PERSISTENT SURVEILLANCE FOR

1
Radiographic Dimension Measurement of Dry DVB
Foam Shells
PERSISTENT SURVEILLANCE FOR PIPELINE PROTECTION
AND THREAT INTERDICTION
Haibo Huang Rich Stephens Brian Vermillion Dan
Goodin Bernie Kozioziemski (LLNL)
HAPL Meeting, Livermore, California June 20-21,
2005
IFT/P2005-072
2
Summary

• IFE program uses 4.1 mm O.D. foam shells
• Require dimension variations measured to lt1 mm
• Optical characterization requires immersion in
  index-matching fluid.
• X-Radiograph system already developed tested
• Contact images on high resolution film
• High precision film digitizer
• Analysis algorithm to handle extreme noise
• For the first time, large dry DVB foam shells can
  be measured

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IFE Point Design for DVB Foam Shells
Average Foam Wall 289 20 mm
Non-concentricity (NC) lt 1
NC (OD/ID Center Offset)/WallAverage
equivalent to WallMax-WallMin lt 6 mm
CH Wall (1-5) 1 mm Out-Of-Round
(OOR) lt 1
OOR(ODmax-ODmin)/RadiusAverage
equivalent to Rmax-Rmin 10 mm
4100 200 mm

• Sufficient to measure interface radii vs angle to
  1 mm

4
Foam is difficult to characterize
interior
wall

• Visible light measurements require index matching
  fluid
• Time-consuming
• Potential dimension errors
• OD changes by 1-5
• Thicker CH, larger OD change
• X-radiographs are noisy due to large density
  fluctuations
• Obscures interfaces

100 mm
Area Average
Single line
Transmission (a.u.)
Radius (um)
5
X-radiography works when digitized properly

• 12bit, 4 MB, Cooled CCD
• Measure whole shell to 0.8 mm
• Plan APO Microscope lens
• Flat field gt CCD compatible
• Large N.A. gt high resolution
• Type K1a film
• Finest grain
• Glass substrate gt stable
• Software
• Noise reduction and rejection
• Edge analysis

6
Accurate interface profiling require lens
correction

• Must correct lens distortion
• Calibrate with stage micrometer
• Verify with circular standards
• Each lens calibrated separately

3µm pixel error
Does radius and shape change with position?
7
Foam structure causes unique analysis problems

• Traditional vision-based analysis does not work
  with low contrast, noisy image
• Reduce noise by azimuthal averaging
• Reject noise by data correlation
• Limit search range
• Interface very wavy with thin overcoat
• Flattening (Step 3)
• Extended interface structure
• Fresnel simulation determines offset

8
Capturing edge information
1) Inspect thickness variation by 360 unwrapping
Angle
Radius
2) Sharpen interface with 2nd derivative
D. Bernat, R.B. Stephens, Fusion Technology, V31,
P473, 1997
Angle
Radius
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Mapping interface requires careful consideration
3) Sharp outside edge good for auto alignment
Separates wavy interfaces gt narrows search range
4) Reject noise by correlating peak/valley
locations
Reduces the image to a set of R(q) files
Angle
Radius
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Calculating interfaces and walls
5) Unflatten and record data
4X lens radius measurement repeatability lt0.4 mm
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Correcting Walls
6) Apply offset correction (under development)

• Measured profile has width
• Relation fixed between profile and interface
• Specific to shell type and lens
• Described by markers (peak/valley) and offsets
• Offset understood by modeling
• Affected by phase contrast, pixel size, X-ray
  spectrum etc.

12
Porosity may affect interface sharpness

• Phase contrast shows as white ring at the sharp
  interfaces of dissimilar materials
• Strong at CH/RF foam, CH/Be interfaces
• but not for CH/DVB Diffused due to pore size?

50 mm
50 mm
0.1 mm pore
1 mm pore
CH on DVB foam
CH on RF Foam
13
Estimated X-Radiography Capabilities
After applying offsets determined by Fresnel
calculation
14
Special concerns for DVB foam shells

• Use low mag. 2nd derivative analysis for foam
• May not resolve thin CH overcoat
• But get the complete foam radius profile
• Determines foam wall, shell diameter, OOR and NC
• Use high mag. transmission analysis for CH
• Noise too high for 2nd derivative method
• Measure local CH wall thickness
• Do NOT apply the offsets for Be/GDP shells
• Offsets specific to shell type and shell size

15
Future Possibilities

• Noise analysis could give quantitative opacity
  variation
• IFE specification lt0.3 density variation over
  50-100um
• No characterization method yet
• Calculate sample opacity from film transmission
• Film model already developed for the ICF program
• Orthogonal views allow 3D NC measurement
• 90 Rotating device
• While sample stays in XRF holder