FABRICATION OF SPECIAL INERTIAL CONFINEMENT FUSION-TARGETS USING A DEPOLYMERIZABLE MANDREL TECHNIQUE

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 text ure on the inside surface. We start with a spherical bead or thin shel l of poly(alpha-methylstyrene) (PAMS) of the desired size, which can b e textured by laser photoablation or overcoated with a thin layer of d iagnostic material. The mandrel is next overcoated with plasma polymer (CH) 2-50 mu m thick. Upon heating, the PAMS depolymerizes to a gaseo us 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 i s textured, the mandrel topology is transferred to the inner wall of t he plasma polymer shell. Likewise, thermally stable coatings on the ma ndrel are transferred to the inner shell wall. (C) 1996 American Vacuu m Society.