Mark Tillack, Lane Carlson, Jon Spalding Laboratory Demonstration of In-chamber Target Engagement HAPL Project Meeting Rochester, NY 8-9 November 2005 Dan Goodin, Graham Flint, Ron Petzoldt, Neil Alexander

We are attempting to demonstrate the “pessimistic” version in-situ target engagement system proposed by Flint 3/05 (Gen II) Key Requirements: 20  m accuracy in (x,y,z) 1 ms response time Goals:  Full integration of all key elements of target engagement  Benchtop demo first: identify and solve problems before investment in full-scale, high-performance demonstration

Glint system: beamlet fine adjustment to compensate drift The system consists of Poisson spot detection, Doppler fringe counting, a simulated driver with steering, and a glint-based alignment The driver beam is simulated with a HeNe laser Doppler fringe counting provides z and timing (v) Poisson spot system measures (x,y)

Initial Poisson spot results were reported at the previous HAPL meeting* We demonstrated Poisson spot detection with 5 µm accuracy in <1 ms using a translation stage and an ex-situ centroiding algorithm * L. Carlson, M. Tillack, D. Goodin, G. Flint, “R&D Plan for Demonstrating Elements of a Target Engagement System”

To perform real-time target engagement on the benchtop, we needed a target transport method CMOS camera illumination laser PSD 4-mm SS sphere We are using various translation stages and rail systems We’re still working on a more prototypical surrogate transport method

Our in-line benchtop centroiding system now runs continuously at <20 ms per measurement – this allows us to begin real-time feedback to beam steering – higher speed will require real-time OS and a faster camera – 1 cm/s target speed over 1 m travel – 100 fps Basler camera – Labview running on Windows XP Breakdown of times

Integration of Poisson spot detection with a “fast” steering mirror was implemented We passed a pseudo driver beam through a 10x beam expander to magnify the range of motion of FSM (±1.5 mm) Determining the location of the driver on the target is difficult – the accuracy of engagement is confirmed with an offset PSD as a surrogate target

Open loop Poisson spot tracking: The Movie ±3 mm CMOS ±1.5 mm PSD white dot: Poisson spot yellow dot: PSD 1.At t=0, PSD initialized at (0,0) 2.Start train moving 3.Measure Poisson spot (x,y) 4.Move FSM to follow sphere 5.Measure accuracy using PSD

Engagement is performed in 23.5 ms, but dynamic errors are too large Sources of errors: rocking of PSD & target speed limitations in PC hardware/ software overly simplistic gain curves FSM quality Breakdown of times x-axis comparison of PS and PSD readings

higher performance will require a better FSM Beam deflection is nonlinear with drive voltage and exhibits severe resonant behavior 595 Hz617 Hz 1 ms We characterized the Thorlabs piezo cage mirror mount using a signal generator

Work has begun on Doppler fringe counting Restrictions on laser power limit the use of a metal sphere, so we’re using an n=2 sphere and flat mirror Single-wavelength (632.8 nm) Errors due to translation stage, vibration, air flow Repeatability demo using micrometer: travel of 5 mm with 10  m increments An N=2 ball lens is a retroreflector:

We performed a fast tracking demo at 1000 Hz using a high-speed pellet and post-shot centroid analysis 1000 fps, 10 ms per frame video sequence of surrogate target coming into, then out of the camera’s FOV, at 150 m/s (Photron camera) Curvature in the target trajectory allows us to avoid a shutter mirror for a range of velocities Speed of gun is too fast, speed of tracking too slow:  work on the benchtop

Next Steps: more integration and more prototypical Poisson system: Acquire a faster camera and real-time OS Doppler system: Demonstrate counting on metal spheres with longer paths Implement dual-wavelength counting Integration of Doppler and Poisson: On-axis demonstration (pseudo-integration) Off-axis demonstration (true integration) Integration of Poisson and FSM: Improve control of the environment, acquire a high-end FSM Glint system Install glint laser and coincidence sensor, align 2 beamlets