NON-LINEAR OPTIMIZATION ELECTROSTATIC LENSES

A method and computer code to design high-transmission cylindrical electrostratic lenses has been developed. Optimized geometries and voltages are determined using the CYLENS program enhanced with the simplex method of non-linear optimization. The possibility of improvements over unipotential lenses used in commercial instruments is predicted. The design of high-transmission unipotential lenses is described for such special purposes as time-of-flight mass spectrometry of organic ions or reflection geometry laser ionization mass spectrometry. Low accelerating voltage, in the first case and large working distance, in the second case have been realized, keeping the objective of high transmission. Asymmetric potential lenses were also investigated and, in the deceleration regime, they turned out to be superior to low accelerating voltage unipotential lenses. Misalignment and stability studies show that lens optimization provides less vulnerability towards anomalies in manufacturing or in operating conditions