An electrode assembly for accelerating or decelerating an ion beam is provided. In one example, the electrode assembly may include a pair of exit electrodes adjacent to an exit opening of the electrode assembly. The pair of exit electrodes may be positioned on opposite sides of a first plane aligned with a first dimension of the exit opening. A pair of pierce electrodes may be adjacent to the pair of exit electrodes. The pair of pierce electrodes may be positioned on opposite sides of a second plane aligned with a second dimension of the exit opening. The second dimension of the exit opening may be perpendicular to the first dimension of the exit opening. Each pierce electrode may include an angled surface positioned such that a dimension of the angled surface forms an angle of between 40 and 80 degrees with respect to the second plane.