Fig. (24) Threshold of mirror surface layer degradation at exposure to multi-pulse laser radiation (wavelength 1.06 µm) as a function of the number of pulses for SC (Mo and W) and PC Cu mirrors, as found experimentally up to N≈1.5x105 (solid points) and approximated up to 108 pulses (open points). The measured thresholds are: F1 = 3±0.5 J/cm2 for Мо, F1 = ~15 J/cm2 for Cu, and F1 = 6.5 ± 0.8 J/cm2 for W [70].