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ABSTRACTIn 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.
A technique was developed for fabricating spherical shell targets for implosion physics experiments with diameters up to several millimeters and with unique structural features such as thin metal layers or texture on the inside surface. We start with a spherical bead or thin shell of poly͑alpha-methylstyrene͒ ͑PAMS͒ of the desired size, which can be textured by laser photoablation or overcoated with a thin layer of diagnostic material. The mandrel is next overcoated with plasma polymer ͑CH͒ 2-50 m thick. Upon heating, the PAMS depolymerizes to a gaseous monomer which diffuses through the thermally stable plasma polymer coating leaving a hollow shell. Shells produced by this technique are uniform in wall thickness, and highly spherical. If the PAMS mandrel is textured, the mandrel topology is transferred to the inner wall of the plasma polymer shell. Likewise, thermally stable coatings on the mandrel are transferred to the inner shell wall.
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