the device power is 330W.Keeping emission current 20mA,current declines only 3.8%.The cathode shows a strong emission capability and fine stability.Then the field emission model of carbon nanotubes was established in the electromagnetic simulation software.The effects of different cathode,grid structures and electron transmission efficiency on electron beam are studied.The electron gun has the maximum efficiency when the passing rate of the grid mesh is about 80%.The lens of square and spoke hole grid mesh is weak and they are easy to form the convergence electron.Secondly,the cold cathode electron gun prototype device was fabricated and tested:(1)The test of different passing rate of the grid mesh demonstrated the results of the simulation analysis;(2)Under the conditions of DC and the device immersed in oil,the results show that the structure of the device can complete field electron emission well.(3)Under the condition of pulse,the problem of electron gun heating can be solved in a certain degree.The emission current of 76mA is obtained,and the anode current is 44mA.Aiming at the shortcomings of the devices shown in the test,the next step of the optimization solutions are put forward.Finally,based on the above theoretical and experimental research,the design and simulation experiments of the cold cathode electron gun for microwave tube are carried out according to the principle of Pierce electron gun.The parallel and spherical injection electron gun are studied respectively.The problems such as electronic injection shape,electron flow and electric field distribution are analyzed.The effect of different focusing poles,anode and assembly and machining errors on the electron gun is analyzed.The results show that the electron guns have good performance electrons.This provides the idea for the next step in the study of cold cathode electron guns.