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Proceedings Paper

Mitigation of laser damage growth in fused silica NIF optics with a galvanometer scanned CO2 laser
Author(s): Isaac L. Bass; Vaughn G. Draggoo; Gabriel M. Guss; Richard P. Hackel; Mary A. Norton
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Paper Abstract

Economic operation of the National Ignition Facility at the Lawrence Livermore National Laboratory depends on controlling growth of laser damage in the large, high cost optics exposed to UV light at 351 nm. Mitigation of the growth of damage sites on fused silica surfaces greater than several hundred microns in diameter has been previously reported by us using galvanometer scanning of a tightly focused 10.6 μm CO2 laser spot over an area encompassing the laser damage. Further investigation revealed that fused silica vapor re-deposited on the surface as "debris" led to laser damage at unexpectedly low fluences when exposed to multiple laser shots at 351 nm. Additionally, laser power and spatial mode fluctuations in the mitigation laser led to poor repeatability of the process. We also found that the shape of the mitigation pit could produce downstream intensification that could damage other NIF optics. Modifications were made to both the laser system and the mitigation process in order to address these issues. Debris was completely eliminated by these changes, but repeatability and downstream intensification issues still persist.

Paper Details

Date Published: 7 June 2006
PDF: 10 pages
Proc. SPIE 6261, High-Power Laser Ablation VI, 62612A (7 June 2006); doi: 10.1117/12.669393
Show Author Affiliations
Isaac L. Bass, Lawrence Livermore National Lab. (United States)
Vaughn G. Draggoo, Lawrence Livermore National Lab. (United States)
Gabriel M. Guss, Lawrence Livermore National Lab. (United States)
Richard P. Hackel, Lawrence Livermore National Lab. (United States)
Mary A. Norton, Lawrence Livermore National Lab. (United States)

Published in SPIE Proceedings Vol. 6261:
High-Power Laser Ablation VI
Claude R. Phipps, Editor(s)

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