Overview of laser damage performance of the third-harmonic frequency conversion crystals on the National Ignition Facility

We report on the laser damage performance of the DKDP third-harmonic frequency conversion crystals (THG) on the National Ignition Facility (NIF) since its operations began in 2009. An in-situ damage inspection system is used to monitor and track status of final optics in the UV section of the laser over time. Most THG optics last between 2 and 5 years on NIF before damage grows large enough that we have to exchange them. The critical damage size is related to our recycle strategy. About 10% of optics have lasted 10+ years which show we are not even close to the inherent limitation for this optic type. The short life THG optics are all limited by a relatively few number of flaws. Here we describe our efforts to understand these flaws so we can manage and, eventually, eliminate them.