Author Topic: Questions about MAN background use  (Read 51750 times)

JonF

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Re: Questions about MAN background use
« Reply #105 on: May 07, 2021, 11:03:46 AM »
I meant to say, I un-did all the corrections on the mdb file for you so that you had a blank database to go at!

JonF

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Re: Questions about MAN background use
« Reply #106 on: May 07, 2021, 11:07:02 AM »

Annoyingly, this isn’t working:

The Fe metal results with Fe interference correction on Co:





Assuming this is right, of course!

John Donovan

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Re: Questions about MAN background use
« Reply #107 on: May 07, 2021, 01:06:45 PM »
Hi Jon,
OMG! You found an honest to God bug in the code!

It's because you first acquired your standards (and unknowns) using off-peaks. But because your backgrounds were not properly selected as seen here:



whereas I would choose backgrounds as seen here (green lines):



The next thing we both overlooked is that the program was warning us with this message (seen in red in the log window):

Warning- Negative interference counts (-0.2100179) for Co ka on interference standard  6012

Unfortunately the program only prints this warning message the first time it occurs because some people were complaining about too many warning messages!

Equally unfortunate is that because you wanted to try MAN backgrounds, even through you acquired your samples using off-peak bgds, you (correctly) selected to use the two Analytical menu check menus (Use Off-Peak Elements for MAN Fits and Use MAN Correction for Off-Peak Elements).  Which normally works just fine.

But, the code that loads the interference correction counts (that is, the pseudo Co counts from the Fe Kb interference), did *not* take into account the fact that the Use Off-Peak Elements for MAN Fits flag was checked!  It does respect this flag in the load MAN intensity code, but somehow I never implemented it into the load standard intensity (and standard interference intensity) code!   :-[

I guess the reason no one (until now) has noticed this is that normally one either acquires things using off-peak acquisitions or using MAN acquisitions. In other words, if you had properly selected the Co off-peak backgrounds, or created a new run using MAN acquisitions, the buggy code would have worked and we wouldn't have found this issue.

So I salute sir!

So here is the old code for loading the standard intensities:

Code: [Select]
' Correct the data for dead time, beam drift and off-peak background (results returned in sample(1).CorData!()) ****commented out 05/07/2021 because it was not handling the Use OffPeakElementsForMANFlag properly****
If Not UseAggregateIntensitiesFlag Then
Call DataCorrectData(Int(0), UpdateTmpSample())
If ierror Then Exit Sub

Else
Call DataCorrectData(Int(2), UpdateTmpSample())     ' skip aggregate intensity load
If ierror Then Exit Sub
Call DataCorrectDataAggregate(Int(2), sample(), UpdateTmpSample())     ' perform aggregate intensity based on unknown
If ierror Then Exit Sub
End If

and here is the corrected code that handles this flag (as it already does everywhere else in the code):

Code: [Select]
' Correct the data for dead time, beam drift (and off-peak background if NOT using off-peak sample elements) (results returned in sample(1).CorData!())
If UseOffPeakElementsForMANFlag = False Then
If Not UseAggregateIntensitiesFlag Then
Call DataCorrectData(Int(0), UpdateTmpSample())
If ierror Then Exit Sub

Else
Call DataCorrectData(Int(2), UpdateTmpSample())     ' skip aggregate intensity load
If ierror Then Exit Sub
Call DataCorrectDataAggregate(Int(2), sample(), UpdateTmpSample())     ' perform aggregate intensity based on unknown
If ierror Then Exit Sub
End If

Else
If Not UseAggregateIntensitiesFlag Then
Call DataCorrectData(Int(1), UpdateTmpSample())
If ierror Then Exit Sub
Else
Call DataCorrectData(Int(3), UpdateTmpSample())     ' skip aggregate intensity load
If ierror Then Exit Sub
Call DataCorrectDataAggregate(Int(3), sample(), UpdateTmpSample())     ' perform aggregate intensity based on unknown
If ierror Then Exit Sub
End If
End If

I do vaguely remember looking at this code when I added the Use Off-Peak Elements for MAN Fits menu feature, but at the time I was just thinking that this only needed to be added to the load MAN intensities code.  But if you're loading standard intensities using this MAN menu flag, then you really need to do it for the standard and interference standard intensities also.  Doh!    >:(

Basically the program was still calculating the interference intensities for the Co Ka in Fe using the off-peak method, which had the poorly chosen off-peak positions.  And yes, it was also loading the standard intensities using off-peak intensities, but of course those are usually very high intensities and the bgd correction would be very small, and so I suspect that is why no one ever noticed this when using the Use Off-Peak Elements for  MAN Fits menu flag for their off-peak acquired standards!

Anyway here are the results with the new code:

Un    2 std6012_Fe_metal_test_01
TakeOff = 40.0  KiloVolt = 15.0  Beam Current = 10.0  Beam Size =    0
(Magnification (analytical) =  40000),        Beam Mode = Analog  Spot
(Magnification (default) =   100000, Magnification (imaging) = 100000)
Image Shift (X,Y):                                         .00,    .00
Number of Data Lines:  12             Number of 'Good' Data Lines:  12
First/Last Date-Time: 05/06/2021 07:27:49 PM to 05/06/2021 07:49:53 PM
WARNING- Using MAN Background Instead of Off-Peak Background Correction

Average Total Oxygen:         .000     Average Total Weight%:   99.708
Average Calculated Oxygen:    .000     Average Atomic Number:   26.000
Average Excess Oxygen:        .000     Average Atomic Weight:   55.847
Average ZAF Iteration:        1.08     Average Quant Iterate:     4.00

Un    2 std6012_Fe_metal_test_01, Results in Elemental Weight Percents
 
ELEM:       Fe      Co
BGDS:      MAN     MAN
TIME:    20.00   20.00
BEAM:    10.00   10.00

ELEM:       Fe      Co   SUM 
    51  99.701   -.006  99.696
    52  99.700   -.004  99.696
    53  99.529   -.020  99.509
    54 100.130   -.007 100.122
    55  99.288   -.001  99.288
    56  99.899   -.008  99.892
    57  99.655   -.017  99.639
    58  99.726    .001  99.727
    59  99.359    .001  99.360
    60  99.492   -.005  99.488
    61 100.149    .011 100.160
    62  99.938   -.022  99.916

AVER:   99.714   -.006  99.708
SDEV:     .277    .009    .277
SERR:     .080    .003
%RSD:      .28 -148.00
STDS:     6012    6013

STKF:   1.0000  1.0000
STCT:   818.74  879.45

UNKF:    .9971  -.0001
UNCT:   816.43    -.05
UNBG:     1.83    2.43

ZCOR:   1.0000  1.0209
KRAW:    .9972  -.0001
PKBG:   446.59     .98
INT%:     ---- -107.45

I am re-compiling now and will upload this code fix in a few hours...
« Last Edit: May 07, 2021, 01:09:24 PM by John Donovan »
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JonF

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Re: Questions about MAN background use
« Reply #108 on: May 07, 2021, 01:34:06 PM »
OMG! You found an honest to God bug in the code!
Good news for me: I thought I was going mad! Thanks for looking in to this!

Although, as you said, it only came to light because I messed up the background position…
I did contemplate putting the low side background on the other side of the Fe Kb, but given the samples are >90wt% Fe, I was concerned about the influence of the Fe K absorption edge on the background intensity:




The above is a wavescan over the Co Ka region on Fe metal. Co Ka position in red, Fe K edge in orange, background positions in green. (the above plot is from the multipoint background window, is there a way to put absorption edges on the Plot! window wavescans?)
I decided to keep the low side background on the same side of the Fe K edge (and Fe Kb) as the Co Ka, and let the exponential background take care of the curvature. That was the plan, anyway...

Thanks again for sorting this so quickly – this would’ve been playing on my mind all weekend!

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Re: Questions about MAN background use
« Reply #109 on: May 07, 2021, 02:02:57 PM »
Yeah, trying to deal with interferences using a fancy background fit is something that I've tried (and recently discussed with our new consultant Will Nachlas), but it just doesn't appear to work most of the time.

Better to get good off-peak background positions and do the interference properly, or even better, just use the MAN background method!  Then one never has to worry about off-peak interferences!

Yes, you can display absorption edges in the Plot! window. Just click the Load X-ray Database button, and check the Show Absorption Edges checkbox, then click Close and Zoom Full to re-draw the graph (see orange marker):

« Last Edit: May 07, 2021, 03:41:56 PM by John Donovan »
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Re: Questions about MAN background use
« Reply #110 on: May 07, 2021, 05:17:30 PM »
OK, we just uploaded v. 12.9.6 of Probe for EPMA which now utilizes the MAN background correction not only for the standards used for the MAN background curve fit, but also for the background correction of the standard intensities and interference standard intensities.  Use the Help menu as usual to update Probe for EPMA.

The point being that when the Use Off-Peak Elements for MAN Fits menu is checked it was using off-peak elements for the MAN curve (by only utilizing the on-peak intensities from the off-peak acquisitions), but it was still using off-peak background correction for loading the standard and interference standard intensities.

So when Jon had the off-peak positions improperly located on the edge of the Fe Kb peak, there were no (positive) interference intensities found and so the program did not apply the interference correction to the sample (what would be the point?).

Now one *could* argue that there should be a separate flag for the background correction of the standard and interference standard intensities, but I think it makes sense that if you're using off-peak elements for the MAN corrections they should be applied to the primary standard (and interference) intensities also.  One still has the option to acquire the unknowns only using MAN acquisitions.

I also adding a warning if one has turned on the interference corrections in the Analysis Options dialog, but no specific interference corrections were assigned in the Standard Assignments dialog.
« Last Edit: May 07, 2021, 07:37:19 PM by John Donovan »
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Re: Questions about MAN background use
« Reply #111 on: May 08, 2021, 03:28:36 PM »
We made one small change to the code today that I think makes explaining what we are doing with these MAN menu flags much easier, and that is what this post will be about.  If you have been following the discussion between Jon Fellowes and I above, read on. If not, you might want to review the above posts. Here I will be discussing these two MAN menu flags found in the Analytical menu as seen here:



Remember, both of these two MAN flags in the Analytical menu only affect the *analysis* of standard or unknown samples, *not* the acquisition of standard and unknown samples! So please keep in mind that when I use the words "acquire" or "acquisition" I mean the actual process of acquiring sample data (from the Acquire! or Automate! windows), but when I use the words "analyze" or "analysis", then that refers to the process of quantifying already acquired sample data (from the Analyze! window or Output menu).

In short when the "Use Off-Peak Elements for MAN Fits" menu is checked, it instructs Probe for EPMA to utilize off-peak elements acquired in standard samples for constructing the MAN background curve fit. Checking the "Use MAN Correction for Off-Peak Elements" menu instructs the software to perform an MAN background correction, when loading primary standard (and interference standard) intensities, and also when performing the background correction during quantification of standard or unknown samples.

So here are the four situations explaining how these (quite useful) MAN menu analysis flags can be utilized:

1. Both "Use Off-Peak Elements for MAN Fits" and "Use MAN Correction for Off-Peak Elements" menu items are unchecked.

This is the default mode of Probe for EPMA and means simply that one can acquire off-peak acquisitions on both one's standard samples and also one's unknown samples. During the actual analysis (as opposed to the acquisition!), the off-peak background correction method will be applied to both standards and unknown samples in the Analyze! window. This is essentially the traditional background acquisition method for EPMA instruments.  But remember, one must have no spectral interferences on any of the off-peak background positions!

Alternatively this is also the situation when using MAN background acquisitions for both one's standard samples and one's unknown sample acquisitions. The easiest way to utilize this option is to click the Change All to MAN button in the Acquisition Options dialog from the Acquire! window, so all elements for both standards and unknowns will be changed from the default off-peak acquisitions to MAN background acquisitions.

2. The "Use Off-Peak Elements for MAN Fits" menu is checked, but the "Use MAN Correction for Off-Peak Elements" menu item is unchecked.

In this case, the user plans to acquire off-peak backgrounds on their standards, but will acquire MAN backgrounds on their unknowns (to reduce acquisition time and/or improve sensitivity). By checking the "Use Off-Peak Elements for MAN Fits" menu, the user can acquire off-peak backgrounds on their standards, but still utilize the on-peak standard intensities for the MAN curve fit to correct the background on their unknown samples. This option also allows one to utilize the "Use Interpolated Off-Peaks for MAN Fit" option in the Analysis Options dialog.

3. The "Use Off-Peak Elements for MAN Fits" menu is unchecked, but the "Use MAN Correction for Off-Peak Elements" menu item is checked.

This option is utilized when the standards are acquired using MAN backgrounds, but the unknown samples are acquired using off-peak backgrounds. Then the user decides that they want to perform the MAN background correction method for the unknown samples. This is a good option when you want to compare the results from both off-peak and MAN background methods, on the same data points.

4. Both "Use Off-Peak Elements for MAN Fits" and "Use MAN Correction for Off-Peak Elements" menu items are checked.

Here the user acquired both their standards *and* unknown samples using off-peak background acquisitions, but wants to analyze their standards and their unknown samples using the MAN background correction method. This is the situation that Jon Fellowes utilized in his above examples.

So after all that explanation(!), here is an analysis of Jon's Fe metal standard which should not contain any Co (run as an unknown), after both these Analytical menus are checked, and the interference for Fe Kb on Co was specified in the Standard Assignments dialog from the Analyze! window:

Un    2 std6012_Fe_metal_test_01
TakeOff = 40.0  KiloVolt = 15.0  Beam Current = 10.0  Beam Size =    0
(Magnification (analytical) =  40000),        Beam Mode = Analog  Spot
(Magnification (default) =   100000, Magnification (imaging) = 100000)
Image Shift (X,Y):                                         .00,    .00
Number of Data Lines:  12             Number of 'Good' Data Lines:  12
First/Last Date-Time: 05/06/2021 07:27:49 PM to 05/06/2021 07:49:53 PM
WARNING- Using MAN Background Instead of Off-Peak Background Correction

Average Total Oxygen:         .000     Average Total Weight%:   99.708
Average Calculated Oxygen:    .000     Average Atomic Number:   26.000
Average Excess Oxygen:        .000     Average Atomic Weight:   55.847
Average ZAF Iteration:        1.08     Average Quant Iterate:     4.00

Un    2 std6012_Fe_metal_test_01, Results in Elemental Weight Percents
 
ELEM:       Fe      Co
BGDS:      MAN     MAN
TIME:    20.00   20.00
BEAM:    10.00   10.00

ELEM:       Fe      Co   SUM 
    51  99.701   -.006  99.696
    52  99.700   -.004  99.696
    53  99.529   -.020  99.509
    54 100.130   -.007 100.122
    55  99.288   -.001  99.288
    56  99.899   -.008  99.892
    57  99.655   -.017  99.639
    58  99.726    .001  99.727
    59  99.359    .001  99.360
    60  99.492   -.005  99.488
    61 100.149    .011 100.160
    62  99.938   -.022  99.916

AVER:   99.714   -.006  99.708
SDEV:     .277    .009    .277
SERR:     .080    .003
%RSD:      .28 -148.00
STDS:     6012    6013

STKF:   1.0000  1.0000
STCT:   818.74  879.45

UNKF:    .9971  -.0001
UNCT:   816.43    -.05
UNBG:     1.83    2.43

ZCOR:   1.0000  1.0209
KRAW:    .9972  -.0001
PKBG:   446.59     .98
INT%:     ---- -107.45

Now we can see that the Co concentration is within 60 PPM of zero with a variance of 90 PPM. Not bad considering!

For those interested in the code, basically we utilize the UseOffPeakElementsForMANFlag in the UpdateGetMANStandards procedure as seen here (this has not changed):

Code: [Select]
' Correct the data for dead time, beam drift (and off-peak background if NOT using off-peak sample elements for MAN fits)
If UseOffPeakElementsForMANFlag = False Then
If Not UseAggregateIntensitiesFlag Then
Call DataCorrectData(Int(0), UpdateTmpSample())
If ierror Then Exit Sub

Else
Call DataCorrectData(Int(2), UpdateTmpSample())     ' skip aggregate intensity load
If ierror Then Exit Sub
Call DataCorrectDataAggregate(Int(2), sample(), UpdateTmpSample())     ' perform aggregate intensity based on unknown
If ierror Then Exit Sub
End If

' Correct the data for dead time, beam drift (and MAN background if using off-peak sample elements for MAN fits)
Else
If Not UseAggregateIntensitiesFlag Then
Call DataCorrectData(Int(1), UpdateTmpSample())
If ierror Then Exit Sub
Else
Call DataCorrectData(Int(3), UpdateTmpSample())     ' skip aggregate intensity load
If ierror Then Exit Sub
Call DataCorrectDataAggregate(Int(3), sample(), UpdateTmpSample())     ' perform aggregate intensity based on unknown
If ierror Then Exit Sub
End If
End If

And in the UpdateGetStandards code we now utilize the UseMANForOffPeakElementsFlag for performing an MAN correction when loading the standard (and interference standard) net intensities as seen here:

Code: [Select]
' Correct the data for dead time, beam drift (and off-peak background if NOT using MAN for off-peak elements)
If UseMANForOffPeakElementsFlag = False Then
If Not UseAggregateIntensitiesFlag Then
Call DataCorrectData(Int(0), UpdateTmpSample())
If ierror Then Exit Sub

Else
Call DataCorrectData(Int(2), UpdateTmpSample())     ' skip aggregate intensity load
If ierror Then Exit Sub
Call DataCorrectDataAggregate(Int(2), sample(), UpdateTmpSample())     ' perform aggregate intensity based on unknown
If ierror Then Exit Sub
End If

' Correct the data for dead time, beam drift (and MAN background if using MAN background corrections for off-peak elements)
Else
If Not UseAggregateIntensitiesFlag Then
Call DataCorrectData(Int(1), UpdateTmpSample())
If ierror Then Exit Sub
Else
Call DataCorrectData(Int(3), UpdateTmpSample())     ' skip aggregate intensity load
If ierror Then Exit Sub
Call DataCorrectDataAggregate(Int(3), sample(), UpdateTmpSample())     ' perform aggregate intensity based on unknown
If ierror Then Exit Sub
End If
End If

Note the first line of each code section which corresponds to the Analytical menus!
« Last Edit: May 09, 2021, 08:04:31 AM by John Donovan »
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JonF

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Re: Questions about MAN background use
« Reply #112 on: May 11, 2021, 01:01:43 PM »
Thanks again for your work sorting out this problem. I've updated our processing computer's version of PfE and reprocessed the user's data and the element ratios are falling exactly where they should. 

I often run the first standardisations in a session as off peak measurements and run a wide range of standards that can be later converted to a MAN curve, as more often than not, the user will at some point want to collect quantitative maps. The extra time required to do this isn't usually a problem, as it'll be running automated overnight. This has also saved my bacon on this occasion!   

One other flag for the creation of a MAN curve - that I initially mis-read as a global "use MAN curve" checkbox - is the "Use Interpolated Off Peaks for MAN Fit" checkbox in the Analysis Options menu:




I think I'm right in saying that this option switches between using the uncorrected (background, interference, matrix...) on peak measured values for elements not present in a standard to populate the MAN curve plot versus using the interpolated off peak positions? The latter has the benefit of removing any error from minor/traces of an element in impure standards, but at the expense of increased error (assuming the backgrounds were measured at 1/2 the time as the on peak measurement), issues with the interpolation (e.g. shape, as above!) and spectral interferences on both the high and low side backgrounds.

I was wondering whether this checkbox would be better suited to the Assign MAN Fits screen, though?

If the rationale for switching to the interpolated off peak measurements for standards in the MAN curve is because of trace contamination in standards, is it worth being able to select on a per element or per standard basis whether we want to use the on peaks or interpolated off peaks? I appreciate that would be a headache-inducing amount of work though, and this is more of an open question as to whether this would be useful for anyone else. Admittedly, I can't think of many times that I would've needed it!

John Donovan

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Re: Questions about MAN background use
« Reply #113 on: May 11, 2021, 09:54:32 PM »
One other flag for the creation of a MAN curve - that I initially mis-read as a global "use MAN curve" checkbox - is the "Use Interpolated Off Peaks for MAN Fit" checkbox in the Analysis Options menu:




I think I'm right in saying that this option switches between using the uncorrected (background, interference, matrix...) on peak measured values for elements not present in a standard to populate the MAN curve plot versus using the interpolated off peak positions? The latter has the benefit of removing any error from minor/traces of an element in impure standards, but at the expense of increased error (assuming the backgrounds were measured at 1/2 the time as the on peak measurement), issues with the interpolation (e.g. shape, as above!) and spectral interferences on both the high and low side backgrounds.

I was wondering whether this checkbox would be better suited to the Assign MAN Fits screen, though?

If the rationale for switching to the interpolated off peak measurements for standards in the MAN curve is because of trace contamination in standards, is it worth being able to select on a per element or per standard basis whether we want to use the on peaks or interpolated off peaks? I appreciate that would be a headache-inducing amount of work though, and this is more of an open question as to whether this would be useful for anyone else. Admittedly, I can't think of many times that I would've needed it!

Hi Jon,
Very reasonable questions (and thank-you again for noticing this subtle issue).

So yes, the purpose of the "interpolated MAN" option is for exactly what you describe: it is possible that many of one's standards are more contaminated with trace elements that one would have expected.  For me that says "get better standards"!  But, this option can also be useful in constructing an MAN curve for say oxygen (dues to surface oxidation), or carbon (due to carbon contamination) on one's standards, etc.  We all could take advantage of this!

This idea for this originally came from Ben Hanson at Corning Glass. The option to utilize off-peak interpolated standards for the MAN curve even though the element in question is declared in the standard database comes from Phil Orlandini at UT Austin.  This is described in more detail in this topic here:

https://probesoftware.com/smf/index.php?topic=987.0

The three of us also wrote this up in an M&M abstract here:

https://www.cambridge.org/core/journals/microscopy-and-microanalysis/article/modified-mean-atomic-number-background-correction-using-offpeak-interpolated-measurements/6EBB9664B8EDFA5703C05F85CD706CAE

Though I do think this is an interesting option, I do have minor concerns when the element in question is present in large concentrations due to absorption edge effects on the continuum, and also off-peak interferences as you mentioned.  But it usually works well for major and minor element background corrections, if (sadly) one has crappy (sorry, impure) standards!.

As to why this option is hidden away in the Analysis Options dialog, well maybe that is because I would consider this an advanced option that should only be utilized by "experts".  Also, this flag requires reloading of all MAN intensities, so honestly it really must be set before attempting to review the fits in the MAN Assignments dialog (I could probably come up with a few other excuses, but let's leave it there for now).   :)

As for assigning this sort of thing on an element by element basis, well, I'll just say that I'll leave it to you and others to present a case for why that would be worth implementing!   ;D
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Re: Questions about MAN background use
« Reply #114 on: June 30, 2021, 09:24:13 AM »
As some of you may know, the Z (or electron) fraction averaging method for calculation of average atomic number (Z-bar) in Probe for EPMA, used in the MAN background fit method, allows one to specify an exponent for the best fit.

Recent work by Moy et al. confirms that there is a small dependency of the continuum intensity on the emission line energy (as a function of the best fit Z fraction Z-bar).

To facilitate testing of this expression and its effect on the MAN curve fit, we have implemented the equation from Moy et al., into the Probe for EPMA Assign MAN Fits menu dialog as seen here:



For most purposes the default exponent of 0.7 seems to work well, but this new button should allow further testing. It will be interesting to try and understand the physics behind all this!
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Rom

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Re: Questions about MAN background use
« Reply #115 on: August 17, 2022, 11:47:52 PM »
Hi John,
Did you find some solutions for possibility of choosing and changing MAN/off peak correction method for different elements after acquisition was done?
Next question is: how I can upload data for MAN curves plotting from earlier (old) sessions which were in the same conditions of course?

Thank you a lot. 
« Last Edit: August 17, 2022, 11:53:39 PM by Rom »

John Donovan

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Re: Questions about MAN background use
« Reply #116 on: August 18, 2022, 08:58:53 AM »
Did you find some solutions for possibility of choosing and changing MAN/off peak correction method for different elements after acquisition was done?

The best explanation is in this post above:

https://probesoftware.com/smf/index.php?topic=4.msg9953#msg9953

In addition to the options described above, using the standard/unknown background options in the Acquire! | Acquisition Options dialog, one can also on a per element basis:

1. Acquire off peaks on standards and unknowns
2. Acquire off peaks on standards and MAN of unknowns
3. Acquire MAN on standards and off-peaks on unknowns
4. Acquire MAN on standards and unknowns.

And then also add to those options, multipoint background (MPB) acquisitions...  Again, on an element by element basis. 

As for changing the background types after one has already acquired data, there are several options, assuming that one acquired the standards and/or unknowns using off-peak or MPB originally.

1. Using the MAN options described in the link above one can analyze off-peak data as though it were acquired using MAN methods.

For instance, one acquires off-peaks on their standards and unknowns, then one can utilize the on-peak measurements from the standards to create MAN cruves, which can then be applied to the off-peak unknowns for MAN analysis of off-peak data.

Or one can acquire MAN data on standards, and off-peak data on unknowns, and again, utilize the MAN method for the unknowns.

Again, see the post linked above for details...

One can also acquire MPB data on standards and/or unknowns and then from the Elements/Cations dialog, switch the MPB options to using one of the off-peak methods. In this case the multiple off-peaks are combined and then utilize one of the off-peak methods, e.g., linear, hi-only, slope-lo, average, etc.

And then, of course, there is the "shared" multi-point background method described here:

https://probesoftware.com/smf/index.php?topic=9.msg1579#msg1579

where one acquires normal off-peak backgrounds on multiple (at least two) elements per spectrometer (at least one), and it creates a pseudo- MPB curves for extrapolating backgrounds using off-peak backgrounds from several elements on that spectrometer/crystal pair...

Whenever I am trying out different background methods on various elements, I generally make a number of sub folders (MAN, Off-peak, etc), and then copy the original MDB file into those sub folders and then set the flags differently for each MDB depending on what I am trying to accomplish, e.g., comparing off-peak to MAN processing for trace elements as described in our 2016 paper here:

https://epmalab.uoregon.edu/publ/A%20new%20EPMA%20method%20for%20fast%20trace%20element%20analysis%20in%20simple%20matrices.pdf

Next question is: how I can upload data for MAN curves plotting from earlier (old) sessions which were in the same conditions of course?

The best method is to utilize the Load File Setup button from the Acquire! New Sample/Setup button and browse to the old run, and select the sample setup you want to load.  Then it will ask if you want to load the standard intensities, and you click Yes.

It will then load all your primary, interference and MAN standards along with the MAN assignments from the old run, into the new run.

Yes. It's like magic!   8)
John J. Donovan, Pres. 
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"Not Absolutely Certain, Yet Reliable"

Rom

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Re: Questions about MAN background use
« Reply #117 on: August 18, 2022, 06:39:48 PM »
Thank you John, let me clarify a bit.
1. Before I am not sure in my "MAN" skills, I want to measure my samples by classic way with off peak background correction. Yes, we can separately calculated the same measuring results with "MAN" and "off peak" methods. Then we can compare  calculation results.
But on this way a little change of calculation concentration of element "A" with changing a calculation method from "off peak" to "MAN" will not affect to concentration another elements which concentration calculated only by "off peak".
This is why I asked you about this possibility.
2. Yes, this way we can upload any standards from "old" acquisitions. But I haven't find the way I can delete some of "old" standards which I uploaded to new (current) MDB. Sometimes the number of standards I want ignore is too much and it will be suitable to delete some of them. Is it possible?
3. Small addition question.
When we plot a MAN curve with standards which include searching element "A", the system uses "off peak" background data. What equation the system apply to calculate "on peak" background for MAN curve - the equation  we have chosen for "off peak" background correction or something else?

John Donovan

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Re: Questions about MAN background use
« Reply #118 on: August 18, 2022, 09:58:35 PM »
1. Before I am not sure in my "MAN" skills, I want to measure my samples by classic way with off peak background correction. Yes, we can separately calculated the same measuring results with "MAN" and "off peak" methods. Then we can compare  calculation results.
But on this way a little change of calculation concentration of element "A" with changing a calculation method from "off peak" to "MAN" will not affect to concentration another elements which concentration calculated only by "off peak".
This is why I asked you about this possibility.

If the background method changes, the change in composition will usually be very small. But that small change in composition will still affect the matrix correction of the other elements. However the change from that will also be an even smaller change.

2. Yes, this way we can upload any standards from "old" acquisitions. But I haven't find the way I can delete some of "old" standards which I uploaded to new (current) MDB. Sometimes the number of standards I want ignore is too much and it will be suitable to delete some of them. Is it possible?

You cannot delete samples in Probe for EPMA. One should never delete scientific data. However, one can disable samples if they are not useful from the Analyze! window.  And/or enable them.

3. Small addition question.
When we plot a MAN curve with standards which include searching element "A", the system uses "off peak" background data. What equation the system apply to calculate "on peak" background for MAN curve - the equation  we have chosen for "off peak" background correction or something else?

If you select the option for using off-peak standards for generating the MAN curves, the program will only utilize the on-peak measurements and simply ignore the off-peak data.

Unless one utilizes the so called "interpolated off-peak  MAN" method:

https://probesoftware.com/smf/index.php?topic=987.0

Then the off-peak (or MPB) fit method is utilized for the on-peak background.
John J. Donovan, Pres. 
(541) 343-3400

"Not Absolutely Certain, Yet Reliable"

Rom

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Re: Questions about MAN background use
« Reply #119 on: August 19, 2022, 12:00:17 AM »
1,2 - thank you.
3 - Yes, I asked you about "interpolated off-peak  MAN" method. What equation the system apply to calculate "on peak" background for MAN curve - the equation we have chosen for "off peak" background correction?