Laser treated surfaces in particle accelerators : relation between superficial topography, particle adhesion and compatibility for ultra-high vacuum applications

Laser-assisted surface structuration was developed at CERN for the treatment of the inside wall of the vacuum system. Grooves were created by material ablation while the laser scanned the surface. A part of this material was redeposed as particle aggregates. This two-scale rugosity efficiently trap electrons. The effects on other surface functionalities had to be assessed. During its operation, the surface is submitted to electro-mechanical forces and cooling cycles which might deteriorate its performances. Two extraction techniques have been developed - laser-shocks and centrifugation - to assess particle adhesion. Although the surface properties are not detrimentally degraded, massive particle detachment during operation or during the treatment itself is an issue that should motivate the choice of alternative treatment parameters or of a cleaning strategy