Presented by Lane Carlson1 M. Tillack1, T. Lorentz1, J. Spalding1, D. Turnbull1
Wallace, Wayne, Host has reference to this Academic Journal, PHwiki organized this Journal Presented by Lane Carlson1 M. Tillack1, T. Lorentz1, J. Spalding1, D. Turnbull1 N. Alex in addition to er2, G. Flint2, D. Goodin2, R. Petzoldt2 (1UCSD, 2General Atomics) HAPL Project Review PPPL, Princeton, NJ December 12-13, 2006 Progress on Target Tracking & Engagement Demonstration Omnipresent Target Engagement Requirement All individual tracking in addition to engagement components have been operated successfully. All components necessary as long as a glint-only hit-on-the-fly demo have been integrated in addition to are operational. Final Key Requirement: 20 µm engagement accuracy in (x,y,z) at ~20 m (10-6) Current tabletop target engagement demo is complete with one simulated driver beam Glint laser now in operation Poisson & fringe counting systems not used in glint-only demo
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Hit-on-the-fly experiment has demonstrated engagement on moving target Update time of Poisson spot centroiding algorithm down from 10 ms to 3.5 ms in software. Fringes off falling target counted over 3 mm. Using crossing sensors, the timing & triggering system triggers all necessary lasers/components on-the-fly. Engaged moving targets with a simulated driver beam by using the glint return signal to steer a fast steering mirror. Verification system has been used to measure error in target engagement. 150 µm range 6 µm resolution A range of tracking/engagement scenarios call as long as different requirements Example 1: no in-chamber gas, glint provides final mirror steering Example 2: in-flight, pre-steering corrections by Poisson, fringe counter 1 Transverse Target Tracking Using Poisson Spot Centroid
Reduced region of interest (ROI) technique further improves update time Update time reduced from 10 ms to 3.5 ms by implementing a dynamic ROI in software. Number of pixels to process is reduced from 307k to 10k. 4mm sphere on translation stage The smaller ROI assumes the target will not move more than a few pixels between frames. ROI is recalculated each frame to follow the Poisson spot centroid. 30x less pixels New centroiding algorithm implements dynamic ROI Target position update time: 3.5 ms (5 µm 1) Closing in on goal of 1-2 ms 2 Axial Target Tracking Using Interferometic Fringe Counting
Fringe counting has been demonstrated over 3 mm Lower-noise photo-detector Higher-power laser (60 mW) => Fringes off falling target counted over 3 mm Similar intensities Mini drop tower setup Target releasing from vacuum needle Free-falling target Signal processing required to obtain countable signal 5 ms/div 20 µs/div time 5 V/div 3 Crossing Sensors & Axial Position Prediction Crossing sensors & real-time operating system compute predicted target location on-the-fly Last time: Established crossing sensors to be sufficiently precise (45 µm 1) to trigger glint laser. Overview of Timing Sequence: Timing sequence initiated by target crossing C1. C2 crossing yields target velocity. Velocity info used to trigger alignment beam, glint laser, verification camera, in addition to driver beam. Disparity between predicted in addition to actual target location is detected by PSD in addition to corrected by steering mirror Timing in addition to triggering system fully operational as long as our demo
4 Glint System All necessary components have been integrated as long as glint-only target engagement demo New Wave 35 mJ, 1064 nm glint laser Optics In Motion fast steering mirror Simulated wedged dichroic mirror Pulsed diode laser (simulated driver) Glint laser – final component of hit-on-the-fly demo has been installed Wedged dichroic mirror compensates as long as glint/chamber center offset Verification camera Simulated wedged dichroic mirror 1 cm
We have engaged moving targets with a simulated driver beam Targets fully engaged ~20% of the time (in 150 µm verification range) Last time we used a simulated glint return from a stationary target to steer a mirror. Now, we have used the real glint return signal from a moving target (5 m/s) to steer a simulated driver beam to engage the target. But does not meet the 20 µm spec yet Snapshots of engaged targets 150 µm diam. verification beamlets 40% 40% 20% 150 µm verification range outside range outside range Ef as long as t to improve engagement accuracy to 20 µm must address & minimize all uncertainties Errors & uncertainties from every subsystem contribute to engagement accuracy. We are working to underst in addition to errors in addition to to address each one. Air fluctuations, sensor noise, b in addition to width limitations, response times PSD signal with ground-looping Erratic 50 mV signal translates to significant mirror steering! (100s microns) Most dominant uncertainty so far is deciphering the glint return on PSD Error contributions to engagement accuracy: Reading glint return (PSD, LabView) ~100s µm Air fluctuations ~20 µm Verification camera ~12 µm Mirror pointing ~6 µm Resolved by plugging all electrical components into same circuit Glint return is used to make one final steering mirror correction depending on PSD reading Glint return on PSD gives targets final position. LabView reads PSD signal, then calculates steering gain to give FSM. LabView loop time is 50 ± 20 µs due to non-deterministic operating system. Glint return on PSD X Glint return on PSD Y Glint laser q-switch Steering signal to FSM X-axis Inconsistent voltage readings grossly in addition to falsely steer the mirror. 2V/div
Peak-hold circuit picks off PSD voltage more consistently than software Peak-hold circuit holds the peak voltage until LabView can read it. Also researching other ways to read glint (photo-diode, quad-cell) Signal held by peak det. (not mirror comm in addition to ) Glint returns on PSD => More work must be done on glint return characterization, PSD response, error/noise reduction. Rise time may also influence reading consistency 2V/div 5 Engagement Verification as long as Hit-on-the-fly Demo Applet post-processes snapshot to verify target engagement accuracy No target Target offset to the right ~ 100 µm Target equally eclipsing beamlets Applet computes light centroid of obscured in addition to un-obscured beamlets. Resolution of 6 µm, 150 µm range target PSD beamlets imaginary target shadow
Summary of progress & plans 1 Moving target engaged by simulated driver beam 2 Transverse Tracking System Using Poisson Spot: Progress: Improved update time to 3.5 ms using dynamic ROI Plans: Implement into system to help pre-steer mirror 3 Axial Tracking & Triggering Prediction: Progress: Faithfully triggering glint, simulated driver beam & verification camera. Also, fringes off moving target counted over 3 mm 4 Glint System: Progress: Glinted target & steered FSM to engage in-flight target Plans: Better characterize glint return & PSD response to meet 20 µm goal 5 Target Engagement Verification: Progress: Engagement verification resolution of 6 µm, 150 µm range Future Goals to Consider: – increase speed capability to couple with a 50 m/s injector – add more driver beamlines at different angles.
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