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Resolve™ Filtersfor alpha source preparation
Charleston, SC
May 4, 2004
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Resolve™ Filters
0.1μ polypropylene
25mm disks
Uniform pore size distribution
Quality control appropriate for α-spectrometry
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Product Development/Validation
• Evaluation of Resolve Filters – Comparison with commercially available filters
• Supplier #1
• Supplier #2
– Evaluate performance (alpha spec) and appearance (SEM)
• Validate lot-to-lot variability of supplier
• Assurance of filter quality
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Reported Lot-to-lot VariabilityFilter Supplier #1, 1500x
Known “poor” performing lot Known “well” performing lot
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SEM Comparison
Supplier #1: 1500 X Supplier #2: 1500 X
Eichrom Filter: 1500 X
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Various Lots of Eichrom Filters
Eichrom lot A Eichrom lot B
Eichrom lot D Eichrom lot C
1500x
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Compared to “Poor Performing” Lot
Eichrom lot A Eichrom lot B
Eichrom lot D Eichrom lot C
Known “poor” performing lot
1500x
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Compared to “Well Performing” Lot
Eichrom lot A Eichrom lot B
Eichrom lot D Eichrom lot C
Known “well” performing lot
1500x
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Filter Blank Comparison1000 minute direct count
Measured activity (pCi) in the U-232 region
Supplier #1 Supplier #2 Eichrom Filter
<0.0155 <0.0040 <0.0259
<0.0321 <0.0022 <0.033
<0.0031 <0.0019 <0.0017
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Alpha Spectra – lot 292218
Am-243FWHM: 32 keV
Am-241FWHM: 31 keV
U-232FWHM: 23 keV
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Alpha Spectra: Lot 264825
Am-243FWHM:28 keV
Am-241FWHM: 32 keV
U-232FWHM:29 keV
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Quality Assurance Program
• Screening of filter material roll stock
• SEM– Visual evaluation
– Pore size uniformity: subjective determination
• Alpha Spectrometry– Am-241/243; 50µg Ce
– FWHM each peak <= 50 keV
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A little background on filters
• Design and specification set on “removal” of particles from liquids.
• Nominal “pore size” related to the size of particles removed from the liquid.
• In alpha spec source prep the major consideration should be a uniform pore size to give the best source.
• “Shiny side” apparent on some types of filters indicating different performance each side.
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“0.1 micron” pore size filter
1µSurface pores > 0.1µ
will occur
Designed to remove 99.98% of particles >0.1µ
Goal of Eichrom product is uniform pore size
15,000x
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Resolve “0.1 micron” pore size filter
1µ
15,000x
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Two sides of the filter“Inside” and “Outside” of the Roll Stock
(5,000x magnification)
Inside Lot 292218 Outside Lot 292218
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Peak Resolution EvaluationFWHM (keV)
Am-243
Outside
Am-243
Inside
Am-241
Outside
Am-241
Inside
36 29 41 26
28 22 33 37
31 38 32 45
32 35 37 44
43 42 37 42
43 41
Ave =34 Ave =33 Ave = 36 Ave = 39
Std dev = 7 Std dev = 8 Std dev = 4 Std dev = 8
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External Product Evaluation
• Barry Stewart, Carlsbad EMRC– “These filters are superb for use in making sources for alpha
spectroscopy.”
• Am 241/243
• With and without substrate
• ASTM C1163-98, LaF3 ppt., 50 µg La carrier
• “Glossy side” up and down
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External Results
Sample Substrate Orientation FWHM keV
Am-243 recovery
Am-241 recovery
1 No Glossy down 28 98.4% 98.4%
2 No Glossy down 25 95.7% 95.5%
3 No Glossy up 22 101.9% 97.6%
4 No Glossy up 26 100.2% 99.3%
5 Yes Glossy down 25 100.5% 96.1%
6 Yes Glossy down 23 98.6% 97.0%
7 Yes Glossy up 25 95.1% 94.8%
8 Yes Glossy up 26 97.6% 95.0%
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Summary
• Eichrom now supplies a 0.1µ polypropylene filter for alpha spec source prep
• Pore size uniformity is monitored by SEM analysis and performance is measured by FWHM of Am-243/241 (specification <= 50 keV.)
• Performance demonstrated at Eichrom and externally.
• Both sides of filter are equivalent: no need to “put the shiny side up.”