Two and three electrostatic lens systems for focusing of charged particles

Abstract

Design of the focusing lens system has been done by using SIMION computer program which is used to trace and simulate the ion beam during its transport. A parallel beam of singly charged nitrogen ions of diameter 2 mm with energy of 3 keV was started at a distance of 50 mm before entering the lens system. In order to design the system, we studied it with different parameters in the presence of space charge. This study includes design and optimization of the operating parameters for the two-and-three cylinder lens systems. In a two-cylinder lens system, the first electrode was set at zero volts and the voltage applied to the second electrode was varied from 0 to –8 kV. Influence of the negative voltage applied at the second electrode for the–two-lens system on both the beam emittance and the beam diameter has been investigated for singly charged nitrogen ion trajectories. Beam emittance and beam diameter as a function of the tube diameter of the two-cylinder lens system have been studied. Also, beam emittance and beam diameter for a singly charged nitrogen ion as a function of the focusing points at different distances measured directly from the end of the-two-lens system has been investigated. Influence of the atomic masses of the different elements has been studied on both the beam emittance and beam diameter. The same study has been done for the-three cylinder-lens system. Key words: Two-and- three cylinder lens systems, acceleration voltage, beam emittance and beam diameter, SIMION computer program.