Presented by Lane Carlson 1 M. Tillack 1, J. Stromsoe 1, N. Alexander 2, G. Flint 2, D. Goodin 2, R. Petzoldt 2 ( 1 UCSD, 2 General Atomics) HAPL Project Workshop Madison, WI Oct , 2008 Improving the Accuracy of a Target Engagement Demonstration IFT\P

Hit-on-the-fly experiment has demonstrated improved engagement on moving targets 1)Implementation of a camera to capture the glint return signal gives a more repeatable & dependable signal. 2)Vacuum chamber nearing completion. 3)Step-by-step improvements have yielded better engagement: Oct µm engagement April µm 42 µm (1  ) engagement for targets in ± 1.5 mm range. Final Requirement: 20 µm engagement accuracy in (x,y,z) at ~20 m (10 -6 )

Tabletop experiment demonstrates key elements of a power plant engagement system Drop tower Crossing sensors Glint laser Coincidence sensor Poisson spot laser Steering mirror Driver beam

Initially used a position sensitive detector (PSD) to detect glint return –PSD spec limits position accuracy to ~50 µm –Non-linear near edges of sensor Camera has replaced PSD and has been fully implemented Noah 4mm x 4mm PSD Basler GigE camera Using a camera allows for direct, linear geometric position reporting of the glint centroid. –Camera accuracy and resolution 1 µm with energy centroiding techniques.

Camera tracks Poisson spot to determine target’s transverse position Poisson spot system is active in: 1.Pre-steering prediction Poisson spot tacking & pre-steering Target released Chamber center ± 1.5 mm Target trajectory Glint location Time 2. Correction for large wedge angle (won’t be necessary in a power plant due to 20 m standoff) 5 ms/div Driver pulse Glint pulse Pre-steering instructions Final steering instructions

Poisson spot system predicts and sets camera’s area of interest (AOI) 6 mm x 4 mm camera image of glint return 80 x 80 pixel AOI 3.Setting glint camera’s AOI Less pixels = faster download, processing time Final Timing Sequence 1.Glint triggers 2.Move AOI using PS prediction 3.Capture image 4.Send to host computer 5.Compute centroid and mirror instructions 6.Steer mirror TOTAL TIME = < 3.0 ms

C1 C2 Initial testing conducted in air from 1.5 m drop tower Crossing sensors Dropper Gravity yields a consistent “injector” for testing, 5.5 m/s after 1.5 m Vacuum chuck releases target Clear view along trajectory Placement accuracy ± 1.5 mm

New vacuum chamber will permit engagement of lightweight targets In air, wake effects on target are minimal for SS BBs but substantial for lightweight targets. 2 m tall Crossing sensors Dropping chamber Engagement chamber In vacuum: –Spurious eddies & wake effects will be eliminated –Prototypic of power plant –Will permit engagement of lightweight targets

Tri-dropper will improve placement accuracy of lightweight targets in vacuum Recoil-free pin extraction ensures precise target release Pins retract for unobscured view of target trajectory Tri-dropper ~25 cm wide Linear ball bearings Solenoids Placement accuracy < 1mm in air w/ SS BB 4-mm BB Ruby-tipped pins 10 drops on carbon paper

High-frame rate camera confirms simultaneous pin extraction

Construction and leak-checking of vacuum chamber is underway Dropping mechanism

Dropping mechanism allows uninterrupted and repeatable target dropping in vacuum

Crossing sensors are implemented into sturdy vacuum-compatible design Photo diode LED Previous design CS1 CS2

Time (ms) Function 0Detect 1 st crossing 50Detect 2 nd crossing, predict glint/driver trigger time 0-244Poisson spot tracking, alignment beam centering by mirror 240Camera’s AOI set 244Glint laser triggered, glint return captured by camera 245Glint return centroid found, steering calculated 246Mirror steered 250Driver pulsed, target engaged, accuracy verified Real-time computers, fast cameras, and LabView software monitor and control all system functions Crossing sensors RT timing & triggering system Glint laser Steering mirror Alignment/ driver laser Alignment/ driver laser LabView host computer RT Poisson spot tracking computer Poisson spot tracking camera Data acquisition I/O card signal trigger control LAN light source Network switch Glint camera Poisson spot laser Verification camera

Identified error sources that contribute to engagement Compare individual errors to observed engagement errors Systematic identification and reduction of errors yields insight on major contributors (Numbers in brackets do not contribute)

A.4:1 mag, defocused B.Focused glint return C.Focused, small aperture D.1:1 magnification E.1:1 mag, improved calibr. F.Glint camera replaces PSD G.Stable beam splitter, small delta steering H.Vacuum chamber and others Systematic error reduction yields step-by-step engagement improvements New data points

Scatter plots of engagement results show tighter spread Dropping in air, stainless steel BB, 5.5 m/s Shows driver beam center incident on 4 mm target August µm RMS error August µm RMS error

We expect substantially reduced errors with full implementation of vacuum chamber  With full implementation of the vacuum chamber and mirror S/N improvement, we can reasonably expect to attain ~20 µm engagement based on these numbers.

Future effort focuses on completing demo and achieving 20 µm engagement goal In summary: We have improved the demonstration of engagement accuracy to 42 µm (RMS). Next steps: Fully implement vacuum chamber, tri-dropper, and mirror. Engage lightweight targets in vacuum. Long-term effort: Mate with a prototypic injector in vacuum.

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