Science of NIF scale capsule development (activities for FY97)

Abstract

The focus of this work is the production of 2-mm PczMS mandrels by microencapsulation for use as National Ignition Facility (NH?) laser targets. It is our findings thus far that the processing techniques used previously for the 0.5mm and I.O-mm targets are no longer usefid for preparation of the larger targets for a few fundamental reasons. The driving force for sphericity (from the minimization of interracial energy) decreases as the radius of curvature increases. Simultaneously, the mechanical robustness /stability of the wateroil-water emulsion droplets decreases as the droplet size increases. The impact of these physical conditions and the possibilities of circumventing these limitations have been examined while attempting to meet the NIF shell power spectrum criteria. Identi&ing the key parameters in the transition (solidification) from a w-o-w droplet to a solid polymer shell has been understood implicitly to be the paramount goal. It is believed through the knowledge gained that it will be possible to minimize the deleterious forces and maximize shell sphericity. At this point it is believed that properties intrinsic to the polymer (i.e., PcxMS) such as its solution behavior and evolution of iilm stresses control the overall shell sphericity.