Charles, do you have pure metal element samples?

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I can give you titanium and a few more for use as calibration points.

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By the way the needed correct 5V power supply arrived for my SI-PIN, so It will be back on lone withing a short time.

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Geo

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----- Original Message -----
From: Charles David Young <charlesdavidyoung@...>
To: [email protected]
Cc: Mike Loughlin <loughlin3@...>, Steve Dubyk <sdubyk@...>, Frank Roberts <froberts@...>
Sent: Sat, 18 Jan 2020 13:21:26 -0500 (EST)
Subject: Re: [XRF] XRF - comparing Dud's with my Si-PIN

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Charles,

Based on the reported percentages the assay you are looking at was
done using the Soils mode which is used when looking at PPM level concentrations.
The Soils mode will well over report percent level concentrations? For samples
with percent grade material they would be shot with the Mining Plus mode.? See
if we shot that sample with both modes and use the Mining Plus mode to try a
cross calibrate with.? It’s doubtful that you’ll get a very good cross cal as its
dependent on the element , matrix effects and detector efficiency over energy
as well as detector / x-ray geometry and x-ray flux.?

Cals are done using the Fundamental Parameter approach or by
running each element using a calibration curve.? A cal curve can be built using
an element oxide and blending it down to PPM levels. That curve is still
dependent on distance of the target to the detector / X-ray geometry (also air
temp and moisture content and air density if you want to get picky) but most
importantly is the x-ray flux and beam filtering.? For your case you would have
to normalize it to the Am-241 signal.? The system needs to have a fixed ROI for
each element and you would use the baseline corrected area in that ROI as the
measured parameter. Complicating that are matrix effects where any other peaks that
are intruding in that ROI must be de-convolved from it and the area corrected
for it. A Gaussian correction could be used The most important thing you need
to do is get a handle on the detector/X-ray/ target geometry. It must be the
same all the time. The beam angle to the target and the detector should be
changed from your dual illumination set up to a single beam path and keep the
angle around 30 deg or so to minimize backscatter.

Quantitative gamma ray spectroscopy is much simpler compared to
quantitative XRF and I never trust my XRF reported values without a great deal
of skepticism and review

Dud

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From:[email protected]
[mailto:[email protected]] On Behalf Of Charles David Young
Sent: Saturday, January 18, 2020 5:45 AM
To:[email protected]; Mike Loughlin; Steve Dubyk; Frank Roberts
Subject: [XRF] XRF - comparing Dud's with my Si-PIN

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Nearly 2 years ago (5/23/18) Dud was kind enough to shoot
some of my specimens with his XRF "gun", which has a pinpoint xray
source.? Several of my rocks were found in the rubble piles of the local
rock shop "Tucson Mineral and Gem World", which has been open for
about 60 years.? One piece is large and ugly:

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Looking at my results (blue scan) the Nb peak is off the
charts!? Even more significant is that Dud's results show the same thing:

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Nb 101.88%

Fe 35.76%

Ta 15.4%

Mn 2.54%

Y 0.279%

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Comparing these percentages to the relative heights of the
same peaks on my scan one finds similar proportions.? It is very
satisfying to know that my results largely corroborate those of Dud's.

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Also plotted is a samarskite from Little Patsy.? It has
a relatively high Y component.

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Charles

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