The optimization of a triode electron gun with a thermionic cathode

This paper describes the systematic method of an electron gun optimization. The properties and quality of high power electron beams formed by an electron gun were evaluated by measuring the electron beam emittance as a very sensitive figure-of-merit. Our objective was to decrease the electron beam emittance by identifying the most significant factors which influence the electron beam quality and selecting the most preferable set of these factor levels. For this purpose we used the experimental design method based on Taguchi techniques for quality engineering. This technique proved to be a useful tool in identifying the significant factors, optimizing its levels and decreasing the electron beam emittance. As a result of our experiments we have obtained an optimized electron gun which produces an electron beam with an emittance by one order of magnitude lower than the emittance of a currently used beam. It was proven that the repeatability of electron beam characteristics after each cathode replacement is quite satisfactory provided that the cathode is placed in its optimum position.