Abstract
This work was concerned with a simulation study of different cathode electrode aperture shapes (pierce, reversed pierce, cone, reversed cone, triangle, reversed triangle, rectangle, circle, and sphere), which confirms that, pierce and cone shapes are the best extraction apertures. The minimum values of ion beam diameter and ion beam emittance, at collector plate which placed at 30 mm distance from cathode electrode were obtained using pierce and cone shapes. Also, the distance of the ion beam trajectories focal point was studied using different shapes for cathode aperture, which found to be decrease with increasing of the voltage applied to the cathode electrode. The main parameter in this study was the applied voltage to the cathode electrode. It was found that the observed changes on the ion beam parameters in the range 100 - 1500 V, but higher than these values the behavior of diameter, emittance and focal point of the ion beam were quasi-saturated. Also, it was found that the general behavior of ion beam diameter and its emittance nearly the same.