A gas injection system, including an extraction plate having an extraction aperture for allowing passage of an ion beam through the extraction plate, the extraction plate further having a gas slot for expulsion of a residue removal gas from the extraction plate. The gas injection system may include a gas conduit extending through the extraction plate between the gas slot and a gas manifold, a gas source connected in fluid communication with the gas manifold, the gas source containing the residue removal gas. The gas manifold may include a valve adjustable between a first position, wherein the residue removal gas is allowed to flow into the extraction plate, and a second portion, wherein the residue removal gas can be vented from the extraction plate. The gas injection system may further include a manifold cover coupled to the gas manifold.