In order to fabricate a large-aperture continuous phase plate(CPP)using atmospheric pressure plasma processing(APPP)with high efficiency and precision,the position dwell mode and velocity mode were proposed and the iterative calculation method was developed for the non-constant removal rate.Two 320 mm×320 mm×2 mm CPPs were fabricated with two processing modes.The experiment results show that the velocity mode is capable of significantly reducing the processing time and shape error.The total processing time is decreased from 13.2 h to 9.3 h,and the surface shape error is decreased from 0.158λto 0.119λ(λ=632.8 nm)(root mean square).
Xing SuLongguang XiaKan LiuPeng ZhangPing LiRunchang ZhaoBo Wang
In order to get ultra-smooth fused silica surface without subsurface damage efficiently, the atmospheric pressure plasma processing( APPP) method has been developed. It is based on chemical reaction between active radicals excited by plasma and workpiece surface atoms,so the subsurface damage caused by contact stress can be avoided and atomic-level precision can be ensured. In this paper,based on the spectral quantitative analysis theory,the influence laws on material removal rate by the key factors of APPP including the flow rate of reaction gases,the input power,the processing distance and time are discussed. In addition,the results that APPP can remove the damaged surface layer and do not introduce secondary damage are proved via the nanoindentation technology.
