Use of mechanical deflection to eliminate metallic vapor deposition on vacuum view ports

Metallic vapor emitted from a source can be deflected prior to depositing on an observation view port by imposing fans whose blades rotate perpendicular to the atoms flight path. The effectiveness of this technique is demonstrated with tin vapor in terms of relative rate deposition and visual examination as a function of the imposed rotation rate. The consequence of fan rotation on sample visibility is shown to be negligible.