Space Electron Beam Isoelectric Focusing System Design,

In this paper, it's put forward that the designing scheme on main focusing system of the domestic space electron beam gun with equidiameter three-cylinder electrostatic unipotential lens on the basis of reading plenty of references articles and according to the developmental situation of space welding technology home and abroad.Equations of electron beams in the column coordinate system are deduced according to fundamental equations of electro motion mechanics.In order to solve above equations with numerical method, firstly compartmentalize the main lens section into meshworks, then use square griddling five-point difference format to rewrite electric field equations, finally use nine-point and EULER methods to solve electron beam movement equations.The influence of space charge in the space electron beam focusing system is introduced. Then liquid-tube method which is used to calculate the density of space charge and the Computer Aided Design (CAD) method are put forward. The result by programming calculation shows that the method is correct.The influence and calculating method of thermal muzzle velocity of electron beams on lens section are analyzed. The minimal radius of the trajectory of electron beams is calculated.All in all, the electrical and geometrical parameters of the focusing system are calculated by using the CAD method and FORTRAN language. The focusing voltage of the unipotential lens is about -1960V, the radius of the EB spot on the workpiece is 1.212mm. Then the data is processed with Origin software and ten electron trajectories are drawn. A satisfying result is gotten which shows that the electrostatic focusing method and the magnetic one have the same effect. Also, the main target and the design method of the electrostatic focusing system are reasonable, the calculation is correct.