CAD Research On Electronic Optics System Of Traveling Wave Tube

Traveling wave tube is a kind of broad-band, high power, high gain microwavemillimeter wave amplifiers. They are widely used in communications, electronicwarfare, radar systems and microwave directional power weapon, taking anirreplaceable role in modern military electronic equipments. However, the manufactureprocess of TWT is so complicated that many kinds of subjects, such as electron optics,magnetics, cathode electronics, microwave electronics, electromagnetic fields theory,material science, mechanics and calorifics are involved in. With developments andapplications of computers, the technologies on TWT have been greatly improved so thatthe design abilities are enhanced, production period is reduced, hardware experimentsare decreased, the performance is improved and the have-known experiences aresolidified. Now CAD technology has become a main tool in TWT's research andmanufacture. Supported by the "95 Plan" pre-study project of Wide Band High Power TWT CADSoftware Package Research and MWT CAD Design Technique Research of GeneralEquipment Ministry, this paper has studied comprehensively the TWT' s electron opticssystem. By PIC method to analyze electron optics system, 3D electrostatic PIC model ofthe whole electron optics system has been established. Based on visualization techniqueof scientific calculation, object-oriented modeling technique and thoughts of softwareengineering, the TWT' s electron optics system CAD software is developed andintegrated in Wide Band High Power TWT CAD Software Package for factorypracticality application and operation. The main work and innovations of this paper are listed as follows: 1,The basic equations of high density electron beam optics, as well as thenumerical analysis methods are studied and built in the dissertation. Especially thephysical models and physical equations in the electrostatic field and magnetostatic fieldin the axial symmetrical system are analyzed fully and deeply, with relativity correctionand space charge effect taken into account in the electron motion equations and theelectron trajectory equations. The finite element method (FEM) and finite differentialmethod (FDM) of the static field, the motion equations, and the space charge density arealso discussed. The vector presentation derived from electron motion equations is IV电子科技大学博士学位论文simpler than that of linear equation solution method used in SLAC. However, theoutcome of the two methods is almost the same. 2,The electron gun, the periodic permanent magnet(PPM) focusing system and themulti-stage depressed collector(MSDC) of TWT are fully analyzed according to theviewpoint of electron optics. The circulating law of emission current between electrodeswith the effect of space charge and initial thermal velocity are researched, and the 3/2square laws has been modified according to the Langmuir diode model in which thespace charge effect and the thermal initial velocity of electron at the cathode areconsidered. At the same time, the influence of the cathode initial thermal velocity on theformation and quality of electron beam is studied, and the design of the grid-controlelectron gun was researched. For PPM, the magnetic field distribution and the ripplerule of electron beam in periodic focusing magnetic field is studied. For collector, theworking principle of multi-stage depressed collector, the efficiency, the secondaryelectron emission and the way for restraining the secondary electron are also researchedin this dissertation. 3,The shortages of the traditional electron optical codes such as the known EGUNprogram for electron trajectory simulation are analyzed deeply. Particle-in-cell (PIC)simulation is introduced to the research of electron optics system. 3-D electrostatic PICmodel of electron gun, PPM and MSDC are set up, so the whole simulation processincluding the emission, forming, focusing (transmission) and collecting is...