Methods and apparatus for reducing energy contamination can be provided to a beam line assembly for ion implantation. Protrusions comprising surface areas and grooves therebetween can face neutral trajectories within a line of sight view from the workpiece within the beam line assembly. The protrusions can alter the course of the neutral trajectories away from the workpiece or cause alternate trajectories for further impacting before hitting a workpiece, and thereby, further reduce energy contamination for more sensitive implants.