John,
I don't know how varied your experience is with different microprobes, but I have a couple questions for you and the forum. I can see that deadtimes can effect the outcome of the concentration of an element to a certain degree. As I mentioned, I am having issues reproducing Mg values on all of my standards with my new JEOL microprobe on both TAP spectrometers, one with LTAP and the other with small TAP. They all come out low when using Fo100 or Fo97 as the calibration standard (both of these standards are synthetic). I will be running tests to check other TAP elements over the next couple days.
Pete McSwiggen at JEOL thinks that now that the deadtimes are tuned on my new JEOL my problems should be over. He thinks there is an issue with my Fo97 and possibly the Fo100 standards, which I find very hard to believe. Though the deadtime correction tuning helped, it did not eliminate the low Mg problem. It just reduced the magnitude of the shift a bit. In the past, I have worked on an JEOL 8600, an ARL-SEMQ, and two Cameca SX-100. All four were not tuned for deadtimes beyond the manufacturers setting. If I remember correctly the SX-100s had flat deadtimes of 3ms for all spectrometers. I have been using the Fo97 as the calibration standard and using the same San Carlos Olivine (NMNH) and Lunar Crater Augite (NMNH), both Jarosewich standards, as reference standards for the last 28 years (on the ARL, and both Cameca probes). All three standards are very homogeneous. I have never had this issue on the past three probes.
Could the tuning of the deadtimes on my new JEOL and changing of instruments from the Cameca to the JEOL change the compositions of my standards by a full 0.50 wt% MgO in the San Carlos (nominal 49.4 wt% MgO, but now analyzing around 48.9) or 0.2 wt% MgO in the Augite (nominal 17.35 wt% MgO, now analyzing around 17.15) while using the identical calibration setup?
I have seen in the past round robin sessions where different labs get different compositions for the same reference standard material, but always assumed this was caused by the use of different standards in the setup routine. Is this a similar case?
What is your opinion?
P.S. I realized I had a pure MgO standard in my collection, and as you recommended, I used it as the calibration standard last night. I analyzed the Fo100, the Fo97, my San Carlos olivine, my Lunar Crater augite, a synthetic MgAl2O, a synthetic MgCr2O4, and the pure MgO standard as unknowns. I fixed the compositions for all of the standards and only analyzed Mg to minimize any secondary problems. Analysis of the pure MgO, came out low (average of 99.1 total). I suspect there was some adsorbed water under the carbon coat, so Pete recalculated it back to 100% (multiplied the results by 1.009). The results for the other standards came out surprising to me (after correction). The Fo100 came out high (58.26 instead of 57.3 MgO). The Fo97, the San Carlos, and the Augite all came out nearly perfect, but the MgAl2O4 came out low (27.96 instead of 28.33) and the MgCr2O4 came out very low (20.05 instead of 20.96). I am amazed the strict synthetics do not reproduce nearly as well as the natural samples, but I don't understand why. Shouldn't the synthetics come out on the same trend between zero and the pure MgO by default?
In your "PS" bit, you say that you standardised on pure MgO and remeasured that same MgO as an unknown but came back with 99.1% totals?
Have you checked that the MgO standard was set to use MgO as the standard?
Or that there were no bad points in the standard data set?
I assume the same beam conditions were used for both standard and unknown, and there were no major changes in ambient air pressure or temperature in the lab between standardising and measuring the MgO as an unknown?
Forgot to mention, I did the analysis through the JEOL software, not PfE. I am brand new to PfE and am still using to use the basic features. With the new probe I am trying to learn PfE, the JEOL software and the Bruker EDS software simultaneously. It is a but overwhelming. So there was no setting to do.
There were no bad points, but as I mentioned, I am pretty sure the standard had water trapped under the carbon coat. Same conditions for standard and sample. Whole run was done in less than two hours, and no change in the room conditions. The only proviso is I don't know where the MgO standard was made, so I don't know about its quality.
Quote from: Joe Boesenberg on January 17, 2025, 10:22:14 PMI don't know how varied your experience is with different microprobes, but I have a couple questions for you and the forum. I can see that deadtimes can effect the outcome of the concentration of an element to a certain degree. As I mentioned, I am having issues reproducing Mg values on all of my standards with my new JEOL microprobe on both TAP spectrometers, one with LTAP and the other with small TAP. They all come out low when using Fo100 or Fo97 as the calibration standard (both of these standards are synthetic). I will be running tests to check other TAP elements over the next couple days.
Me? I started on an ARL SEMQ but purchased and performed acceptance testing on two Cameca instruments.
https://smf.probesoftware.com/index.php?topic=924.msg9758#msg9758
First question: when you analyze Fo100 against Fo97 do they agree with each other at high precision with high accuracy?
The real question on standards here is: "what is the truth"?
In my book I would trust a high purity single crystal synthetic MgO, Mg2SiO4 and/or Mg2Al2O4, assuming that they has been properly characterized for trace elements and gave consistent results from XRD. Based on the FIGMAS round robin tests we did on such materials in 2023 or so, a group of us (on both JEOL and Cameca instruments) got excellent results analyzing MgAl2O4 using MgO and Al2O3 as primary standards:
https://smf.probesoftware.com/index.php?topic=1466.msg11076#msg11076
even at 120 nA! With dead times properly calibrated using the constant k-ratio method of course...
Quote from: Joe Boesenberg on January 17, 2025, 10:22:14 PMPete McSwiggen at JEOL thinks that now that the deadtimes are tuned on my new JEOL my problems should be over. He thinks there is an issue with my Fo97 and possibly the Fo100 standards, which I find very hard to believe. Though the deadtime correction tuning helped, it did not eliminate the low Mg problem. It just reduced the magnitude of the shift a bit. In the past, I have worked on an JEOL 8600, an ARL-SEMQ, and two Cameca SX-100. All four were not tuned for deadtimes beyond the manufacturers setting. If I remember correctly the SX-100s had flat deadtimes of 3ms for all spectrometers. I have been using the Fo97 as the calibration standard and using the same San Carlos Olivine (NMNH) and Lunar Crater Augite (NMNH), both Jarosewich standards, as reference standards for the last 28 years (on the ARL, and both Cameca probes). All three standards are very homogeneous. I have never had this issue on the past three probes.
I would tend to agree. Especially at count rates below 30 kcps.
A couple of points though, first regarding dead time calibrations: the "manufacturers settings" are merely a starting point, especially if one is attempting to push accuracy below 2% relative. Especially on a Cameca EPMA which has dead time constants roughly twice the magnitude of JEOL EPMA instruments. But of course it depends on the beam currents used, in other words count rates. The dead time effect is very dependent on count rates. And the dead times change as ones detectors age over time.
On a large TAP crystal because of the relatively low sin theta of Mg Ka, it is easy to get count rates over 30 kcps at typical beam currents. We already know those count rates can be problematic using a traditional linear dead time correction:
https://academic.oup.com/mam/article-abstract/29/3/1096/7165464
Here is what Anette found on her JEOL iHP200F instrument:
Ti Ka dead times, JEOL iHP200F, UBC, von der Handt, 07/01/2022
Sp1 Sp2 Sp3 Sp4 Sp5
PETJ LIFL PETL TAPL LIFL
1.26 1.26 1.27 1.10 1.25 (usec) optimized using constant k-ratio method (six term expression)
1.52 1.36 1.32 1.69 1.36 (usec) JEOL engineer using traditional method
Second, we already know that the San Carlos olivine is a crap standard because it includes a wide range of compositions as documented by John Fournelle and Will Nachlas. Even Gene Jarosewich who performed the original wet chemistry on this material commented in his reports that one must average intensities from many different grains in order to obtain an accurate measurement!
As for Fo97, where was this material obtained? You mentioned it was synthetic, but this sounds like a "doped" (impure) material and therefore it cannot be trusted. Yes, one could characterize it using a technique which is known to be accurate but then there's the question of homogeneity. Therefore my suggestion to utilize instead *high purity* end member synthetics.
Quote from: Joe Boesenberg on January 17, 2025, 10:22:14 PMCould the tuning of the deadtimes on my new JEOL and changing of instruments from the Cameca to the JEOL change the compositions of my standards by a full 0.50 wt% MgO in the San Carlos (nominal 49.4 wt% MgO, but now analyzing around 48.9) or 0.2 wt% MgO in the Augite (nominal 17.35 wt% MgO, now analyzing around 17.15) while using the identical calibration setup?
I need to see averages and standard deviations to judge these numbers. But depending on the difference in the count rates between the primary and secondary standard it could make a difference. One way to mitigate this dead time dependency is to count at very low count rates, say 10 nA. Of course this means counting longer to obtain the necessary statistics for accuracy.
In fact, because most labs have not properly calibrated their dead time constants (e.g., have not utilized a non-linear dead time correction using the constant k-ratio calibration method), a beam current of 10 nA was recommended by Will Nachlas and Aurelien Moy for the MgAl2O4/MgO/Al2O3 round robin measurements.
For what it's worth, I would say is that if your count rates on your standards (for the high concentration elements), are below 30 kcps, the problem is probably not the dead time calibrations. Which is why Will and Aurelien suggested using 10 to 20 nA beam currents for these round robin tests.
The other thing I would do (which is easy with the single mount provided by Will and Aurelien), is to re-polish and re-coat both the primary and secondary standards at the same time. I'm sure if you write Will, he would send you a mount to try...
Another point, which is important for Mg Ka because of the large absorption correction, is to check the effective take off angle for each spectrometer. This is done by measuring k-ratios on multiple spectrometers. A statistically significant difference in the k-ratios between spectrometers indicates a geometry problem either in the spectrometer alignments, stage or column.
This was found to be a serious problem at Cal Tech some years ago. First, that the "hot" Bragg crystals were diffracting asymmetrically (so those were swapped out), and second, the electron column was *not centered* in the spectrometer housing! They had to get a new spectrometer housing for their instrument which took JEOL 4 years to replace!
Here is a specification I utilized in both of my instrument acceptance tests at Berkeley and Oregon:
https://smf.probesoftware.com/index.php?topic=369.msg1948#msg1948
If one does not run this test, one will not know. Here are the results from our SX100 testing at Oregon (see specification 13.3.9 on page 18 here):
https://epmalab.uoregon.edu/reports/Additional%20Specifications%20New.pdf
Quote from: Joe Boesenberg on January 17, 2025, 10:22:14 PMI have seen in the past round robin sessions where different labs get different compositions for the same reference standard material, but always assumed this was caused by the use of different standards in the setup routine. Is this a similar case?
Yes, this is a known problem that different EPMA labs produce *consistently* different results. Or at least it should be well known! This problem is documented in this recent paper:
https://academic.oup.com/petrology/article-abstract/64/2/egac126/6965244?redirectedFrom=PDF
The problem is that each lab utilizes primary standards that do not agree with one another. One culprit is San Carlos olivine as originally described by John Fournelle.
https://ui.adsabs.harvard.edu/abs/2009AGUFM.V31E2009F/abstract
and more recently here:
https://www.sciencedirect.com/science/article/pii/S0009254122002625
Your difficulty getting these standards to agree with each other is actually a service to our community (in spite of your pain!). The fact that our (top!) labs obtain results that are consistently difference from each other should alarm all of us greatly.
Again, read the "Barometers behaving badly..." paper linked above.
The solution I think (after you have and re-polished and re-coated your standard materials (together!), and checked your dead times using constant k-ratios, and checked your spectrometer, stage and column geometries using simultaneous k-ratios, is to
throw away these problematic materials and use high purity end member compositionally constrained synthetic standard materials.
I describe some of these efforts in this presentation:
https://www.youtube.com/watch?v=mOca7-G4FvQ&ab_channel=ProbeSoftwareInc
This is what Will Nachlas, John Fournelle, Aurelien Moy, Ed Vicenzi (and the FIGMAS group and I) have been advocating for decades, and possibly we are starting to make some small progress in this effort.
Quote from: Joe Boesenberg on January 17, 2025, 10:22:14 PMP.S. I realized I had a pure MgO standard in my collection, and as you recommended, I used it as the calibration standard last night. I analyzed the Fo100, the Fo97, my San Carlos olivine, my Lunar Crater augite, a synthetic MgAl2O, a synthetic MgCr2O4, and the pure MgO standard as unknowns. I fixed the compositions for all of the standards and only analyzed Mg to minimize any secondary problems. Analysis of the pure MgO, came out low (average of 99.1 total). I suspect there was some adsorbed water under the carbon coat, so Pete recalculated it back to 100% (multiplied the results by 1.009). The results for the other standards came out surprising to me (after correction). The Fo100 came out high (58.26 instead of 57.3 MgO). The Fo97, the San Carlos, and the Augite all came out nearly perfect, but the MgAl2O4 came out low (27.96 instead of 28.33) and the MgCr2O4 came out very low (20.05 instead of 20.96). I am amazed the strict synthetics do not reproduce nearly as well as the natural samples, but I don't understand why. Shouldn't the synthetics come out on the same trend between zero and the pure MgO by default?
So MgO was the primary standard? Do you know the Ca concentration and was it freshly polished?
Second, results should not be re-normalized like that! There's a problem there and it needs to be looked into... Second, without variances, it is difficult to evaluate these results. Remember just because a material claims to be stoichiometric and pure, does not mean that it is. That is why Will has been carefully characterizing small amounts of these materials using multiple techniques before purchasing larger amounts for distribution.
And yes, ideally these results should all on a line between a blank standard and the primary standard (ideally the pure end member), if these materials are re-polished and re-coated together and the instrument geometries are correct and the dead times well calibrated. Which is pretty much what we saw with the FIGMAS round robin testing. When well characterized materials are compared we obtained excellent results.
That is until each lab goes back to its "favorite" primary standards and then we are consistently different again!
See the use of the Evaluate application in your Probe Software software:
https://smf.probesoftware.com/index.php?topic=340.msg10757#msg10757
In summary:
1. Obtain carefully characterized high purity synthetic materials.
2. Re-polish and re-coat them together.
3. Check your dead time constants using the constant k-ratio method. Adjust the dead time constant until one obtains a constant k-ratio from low count rates to high count rates. This is documented from the Probe for EPMA Help menu.
4. Check your simultaneous k-ratios... do you obtain the same k-ratios within statistics? If your spectrometers do not produce consistent k-ratios you have a spectrometer, stage or column geometry problem.
5. Note that one can measure constant k-ratios and simultaneous k-ratios if you can measure the same line on multiple spectrometers, say Ti Ka on LiF and PET crystals. There are many posts about these measurements on this user forum.
6. Have a beer and relax. This will all get figured out!
I decided to go through my own data and found a couple of analyses using pure synthetic MgO as a primary standard (largest contaminant we found in that material was Ca at ~200 PPM).
So here is a natural (close to end-member) natural diopside that I developed many years ago (largest contaminant was Fe at ~500 PPM):
St 358 Set 1 diopside (Chesterman)
TakeOff = 40.0 KiloVolt = 15.0 Beam Current = 20.0 Beam Size = 5
St 358 Set 1 diopside (Chesterman), Results in Elemental Weight Percents
ELEM: Si Al Fe Mg Cr Ti Mn Ca O SUM
146 25.846 .019 .050 11.129 -.017 -.020 .014 18.377 44.316 99.715
147 25.813 .024 .058 11.075 -.013 -.017 .009 18.492 44.316 99.756
148 25.859 .016 .028 11.084 .031 -.040 .077 18.467 44.316 99.838
149 25.890 .028 .070 11.127 .020 .009 .029 18.462 44.316 99.951
150 25.831 .015 .058 11.039 .004 .000 .047 18.638 44.316 99.948
AVER: 25.848 .020 .053 11.091 .005 -.014 .035 18.487 44.316 99.842
SDEV: .029 .006 .016 .038 .021 .019 .028 .095 .000 .108
SERR: .013 .003 .007 .017 .009 .008 .012 .042 .000
%RSD: .11 27.38 29.46 .34 401.67 -137.67 79.57 .51 .00
PUBL: 25.925 .016 .047 11.192 n.a. .000 .000 18.489 44.316 99.985
%VAR: -.30 27.92 12.68 -.90 --- .00 .00 (-.01) .00
DIFF: -.077 .004 .006 -.101 --- .000 .000 (.00) .000
STDS: 14 13 395 12 24 22 25 358 ---
As one can see, the percent variance (%VAR:) from our "accepted" value is -0.90 % relative or -0.1% absolute (DIFF:) . Here's another secondary standard of synthetic Mg2SiO4:
St 273 Set 1 Mg2SiO4 (magnesium olivine) synthetic
TakeOff = 40.0 KiloVolt = 15.0 Beam Current = 20.0 Beam Size = 5
St 273 Set 1 Mg2SiO4 (magnesium olivine) synthetic, Results in Elemental Weight Percents
ELEM: Si Al Fe Mg Cr Ti Mn Ca O SUM
136 19.958 .006 .040 34.650 -.007 -.020 .008 .000 45.486 100.122
137 19.954 -.011 -.022 34.794 -.013 .000 .033 .009 45.486 100.230
138 19.901 .004 .024 34.639 .015 .000 -.007 .014 45.486 100.076
139 19.948 .005 .013 34.678 -.004 .023 -.019 .005 45.486 100.135
140 19.907 -.006 -.008 34.703 -.016 .042 .004 .013 45.486 100.125
AVER: 19.934 -.001 .010 34.693 -.005 .009 .004 .008 45.486 100.138
SDEV: .027 .008 .025 .062 .012 .024 .019 .006 .000 .057
SERR: .012 .003 .011 .028 .005 .011 .009 .003 .000
%RSD: .14-1119.61 252.60 .18 -236.08 264.62 519.51 69.67 .00
PUBL: 19.960 n.a. n.a. 34.554 n.a. n.a. n.a. n.a. 45.486 100.000
%VAR: -.13 --- --- .40 --- --- --- --- .00
DIFF: -.026 --- --- .139 --- --- --- --- .000
STDS: 14 13 395 12 24 22 25 358 ---
This time we're within 0.40% relative or 0.14% absolute. So reasonable accuracy can be achieved using high purity end member synthetics!
If one cannot attain this sort of accuracy, there is a problem that needs to be determined and corrected. This is the value of using these extrapolations from high concentrations to lower concentrations. Such measurements ensure your instrument is operating properly.
Quote from: Joe Boesenberg on January 18, 2025, 07:44:57 AMForgot to mention, I did the analysis through the JEOL software, not PfE. I am brand new to PfE and am still using to use the basic features. With the new probe I am trying to learn PfE, the JEOL software and the Bruker EDS software simultaneously. It is a but overwhelming. So there was no setting to do.
There were no bad points, but as I mentioned, I am pretty sure the standard had water trapped under the carbon coat. Same conditions for standard and sample. Whole run was done in less than two hours, and no change in the room conditions. The only proviso is I don't know where the MgO standard was made, so I don't know about its quality.
I think the first thing I would be doing would be proving to myself that the machine can standardise on a material and re-measure that same material and get 100% totals. If your primary/calibration standards are homogeneous, then this shouldn't be a problem (unless as you say there is an issue with the polish, as on your MgO).
If this comes out ok, then I would start measuring the unknown at increasing concentrations and plotting c/s/nA vs c/s and see how that looks: this will highlight any deadtime issues as you
should get a horizontal line. If it starts to dip off at higher count rates, then your deadtime is too low.
What background positions are you using for Mg?
When attempting to obtain high accuracy from high concentrations to low concentrations (high to low count rates), it is essential to look at all possible sources of error. For example, are the PHA settings properly tuned?
In cases where we are extrapolating from high to low count rates, we need to center the PHA peak in the PHA voltage range and keep the baseline as low as possible. See here for details:
https://smf.probesoftware.com/index.php?topic=1526.msg11802#msg11802
Quote from: JonF on January 21, 2025, 02:37:42 AMWhat background positions are you using for Mg?
Good point. Yes, if the accuracy seems to get worse as one approaches minor concentrations, one should consider problems with the background.
Because JEOL has a smaller Rowland circle than the Cameca, one may need to locate one's off-peak positions further away from the peak, and the background may be more curved.
The above diopside and Mg2SiO4 quant data was acquired on the Berkeley SX51 and here is the Mg peak scanned on a chromite sample for checking off-peak positions:
(https://smf.probesoftware.com/gallery/395_21_01_25_7_36_42.png)
Zooming in we see this:
(https://smf.probesoftware.com/gallery/395_21_01_25_7_36_57.png)
Note the secondary lines relatively close to the main emission line. Always a good idea to carefully scan the region around the off-peak positions and the main peak. The tails of the main emission line need to be avoided for best accuracy.
Another thought, does the relative error away from your "known" concentrations increase or decrease as you approach lower concentrations? If they increase with decreasing concentration, that would seem to indicate more of a problem with your background measurement, rather than your primary standard.
It's also worth mentioning that tests performed using the constant k-ratio or simultaneous k-ratios methods (which can be done at the same time), do NOT require that the compositions of the two materials be known. The two materials for the k-ratio could even be unknown, so long as their concentrations (count rates) are sufficiently different, and the materials are beam stable and homogeneous.
All we are trying to do is check that the k-ratios of the two materials are "constant" as the beam current is increased (for the constant k-ratio method) and/or that the same k-ratios (within statistics) are obtained from multiple spectrometers when using the same emission line, independent of the Bragg crystals utilized (for the simultaneous k-ratio method).
John
First, let me say. THANKS to all who responded here on via email. Really appreciate the help. I THINK my problem are the standard blocks. I repolished my 4 main standard blocks in August prior to the new probe and though I left them in my carbon coater under 10-7 torr vacuum for two days, they apparently still did not dry out. I can see water boiling under the carbon coat with the beam on for several standards. I suspect the entire blocks have water which is screwing up the calibration. Not quite sure why Mg (and Si) are primarily effected and not the other non-TAP elements, but maybe the Fo97 and Diopside I used for Mg and Si calibration had substantial trapped water in them. I need to repolish, dry out thoroughly, recoat and retry the analysis.
To answer some of the questions posed in the forum:
Yes, I have used the Fo100 and Rockport Fayalite to analyze the Fo97 and it comes out fine with good stoichiometry. I don't think I have ever actually analyzed the Fo100 until last week when I found I had MgO (periclase) as a standard.
I recognize that there are issues with San Carlos, but mount I use has chips from a single grain, and though it is not the exact NMNH quoted composition (it has 9.8 wt% FeO instead of 9.55), it is quite homogeneous. I don't use the San Carlos for a primary calibration standard. I use it along with the Lunar Crater Augite as reference standards for oliv and pyx runs. They have nice mid-range compositions that are often in the same range as the unknowns, so they are a good judge of the calibration accuracy.
Fo97 was made at URI in the 90's. I think Steve Carey made it. I came across it at AMNH in the 90's via Charlie Mandeville, who was the probe manager at AMNH (and was one of Steve's former grad students).
All of my analyses were run at 15kv and 20nA and 30-45 sec count times on peak with a point beam. On the JEOL, I have been using 4.1 mm for the negative backgrd and 4.7 mm for the positive background. These are considerably larger than the -1150 and 1150 backgrounds I used on the SX-100 for Mg Ka.
Yes, I used MgO for the first time for the analysis. I forgot I had it. Not sure about its CaO content. Has to be pretty low. Don't see any peak in the Bruker EDS. It was one of the standard blocks I polished in August.
The concern I had/have with the analyses I was getting, was they were all clustered, but none of the analyses were ever over the nominal MgO concentrations.
Quote from: Joe Boesenberg on January 23, 2025, 06:17:39 PMFirst, let me say. THANKS to all who responded here on via email. Really appreciate the help. I THINK my problem are the standard blocks. I repolished my 4 main standard blocks in August prior to the new probe and though I left them in my carbon coater under 10-7 torr vacuum for two days, they apparently still did not dry out. I can see water boiling under the carbon coat with the beam on for several standards. I suspect the entire blocks have water which is screwing up the calibration. Not quite sure why Mg (and Si) are primarily effected and not the other non-TAP elements, but maybe the Fo97 and Diopside I used for Mg and Si calibration had substantial trapped water in them. I need to repolish, dry out thoroughly, recoat and retry the analysis.
Sounds good. There is nothing wrong with re-polishing and re-coating your standards, ideally in the same mount at the same time. At Oregon we have a small drying oven that sits at 60C all the time and everything goes in there after polishing and cleaning before coating for 5 to 8 minutes to remove any adsorbed water.
Mg Ka is a relatively low energy x-ray so surface prep is important.
Quote from: Joe Boesenberg on January 23, 2025, 06:17:39 PMYes, I have used the Fo100 and Rockport Fayalite to analyze the Fo97 and it comes out fine with good stoichiometry. I don't think I have ever actually analyzed the Fo100 until last week when I found I had MgO (periclase) as a standard.
Good. What happens when you analyze Fo100 using MgO as a primary standard? Assuming they both really are 99.999% pure (and that needs to be checked!).
Quote from: Joe Boesenberg on January 23, 2025, 06:17:39 PMI recognize that there are issues with San Carlos, but mount I use has chips from a single grain, and though it is not the exact NMNH quoted composition (it has 9.8 wt% FeO instead of 9.55), it is quite homogeneous. I don't use the San Carlos for a primary calibration standard. I use it along with the Lunar Crater Augite as reference standards for oliv and pyx runs. They have nice mid-range compositions that are often in the same range as the unknowns, so they are a good judge of the calibration accuracy.
How do you know this olivine is 9.8wt% FeO. Is this from another probe measurement? If so, it is worthless because we are testing the EPMA accuracy!
Quote from: Joe Boesenberg on January 23, 2025, 06:17:39 PMFo97 was made at URI in the 90's. I think Steve Carey made it. I came across it at AMNH in the 90's via Charlie Mandeville, who was the probe manager at AMNH (and was one of Steve's former grad students).
Again how do we know its composition? Check your synthetic MgO and Fo100 for traces and use those! Or get well characterized materials from Will Nachlas or buy them.
Quote from: Joe Boesenberg on January 23, 2025, 06:17:39 PMYes, I used MgO for the first time for the analysis. I forgot I had it. Not sure about its CaO content. Has to be pretty low. Don't see any peak in the Bruker EDS. It was one of the standard blocks I polished in August.
But again, you don't know its purity. You need 99.999% purity, then (maybe) you can assume stoichiometry in freshly polished materials. Contact Will Nachlas and buy some materials from his sources. He would be happy to share what he has found.
MgO, MgAl2O4 and Mg2SiO4 plus a 99.999% SiO2 and Al2O3 to check for blank accuracy.
Note, that if you're trying to characterize trace elements, you can use the EPMA assuming you also run a blank sample to check for trace accuracy. But one cannot use EPMA to determine major element chemistry! That is circular reasoning...
Quote from: Joe Boesenberg on January 23, 2025, 06:17:39 PMThe concern I had/have with the analyses I was getting, was they were all clustered, but none of the analyses were ever over the nominal MgO concentrations.
Yes, that is the problem. But we need to get back to first principles to determine exactly what is going on here. If I were you and I wanted to know how well my instrument is performing I would get 99.999% pure synthetic MgO, MgAl2O4 and Mg2SiO4. Also 99.999% SiO2 and Al2O3 for zero blank checks. I'm going to summarize here one last time:
1. Obtain these high purity synthetic materials. Mount and polish, clean, dry and coat them together.
2. Make sure your PHA settings are "wide open". That is, when your PHA peak (on the highest concentration material, e.g., MgO) is roughly centered in your PHA distribution, set your baseline to 0.5 volts or so and leave the differential mode OFF. This way, as you go to lower count rates and the PHA peak shifts up, your counter response will remain linear:
https://smf.probesoftware.com/index.php?topic=1466.msg11450#msg11450
3. You already performed dead time calibrations using the constant k-ratio method so you should be good there.
https://smf.probesoftware.com/index.php?topic=1466.msg11102#msg11102
The point being, one should be able to obtain the same k-ratios in say MgAl2O4 (secondary) and MgO (primary) at count rates (beam currents) from 1 kcps to 300 kcps using the logarithmic dead time correction.
4. Measure simultaneous k-ratios on multiple spectrometers, using two materials with a large absorption correction relative to each other, e.g., MgO and Mg2SiO4:
https://smf.probesoftware.com/index.php?topic=1569.msg12249#msg12249
The point being to stress the absorption correction to determine that all our spectrometers yield the same k-ratio within statistics. See here to model this in CalcZAF:
https://smf.probesoftware.com/index.php?topic=598.msg12062#msg12062
These simultaneous k-ratio checks test our spectrometer, stage and column geometries.
5. Once these above checks have been performed we are ready to proceed with quantitative tests using these same synthetic materials. For example, measure MgO (60.303 wt% Mg) as the primary standard, next measure Mg2SiO4 (34.554 wt% Mg) and MgAl2O4 (17.084 wt% Mg) as secondary standards.
Of course it doesn't hurt to measure synthetic Al2O3 or SiO2 as blank samples for zero Mg also. The Evaluate application is very helpful for these comparisons:
https://smf.probesoftware.com/index.php?topic=340.msg10757#msg10757
This difficulty you are experiencing is not only a problem in your lab. We see this in every EPMA lab. We are all having a crisis of inter-laboratory reproducibility. We know there's a problem in the microanalysis community because we can see that different labs consistently report different values for the same materials :
https://smf.probesoftware.com/index.php?topic=1415.0
See Wieser (2023) attached below.
Let's fix it by using the same high purity, homogeneous synthetic standards in our labs and performing the above tests on our instruments!
You can see water boiling off? This much water?? Seriously??
If you could post a photo of the block then its manufacturer and probable epoxy might be identifiable. That would give you options for "safe" solvents to try.
Light elements would be more impacted than other materials, whether this is water or oil or some other substance. We have to ask what would cause a measurable amount of water to adhere to clean polished surfaces. I suppose that the water-ethanol azeotrope is this stable under vacuum but that is 96% ethanol and 4% water. Neither is a recommended solvent for mounts.
VERI important to use clean dry HPLC grade solvents. One litre each of isopropanol and isohexane should last a year. Use a portion ONCE and discard to a beaker to evaporate in a fume hood. If you have some already in clean bottles, then adding anhydrous Na2SO4 sodium sulfate will dehydrate sufficiently to be able to clean mounts. Add the solid until large clear crystals form. Mush is evidence that water is still present.
We've always just used 190 proof ethanol (not denatured which contains other solvents), rubbing with a Kimwipe until dry, followed by heating in a 60C oven for 5 minutes to remove any adsorbed water, then immediately coating to avoid these issues.
My problems with the Mg and Si concentrations were finally solved over this past weekend. First, new dead time corrections were applied to all five spectrometers (thanks to Scott Boroughs for helping do this) which eliminated about half the concentration shift I was seeing on my analyzed standards. Second, I polished off the carbon coat and spent four days baking the water out of the standard blocks and using a mini vacuum chamber that I could place on a hot plate at 120F. After four days, I recoated and did a full calibration. The new results largely show the proper concentrations I expected. There are still some differences between the concentrations that I get when I analyze olivine versus pyroxene, but I think this is a function of the standards I am using, not anything to do with the mechanics of the probe. Thanks to everyone for the advice.
In response to Crystal Grower, yes, you can see water boiling under the carbon coat when the beam is on the standard. This is a fairly common issue, since most of the people I know still polish with a slurry of water and grit, not alcohol, which can really smell up a room in a university. You can sometimes evaporate the water source with the beam if it is small. You most often see this on the optical microscope particular when doing relative high magnification work with the BSE or SE running.
My problem was probably exacerbated by the fact that I polished and carbon coated in August, one of the most humid months of the year along east coast.
Joe
100% isopropanol didn't cause a smell when used for the last manual finish polish with 0.25u alumina. The polishing station was in the opposite corner from the standard sized fume hood.
Fine grained Rhum anorthosite that was cut under water NEVER dried out even in a vacuum oven at 200C. The water seeped between the grains faster than you might think. It sparked like crazy under an electron beam.
There is also a consideration that some sulfide minerals (for example MoS2) are more than slightly soluble in water under pressure.
And I hate to think what a metals mount looks like after the grinding with water: you can kiss your Fe, Zn, Ag, Cd, Th goodbye. Ditto for a product mounted into Woods metal.
Well, it turns out, after checking and double-checking everything mentioned in the above posts regarding dead time calibrations, standard polishing, standard compositions, etc., Joe Boesenberg at Brown is still having issues getting reasonable numbers when extrapolating from high Mg concentrations to low Mg concentrations on both TAP spectrometers. Interestingly, his Al numbers seem to be OK. His Mg k-ratios always appear to be a few percent lower than expected.
Here is a measurement where he measured an MgCr2O4 synthetic material using synthetic Mg2SiO4 as a primary standard:
ELEM: Si Fe Mg O Cr SUM
316 .058 .024 11.482 32.592 54.079 98.235
317 .055 .033 11.463 32.579 54.079 98.210
318 .059 .032 11.569 32.652 54.079 98.392
319 .048 .035 11.502 32.596 54.079 98.260
320 .054 .019 11.499 32.597 54.079 98.249
AVER: .055 .028 11.503 32.603 54.079 98.269
SDEV: .004 .007 .040 .028 .000 .071
SERR: .002 .003 .018 .013 .000
%RSD: 8.10 23.10 .35 .09 .00
PUBL: n.a. n.a. 12.640 33.281 54.079 100.000
%VAR: --- --- -8.99 -2.04 .00
DIFF: --- --- -1.137 -.678 .000
STDS: 226 72 226 --- ---
As one can see, the totals are low due to the low Mg.
But finally, he was able to obtain an MgO, Al2O3, MgAl2O4 mount from Will Nachlas (from the FIGMAS round robin tests last year), and polished and re-coated it and ran some tests. Here is a measurement of the MgAl2O4, again using synthetic MgSi2O4 as a primary standard:
ELEM: Si Fe Mg O Al SUM
341 .037 .007 16.352 44.546 37.932 98.875
342 .040 .016 16.458 44.622 37.932 99.068
343 .032 .000 16.553 44.670 37.932 99.187
344 .034 .009 16.413 44.584 37.932 98.972
345 .033 .002 16.392 44.567 37.932 98.926
AVER: .035 .007 16.434 44.598 37.932 99.006
SDEV: .003 .006 .077 .049 .000 .124
SERR: .002 .003 .034 .022 .000
%RSD: 9.72 94.27 .47 .11 .00
PUBL: n.a. n.a. 17.084 44.984 37.932 100.000
%VAR: --- --- -3.81 -.86 .00
DIFF: --- --- -.650 -.386 .000
STDS: 226 72 226 --- ---
Again, Mg is low. Then he made a new run, this time using the MgO and Al2O3 as primary standards in the MgO, Al2O3 and MgAl2O4 FIGMAS mount and measuring both Mg and Al in the MgAl2O4 synthetic spinel:
ELEM: Mg Al O SUM
311 16.575 37.920 44.641 99.136
312 16.641 37.975 44.732 99.348
313 16.574 37.649 44.398 98.621
314 16.570 37.686 44.429 98.685
315 16.602 37.616 44.388 98.606
AVER: 16.592 37.769 44.518 98.879
SDEV: .030 .166 .158 .341
SERR: .013 .074 .071
%RSD: .18 .44 .36
PUBL: 17.084 37.931 44.985 100.000
%VAR: -2.88 -.43 -1.04
DIFF: -.491 -.162 -.467
STDS: 411 410 ---
and again a second time after running all three standards again:
ELEM: Mg Al O SUM
326 16.679 38.260 45.011 99.951
327 16.678 38.102 44.870 99.649
328 16.575 38.162 44.855 99.592
329 16.426 37.705 44.351 98.483
330 16.527 38.003 44.683 99.213
AVER: 16.577 38.046 44.754 99.378
SDEV: .107 .212 .254 .565
SERR: .048 .095 .113
%RSD: .65 .56 .57
PUBL: 17.084 37.931 44.985 100.000
%VAR: -2.97 .30 -.51
DIFF: -.507 .115 -.231
STDS: 411 410 ---
So again, Mg appears to be low, but Al seems OK.
Note that Mg is on one spectrometer (SP1), but Al is on another spectrometer (SP3). Therefore we begin to speculate about the spectrometer alignment at higher sin thetas and Pete McSwiggen, whom we had been working with on these issues), had a very interesting idea to test this hypothesis... more about this in the next post!
By the way, if one is concerned about the possibility of the MgO having a surface layer of hydrated MgO (brucite), and contributing to the low k-ratios in the previous post, that doesn't make sense because if the primary standard had a lower concentration of Mg, that would make the k-ratios in the Mg secondary standards higher, not lower.
Another point: why are we using Mg Ka and Al Ka for these tests? It's because the absorption corrections for these extrapolations from their primary standards are quite large, which is why they were selected in the first place (since we are interested in testing the geometry/alignment, that is,
the effective takeoff angle of our instrument!). Here is a matrix model for Al and Mg Ka in MgAl2O4:
ELEMENT ABSCOR FLUCOR ZEDCOR ZAFCOR STP-POW BKS-COR F(x)u Ec Eo/Ec MACs
Al ka 1.3734 1.0000 1.0450 1.4351 1.0647 .9815 .6461 1.5600 9.6154 1603.98
Mg ka 1.3033 .9810 1.0120 1.2938 1.0233 .9889 .6648 1.3050 11.4943 1464.54
O ka 1.9089 .9988 .9574 1.8254 .9420 1.0164 .3671 .5317 28.2114 3976.77
Even better is the MgCr2O4 synthetic that Joe had obtained from Oak Ridge lab some time ago:
ELEMENT ABSCOR FLUCOR ZEDCOR ZAFCOR STP-POW BKS-COR F(x)u Ec Eo/Ec MACs
Cr ka .9971 1.0000 1.0967 1.0935 1.1389 .9629 .9827 5.9900 2.5042 73.0353
Mg ka 1.9447 .9996 .9507 1.8481 .9194 1.0340 .4456 1.3050 11.4943 3200.17
O ka 1.4877 .9937 .8922 1.3189 .8445 1.0565 .4711 .5317 28.2114 2754.86
An ~90% absorption correction is pretty impressive! Does anyone know where we can obtain more of this MgCr2O4 synthetic material?
Anyway to continue... so during a discussion with Pete McSwiggen and Joe Boesenberg about what might be going on with these low Mg Ka k-ratios, Pete suggested we try and measure Mg Ka k-ratios using both 1st order and 2nd order Bragg reflections. Because the k-ratios should be the same for both 1st and 2nd orders, if the spectrometer is properly aligned. Here are these nominal spectrometer positions as calculated by CalcZAF:
Spectro position for mg ka on TAP (140 mm), is 107.798 (with refractive index correction, k= 0.00218)
Spectro position for mg ka (II) on TAP (140 mm), is 215.2433 (with refractive index correction, k= 0.00218)
What a brilliant idea by Pete! I suggest we call this the Bragg order k-ratio test and include these in our instrument acceptance testing from now on:
https://epmalab.uoregon.edu/pdfs/Donovan_Community%20Specifications%20for%20EPMA-SEM.pdf
also see the topic here:
https://smf.probesoftware.com/index.php?topic=369.0
So then Joe tuned up Al and Mg Ka (I) and Al and Mg Ka (II) and here is what he obtained for Al Ka extrapolating from Al2O3 to MgAl2O4:
(https://smf.probesoftware.com/gallery/395_29_03_25_7_30_23.png)
So pretty reproducible! Next for Mg Ka:
(https://smf.probesoftware.com/gallery/395_29_03_25_7_30_38.png)
Ok, I'd say there's a spectrometer/crystal alignment problem that gets worse at higher sin thetas!
The point being that whatever the two material compositions actually are, the k-ratios for these two different Bragg orders should be the same within statistics.
JEOL is now checking Joe's spectrometers, but in the meantime if anyone would like to perform some of these Bragg order k-ratio tests themselves, we would be very interested in seeing what you obtain!
And do check this new topic devoted to this spectrometer Bragg order-ratio alignment testing:
https://smf.probesoftware.com/index.php?topic=1739.0
Hi All
So I thought I would update you on the microprobe adventure/disaster I had. As many of you know, a new JEOL ISP-100 was installed at Brown in Sept-Oct. 2024. After several delays, the microprobe and Bruker EDS were installed by mid-December. Scott Boroughs visited in early January 2025 to install PfE, which was essentially the last part of the installation. While teaching me PfE, Scott corrected the dead times on the spectrometers for me, and then we started doing quantitative test analyses on olivines and pyroxenes. Problems showed up immediately. We were getting low totals (low 98s), with Mg consistently low (4-5% relative), Si sometimes coming out high and sometimes low, and Al seemed okay nearly every time. We couldn't explain what was going on. Scott left after the PFE installation and I talked to JEOL about my poor analyses, who basically suggested it was a problem with my standards, not my spectrometers. I did some additional analyses and soon realized the errors with Si and Mg on TAPL were duplicated on the TAPJ. Both crystals were giving the same wrong answers and to the same magnitude. Sometime around this point I chimed in on the forum and started asking questions and many of you suggested various tests. I re-carbon coated my standards in the meantime and initially thought I had solved my problems. I soon realized however that I had simply had a fortuitous accident in analysis that I misinterpreted. So I continued to do various test analyses to no avail. In February, JEOL sent a service engineer to tweak the two TAP spectrometers and to see if they could find anything wrong. The engineer found nothing wrong, so nothing changed analytically. I was still always getting low totals and specifically low Mg. My suspicion was the TAP crystals were either somehow not properly aligned or the program that the JEOL engineers used to align the spectrometers was somehow giving consistent, but wrong results for the TAP crystals.
So after being told repeatedly that it was a problem with my standards through most of March, and now frustrated beyond compare, I asked John Donovan to look over my shoulder while I did some simple olivine analyses. He kindly agreed. My argument was simple. Even if many of my standards are wrong (and I have worked with many of these for near two decades), I should be able to take a synthetic Fo100 and a near endmember fayalite (Rockport), and get nearly 100% totals on any unknown olivine by analyzing Fe, Mg and Si. However, I could not. I kept getting totals of 97-98 and MgO was always low. John was quickly convinced something weird was going on, so he sent me the FIGMAS Al2O3-MgO-spinel standard block via Will Nachlas. When I couldn't get realistic results with those standards, he came to the conclusion that either the two TAP crystals, the column and/or the stage were misaligned. John then graciously talked to Pete McSwiggen at JEOL on my behalf and convinced him that the problem with my instrument was real.
At this point we started doing a test designed by Pete and discussed by John in this forum, the so called Bragg k-ratio test, which involves looking at both the first and second order peaks for both Mg and Al on the TAP crystals. In March, this is what my TAPL looked like using those standards.
(https://smf.probesoftware.com/gallery/2892_25_06_25_8_09_49.jpeg)
Edit by John: The Bragg order k-ratio test that Joe is referring to is discussed here in more detail:
https://smf.probesoftware.com/index.php?topic=1739.0
The k-ratio value that most labs got for the first order Mg, when they did the round robin with this standard block, was 0.272. The ideal Al value should be 0.605. As you can see the first order Mg is a bit low, but the second order Mg ratio is quite a bit off (and should be theoretically be giving the same ratio value as the first order), while Al appears nearly perfect.
Given the shift on the Bragg test, Pete talked to the JEOL engineers, and they came back in late April to my lab to re-align the two TAP crystals. After they left, I re-ran the Bragg k-ratio tests only to discover that both crystals were still misaligned, and were now slightly worse than before.
(https://smf.probesoftware.com/gallery/2892_25_06_25_8_10_32.jpeg)
(https://smf.probesoftware.com/gallery/2892_25_06_25_8_11_01.jpeg)
Now in May, John and I had a meeting with about 7 people from JEOL via Zoom. The conclusion of the meeting was Pete, as the JEOL microprobe expert, needed to do extensive testing on the instrument to determine the problem. Meanwhile, all of the data from the tests I had run were sent to the engineers main JEOL office in Japan.
So Pete basically started from scratch and documented all of the tests and parameters on the probe. He analyzed a bunch of olivines and re-did the Bragg tests. One of the issues Pete found with the Bragg test was that there was a peak shift in Mg on the MgO versus the spinel. The effect is not drastic, but certainly was making the problem look mildly worse than what it was.
Meanwhile, both John and myself had heard many good things about one of the JEOL engineers, John Glass. I had mentioned John G. to the JEOL service manager, Keith, at some point, and by sheer dumb luck, John G. was sent to my lab in June to attempt to re-align the two TAP crystals for a third time. After re-aligning the TAPL, we initially didn't think much had changed. We ran the Bragg test while John G. was there. The shift difference between the first and second order had certainly gotten better, but the second order was still about 1% low.
(https://smf.probesoftware.com/gallery/2892_25_06_25_8_11_29.jpeg)
Part of the improvement was we were now correcting for the Mg peak shift. John G. left thinking nothing had improved substantially. Before he left, however he mentioned to me that he had done a minor manual re-alignment of the electron column. The next day, almost on a lark, I did a simple three element olivine analysis, wondering how far off MgO still was. To my surprise, the totals were now all clustering around 100%, and the MgO values for the olivines were realistic. John G. came back the following week and re-aligned the TAPJ, and after testing, showed it is nearly perfectly align with respect to both the first and second order peaks of Mg.
(https://smf.probesoftware.com/gallery/2892_25_06_25_8_11_55.jpeg)
Subsequent analysis on olivines showed everything was now analytically reasonable.
Several quandaries remain:
1) What changed during the final re-alignment visits? Was the TAPL crystal that far off from alignment or was there something else weird going on in the column (like a stuck condenser lens), that got freed up when John G. manually re-aligned the column? Up to that time, I had been using the auto alignment function for the tilt and shift of the beam. not manual.
2) Why is there still a 1% shift in Mg for the first order and second order ratios on the TAPL? Is this simply the limit of the alignment accuracy given the rather coarse adjustments possible in aligning the crystal and using the JEOL alignment program?
3) The theoretical value based on CalcZAF, looking at Mg and using MgO and spinel at 15kv should give a k-ratio value of 0.279, not 0.272, which is the avg for all of the FIGMAS labs. A ratio of 0.272 actually correlates with a takeoff angle of around 15 degrees, not 40. Why the difference?
4) Why were the Al ratios always correct, while Mg varied with every new re-alignment attempt?
In the end, the lab is now getting realistic quantitative results, but it took an extra six months, John Donovan, Pete McSwiggen, John Glass, and a whole lot of persistence on my part.
Thanks
Joe
All
I forgot to mention, following all of the re-alignments, both TAP crystals passed whatever spectrometer qualifications the JEOL engineers use to "certify" the spectrometer. The problem I saw is that they appear to use the intensities of certain elements on specific standards, rather than any sort of alignment test or analytical test to pass the spectrometer/crystal.
Cheers
Joe
Quote from: Joe Boesenberg on June 25, 2025, 08:33:14 AMSubsequent analysis on olivines showed everything was now analytically reasonable.
Several quandaries remain:
1) What changed during the final re-alignment visits? Was the TAPL crystal that far off from alignment or was there something else weird going on in the column (like a stuck condenser lens), that got freed up when John G. manually re-aligned the column? Up to that time, I had been using the auto alignment function for the tilt and shift of the beam. not manual.
I find it difficult to believe that the column alignment could be the cause of this problem. It's true that there was an incident back in the 1990s where Cal Tech discovered on their new JEOL 733 that the column had been mounted off-center from the spectrometer circle, so opposing spectrometers produced k-ratios that were either too high or too low. But that was a mechanical offset on the order of many millimeters, so probably a degree of misalignment that could not be duplicated by a mere lens alignment issue:
https://smf.probesoftware.com/index.php?topic=1466.msg11143#msg11143
But it's probably worth recording the current condenser lens values, then run an auto-alignment and re-measure the FIGMAS mount k-ratios.
Quote from: Joe Boesenberg on June 25, 2025, 08:33:14 AM2) Why is there still a 1% shift in Mg for the first order and second order ratios on the TAPL? Is this simply the limit of the alignment accuracy given the rather coarse adjustments possible in aligning the crystal and using the JEOL alignment program?
Good questions. It would be interesting to hear from John Glass how the spectrometer alignments performed by him differed from the methods used by the previous technicians...
Quote from: Joe Boesenberg on June 25, 2025, 08:33:14 AM3) The theoretical value based on CalcZAF, looking at Mg and using MgO and spinel at 15kv should give a k-ratio value of 0.279, not 0.272, which is the avg for all of the FIGMAS labs. A ratio of 0.272 actually correlates with a takeoff angle of around 15 degrees, not 40. Why the difference?
Joe is referring to the FIGMAS round robin k-ratio measurements that were performed on these materials a couple of years ago by a number of labs globally:
(https://smf.probesoftware.com/gallery/395_26_06_25_8_14_20.png)
https://academic.oup.com/mam/article/29/Supplement_1/225/7228643
The theoretical value from CalcZAF very much depends on the matrix correction utilized. Badgerfilm (using XPHI?), predicts a value of around 0.272 which is pretty darn close the average of the experimental measurements. The value of 0.279 from CalcZAF is only about 2.5% different from 0.272 but it very much depends on what specific matrix correction (and MACS) are selected in CalcZAF (which ones did you select?).
And looking at all matrix corrections in an elemental calculation of MgAl2O4 (relative to the pure elements) we get these theoretical k-ratios:
Mg2AlO4, sample 1
40 degrees and 15 keV
LINEMU Henke (LBL, 1985) < 10KeV / CITZMU > 10KeV
"Al K-RAT" "Mg K-RAT" "O K-RAT "
1 .113792 .265524 .266787 Armstrong/Brown/Scott-Love (prZ)
2 .112964 .267640 .265805 Philibert/Duncumb-Reed
3 .110439 .260813 .273097 Heinrich/Duncumb-Reed
4 .111961 .263550 .264162 Love-Scott I
5 .113929 .266351 .265634 Love-Scott II
6 .113103 .264478 .281269 Packwood Phi(prZ) (EPQ-91)
7 .108068 .251155 .267156 Bastin (original) (prZ)
8 .106716 .255334 .260955 Bastin PROZA Phi (prZ) (EPQ-91)
9 .108120 .257614 .260070 Pouchou and Pichoir-Full (PAP)
10 .109804 .259592 .268052 Pouchou and Pichoir-Simplified (XPP)
11 .113928 .265921 .265513 PAP/Donovan and Moy BSC/BKS (prZ)
AVER: .111166 .261634 .267136
SDEV: .002662 .005235 .005830
SERR: .000802 .001579 .001758
MIN: .106716 .251155 .260070
MAX: .113929 .267640 .281269
Looking at the MIN/MAX for Mg Ka we see about a 7% difference! Even just comparing two modern matrix corrections (Armstrong-Brown and PAP), we see a 3% difference. So I wouldn't worry too much about this particular theoretical k-ratio from CalcZAF.
Quote from: Joe Boesenberg on June 25, 2025, 08:33:14 AM4) Why were the Al ratios always correct, while Mg varied with every new re-alignment attempt?
It's another good question. When I performed my own Bragg order k-ratio measurements, I saw both Mg and Al Bragg orders k-ratios looking consistent on two of my TAP spectrometers, but inconsistent only for Mg on one of them:
https://smf.probesoftware.com/index.php?topic=1739.msg13407#msg13407
Why would Mg Ka k-ratio be so much more sensitive to the spectrometer alignment? It's at a higher sin theta than Al Ka and the absorption correction is smaller than for Al Ka...
Quote from: Joe Boesenberg on June 25, 2025, 08:33:14 AMIn the end, the lab is now getting realistic quantitative results, but it took an extra six months, John Donovan, Pete McSwiggen, John Glass, and a whole lot of persistence on my part.
It takes a village! :D