2.B Increased Retention Time for Hydrogen and Other Gases by Polymer Shells Using Optically Transparent Aluminum Layers

A key difficulty infabricatingfuel capsules with polymer wallsfor inertial fusion is the high permeability of most polymers to the hydrogen isotopes used as fuel gases. In this article, it is shown that a thin aluminum layer can increase the retention time of a polymer shell for D2 from several minutes to several hours, while remaining transparent enough to allow interferometric measurement of changes in gas content. Having achieved a time constant for gas retention of an hour or more, a shell can be filled with fuel gas (along with a diagnostic gas such as Ar or Ne), and the A1 layer thickened before a significant amount of thc gas pemleates out. This thicker A1 layer greatly increases the time constant, but being opaque, prevents further interferometric characterization. Because many days may elapsc before the capsule is used in an inertial-fusion experiment, slow loss of fuel is prevented by storing the capsulc in pressurized fuel gas until the day or use.