Removal of carbon contamination on oxidation-prone metal-coated mirrors using atomic hydrogen

In synchrotron radiation (SR) optical devices coated with oxidation-prone metal, such as Ni and Cr, the UV-O₃ ashing method cannot be used for removal of the contaminated carbon film deposited during use in the beamline. We have demonstrated that surface treatment technology using atomic hydrogen is effective as a new contaminated carbon film removal technology. Hydrogen gas was flowed into contact with a tungsten mesh (catalyst) heated to 1700°C to obtain atomic hydrogen. By flowing this atomic hydrogen on the surface of the SR mirror, deposited contaminants could be almost completely removed. The reflectance of the mirror recovered from about 14% to about 70% at the C-K absorption region. The reflectance also increased by about 20% at a photon energy greater than 300 eV because of the removal of carbon film and the reduction of native oxide at the mirror surface.