Abstract
The impact of storage conditions on laser induced damage density at 351 nm on bare fused polished silica samples has been studied. Intentionally outgassing of polypropylene pieces on silica samples was done. We evidenced an important increase of laser induced damage density on contaminated samples demonstrating that storage could limit optics lifetime performances. Atomic Force Microscopy (AFM) and Gas Chromatography -Mass Spectrometry (GC-MS) have been used to identify the potential causes of this effect. It shows that a small quantity of organic contamination deposited on silica surface is responsible for this degradation. Various hypotheses are proposed to explain the damage mechanism. The more likely hypothesis is a coupling between surface defects of optics and organic contaminants.
Highlights
High power laser facilities such as Laser MegaJoule (LMJ) [1] or National Ignition Facility [2] are currently being developed for inertial confinement fusion (ICF) experiments and for the study of matter at extreme energy densities and pressures
Natural polypropylene (NPP) pieces similar to the one used in LMJ optics frames were analyzed by means of ThermoDesorption-Gas Chromatography-Mass Spectrometer (TD-GSMS) in order to determine the nature of the outgassed species
Damage tests reveal that clean and heated samples are similar. It demonstrates that the outgassing protocol without NPP has no effect on damage density
Summary
High power laser facilities such as Laser MegaJoule (LMJ) [1] or National Ignition Facility [2] are currently being developed for inertial confinement fusion (ICF) experiments and for the study of matter at extreme energy densities and pressures. In various studies, chemical contamination has been evidenced to be responsible for laser induced damage with high repetition rate laser [9,10,11,12]. In these cases, contaminants are organics such as aromatics, siloxanes derivatives and phthalates; chemical pollution is photo-deposited. Single shot laser impact studied by Ravel cannot be compared with laser induced damage with high repetition rate laser implying photo-induced chemical mechanism [9]. Considering Ravel results, we study the impact of polypropylene outgassing on laser induced damage at 351 nm of bare fused polished silica surfaces
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