Coulomb interactions in a low-voltage focussed ion beam system

To be able to further optimise a low-voltage focussed ion beam system with immersion lenses and booster principle it is necessary to investigate the influence of Coulomb interactions in such a system in more detail. Therefore, Monte Carlo simulations have been done for an example system consisting of two immersion lenses separated by a drift space set to high potential (booster voltage) using both the commercial software package IMAGE by Mebs Ltd. and the programme MONTEC developed by G.H. Jansen. Parameters varied here are the total column length, the working distance as well as the internal operating mode of the objective lens. Results will be presented for landing energies of 3, 2 and 1 keV.