XRF at the WSU GeoAnalytical Lab - University of Western Ontario
XRF at the WSU GeoAnalytical Lab - University of Western Ontario
XRF at the WSU GeoAnalytical Lab - University of Western Ontario
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� diamond grinding in w<strong>at</strong>er is fast (total 2-3 min/bead)<br />
� final cleaning in sonic<strong>at</strong>or with ethanol<br />
� lapping removes diffusion pr<strong>of</strong>ile <strong>at</strong> contact <strong>of</strong> glass and crucible - final surface finish is 15 microns<br />
29 mm 15 mm 8 mm<br />
Mask Sample wt Minimum wt<br />
29 mm 3.5 gm 1.5 gm<br />
15 mm 1.1 gm 0.5(?) gm<br />
8 mm 0.4 gm 0.2(?) gm<br />
Sizing/lapping <strong>of</strong> graphite fused beads<br />
machined templ<strong>at</strong>e assures accur<strong>at</strong>e sizing<br />
We calibr<strong>at</strong>e with smaller masks for beads down to 8 mm diameter<br />
Not simply a reduction in counts across <strong>the</strong> spectrum - varies with 2<strong>the</strong>ta<br />
because <strong>of</strong> crystal geometry so many parameters change<br />
Precision varies as square root <strong>of</strong> counts so degraded by factor ~2 each<br />
step down in size - we count twice as long <strong>at</strong> 15 mm and 4x <strong>at</strong> 8 mm<br />
Small sample analyses<br />
1600<br />
1400<br />
1200<br />
1000<br />
800<br />
600<br />
400<br />
200<br />
0<br />
Concentr<strong>at</strong>ion (ppm)<br />
vs. m<strong>at</strong>rix corrected<br />
intensity (kcps)<br />
Zr calibr<strong>at</strong>ion <strong>at</strong> 8 mm<br />
SEE = 4.2 ppm; n =14<br />
r 2 = 0.9999<br />
0 0.2 0.4 0.6 0.8 1
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