Gas Retention in Multilayer Alternate Ablator Capsules

The fabrication of three multilayer Omega-scale capsule designs with combinations of materials such as beryllium, silicon, tungsten, and copper were evaluated as part of the fabrication and delivery process. These opaque capsule designs presented characterization challenges in that nominal optical characterization techniques for Omega-scale designs were not sufficient to fully characterize the capsules. Alternate techniques such as X-ray fluorescence, radiography, scanning electron microscopy, and spectroscopy needed to be utilized in order to characterize these capsule designs. Additionally, the permeability of each material varies; therefore, each capsule design required a different approach to fill the capsule for the experiment. Three techniques were used to deliver gas-filled capsules to the experimental teams: (a) filling through the drill hole, sealing with glue under pressure, and minimizing the glue mass using laser ablation; (b) attaching a capsule fill tube assembly into the drill hole; and (c) gas permeation through the wall. The issues encountered with these techniques and their solutions are presented.