Abstract: Deposition of debris produced in laser ablation of a workpiece situated in a vacuum chamber is reduced by introduction a background gas into the vacuum chamber prior to or during laser ablation. The background gas can be introduced diffusely into the vacuum chamber and can reduce contamination of surfaces such as a surface of an optical window that faces the workpiece during processing. Directed introduction of a background gas can be used as well and in some cases the same or a different background gas is directed to a workpiece surface at the same or different pressure than that associated with diffuse introduction of the background gas to reduce contamination of the workpiece surface with laser ablation debris.