Study Of Electromagnetic Wave Interacted With Sheet Electron Beam In Staggered Double Vane Traveling Wave Tubes

Exploring the high-frequency and high power field has been becoming the trend of traveling wave tubes(TWTs).The staggered double vane(SDV)TWTs have been increasingly popular due to their extraordinary performances and enormous potentials at high frequencies and with high power.With more researches and design of SDV TWTs,there unveil more shortages and incompletions of current theories and simulation methods of SDV TWTs.In this dissertation,with electromagnetic theories and numerical methods of computational electromagnetics,the dispersion characteristics and beam-wave interactions processes in periodic structures,attenuators and transition sections are analyzed by both theoretical and numerical methods.A high-speed simulation program solving the beam-wave interactions in the sheet electron beam SDV TWTs is giving.Verifications of the simulation program of this paper is given by comparison with other3 D electromagnetic(EM)wave simulators and experimental results.Prime works and notable innovations of this paper are as follow:1.Solve the high frequency characteristics of SDV TWTs by the equations of the electromagnetic field in the SDV structures by solves of Maxwell's equations in SDV structures giving by Galerkin method.With the field equations,the dispersion characteristics of SDV structures is calculated,and the relation between phase velocity and frequency is given.By field equations and definitions of Pierce impedances,the equations of Pierce impedances in SDV structures are solved.The field methods and equivalent circuit methods for reflection characteristics are discussed.The scattering matrix of single-period SDV structures is calculated by equivalent circuit method.The dispersion curves calculated by this novel method agrees ones by 3D EM wave simulator with finite element method well.2.Derive the EM field equations of sheet electron beam SDV TWT under PEC hypothesis from the equations of traveling wave fields and space charge fields from Maxwell's equations.Reflect the differences of type of slow wave structures by few parameters such as Pierce impedance and normalized phase velocity,decouple the shape of slow wave structure and solving methods of field equations in the electron beam channel as possible.Simulate sheet electron beam by macro particles,solve kinematics equations of macro particles by difference method,and process the energy exchanges between wave and beam by principle of conservation of energy.The output power of single section TWT simulated by this novel method agrees with the 3D EM simulator with finite difference time domain(FDTD)method.The simulation speed of this novel method is around ten time faster than FDTD method.3.Provide the theory of the process the beam-wave interactions considering the metal losses and reflections in the SDV TWTs in realistic scenario.Inside the beam channel,the equations of field are obtained by electromagnetic theories.Get the surface current on the beam channel walls by surface magnetic field,and then the metal losses on the beam channel walls.Outside the beam channel,the metal losses are analyzed by equivalent circuit method.Give the method of calculating the scattering matrix of two-port network by scattering matrices of two-port subnetworks.The convergences of algorithm are discussed.The output power of single section TWT simulated by this novel method agrees with the 3D EM simulator with FDTD method.The simulation speed of this novel method is much faster than FDTD method.This novel method is with good convergence.4.Build the theory of the beam-wave interaction process in the SDV TWTs with attenuator.Based on the theories of energy exchanges and metal losses during beam-wave interaction in the SDV periodic structures,the physical processes in attenuator and transition sections are analyzed.Show the algorithms of metal losses in the attenuator and transition sections and the media losses in the attenuator.Analyze the influence of space charge in the attenuator and transition sections,also the radiations of space charge.The plasma frequency reduction factor of sheet beam in the rectangular waveguide is analyzed.The output power of double section TWT simulated by this novel method agrees with the 3D EM simulator with FDTD method.5.Intergrate and verify the analysis program of SDV TWTs beam-wave interaction.The analysis algorithms and programs of dispersion characteristics,beam-wave interactions,losses,attenuator and transition sections are integrated.The interface of SDV TWT analysis program is designed.The simulation results and the experimental results are compared.The simulation results can forecast the experimental results.