| Abstract: |
Electron beams are used widely in many different applications for industrial production as well as scientific and medical instruments. The beam requirements for each use can be defined in terms of intensity, beam angle, divergence and other characteristics. It is the role of the electron gun designer to use modelling tools to optimise gun design. Usually, tentative gun designs are produced, simulated using modelling software and then the resultant beam is analysed in comparison to the requirements. This is essentially a trial and error approach which continues until a satisfactory design is derived and it is labour intensive. This work presented concerns the development of algorithms to automatically derive an optimum gun design. The method uses a genetic optimisation algorithm which seeks to optimise beam characteristics which are derived from the simulation of tentative gun geometries. This offers a rapid method of customising gun designs and allows radical design approaches to be examined. The design process has been applied to a novel plasma cathode gun design developed to give high beam intensity, for an electron beam machining application. This type of gun uses RF to excite a plasma from which the electrons are extracted. It has a number of advantages over conventional, thermionic cathode, electron guns, including no cathode wear, the ability to work in coarse vacuum and the ability for emission rapidly pulsed, which enables a high speed pulsed diode electron gun design configuration. The design process is outlined and the practical realisation is described.
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