Multilayer reflectance during exposure to EUV radiation

摘要

Mo/Si multilayer mirrors have been exposed to intense monochromatic EUV radiation in order to investigate a possible deterioration of the mirror reflectance under different vacuum conditions. Power densities up to 3 mW/mm~2 were applied at the PTB undulator beamline at BESSY II, applying a hydrocarbon enriched vacuum. The mirror reflectance has been monitored in situ during several hours of exposure. vacuum pressures of 3x10~(-8) mbar (without hydrocarbons) and 10~(-7) mbar (with hydrocarbons) at EUV intensities of 3 mW/mm~2, respectively 0.2 mW/mm~2 have been applied. The reflectance of the mirrors decreased when exposed to EUV radiation in hydrocarbon enriched vacuum, while no loss in reflectance was observed when no hydrocarbons were added to the vacuum.