Analysis on the material removal stability for the finishing of the optical surface using atmospheric pressure plasma jet

Atmospheric pressure plasma processing is a method using chemical reaction between active radicals excited by plasma and workpiece surface atoms, which cannot damage the optical surface. A novel atmospheric pressure plasma jet generator has been designed based parallel plate electrode capacitive coupled, in which active fluorine atoms are excited from sulfur hexafluoride when helium acted as plasma generate gas and sulfur hexafluoride and oxygen acted as reactive gas. The removal profile is pseudo-Gauss curved surface, so this method suit for deterministically finishing aspheric and free optical surface controlled by computer. Furthermore, the material removal stability is a key factor for machining deterministically. The Influencing factors of material removal stability have been analyzed include helium flux, machining distance from jet outlet to workpiece and the tilt angle between jet effluent and the surface normal direction. Experiment was conducted with fused quartz material. The results show that the material removal rate is insensitive to the helium flux, machining distance and tilt angle between jet nozzle and workpiece surface at a certain parameters scope.