Research On Electron Optical System Of Terahertz Folded Waveguide Traveling Wave Tube

Terahertz Science and technology as an emerging discipline, has broad application prospects, Countries are actively engaged in research, so it develop quickly. As the basis of terahertz technology, terahertz source has been the focus of development. FWTWT (folded waveguide traveling wave tube) as an electric vacuum amplifier, because its high power, broadband output characteristics in the terahertz frequency range, simple structure, and can use mature modern micro processing technology, is the most development potential of the miniaturization broadband and high power terahertz source, has become hot at home and abroad.When the frequency increases rapidly, electric vacuum device give the more stringent requirements to the design of electron optical system, higher current density, smaller fluctuation of electron beam, and good laminarity. High current density means the intensive space charge effect. In this case, the research and design of the electron gun has become hard; and how to realize small fluctuation electron beam transmission in the diameter of less than 0.2mm interaction channel, is one of the key problems which designer needs to solve, and greater challenges for the design of focusing system.The THz folded waveguide TWT electron optical system is the research object, the main research work is follows:Derive axisymmetric electrostatic field distribution equation and the paraxial electron trajectory equation. Combined with periodic permanent magnetic focusing system, derive Laminar electron beam motion equations.The three-dimensional simulation software is used to establish simulation model, electron gun is the Pierce electron gun, structure of gun based on the existing one we had used, scan the important parameters, find out the correlation between structure parameters and the parameters of the electron beam, design electron gun for the demand of terahertz folded waveguide TWT. Calculated the periodic magnetic field peak and cycle length by the formula, establish periodic permanent magnetic structure model with magnetic field simulation software 2D patterns for periodic magnetic field distribution simulation and parameter optimization, to obtain the optimal magnetic field distribution. Brought the magnetic field distribution curve into particle studio to established the whole bundle flow transmission model, through the simulation optimization, get electron beam transmission rate 96%.Design test fixture for the periodic magnetic field, to measure the actual distribution of the magnetic field, verify the accuracy of the simulation of the magnetic field distribution. Optimization and developed 0.22THz FWTWT transmission tube, launched preliminary experiments, to verify the consistency of actual electron beam passing rate 95% and beam simulation, and access to domestic first DC operation 0.22THz folded waveguide traveling wave transmission tube. Finally, on the basis of the electron optical system developed 0.22THz FWTWT high frequency tube, output power 200mW of 12GHz bandwidth, peak of output power 350 mW, bandwidth of 3dB is larger than 12GHz, and running longtime in continuous mode. Then eveloped another 0.22THz FWTWT high frequency tube, output peak of output power 1.2W, bandwidth of 3dB is 3.5GHz.