Analysis on Electron Beams of CRTs with Axi-asymmetric Electron Guns

Abstract

This paper introduces a newly developed electron beam simulator for CRTs with axi-asymmetric electron guns. Effects of space charge, thermal spread, and deflection defocusing were all taken into consideration in the development process.
In this simulator, the electron beam is divided into Gaussian beamlets, with each having a main trajectory and paraxial trajectories around it. For calculating the electrostatic field in the main lens, the multipole field expansion method was used together with the surface charge method to reduce CPU time and to simplify data input for complicated electrodes.
The simulator was used to investigate dynamic astigmatism correction using a quadrupole lens in the main lens, and the cancellation of an astigmatism using slits and square apertures in the beam-forming region. Calculations of the beam spot diameters closely matched the actual measurements (differences were 10% at most). This test confirmed the simulator's effectiveness in investigating and designing CRT axi-asymmetric electron guns.