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
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.
“0.1 micron” pore size filter 1µ Surface pores > 0.1µ will occur Designed to remove 99.98% of particles >0.1µ Goal of Eichrom product is uniform pore size 15,000x
Two sides of the filter “Inside” and “Outside” of the Roll Stock (5,000x magnification) Inside Lot Outside Lot
Peak Resolution Evaluation FWHM (keV) Am-243 Outside Am-243 Inside Am-241 Outside Am-241 Inside Ave =34Ave =33Ave = 36Ave = 39 Std dev = 7Std dev = 8Std dev = 4Std dev = 8
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 C , LaF 3 ppt., 50 µg La carrier “Glossy side” up and down
External Results SampleSubstrateOrientationFWHM keV Am-243 recovery Am-241 recovery 1NoGlossy down2898.4% 2NoGlossy down2595.7%95.5% 3NoGlossy up %97.6% 4NoGlossy up %99.3% 5YesGlossy down %96.1% 6YesGlossy down2398.6%97.0% 7YesGlossy up2595.1%94.8% 8YesGlossy up2697.6%95.0%
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.”