Target tracking and engagement for inertial fusion energy - A tabletop demonstration

In the High Average Power Laser program, we have developed an integrated target tracking and engagement system designed to track an inertial fusion energy target traveling 50-100 m/s in three dimensions and to steer driver beams so as to engage it with +/- 20 pm accuracy. 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 laser "glint" from the target itself. Transverse tracking of the target uses the Poisson spot diffraction phenomenon, which lies exactly on axis to the centroid of the target. The spot is imaged on a digital video camera and its centroid is calculated in similar to 10 ms with 5 Mm precision. In our tabletop demonstration, we have been able to continuously track a target falling at 5 m/s and provide a fast steering mirror with steering commands. We are on the verge of intercepting the target on-the-fly and of verifying the accuracy of engagement. Future work entails combining transverse tracking, axial tracking, triggering and the final "glint" system. We also will implement a verification technique that confirms successful target engagement with a simulated driver beam. Results and integration progress are reported.