Tungsten Sputter Coating Development to Produce High Z Shells

We developed a production tungsten sputter coating process to uniformly deposit tungsten on 840 m outer diameter GDP shells using a bounce coating technique. We were able to control the tungsten-coating rate and therefore coating thickness based on gravimetric analysis. At the end of our work we could routinely produce uniform 0.5 m tungsten coatings on GDP shells with a Δ wall 0.04 m. Techniques were developed and applied to measure coating uniformity based on x-radiography and x-ray fluorescence data. Typical surface roughness values for bounce coated shells having a 0.5 m tungsten coating were 40 to 50 nm RMS. Stationary GDP shells were coated with 0.5 m tungsten and found to have surface roughness approaching 10 nm RMS, which was similar to the roughness of the underlying GDP mandrel surface. This result indicates that coating processes with less agitation such as tap or roll coating may produce much smoother tungsten coatings