An ion implantation system may comprise a plasma source for providing a plasma and a workpiece holder arranged to receive a bias with respect to the plasma to attract ions across a plasma sheath toward the substrate. The system may also include an extraction plate arrangement comprising a multiplicity of different apertures each arranged to provide an ion beam having ions distributed over a range of angles of incidence on the workpiece, wherein a first ion beam extracted from a first aperture has a first beam profile that differs from a second ion beam extracted from a second aperture.