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AbstractIn 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 μm 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 ˜10 ms with 5 μm 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.

AbstractTarget engagement is the process of measuring the target trajectory and directing the driver beams to hit the target at a position that is predicted based on these measurements. New target engagement concepts have been proposed in the last few years to continuously track the targets and to verify that the tracking system is aligned with the driver beams for each shot.For transverse position, a laser beam continuously backlights the target and the position of the Poisson spot in the center of the target’s shadow is measured. Axial target displacement is measured using a laser interferometer and counting interference fringes as the target moves away from the laser source. Final steering corrections use a “glint” reflected off the target ˜1 ms prior to firing the laser beams and collected in a separate Position Sensitive Detector (PSD) for each driver beamlet. The position of the glint on the PSD is compared to the position of an alignment beam that is collinear with the driver beam. Steering corrections are then made based on the difference in position of the two spots reaching the PSD.

Several letters to the editor are presented in response to articles in the previous issues including the use of generators in sail boats in the December 2010 issue, the correction of information regarding the oldest golf course which is the Royal Montreal Golf Club in the January 2011 issue, and the concerns on proper disposal of old flares in the January 2011 issue.

Several letters to the editor are presented in response to articles in previous issues including "Northern Defender," by Peter Marshall, "Tales From the Lakeview," and "Refresh Your Memory," all in the January-February 2012 issue.