Simulation Research Of 8mm Nano-Cold Cathode Traveling Wave Tube

Carbon nanotubes as become one of the most promising novel electron emission materials a new type of nanomaterials due to their excellent performance.About the merit of cold cathode,its response time is very fast,its structure is simple and size is small,so it has high research value and application prospects.Using cold cathode electron guns to replace traditional hot cathode electron guns to achieve miniaturization of electric vacuum devices becomes a hot research direction for scholars.The traveling wave tube has high power and wide frequency band,and is widely used.It is very important to study the nanomaterials cold cathode traveling wave tube.Based on the above background,an 8mm carbon nanotube cold cathode traveling wave tube is designed and studied.The specific work content is as follows.A new type of CNT cold cathode electron gun is designed for traveling wave tube.The theory of field emission is explained,and the performance of carbon nanotubes in field emission mode is studied with theoretical results and experimental data.According to the principle of the magnetron electron gun and the requirements of the traveling wave tube,a magnetron electron gun with uniform cathode magnetic field is designed.First of all,the structure of the electron gun is preliminarily established.Then,the model of the magnetron electron gun is finally determined through research and optimization of the main structural parameters of the electron gun.The simulation results show that the electron injection trajectory is good,the current emission density of the electron gun can reach 1.5A/cm2,and the emission current can reach 42mA.The high frequency slow wave structure and input/output system of 8mm traveling wave tube are designed and optimized.Firstly,the structural model of the coupling cavity is determined,and the symmetrical structure of the double-coupling holes is selected;the dispersion characteristics and pierce impedance are related to structural parameters,and the influence is studied so that the final model is determined.In order to get a great match,A stepped waveguide is adopted in the system.The reflection coefficient is less than-20dB within the working bandwidth of the traveling wave tube,which prevents the occurrence of self-excited oscillation of the traveling wave tube.The particle simulation research and analysis is completed at last.The electron-wave interaction,output power,gain,and bandwidth of the TWT are analyzed.The results show that when the transmitting voltage is 22kV and the current is 42mA,the output power of this TWT can reach 139W,the gain is 31dB,and the bandwidth is about 1.1GHz.