Laser Forming of Shaped Fill Holes in Beryllium Targets for Inertial Confinement Fusion Experiments

A variety of shaped fill holes is needed in beryllium capsules for inertial confinement fusion experiments to allow for pyrolysis of the plastic (CH) mandrels, deuterium (D₂) or deuterium-tritium gas fill, and fill tube attachments. The holes required include through-holes ranging in diameters from ~5 to 30 m and counterbores ranging in diameters from ~13 to 17 m with depths <37 m. These holes are laser drilled using a double-pulse nanosecond format. Hole diameter and depth can be controlled by altering pulse format, energy, and beam delivery optics. Furthermore, according to National Ignition Campaign specifications, there is a tight tolerance for perturbations on capsule surfaces, so we have developed a technique to eliminate material redeposition through the use of sacrificial foils stretched over the targeted areas.