Simulation And Design Of Electronic Optical System Of 220GHz Sheet Electron Beam Traveling Wave Tube

Terahertz offers a wide range of applications due to its high frequency,big bandwidth,and high confidentiality.Terahertz sources are a key link in the application of terahertz technology,and the traveling wave tube is a frequently used high-power terahertz source device.In the traveling wave tube,the electronic optical system's ability to offer a high-quality electron injection is critical to the tube's performance.At the same time,the electron device size is reduced in the terahertz,and precise machining and assembly of the structure is tough,while the design and execution of the electronic optical system frequently become the top priority of attention.The traditional electron gun design requires extensive optimization of electrode structures,whereas the sheet beam(SB)electron gun cannot use a two-dimensional model to reduce design time because the gun is not axisymmetric.As a result,the current SB gun design needs more computational resources and a greater reliance on the designer's experience.Based on the paraxial trajectory equation and the Ovcharov theory,a two-dimensional synthesis method for a SB electron gun is programmed and implemented in this study.A SB electron gun was designed rapidly by this method,and the gun's three-dimensional model was built for simulation.Finally,a long-range sheet beam gun with a high compression ratio(area compression ratio of 22)is obtained.This thesis has finished the optimal design of a gun,a magnetic focusing system,and a buck collection pole for the target requirement of 220 GHz sinusoidal waveguide traveling wave tube output power of 100 W.Using CST,the gun that fulfills the design index is optimized based on the rapid comprehensive design.The gun works voltage is23.5 k V,the electron beam current is 200 m A,and the electron injection waist radius was 0.646 mm × 0.09 mm.There was a sensitivity analysis of the possible flaws of the electronic optical system during its actual manufacturing and assembly.Then,a rapid design of the uniform magnetic focusing system was achieved.A magnetic focusing system with a peak magnetic field of 0.9T and a uniform field length of 48 mm were obtained to meet the design requirements.After the joint simulation of the gun and magnetic system,the goals about the formation of a beam and its intercept-free transmission in a drift tube with a transverse dimension of 0.75mm×0.14 mm and a length of 48 mm were achieved.Two depressed collectors were designed at the end.When secondary electrons are taken into account,the efficiency of the single-stage depressed collector is 88.79% and the efficiency of the second-stage depressed collector is 91.46%.Furthermore,because the electron gun emits electrons through a hot cathode,the thermal deformation of the electrode in the electron gun,particularly the cathode,will cause considerable changes in the current magnitude and electron trajectory as the device's operating frequency rises.As a result,after finishing the optimal design of electrical parameters and structural design of the 220 GHz sheet beam electron gun,ANSYS software does the thermal analysis and thermal deformation analysis.