Research And Design Of High Current Density Cold Cathode Eelectron Gun

Carbon nanotube cold cathode electron gun has broad application prospects in the filed of high-power microwave vacuum electronic devices for its high emission current density, posibility of room temperature operation, instantaneous start, current-voltage characteristics of quasi-linear. However, some problems still exist in obtaining the carbon nanotube cold cathode electron gun, such as poor performance of cathode emission in maximum emission current and emission stability, high gate electronic interception rate and poor effect of electron beam focusing. To deal with the problems in the application process of the carbon nanotube cold cathode electron gun, this paper mainly researches and analyses carbon nanotubes cold cathode and electron guns.In the study of emission performance in high current density of cold cathode cathode, the theoretical analysis and experimental research methods is used in analysis of impact on high current density carbon nanotube cold cathode emission properties due to the change temperature, mainly because of the obvious difference in emmision performance with different temperature conditions in cold water or not. Emission characteristics of the prepared current density of cold cathode material in this paper could basically meet the requirements of traveling wave tubes and other electronic devices for microwave vacuum electron gun. In online DC test conditions, the maximum emission current could reach to 33.5mA, corresponding to the emission current density of 4.27A/cm2 with the emitting area of 0.785mm2, and the device power consumption is 340 W. In the stability measurement test with high current of 20mA, untill 27 hours of online direct water-cooled, the carbon nanotube cathode shows good stability, the corresponding field emission current density is 2.52A/cm2, and the current decreases maximally to 5.3%.Based on the above electron optical properties of the electron gun, this paper completes the simulation design of electron guns including cathode structure, grid parameters and electron beam focusing system. Under the guidance of the theoretical simulation results, and according to the requirements and testing program of practical hot cathode TWT electron gun electrode assembly, physical processing and performance test of electron guns are finished. Effects of temperature are considered in the testing process which is that online test of oil-cooled DC is very difficult to take away the heat accumulated on the gate so that it will inhibit the cathode-electron emission, therefore method of online pulse testing is used. In the conditions of pulse, the maximum emission current could reach to 76mA, electron beam current 42mA and electronic gate interception rate at around 45%, which basically meets the application requirements of small power traveling wave tube microwave vacuum electronic devices. Related electron beam focusing system and electronic system design drift are deeply reseached, and when the related issues are resolved, the carbon nanotube cold cathode electron gun will certainly be popular in the applications of current device.