Abstract: A fluid flow control for use with a process chamber. In the disclosed embodiment, the process chamber is for ion implantation of a workpiece such as a silicon wafer and the fluid flow control is to assure the flow rates are maintained at values which are efficient in evacuating and pressurizing the chamber do not dislodge particulate contaminants from the process chamber walls. In the disclosed design, wafers are inserted into the chamber by use of a loadlock which avoids the requirement that the process chamber be cyclicly pressurized and depressurized. A diffuser plate intercepts fluid flowing into and out of the process chamber.