| Traveling wave tubes(TWTs) are broadband, high power, high gain microwave/millimeterwave amplifiers, which, taking an irreplaceable role in modern military electronic equipment, are widely used in communications, electronic warfare and radar systems. However, manufacture of TWTs is quite complicated involved in many disciplines, such as electron optics, magnetics, cathode electronics, microwave electronics, electromagnetic fields theory, materials, mechanics and pyrology. The technologies on TWTs have been making great progress with developments and applications of computers, which, enhancing design abilities, reducing production periods, decreasing hardware experiments, improving performance, solidifying known experiences, all of these are deeply dependent on. CAD has become a key technology in producing TWTs. TWT electron optics system, which consists of electron gun, focusing system and collectors, deals with the generation, formation, sustentation and collection of electron beam, is the important part of TWTs. The quality of electron beam, which offered by electron optics system, determines fundamentally the TWTs'crucial parameters such as efficiency, gain, working stability and noise characteristic etc. Using computer simulation and CAD technique is a significant way to ameliorate and optimize design for advancing the quality of electron beam. Supported by the"95 Plan"pre-study project of Wide Band High Power TWTs CAD Compositive Software Package Research and MWTs CAD Technique Research of General Equipment Department, this paper studied comprehensively and deeply the TWTs electron optics system, and bring in PIC method to solve availably the shortage of traditional trajectory equation, and established 3D electrostatic PIC model of whole electron optics system. Based on this, author of this paper develop the TWTs electron optics system CAD software. The main works and innovations of this paper are listed as follows:In this paper, particle-in-cell(PIC) method is reviewed and summarized. The fundamental of PIC method is introduced, including the Marco particle model, the finite-size particle model and the electrostatic model which is used in this paper to simulate the electron gun system. Particle simulation software MAGIC and MAFIA is summarized and contrasted.The development of Piercegun is introduced and its pivotal design parameter is summarized. For electron gun, the pivotal designing parameter , fast integrated design method and emission current's circulating law between electrode with the effect of space charge effect and electronic initial thermal velocity effect are researched, and the 2/3 law had been corrected. As the same time, the problems that the cathode initial thermal velocity make a difference to formation and quality of electron beam were studied, and the design of the grid control electron gun was researched.Numerical calculation methods in TWTs are discussed. Solutions of the static field and the electron movement equation are discussed. The effect of space charge is an important character of the high density electron optics, so the accuracy of its distribution has great effect on electron optics. The usual solutions of the pace charges density are also discussed, contrasted and analyzed.The paper is to simulate the movement of axial symmetry electron beam located between infinite parallel by using particle simulation method in FORTRAN platform. Particle movement is simulated for the A12 electron gun in Optimization of High-current Electron Gun Series. The results were contrasted with results by MAGIC simulation. |
