A high flux source of energetic oxygen atoms for material degradation studies

A novel technique for generation of a high flux of energetic (nominal ~5 eV) oxygen atoms has been demonstrated in the laboratory. The generation technique involves a laser-induced breakdown of molecular oxygen followed by a rapid expansion of the recombining plasma, resulting in the production of a flux of nearly monoenergetic oxygen atoms. We have developed consistently high velocity streams of oxygen atoms in an evacuated hypersonic nozzle. The oxygen flow is introduced into the nozzle through the mediation of a fast (~ 100 IJLS) pulsing valve and broken down with a CO2 laser. We have measured average oxygen atom velocities of ~ 5 to 13 km/s with an estimated total production of 10 18 atoms per pulse over pulse durations of several jis. Although these were single pulse measurements, scaling to a repetitively pulsed device appears straightforward. The O-atom source was used to irradiate sample targets, including Al, Fe, and polyethylene, and target-materialspecific radiation was observed above the target surfaces, indicating energetic O-atom induced mass removal.