Protected Silver Coating for NIF Flashlamp Reflectors*

Abstract

The National Ignition Facility at Lawrence Livermore National Laboratory will be a national center to study inertial confinement fusion and the physics of high energy and pressure. The $1.2 billion project consists of 192 laser beams which will direct more than 500 trillion watts towards a tiny target in a pulse only a billionth of a second long. The laser contains neodymium glass amplifiers which are pumped by xenon flashlamps. The flashlamps have silver reflectors to direct the light toward the glass laser slabs. Silver is ideal because of its high reflectance from 400 to 1000 nm wavelength which matches the neodymium absorption cross-section. In order to maintain the overall efficiency of the laser beams, there is an effort to prevent the corrosion of the silver reflectors by various means. One solution is the use of durable protected silver coatings which must survive 24,000 exposures to intense flashlamp light over a 30-year period while being exposed to small levels of atmospheric corrodants. One protected silver reflector has survived 20,717 flashlamp discharges so far in 100% Livermore atmosphere with no change in reflectance. This paper describes another protected silver reflector which is very durable.