Investigation of an automated cleaning system for LMJ coating sol-gel process

摘要

The French Commission for Atomic Energy is currently involved in a project which consists in the construction of a 2MJ/500TW (351nm) laser, so called LMJ (Megajoule-class laser) devoted to Inertial Confinement Fusion (ICF) research in France. For this high power lasers, the sol-gel process has been selected for 95percent of laser optical coated area because of room temperature and atmospheric pressure conditions with guarantee for high optical and laser induced damage threshold (LIDT) performances at a low cost compared to conventional vacuum deposition processes. The production rate of sol-gel coatings for the LMJ optical components will require an automated cleaning surface step during sol-gel process. We are investigating a spraying system and wash cycles compatible with the two sol-gel deposition methods: dip and laminar-flow coating. The challenge is to achieve the same cleaned optical surfaces as manual process without using organic solvents. Therefore the main specifications of the cleaning quality are the following ones: a high surface energy over all optical sides (up to 400X400 mm~(2) area) and no degradation of polished sides (surface defects and LIDT). We present the metrologies carried out and the first results obtained from different wash cycles. These one mainly consist in measurement of contact angles, defects inspections under specific lighting conditions and LIDT tests. Several parameters of wash cycles have been investigated such as washing and rinsing temperatures, water quality, type and concentration of detergents, wettability effects...