Transcript ppt

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
Summary
• IFE program uses 4.1 mm O.D. foam shells
• Require dimension variations measured to <1 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
IFE Point Design for DVB Foam Shells
Average Foam Wall: 289 ±20 mm
Non-concentricity (NC): < 1% *
* NC= (OD/ID Center Offset)/WallAverage
equivalent to WallMax-WallMin < 6 mm
CH Wall: (1-5) ±1 mm
Out-Of-Round (OOR): < 1% **
4100 ±200 mm
** OOR=(ODmax-ODmin)/RadiusAverage
equivalent to Rmax-Rmin = 10 mm
• Sufficient to measure interface radii vs angle to ±1 mm
Foam is difficult to characterize
interior
• Visible light measurements
require index matching fluid
wall
100 mm
– Time-consuming
– Potential dimension errors
• OD changes by 1-5%
• Thicker CH, larger OD change
Area Average
• X-radiographs are noisy due
to large density fluctuations
– Obscures interfaces
Transmission (a.u.)
Single line
Radius (um)
X-radiography works when digitized properly
• 12bit, 4 MB, Cooled CCD
– Measure whole shell to 0.8 mm
• Plan APO Microscope lens
– Flat field => CCD compatible
– Large N.A. => high resolution
• Type K1a film
– Finest grain
– Glass substrate => stable
• Software
– Noise reduction and rejection
– Edge analysis
Accurate interface profiling require lens correction
Distortion (um)
3
2
3µm pixel error
1
– Calibrate with stage
micrometer
– Verify with circular
standards
0
-1
-2
-3
-800
• Must correct lens
distortion
-400
0
400
800
Radius from Image Center (um)
Does radius and shape
change with position?
• Each lens calibrated
separately
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
Capturing edge information
Angle
1) Inspect thickness variation by 360˚ unwrapping
Radius
2) Sharpen interface with 2nd derivative
Angle
D. Bernat, R.B. Stephens, Fusion Technology, V31, P473, 1997
Radius
Mapping interface requires careful consideration
3) Sharp outside edge good for auto alignment
Angle
Separates wavy interfaces => narrows search range
visualize wall thickness variation
Radius
4) Reject noise by correlating peak/valley locations
Angle
Reduces the image to a set of R(q) files
Radius
Calculating interfaces and walls
5) Unflatten and record data
4X lens radius measurement repeatability: <0.4 mm
CH Wall (4X)
Wall Variation: 1.1 +/- 0.4 um
Wall Thkn
(um)
Interface Marker (4X)
1500
14
12
10
8
0
100
OD: 3200 ± 3 m m
200
300
Angle (degree)
1400
DVB Foam Wall (4X)
Non-Concentricity: 2.7 +/- 0.2 %
OOR: 0.88 ± 0.04 %
1300
Wall Thkn
(um)
Radius (um)
1600
1200
0
100
200
Angle (degree)
300
352
342
332
0
100
200
Angle (degree)
300
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.
Fresnel calculation of 15umGDP/20umBe @ 10X
Amplitude
GDP surface
Be/GDP interface
Be surface
0.4
2nd Derivative
1
0.2
0
0.5
-0.2
Transmission
0
975
980
985
990
995
1000
1005
Radius (um)
1010
1015
1020
1025
-0.4
1030
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
~0.1 mm pore
CH on RF Foam
50 mm
~1 mm pore
CH on DVB foam
Estimated X-Radiography Capabilities
Lens
Image
resolution
(mm)
Maxim Minim
OD
Resolvable
(mm) Layer (mm)
Profile
Wall thkn Method
Repeat- Accuracy
ability
(mm) *
(mm)
2X
3.7
6.0
10
0.8
1
2nd Deriv.
4X
1.9
3.3
6
0.4
0.5
2nd Deriv.
10X
0.8
1.4
2
N/A
1
Transmission
20X
0.4
0.7
1
N/A
0.5
Transmission
* After applying offsets determined by Fresnel calculation
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
Future Possibilities
• Noise analysis could give quantitative opacity
variation
– IFE specification: <0.3% 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