The impact of molecular contamination on the lifetime of fused silica UV optics used in high power laser facility is
studied. In our particular case corresponding to Laser MégaJoule (LMJ) beams, the irradiation conditions are a fluence
higher than 10 J/cm<sup>2</sup> at a wavelength of 351 nm (3 ω) for 3 ns pulse duration and a single shot/day frequency. A confine
environment, a long period of exposition and proximity of the optical components with outgassing materials are critical
parameters for the optics contamination. Consequently, experiments were performed in the UV section of the Ligne
d'Intégration Laser (LIL), actual prototype of the LMJ. Moreover, the optics storage conditions were studied. Indeed, to
ensure an efficient replacement of the optics on the laser bundle, many optical components are fabricated long before.
They are stored during months in polypropylene frames put in containers. Then, we intentionally contaminated silica
samples with one sort of polypropylene. We evidenced an important increase of laser induced damage density on
samples contaminated by both bundle and storage environments. Surface analyses have been used to identify the
potential causes of this effect. Various hypotheses of damage mechanisms are proposed.