[en] The design and performance of a simple two element electrostatic lens which maintains good beam focal quality for the acceleration and deceleration of heavy ion beams, of high intensity, over a wide range of energy ratios is described. Experimental results are in close agreement with the lens behaviour predicted by digital computer simulation of the electrode structure. Space-charge effects are minimised by the use of small axial dimensions. The lens, which is used routinely on an ion-implantation facility, has operated reliably at voltages up to 160 kV over a period of several years. Using triply charged ions it has allowed the energy range of the small accelerator to be extended up to 600 keV. (author)