Final optics damage inspection (FODI) for the National Ignition Facility

Abstract

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory (LLNL) routinely fires high energy shots (> 6 kJ per beamline) through the final optics, located on the target chamber. After a high fluence shot, exceeding 4J/cm² at 351 nm wavelength, the final optics are inspected for laser-induced damage. The FODI (Final Optics Damage Inspection) system has been developed for this purpose, with requirements to detect laser-induced damage initiation and to track and size it's growth to the point at which the optic is removed and the site mitigated. The FODI system is the "corner stone" of the NIF optic recycle strategy. We will describe the FODI system and discuss the challenges to make optics inspection a routine part of NIF operations.