The technical method for the surface modification is improved according to the material speciality of RB-SiC witch is to fulfil the application requirement for high surface quality of the space used

large scale and complicated light weighted RB-SiC mirror.It is to use the high energy kaufman ion source for IBAD;to carbonize the substrate and then prepare a carbon buffer layer befor the deposition of Si coating for surface modification.The testing re-sults show that the coating grows more compact and uniformity contrast to the method of simply using Hall ion source.So the characteristic for polishing is nicer.After the surface modification the surface roughness(rms) reduce to 0.635nm witch has reached the level of S-SiC;the surface reflectance is obviously enhanced and is correspond to that of fine polished zerodur glass.The conclusion can be drawn that this technical method for the surface modification of RB-SiC mirror is quite reasonable and effective.