Investigations are presented of the initial phase of operation of multi-edge cathodes for large-aperture electron guns. The influence of the form and amplitude of the supply voltage on the spatial distribution of the electron beam current density is shown. It was demonstrated that whilst the voltage is rising the cathode plasma is generated by the groups of operating edges and has a spot structure. An approximate analytical dependence between the number of operating edges and the voltage applied to the gun electrodes was determined. Quantitative results illustrating the dependence of the current distribution uniformity on the steepness of the voltage pulse front were obtained.
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