Particle Simulation Study On S-band High Power Multibeam Klystron

The klystron is a kind of microwave amplifying with relatively perfect results and rapid development.The premise basis of multi-injection klystron development is single-injection klystron.Compared with single-injection klystron,multi-injection klystron has the advantages of lower operating voltage,wider bandwidth,higher frequency and higher gain.Klystrons occupy an irreplaceable position in microwave amplifying devices,and also have broad application prospects.Particle simulation plays an important role in the process of its research.The thesis mainly studies the basic theory and does three-dimensional particle simulation of the S-band TM₀₁₀10 multi-injection klystron.Combined with various of particle simulation software,the resonant cavity,input and output structure and whole tube of the klystron are completely analyzed.The theoretical research mainly includes basicvelocity modulation,densitymodulation,spacechargetheory,and multi-electronic injection force and focus.The basic research part mainly combines CHIPIC,MAGIC,CST,HFSS and other particle simulation software to analyze the various performance parameters of the klystron input and output loop and resonant cavity in the cold cavity state,including the electromagnetic field distribution,mode coupling transformation,resonant frequency and other performance parameters.The electromagnetic field distribution and the mode transformation of the output structure?-mode double gap,and the influence of the structural size of the cylindrical intermediate cavity on the resonance frequency f,the characteristic impedance R/Q,and the quality factor Q are also studied.The thesis mainly uses the CHIPIC particle simulation software to do the full three-dimensional particle simulation research of the 18-electron multi-injection klystron in S-band TM₀₁₀10 mode.Considering the computer performance memory and simulation time,using the multi-threaded particle simulation.Considering the accuracy of the simulated structure,using non-uniform meshing.Firstly,the three-dimensional model is established,the influence of the focusing system on the electron injection is studied based on the conclusion of the cold cavity,and the current and voltage isoelectric parameters are also studied;Secondly,the electron velocity distribution in the state of zero input signal is analyzed to ensure that the self-oscillation of the resonant cavity is not generated;Finally,the high-frequency signal is input without self-oscillation,and the hot cavity particle simulation study is performed on the whole multi-injection klystron.Particle simulation results show when input a high-frequency singal with a frequency of 2.85 GHz whose cathodic anode voltages are 17.4KV,total current of all electrons is 20.9A,average current density of each electron beam is3.25A/mm²,total average current of 18 electrons is 58.5A/mm²,diversion coefficient is1.26?P and input average power is 33W,the peak power of the output high-frequency microwave signal is 207KW,and the average power of the output high-frequency microwave signal is 103.5KW,and the output frequency is 2.85GHz,the frequency spectrum is single,there is no spurious frequency.The calculated efficiency is about29%,and the gain is about 35dB.