In the High Average Power Laser (HAPL) program, we have developed an integrated target tracking and engagement system designed to track an inertial fusion energy target traveling 50-100m/s in three dimensions and to steer laser driver beams so as to engage it with ±20 m accuracy from a stand off distance of ~20 meters. The system consists of separate axial and transverse detection techniques to pre-steer individual beamlet mirrors, and a final fine-correction technique using a short-pulse "glint" laser to interrogate the target's position 1-2 ms before the target reaches chamber center.

We are working to demonstrate the viability of this concept by conducting a table top engagement demonstration at reduced speeds and distances. Integration of the various components has been completed and hit-on-the-fly experiments are now being conducted. Initial engagement efforts from a simulated driver beam overfilling a falling target yielded a 150-m standard deviation for targets placed ±1.5mm from chamber center. Since then, our efforts have focused on systematically defining and eliminating all sources of error in each component and subsystem. Current engagement accuracy is 42m RMS. The engagement effort and the step-wise improvements realized are reported, as well as the path toward our goal.