Ion beam studies: Part IIIa: The modelling of electrostatic mirrors for the manipulation and focussing of heavy ions

Abstract

Electrostatic mirrors have been used to steer, focus and scan intense beams of heavy ions. In this paper, an account is given of the computer modelling of such mirrors. Consideration is given to aperture effects in the lens and it is shown that shaped fields can be used to control the focussing behaviour. The mirror structure incorporates an additional negatively-biased electrode to prevent the penetration of the electric field through the apertures and along the beam trajectories outside the mirror space. This factor and the compact design minimise the space-charge defocussing effects which normally militate against the use of such electrostatic lenses with high intensity ion beams. The experimental verification of the modelling for a variety of ion-beam manipulation requirements will be described in a subsequent paper.