An accelerator assembly includes an acceleration channel that passes in a straight line through a plurality of accelerator cells. Each cell includes an acceleration region and a drift region. The drift region includes a high voltage plate and a grid electrode, where the grid electrode is disposed between the high voltage plate and the channel. In each cell, a large DC voltage is present on the high voltage plate. A voltage on the grid electrode is controlled such that at a first time an ion in the channel is attracted toward the high voltage plate, and such that at a second time the ion is shielded and is not attracted toward the high voltage plate. In one specific example, the assembly is part of a Direct Write On Wafer (DWOW) printing system that can direct write an image onto a 300 mm diameter wafer in one minute.