Author Topic: Questions about MAN background use  (Read 22444 times)

Ben Buse

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Re: Questions about MAN background use
« Reply #75 on: September 06, 2017, 05:17:13 am »
I wonder if its the very high MACs for F in Ti and Cr that are the problem when using absorption correction. I've tried it for TAP crystal where interferences no longer problem - such as Fe. And Ti and Cr still elevated. - Picture to be uploaded

I guess the point is for F when generating MAN curve, avoid interferences and high MACs where possible

Ben
« Last Edit: September 06, 2017, 08:04:50 am by Ben Buse »

Malcolm Roberts

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Re: Questions about MAN background use
« Reply #76 on: September 06, 2017, 11:32:44 pm »
About time I said something. Too quiet for too long. I've taken to always doing F by MAN along with everything else. Ben W... your ideas on stds for this are good and in line with those I tend to apply too. Interferences stick out like a dog's balls and can be removed easily, but make sure you've plenty of standards to give choice. I've been doing this routinely for plenty of apatites - along with the STDI corrections to sort out issues for F analysis on apatite (and restricting the counting time to 40 s) - and phyllosilicates. I make abundant use of references to provide confidence in what I am up to.

Probeman

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Re: Questions about MAN background use
« Reply #77 on: September 08, 2017, 10:09:49 am »
Hi John
Yes its definitely related to displaying the error bars. You are right its a little random when it will happen or not. Sometimes after excluding a standard and updating the fit it will appear, sometimes not. Sometimes after zooming in and out on the MAN fit it will appear, sometimes not...
I will email you the dropbox link for the displayed MDB file

Cheers

Hi Ben,
I found and fixed the MAN display issue you noticed with regard to errors bars and the "Defaults" button.  You should be able to update later tonight and all should be good.
john
« Last Edit: September 08, 2017, 12:30:01 pm by Probeman »
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Probeman

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Re: Questions about MAN background use
« Reply #78 on: September 08, 2017, 12:30:56 pm »
About time I said something. Too quiet for too long. I've taken to always doing F by MAN along with everything else. Ben W... your ideas on stds for this are good and in line with those I tend to apply too. Interferences stick out like a dog's balls and can be removed easily, but make sure you've plenty of standards to give choice. I've been doing this routinely for plenty of apatites - along with the STDI corrections to sort out issues for F analysis on apatite (and restricting the counting time to 40 s) - and phyllosilicates. I make abundant use of references to provide confidence in what I am up to.

Hi Malc,
If you get a chance it would be interesting to see a few of your MAN plots for fluorine.
john
« Last Edit: September 08, 2017, 01:36:56 pm by Probeman »
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BenjaminWade

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Re: Questions about MAN background use
« Reply #79 on: September 11, 2017, 10:43:54 pm »
Hi all
Following on from Ben's data, I have collected a bit more data for F on PC0 and TAP xtals, and attached images of the MAN fits on PC0 and TAP with/without continuum correction. I think at least on my setup, I arguably get a better fit with absorption correction (esp. in the specific higher Z stds I am using).

Interestingly for both PC0 and LTAP, std 559 (TiO2) sits above the plot with continuum absorption correction ON, much like your data. As per the database there is a 6th/7th order overlap of Ti on F for PC0...buts its so miniscule and high order that it has to be inconsequential? There is no reported overlap for Ti on F for TAP?

On PC0, when the absorption correction is removed, the point sits far below the fitted line. Conversely on LTAP when absorption correction is removed the point sits in line with other data.

Any thoughts..?

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Probeman

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Re: Questions about MAN background use
« Reply #80 on: September 11, 2017, 10:50:23 pm »
It has to be an interference from Ti L or oxygen K. Anyone have a high precision scan of F Ka in TiO2 handy?
john
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BenjaminWade

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Re: Questions about MAN background use
« Reply #81 on: September 12, 2017, 05:16:32 pm »
I have one and it's not super high resolution or super high count times (steps of 4 units, 4 sec/point), but I still can't see anything obvious in this scan on one of my TiO2?

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Malcolm Roberts

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Re: Questions about MAN background use
« Reply #82 on: September 13, 2017, 12:56:01 am »
Here you go John... as requested. One of the more recent ones.......

Probeman

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Re: Questions about MAN background use
« Reply #83 on: September 13, 2017, 07:30:55 am »
Hi Malc,
It would be really interesting to see how your TiO2 standard plots on this curve. Do you have a F ka MAN plot with TiO2?
John
« Last Edit: September 13, 2017, 07:48:27 am by Probeman »
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Probeman

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Re: Questions about MAN background use
« Reply #84 on: September 13, 2017, 07:46:55 am »
It would also be interesting to see how Ti metal plots up on these F Ka MAN curves, but it would be important that the Ti metal is freshly polished at least. The F Ka emission volume is very shallow, so the oxidation layer should be as thin as possible so the continuum absorption calculation is accurate.
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Probeman

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Re: Questions about MAN background use
« Reply #85 on: September 13, 2017, 11:50:01 am »
With regard to Ben Wade's MAN plots for F Ka on TAP and the TiO2 outlier, here are some more of my wandering thoughts.

1. The MACs for F Ka in TiO2 are quite large.  For F Ka in Ti the tables MACs (from CalcZAF) are:

MAC value for F Ka in Ti =   14588.35  (LINEMU   Henke (LBL, 1985) < 10KeV / CITZMU > 10KeV)
MAC value for F Ka in Ti =   14540.00  (CITZMU   Heinrich (1966) and Henke and Ebisu (1974))
MAC value for F Ka in Ti =        .00  (MCMASTER McMaster (LLL, 1969) (modified by Rivers))
MAC value for F Ka in Ti =   14986.59  (MAC30    Heinrich (Fit to Goldstein tables, 1987))
MAC value for F Ka in Ti =        .00  (MACJTA   Armstrong (FRAME equations, 1992))
MAC value for F Ka in Ti =   14277.71  (FFAST    Chantler (NIST v 2.1, 2005))
MAC value for F Ka in Ti =   14500.00  (USERMAC  User Defined MAC Table)

and for F ka in O they are:

MAC value for F Ka in O =   12439.63  (LINEMU   Henke (LBL, 1985) < 10KeV / CITZMU > 10KeV)
MAC value for F Ka in O =   12390.00  (CITZMU   Heinrich (1966) and Henke and Ebisu (1974))
MAC value for F Ka in O =        .00  (MCMASTER McMaster (LLL, 1969) (modified by Rivers))
MAC value for F Ka in O =   11927.75  (MAC30    Heinrich (Fit to Goldstein tables, 1987))
MAC value for F Ka in O =        .00  (MACJTA   Armstrong (FRAME equations, 1992))
MAC value for F Ka in O =   11863.62  (FFAST    Chantler (NIST v 2.1, 2005))
MAC value for F Ka in O =   12400.00  (USERMAC  User Defined MAC Table)

I don't have Ben's MDB file handy at the university, but yesterday from home I tried selecting the lowest MAC table values (FFAST), and the MAN fit for TiO2 (#559) was still about the same amount over the trend line.  So it doesn't seem possible that the MAC could be off that much.

Interestingly if we look at the calculated MAN absorption corrections as seen here (from running PFE in DebugMode):

MAN fit data for Mg ka, SP4 TAP, 15 keV
     Std       J  MANSet    Npts   Z-bar     Cps  AbsCor
     504       1       1       1 14.3913 .715813 1.58141
     501       2       1       2 10.7106 .523931 1.49128
     541       3       1       3 12.0184 .548867 1.43226
     559       4       1       4 16.3937 .584618 1.83249   <- TiO2
     578       5       1       5 20.5879 .668368 2.41281
     701       6       1       6 10.7190 .618357 1.33443
     503       7       1       7 13.4430 .615176 1.54753
     549       8       1       8 6.12880 .349537 1.25008
     571       9       1       9 11.7470 .557961 1.40367
     575      10       1      10 10.6460 .638117 1.31164
     589      11       1      11 14.0000 .831370 1.09576
     594      12       1      12 4.00000 .280255 .964030
     602      13       1      13 27.0000 .713668 3.01841
     619      14       1      14 21.0000 .834364 1.82118
     514      15       1      15 26.6522 .592982 3.27371

we can see that the largest corrections are for F Ka in some of the other standards. So it could be the MAN continuum absorption correction, but why is TiO2 more of an outlier than the other standards with larger corrections?

Note: many years ago I attempted to apply a true continuum absorption correction using Myklebust's continuum expression, but I got worse regression results than just using the normal phi-rho-z bulk absorption correction...
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John Donovan

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Re: Questions about MAN background use
« Reply #86 on: November 29, 2017, 10:37:45 pm »
I split off the rest of the discussion regarding this F Ka ROI mystery peak artifact on TAP crystals (and possibly related standards containing Ti) to a new topic:

http://probesoftware.com/smf/index.php?topic=992.0

This is because we suspect this mystery peak to be a diffraction artifact of some kind.  Another topic of interest could also be this one:

http://probesoftware.com/smf/index.php?topic=611.0

on JEOL H-type crystal artifacts, or this one on peak shape changes over time:

http://probesoftware.com/smf/index.php?topic=854.0

john
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