Digital Computer Analysis of Crossed-Field Electron Guns

摘要

A digital computer program written in the IBM 7090 FORTRAN programming system is described and then employed in the analysis of several crossed-field guns. The digital program employs relaxation techniques while alternately computing electric fields and trajectories. One cycle through the program consists of three basic parts. (1) Calculation of the voltages within the gun by solving Poisson's equation, in difference form, on a 7200 point matrix on which electrode potentials are laid out. (2) Calculations of new current densities along the cathode and the setting up of trajectory starting points along the cathode to simulate these densities. (3) Calculation of trajectories and comparison of the new beam with the previous one. Thermal effects and direct particle-particle interaction effects are ignored but space-charge effects, introduced through the field calculations, tend to prevent excessive or unusual trajectory crossings. Execution time on a 7090 varies from 5 to 10 minutes depending on gun design, with better designed guns generally running faster. Results produced by the program are presented and compared with experimental and analytical results. Agreement with experimental results within 5 percent should be obtainable. (Author)