Study Of 340GHz Extended Interaction Klystron High Frequency System

The extended interaction klystron（EIK）is widely used as a high-power millimeter wave/terahertz radiation source in fields such as deep space exploration,active denial systems（ADS）and counter-terrorism,biomedical devices,and high-resolution imaging due to its compact structure,high power,and stable durability.In the terahertz frequency range,EIK has become a hot topic of current research.However,as the frequency increases to the terahertz band,the size of the EIK high-frequency system becomes smaller,making it difficult to simultaneously achieve output power,gain,and efficiency.In this thesis,we study the 340GHz EIK high-frequency system with a narrow-coupled through-coupled cavity,a trapezoidal multi-gap cylindrical electron channel,and apply the phase velocity jump technique from the traveling wave tube to the EIK output resonant cavity,analyzing the key influencing factors to improve the interaction between the electron beam and the wave and achieve hundred-watt level output power.The main contents of this thesis are as follows.（1）The development background of terahertz and EIK,as well as the current main technical challenges,are investigated in this thesis.A comprehensive theoretical analysis of the electron velocity modulation and electron drift bunching in the EIK high-frequency system is conducted.Additionally,the key characteristic parameters of the resonant cavity in the EIK high-frequency system are interpreted.（2）A study on the cold cavity of the 340 GHz EIK high-frequency system was conducted.Firstly,the narrow-coupled through-coupled cavity with a trapezoidal multi-gap cylindrical electron channel resonant cavity was selected as the basic structure of the resonant cavity for this study,with the₁₁-2mode as the operating mode.Secondly,the width of the narrow-coupled cavity,gap width,and electron beam channel radius were determined to have the greatest impact on the dispersion and resonance frequency of the resonant cavity by analyzing the dispersion and resonance characteristics of the resonant cavity in the cold cavity and their relationship with the parameters.This led to the preliminary determination of the structural parameters of the single-period cavity.Next,the effect of the number of periods on the characteristic impedance/,effective characteristic impedance²（/）,and electron conductivity2)₀)of the entire multi-period resonant cavity was simulated and calculated.The optimal number of periods for the high-frequency resonant cavity slow-wave system was determined to be5,7,9,and 11.Finally,two different input and output coupling slot schemes were proposed,with the tapered coupling slot used as the input coupling slot and the rectangular coupling slot used as the output coupling slot.（3）A thermal cavity simulation analysis was conducted on the EIK high-frequency system.To improve the efficiency of interaction between the electrons and the high-frequency field,the phase velocity jump principle was applied to the output resonant cavity,which was divided into two groups,A and B.The optimal position of the output cavity was determined by adjusting the overlap length between the two groups of resonant cavities and analyzing the output cavity electric field characteristics using the eigenmode analysis.Under the conditions of an overlap length of-5μm,an A-group gap length of0.120 mm,a B-group gap length of 0.128 mm,an electron beam voltage of 18.3 k V,a current of 0.2 A,a uniform magnetic field of 0.57 T,and input signal frequency and power of 339.85 GHz and 20 m W,respectively,the center frequency of the output cavity was339.85 GHz,the average output power was 108.432 W,the-3d B bandwidth was 300 MHz,the gain was 37.34 d B,and the efficiency was 2.96%.Through theoretical simulation,the hundred-watt level average power output of the 340 GHz EIK high-frequency system was achieved.