CLEANING OF OPTICAL-SURFACES WITH PHOTOGENERATED REACTANTS

Cleaning of synchrotron radiation optics with photogenerated reactants has several advantages over discharge cleaning methods. In discharge cleaning, reactive species from the discharge must react with contamin ation on the surface while the surface is shielded from the harsher el ements of the discharge which can contaminate or degrade the surface. In contrast, if reactive species can be generated near the surface by photons, the problem of shielding can be eliminated and in some cases higher cleaning rates can be obtained. Different cleaning methods were evaluated by measuring the rates of removal of polymethylmethacrylate films with a thickness monitor. A number of different light sources a nd geometries were tested. The highest cleaning rates were observed wi th atmospheric-pressure UV/ozone cleaning. This method has been extens ively investigated for cleaning of hydrocarbon contamination from semi conductor surfaces. Our studies indicate that it is also effective in removing the graphite-like contamination from synchrotron radiation op tics. Compared to lower pressure methods it is simple, low cost, faste r, and more selective. It does require venting of vacuum chambers; how ever, in many cases optics can be cleaned without demounting, saving c onsiderable time and effort. This method has been used successfully to clean gratings and mirrors in several beamlines.