Automation of NIF Target Characterization and Laser Ablation of Domes Using the 4pi System

Capsules for inertial confinement fusion require precise measurement of isolated features and domes on the capsule's outer surface. Features that are too large must be removed. A 4pi capsule mapping and characterization system has been developed to map, identify, and measure domes using a Leica confocal microscope. An ultraviolet wavelength laser was integrated to laser-ablate the offending domes that exceed the allowable mix mass. Current process methods to remove domes require three different stations in different locations. The 4pi system achieves automated capsule handling, metrology, and laser polishing/ablation of domes on one device without losing track of the capsule's orientation. The measurement technique and metrology accuracy are compared to patch atomic force microscopy scans and phase-shifting diffraction interferometer measurements with good correlation. The laser polishing method has demonstrated analogous results to the current process methods, but in an automated fashion. Additionally, the 4pi capsule-handling capability of the system has been used to laser-ablate purposeful engineered designs into specialty capsules.