Presented by Lane Carlson1

M. Tillack1, J. Stromsoe1,N. Alexander2, G. Flint2, D. Goodin2, R. Petzoldt2

(1UCSD, 2General Atomics)

HAPL Project WorkshopMadison, WI

Oct. 22-23, 2008

Improving the Accuracy of a Target Engagement

Demonstration

IFT\P2008-082

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 2007 - 150 µm engagement

• April 2008 - 80 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

Tim

e

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-steeringinstructions

Final steeringinstructions

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 Sequence1. Glint triggers2. Move AOI using PS prediction3. Capture image4. Send to host computer5. Compute centroid and mirror

instructions6. 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

QuickTime™ and aCinepak decompressor

are needed to see this picture.

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

QuickTime™ and aPhoto - JPEG decompressor

are needed to see this picture.

Crossing sensors are implemented into sturdy vacuum-compatible design

Photo diodeLED

Previous design

CS1

CS2

Time (ms)

Function

0 Detect 1st crossing

50 Detect 2nd crossing, predict glint/driver trigger time

0-244 Poisson spot tracking, alignment beam centering by mirror

240 Camera’s AOI set

244 Glint laser triggered, glint return captured by camera

245 Glint return centroid found, steering calculated

246 Mirror steered

250 Driver pulsed, target engaged, accuracy verified

Real-time computers, fast cameras, and LabView software monitor and control all system functions

Crossing sensorsCrossing sensors

RT timing & triggering

system

RT timing & triggering

system

Glint laserGlint laser

Steering mirrorSteering mirror

Alignment/driver laserAlignment/driver laser

LabView host

computer

LabView host

computer

RT Poisson spot tracking

computer

RT Poisson spot tracking

computer

Poisson spot

tracking camera

Poisson spot

tracking camera

Dataacquisition

I/O card

signal

triggercontrol

LAN

light source

Networkswitch

Glint camera

Glint camera

Poisson spot laser

Poisson spot laser

Verification camera

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)

Target Engagement ImprovementsDriver beam ovefilling target in flight

0

20

40

60

80

100

120

140

160

A B C D E F G H

Improvement

Total Engagement (µm)

Total eng. error

Total RMS eng. error

PSD limit

Goal

A. 4:1 mag,

defocusedB. Focused glint

returnC. Focused, small

apertureD. 1:1 magnificationE. 1:1 mag, improved

calibr.F. Glint camera

replaces PSDG. 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

targetAugust 2007

150 µm RMS error

August 2008

42 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:In summary:

• We have improved the demonstration of engagement accuracy to 42 µm (RMS).

Next steps:Next steps:• Fully implement vacuum chamber, tri-dropper,

and mirror.• Engage lightweight targets in vacuum.

Long-term effort:Long-term effort:

• Mate with a prototypic injector in vacuum.

End of slideshow