The process of damage accumulation in thin ruthenium films exposed to multiple femtosecond extreme ultraviolet (XUV) free-electron laser (FEL) pulses below the critical angle of reflectance at the FEL facility in Hamburg(FLASH) was experimentally analyzed. The multi-shot damage threshold is found to be lower than the single-shotdamage threshold. Detailed analysis of the damage morphology and its dependence on irradiation conditionsjustifies the assumption that cavitation induced by the FEL pulse is the prime mechanism responsible formulti-shot damage in optical coatings.
|Number of pages||7|
|Journal||Journal of the Optical Society of America B: Optical Physics|
|Publication status||Published - 1 Nov 2018|