Atomic Layer Deposition Coating for Permeation Half-Life Control of GDP Ablator Capsules

The atomic layer deposition technique generates very thin Al₂O₃ films to control the hydrogen diffusion half-life of glow discharge polymer (GDP) inertial confinement fusion shells. The films generated by this process have an easily controlled thickness and are pinhole free. As a result, they can be used to set the hydrogen diffusion half-life of a GDP shell to the required value of hours, from an uncoated value of minutes. Such diffusivity control is much harder to achieve with the currently used sputtered Al coating, which also renders the shell opaque, causing difficulties with ice-layer characterization. The [approximately]10-nm oxide is also less intrusive to target performance than an [approximately]100-nm (and highly nonuniform) metal coating such that it can be safely ignored by the target designer.