Adapting the Decomposable Mandrel Technique to Build Specialty ICF Targets

In this paper we describe our efforts to produce ICF target capsules with either controlled inner surface roughness or thin metallic diagnostic layers by adapting the decomposable mandrel technique previously developed at LLNL. To modify the capsule's inner surface we laser ablated a pattern on a poly(α-methylstyrene) (PAMS) shell, overcoated it with plasma polymer and then thermally decomposed the inner mandrel to leave the plasma polymer shell with the imprint of the laser ablated mandrel pattern. In this fashion we have been able to produce shells with controlled inner surface bumps. However, these bumps are correlated with outer surface pits. To place a thin metallic diagnostic layer on the inner capsule surface we applied a 50 Å titanium sputter coating to a smooth PAMS shell, overcoated with plasma polymer, and then thermally decomposed the mandrel to leave a plasma polymer shell with the titanium layer on the inner surface. Surface analysis showed that this process resulted in shells with a relatively long wavelength roughness, possibly due to the action of the metallic layer as a permeation barrier.