SEDL / STP / STP1038-EB / STP24427S

Damage to Fused Silica Windows while Under Simultaneous Exposure to Flowing Solvents and Laser Radiation at 308 nm

Mauro, BR
Los Alamos National Laboratory, Los Alamos, NM

Folryn, SR
Los Alamos National Laboratory, Los Alamos, NM

Sanders, V
Los Alamos National Laboratory, Los Alamos, NM

Pages: 4    Published: Jan 1988

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Abstract

This paper reports the results of a study to determine the degrading effects of flowing dye solvents on the laser damage threshold of fused-silica windows at 308 nm. Thresholds were measured at the SiO²solvent interface in a test cell. Bare SiO² tested in air at 308 nm (20 ns) typically exhibits a threshold ranging from 4 to 10 J/cm²; with the solvent cyclohexane in contact, a threshold as low as 0.3 J/cm² was measured. The damage data indicate that window lifetime (number of shots) is independent of fluence at higher levels, and asymptotically approaches infinity at levels near threshold. Dielectric coatings were tested as possible damage-resistant barriers between the solvent and SiO²; the results show some improvement in damage threshold. When cyclohexane is replaced with the solvent dioxane, thresholds measured for SiO² windows are within the range cited above for thresholds measured in air.