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Here we go Charles, your Bassetite sample under XRF via X-Ray tube, shown here in LINEAR representation to give an idea of proportion, +/- sensor efficiency and beam peak energy. Before anyone runs out and installs a LIXI or any other source like it, keep in mind the safety equipment, measures and training that must accompany that investment. Below is a picture rare picture showing just the tip of the iceberg- an L Block, of which I own and use a dozen, along with lead glass plates and bricks up to 2" etc. etc.plus a full sized rolling lead "wall" shield, with lead glass window, not to mention the lead garments, and especially the low energy ion-chamber type X-Ray test equipment. Staying out of the beam is important, but the insidious danger are scattered rays that appear where they would not likely be expected. The lower the energy either being generated, or that is left once a beam is deflected, the more it is absorbed by biologicals. Specialized beam detectors as used in the counting room.

It is still early but here are some of the strongest peaks: Fe Y Zr I'll send the .mca later when I have some decent counts. Charles

Portable, not handheld! LIXI C-Arm X-Ray Head and controller Graded shield/sample chamber Amptek Si-PIN Sensor Lid closed ready to make test run Always running near minimum

One of the half-dozen or so minerals used in the study to compare various exciters and sensors used for XRF and Gamma Spectrometry. First up is the "Microlite in Rose Muscovite" In one of the Am-X8 exciter jigs with Amptek Silicon Detector. Attached are the .mca files for the 14,400 second isotope scan, then the 150 second X-Ray tube scan (set at only 10 microamps). Since the Rb K X-Rays could have been interfered with by the Np-237 X-Rays from the source, the X-Ray tube scan removed any doubt. Geo

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: https://www.mindat.org/photo-969849.html 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: Nb 101.88% Fe 35.76% Ta 15.4% Mn 2.54% Y 0.279% 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. Also plotted is a samarskite from Little Patsy. It has a relatively high Y component. Charles

This is a scan that ran for 1 1/2 days using Am241 to excite. It has a lot of stuff in it and I will need everybody's help to interpret it (i.e. Dud). One complicating factor is that even with the Am241 the count rate was quite low. This causes the Am241 Np peaks (along with Au and Ag) to appear so they have to be sorted out. Here are my notes in the comment box: bassetite? White Signal Fe2+(UO2)2(PO4)2·10H2O main elements identified: Fe Pb Rb Y Sn Te Cs Ba Ce RbKa1 could be ULa1&2 YKa1 could be RbKb1 NpLb2 seems too big and could contain YKb1 Charles

Setup is Amptek 1-2-3 SDD Sensor/MCA, the X-Ray tube excited ones were with a LIXI-Kevex microfocus low power X-Ray tube, parameters listed in the scans. Current settings are always in microamps not milliamaps. kVp= peak voltage of Bremsstahlung X-Ray, always below the tungsten target K edge. Isotope excited ones are with an Am X 8 ring, various attack angles, 90/45/22.5 degrees and those parameters will be listed. US Steel cent, showing Fe core and Zn plating. SIlver "War Nickel": Have fun Geo

Sent: Sunday, January 19, 2020 11:19 AM To: [email protected] Subject: [XRF] Currency XRF Quiz Here’s Geo’s 1958 copper nickel in log space. What do we have here? Anyone?, anyone? Beuller?... Beuller? Dud Since no one had a correct answer and undoubtedly the question will come up on any future final exams the answer is: First peak is the Si escape peak at 6.3 keV from Cu Ka at 8.05 keV (8.05 Ka – 1.74 Si Ka) The next 3 peaks are the characteristic X-rays from Ni Ka1 at 7.48, Cu Ka1 at 8.05, and Cu Kb1 at 8.9 keV The next set of peaks (first clue) looks just like the Ni and Cu characteristic x-ray complex. It does that because it’s the sum peaks of the Ni and Cu due to the high count rate (46% dead time remember) and high concentrations. The first peak at 15.6 keV is the coincident sum peak of 8.05 keV Cu and the 7.52 keV Ni The second peak at 16.1 is the sum peak of the 8.05 Cu and 8.05 Cu The third peak at 16.9 is the sum peak of the 8.05 Cu and the 8.9 Cu. Sum peaks are 2 photons arriving at the detector at the same time. That can be a Ka+Ka or Ka + Kb and a mix between high concentration elements as seen here. This can also be seen with coincident decay (i.e. Co-60) and in high concentration samples with a high count rate.. Keep the sample at a distance rather than close up (for an gamma spec sample not XRF). Keep your Dead time less than 10%. The escape peaks occur when the Si in the detector absorbs some of the energy from an x-ray and produces a peak (Si Ka) 1.74 keV below the element’s Ka or La . You’ll see this in the lower Z elements or at high concentration. Dud From: [email protected] [mailto:[email protected]] On Behalf Of Dude everyone Sent: Sunday, January 19, 2020 11:19 AM To: [email protected] Subject: [XRF] Currency XRF Quiz Here’s Geo’s 1958 copper nickel in log space. What do we have here? Anyone?, anyone? Beuller?... Beuller? Dud _._,_._,_

Here’s Geo’s 1958 copper nickel in log space. What do we have here? Anyone?, anyone? Beuller?... Beuller? Dud

Charles, Attached is a bigger blowup of the Strickland. The Cursor is at Ti Ka 4.5 keV. The Si Escape peak is 9 channels to the right at 4.66 keV (on the right side of the 2 equal sized peaks past the 4.6 KeV grid line) There is as much signal in this as there is noise and both peaks will be merged if they are there as it’s at the detector’s resolution limit. Something is trying to be born here but clearly this needs a lot more counts with better granularity to say much about it. Dud From: Charles David Young <charlesdavidyoung@...>

Thanks Steve I’ll pass it on. The assay 107 does show the incorporation of Ti which can be seen in Charles’s XRF at 4.5 between ROI 2 and 3 as an isolated peak. I can find no other emission other than Fe that could represent the Fe peak. Mn at 5.9 is the closest and it is seen to the left and adjacent to the Fe at 6.4 keV. The 107 assay does show some As and Si but no Rb which is curious as Charles’s xrf does show Rb in a broad mixed peak. Was it not found or not calibrated and reported? Note that both Fe and Rb are found in micas and I wonder if maybe the host rock had some mica in it that got illuminated and showed up? Was this a single xtal or xtal on matrix. I don’t have the natural source.mca file to look at. Ca I’m sure is there but it’s covered due to the low end detector noise. ROI keV 1 As 1.28 2 Rb 1.74 or possibly Si 3 Fe 6.4 4 Ta 8.1 5 Ta 9.3 6 As 10.5 7 Rb 13.4 8 Nb 16.6 9 Am-241 59.5

Steve Dubyk gave me these small (1mm) microlite crystals. They provide a good application of Am241 to excite because otherwise their internal radiation is very small. https://www.mindat.org/photo-969401.html I plotted the microlite in blue against the Am241 in orange to help weed out the microlite peaks from possible inteference with Np peaks. One thing I have observed about Am241 is that it does not seem to excite much above 30keV. The peaks below 20keV really light up though. For instance, TaKa1 is hardly visible but the TaLa1 and La2 peaks dominate the lower region. Thus, I have chosen to display only the lower region to get better visibility into what is going on there. Indeed it seems that if an element is present it will show up there where the Si-PIN is most sensitive, especially with Am241. It seems that the only peaks of real significance are Ta, Fe, and Nb. The Fe could have an Am241 component but it seems to be too strong to only be from Am241. Once again the NbKa1 peak is curious but seems to be confirmed by a nice NbKb peak. Steve, do you have an analysis of this specimen? It would be very interesting to compare. Charles

This is an interesting specimen in that it was identified as both columbite (Fe2+Nb2O6) and samarskite (YFe3+Nb2O8), the only difference being the presence of Y. Here is a comparison of 2 different sides, one with a columbite crystal and the other a more shiny fracture. The latter shows the Y, conspicuously missing from the columbite side. https://www.mindat.org/photo-999240.html

I bought a couple of nice microlites from Tony Albini a while back. One was actually identified as xenotime but my NaI scan showed a strong Ta presence so I proposed that it was actually microlite and Tony agreed. The Si-PIN scans confirm these ids, which are remarkable for the number of elements identified that can be in microlite. https://www.mindat.org/photo-998272.html https://www.mindat.org/photo-969390.html Microlite is a complex mineral with many possible elements. One constant though is the presence of Ta, which really stands out in my attached NaI scans. In the Si-PIN scans the Ta up at 57.5 is not as prominent but I believe that is because the Si-PIN is not as sensitive in the higher energies. microlite formula: A2-mTa2X6-wZ-n The A site may host Na, Ca, Sr, Pb2+, Sn2+, Sb3+, Y, U, or H2O or Ag, Mn, Ba, Fe2+, Bi3+, Ce, Sc or Th. elements identified by Si-PIN: Ta Hf Pt Sn Rb Ce Fe Yb

For using Am241 as an exciter I decided to label all the associated peaks so that I could ignore them when looking for target peaks. To my surprise I saw what could only be Au peaks so I looked up Am241 in wikipedia. Check out my attached scan. The only peak I am unsure about is the one about 11.9. Br? The process for making the americium used in the buttons on ionization-type smoke detectors begins with americium dioxide. The AmO2 is thoroughly mixed with gold, shaped into a briquette, and fused by pressure and heat at over 1470 °F (800 °C). A backing of silver and a front covering of gold (or an alloy of gold or palladium) are applied to the briquette and sealed by hot forging. The briquette is then processed through several stages of cold rolling to achieve the desired thickness and levels of radiation emission. The final thickness is about 0.008 inches (0.2 mm), with the gold cover representing about one percent of the thickness. The resulting foil strip, which is about 0.8 inches (20 mm) wide, is cut into sections 39 inches (1 meter) long. The sources are punched out of the foil strip. Each disc, about 0.2 inches (5 mm) in diameter, is mounted in a metal holder, usually made of aluminium. The holder is the housing, which is the majority of what is seen on the button. The thin rim on the holder is rolled over to completely seal the cut edge around the disc.[15]

In case there was any doubt: Ka-Kb heavy metals do exist and can be stimulated quite easily with a source of energy above the K-edge. Ba-133 10 uCi Disk Source (31 keV X-Ray, 81 keV Gamma) + Kr-85 (Beta-251 average) thin Pb lead sheet "stamp" target. Sensor= CdTe

A nice peak from pure silicon, the sample is 1 3/4" diameter slice of pure silicon, grown as a single crystal, in long bars.Small by today's standards. XRF via Am_X8 exciter, SSD detector, 30 minutes. Geo