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Finite Difference Software to Analyse Electron Guns

 

Further Development of Finite Difference Software for the Analysis of High Current Electron Guns

TWI Industrial Member Report Summary 451/1992

By V J Pinfield

Background

This work describes the recent development of finite difference software for use in the analysis of electron guns. In order to produce a suitable electron beam for welding purposes, an electron gun must be designed to achieve the required characteristics, such as beam convergence angle, primary focus position and beam diameter. As more stringent industrial requirements are made of electron beam welding equipment especially for thick section welding, it has become necessary to be able to analyse the change in beam parameters due to extremely small differences in electrode (particularly cathode) detail, in order to optimise the beam shape.

Whilst the region to be analysed may be typically some 200mm long, cathode changes as small as 0.01mm may have an effect on the beam. Although such fine detail may be analysed by simply using a smaller mesh size, this dramatically increases the required computer storage and calculation time. The developments described in this report allow fine electrode detail to be analysed without resorting to a smaller mesh size. Although the work has concentrated on systems having cylindrical symmetry, much of the, work is applicable to 2D, x-y systems.

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