Target Tracking Experimental System Update

1
Target Tracking Experimental System
Update Neil Alexander, Dan Frey, Dan Goodin,
Kevin Jonestrask, Bob Stemke, Emanuil Valmianski
and Brian Vermillion Presented by Ron
Petzoldt Princeton HAPL Meeting October 27-28,
2004
2
Progress since June meeting

• Since the UCLA meeting we have
• Modified detectors at station 2 and at the DCC
  for increased field of view
• Calibrated all detectors (with stationary
  stage)
• Aligned detectors with target trajectory
• Performed full length (air rifle) testing of
  tracking system
• Tracked pellets at all three detectors for
  vertical position
• Tracked pellet arrival times at all three
  detectors
• Correlated data from all three detector stations
  and determined initial position prediction
  accuracy

3
Two position measurements are used to predict
final target position ( 14 ?m accuracy required)
Pump
Sabot Removal
Detector Light Source
Potential Flight Paths
Gas Removal
Target
S
a
b
ot
Detector D2
Detector DCC
Detector D1
3.5 m
4.5 m
9 m
DCC measurements are compared to prediction
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Transverse Position Detection accomplished with
laser illuminated line scan camera
Tracking Detector Assembly
Line Scan Camera
Collimating Lens
Line Generating Laser Diode
Target
1 meter
Axial timing is measured with photodiodes and
time to digital converter
5
We have improved the tracking detectors with a
number of modifications
Timing circuit board
Line scan camera
Detector 1 14 mm FOV
Illuminating lasers
Larger window
Lens
Detector 2, 3 30 mm FOV
Line scan camera
Collimating lens
All three position detector stations are now
operational and working together
6
Detectors were calibrated with translation stages
Repeatability is lt 1 pixel
1 Pixel 6 ?m
Flat field corrected data
Surrogate target
Micrometer
Calibration stages
In use, flat field correction is done
milliseconds prior to each measurement
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The spherical aberration in our initial setup was
evaluated
25 mm
Target height
Laser
0 mm
Measurements taken in two horizontal positions
10 Pixel 60 micron error
Rays diverge through most of the beam
Spherical aberration can be improved by a more
complex set of optics.next step
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Pellet arrival times were measured by the
tracking system
Example Data Set
(Insert photo of me firing air rifle)
Surrogate target injector

• Shots taken in air.
• 0.14 speed uncertainty due to aerodynamic
  slowing.
• Would cause 12 mm axial position prediction error.

9
Pellets were tracked by all three detectors
DCC Tracking (raw data)
sDCC 4.4 mm spred error 2.0 mm

Missing shots were not tracked at all detectors

• Primary causes of prediction error
• Aerodynamic effects on pellet trajectory
• Horizontal effect on vertical position
  measurements (spherical aberration)
• The air rifle was useful for initial integrated
  tracking system testing

10
Summary and Conclusions

• Target tracking and timing systems are
  operational and tracking pellets
• Steps to improve the position prediction
  accuracy
• Provide better collimation
• Shoot into vacuum for accurate timing and
  ballistic trajectory
• Next we will implement the real time position
  and timing prediction software