Agenda

1. * Work performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Security, LLC, Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

2. Agenda • Introduction to NIF and automatic alignment • Control system architecture • Coordination and scaling • 3,800 closed loop adjustments using 12,000 devices • Management of shared laser components • Image processing • Algorithm robustness in a laser environment • Subpixel accuracy • Reliability and off-normal image detection

3. NIF concentrates all the energy in a football stadium-sized facility into a mm3

4. Beampath Movie

5. Target Alignment Sensor Beams are aligned along NIF’s 500-meter path to focus on the mm-size target within 10 microns In an analogy to baseball, this requirement is like hitting the strike zone with a pitch thrown from 350 miles away

6. Alignment uses sensors and actuators within Line Replaceable Units

7. Symmetry & nomenclature National Ignition Facility

8. ICCS shot cycle automatically aligns, fires and diagnoses laser shots every 4 hours Fire main amplifiers Fire pre-amplifier Shot Shot Amplifier cooling Shot Shot Preparation Archive Verify Archive 30-m 30-m 2-s 20-m Automatic Alignment 4 hours Automated Shot Cycle • Input shot goals from laser physics model • Perform automatic alignment • Configure diagnostics and laser settings • Conduct countdown (SW: 4-m, HW: 2-s) • Assess shot outcome and archive data

9. Pointing error at the Input Sensor 5 4 3 2 1 0 -1 -2 -3 -4 -5 -6 Micro radians Required Tolerance 0 100 200 300 400 500 600 700 Minutes from starting time The automatic alignment system compensates for optical system drift

10. Single operator oversees Beam Control Requirements led to significant technical challenges • Minimize operator effort • Situational awareness • Manual controls • Deliver subpixel accuracies • Algorithms tolerant to • Varying light levels • Laser diffraction effects • Equipment anomalies • Reject off-normal images • Rapidly align 192 beams • Parallel operation • Computational resources • Many devices are shared

11. Shot Sequencer Target Bundle 1 Bundle 24 Bundle Coordinator Bundle Coordinator Bundle Coordinator Beam Control Beam Control Beam Control Supervisory Layer Replicated Bundles Automatic Alignment Automatic Alignment Automatic Alignment Video Sensors Video Sensors Video Sensors Front-End Layer Actuator Controls Actuator Controls Actuator Controls The bundle architecture assures full-scale performance of the alignment control system Replicated bundles are activated by starting new processes in the database

12. Common Control System Bundle 11 Controls LINUX Cluster Shot Beam Control B11 Manager B11 Automatic Alignment Director Supervisor CORBA Alignment B11 Video Controller Timing Controller Configuration Logging Archiving Reservations B11 B11 etc. Actuators Sensors Process distribution example for beam control

13. Spatial Filter (Low Pass) Pinhole Centering Laser Beam Pointing Motorized Mirrors Beam Tube Lens The alignment system maintains the beam within the optical clear aperture Centering definition • Translates beam position without affecting pointing • Sensor configured to near-field mode Pointing definition • Adjusts angle of propagation without affecting centering • Sensor configured to far-field mode

14. Setup Reference Acquire Image Locate Reference Setup Beam Acquire Image Locate Beam Done Adjust Optic Generic control loop flow diagram

15. Centering Alignment Principle Near-field camera image Automatic Alignment Beam Center Network Image Acquisition Actuator Controls Control Firewire Motorized Turning Mirrors Fixed Sampling Mirror Light Source CCD Camera Beamline Beam Reticule Mask Reference Reticule Mask The image of the beam reticule (circle) is adjusted to the midpoint between the reference reticules (squares)

16. Light Source Pointing Alignment Principle Automatic Alignment Far-field camera image Network Image Acquisition Actuator Controls Firewire Motorized TurningMirrors Pinhole Illuminator Pinhole CCD Camera Pinhole Lens The source sub-image is aligned to the center of the pinhole shadow

17. Beam Control Supervisor Bxx Automatic Alignment Database Segment Manager LINUX Cluster Component Manager • - Alignment Plans • Segments, Loops • Components • Devices Video Sensors Actuator Devices Managers coordinate resources and activities • Supervisor • Manual controls • Status • LINUX Cluster • Image processing • Self-leveling • Segment Manager • Alignment plans • Loop definitions • Sequence control • Component Manager • Device sharing • Throughput optimization

18. A Segment Manager Alignment Plan 1 Control Loop 1 Control Loop 2 … Adjust Optic Reference Beam Setup Locate Setup Locate Check 1 minute NIF’s beamline architecture was designed to permit alignment of segments in parallel A NIF Beamline Preamplifier Segment Manager Main Laser Segment Manager Target Area Segment Manager Camera Camera Camera 3w CW Source 1w CW Source 1w Pulsed Source 1w CW Source Camera Loop Timing The Segment Manager executes alignment plans efficiently to achieve the required performance

19. The Component Manager optimizes task processing throughput • Component Managers • Orchestrate setting up laser configurations • Contain multiple device grouping called mediated components • Mediated components • Manages device positions • Can include other mediated components • Reservations lock the configuration • Task queues • Requests wait until devices become available • Deadlocks eliminated by enforcing priority • Queue optimization actively minimizes required movements The main laser sensor is a mediated component One out of every four devices in the alignment system are shared

20. Example of a Clipped Image Image processing must always be reliable • Precision and accuracy required to 0.3 pixels • Robustness is challenged by • Gradient illumination • Noise • Diffraction effects • Defocus • Magnification • Discard off-normal images • Extraneous blobs • Saturation • Clipping … while still being robust to varying laser conditions !

21. Weighted Centroid Template Match Hough Transform Spiral Search GaussianBeam Pinhole CrosshairGrid CornerCube CrosshairGrid Fiber Source Dark Stop Matched filter Shot Mask GlassGrid Crystalreflection Reticule Many processing algorithms are used …

22. Discard Off-normal Images Calculate Position Check Position Uncertainty Good Bad Images undergo three processing steps

23. Image quality is measured by estimating algorithm uncertainty • Uncertainty Definition • Instability in the position determination • Obtained by varying either thresholds or noise • Threshold-based method (e.g. weighted centroid) • Image processed with thresholds at 10 different levels • Delivers subpixel accuracy as a byproduct • Uncertainty: variability of the position estimates • Noise-based method (e.g. matched filter) • Monte Carlo model of known uncertainty is constructed for the image using prescribed amounts of noise • Uncertainty: estimated from the model based on noise present in the input image Low uncertainty confirms a high quality input image, with confidence that algorithm results can be trusted

24. Example of sub-pixel position estimation confirms accuracy is within tolerance Gaussian Image Centroid Plotted at Various Thresholds Tolerance limit 1 pixel (Y) Lineout 90% Intensity 10% 1 0 Distance (p) 76 1 pixel (x)

25. Defocused Gaussian Image 90% 10% Poor laser wavefront prohibits a successful alignment outcome in this uncertainty example Centroid Plotted at Various Thresholds Tolerance limit Lineout OUT OF TOLERANCE! 5x5 (x,y) pixel grid High uncertainty halts the automatic alignment process

26. Architectural enhancements achieved the required performance Sequential Mediated 4 beam sequentially aligned to Target Chamber Alignment Time (Minutes) Required alignment time Target camera bottleneck Year

27. 192 beams 2/3 of 96 beams Number Control Loops 144 beams 2/3 of 16 beams 2/3 of 8 beams 1/2 of 1 beam 1/3 of 1 beam 4 beams 4 beams Year Full automation of all 192 beams is moving rapidly toward completion

28. We’ve exceeded performance goals with a automatic system that is robust and reliable Remaining work extends automation of all 192 beams to the target for ignition experiments beginning in 2010

30. Database • - Alignment Plans • Segments • Loops • Components • Devices Component Manager Beam Control Supervisor NIF Automatic Alignment LINUX Cluster • Segment Manager • Sequence Queues Video Sensors Actuator Devices Queues

31. CrosshairGrid CrystalReflection b) Hough Transform a) Weighted Centroid Dark Stop Shot Mask c) Template Match d) Matched Filter Many processing algorithms are used …

32. Tolerance limit OUT OF TOLERANCE! 5x5 (x,y) pixel grid