Glint system integration into an IFE target tracking and engagement demonstration

In the High Average Power Laser (HAPL) program, we are developing an integrated target tracking and engagement system designed to track in three dimensions an IFE target traveling 50-100 m/s and to steer simulated driver beams so as to engage it at chamber center with ±20 μm accuracy. The system consists of separate axial and transverse target detection techniques, and a short-pulse 'glint' laser to provide final steering instructions for beamlet alignment and target engagement by using the target itself as the final reference point. The glint laser overfills the target with a pulsed illumination beam 1-2 ms before chamber center, thus reflecting a 'glint' off the target in all directions. The glint return propagates back through the driver beamline and is collinear to the outgoing driver beam except for an offset determined by a wedged dichroic mirror. The wedged mirror accounts for the predefined transit distance of the target between the glint location and the driver beam arrival. This technique allows both the glint return and the driver beam to share a common path. Thus, the glint return represents the target's final position, but at a small discrete offset from chamber center, and therefore can be used to steer the driver beams to intercept the target at chamber center. We are currently prototyping this tracking and engagement system on the tabletop at reduced speeds and dimensions to verify feasibility. All subsystems have been characterized and currently we are integrating the glint system into the tabletop demo and using the glint return signal to provide the final steering instructions for the mirror. The glint system's integration into the tracking and engagement demo and current engagement results are reported