Abstract :
In this paper, design and optimization for three diaphragm lens system were done by using SIMION computer program. An oxygen ion beam of diameter 3 mm with energy of 5 keV was extracted from an ion source and the ion beam entered the lens system from a distance of 100 mm. Seven design parameters were identified as variable parameters in the presence of space charge current of 0.1 mA. These parameters are the separation between each electrode of the lens, the aperture diameter of the outer electrodes of the lens system, the aperture diameter of the intermediate electrode, the focusing points at different distances for singly charged oxygen ion trajectories, the applied voltage to the intermediate electrode and the influence of space charge on beam quality and also study of the influence of the mass for the different elements has been investigated. Beam quality was significantly improved when the applied voltage to the intermediate electrode was optimized and found at V2 = - 4500 V, separation distance (gap between each electrode) = 20 mm, the aperture diameter of the lens system = 40 mm and finally the best focused point was found at a distance of 550 mm from the end of the lens system.
