Multi-element cylindrical electrostatic lens systems for focusing and controlling charged particles

This paper describes theoretical modeling of electrostatic lenses based on three, four and five closely spaced cylindrical electrodes. In each case, modeling is carried out numerically using commercial packages SIMION and LENSYS, and a variety of performance parameters are obtained. Special cases such as a zoom lens (i.e., lenses whose magnification may be changed without losing focus) are considered. Results are obtained as a function of the ratios of the electrode lengths and gaps, and as a function of ratios of the controlling voltages. As a result, how a multi-element lens system can be operated with the whole focal properties in a useful mode for experimental studies is shown.