pymca-users

[PyMca] coherent scatter from mono-energetic excitation

[PyMca g. p. m. list. <pym...@li...>]

Hi Everyone,

We have been using PyMca for years for fitting spectra from both synchrotron applications and from applications with a small lab-based portable XRF system.

For the portable system, we are currently interested in quantifying the coherent scatter peak area. The excitation source for this system is a mono-energetic beam resulting from the K alpha energy of a molybdenum target x-ray tube (so the resulting coherent scatter energy is at approximately 17.5 keV).

To this point, the best way we have come up with to quantify this peak area is to enter an artificially high excitation energy for the system (for example, 20 keV) and then simply fit the coherent scatter peak at 17.5 keV as resulting from Mo K alpha characteristic X-ray emissions. An example of the coherent peak fitting from this approach is shown in the attached picture file.

We have two questions: 1) Does our approach make sense? 2) Is there a better way to do it?

Many thanks,
David Fleming

Re: [PyMca] coherent scatter from mono-energetic excitation

[PyMca g. p. m. list. <pym...@li...>]

Hi David,

If your beam is monochromatic, there should not be any difference 
compared to using synchrotron radiation as excitation source. In the 
BEAM tab of the fit configuration window you enter 17.5 as energy with 
weight 1 and make sure the magenta checkbox is selected.

You will then have the scatter peak area as Scatter Peak000.

See you,

Armando

On 12/05/2022 18:44, PyMca general purpose mailing list. wrote:
> Hi Everyone,
>
> We have been using PyMca for years for fitting spectra from both 
> synchrotron applications and from applications with a small lab-based 
> portable XRF system.
>
> For the portable system, we are currently interested in quantifying 
> the coherent scatter peak area. The excitation source for this system 
> is a mono-energetic beam resulting from the K alpha energy of a 
> molybdenum target x-ray tube (so the resulting coherent scatter energy 
> is at approximately 17.5 keV).
>
> To this point, the best way we have come up with to quantify this peak 
> area is to enter an artificially high excitation energy for the system 
> (for example, 20 keV) and then simply fit the coherent scatter peak at 
> 17.5 keV as resulting from Mo K alpha characteristic X-ray emissions. 
> An example of the coherent peak fitting from this approach is shown in 
> the attached picture file.
>
> We have two questions: 1) Does our approach make sense? 2) Is there a 
> better way to do it?
>
> Many thanks,
> David Fleming
>
>
>
> _______________________________________________
> PyMca-users mailing list
> PyM...@li...
> https://lists.sourceforge.net/lists/listinfo/pymca-users

Re: [PyMca] coherent scatter from mono-energetic excitation

[PyMca g. p. m. list. <pym...@li...>]

Thank you, Armando. This makes sense. Using this approach with our system, while we get a decent fit to the coherent peak, the Compton peak fit is too narrow compared with the observed data. In the example shown below, the coherent peak fit is decent but is probably too large in area - a result that in turn is likely linked to the shape of the fit provided for the Compton peak.

I'm wondering if we would do better if we provided more information about the XRF system under the tabs such as Attenuators. We do not know much about the properties of the system itself, so have not entered anything under that particular tab. Likewise, there may be other pieces of useful information about the system that we simply do not have.

Many thanks,
David

[cid:0418c21f-9e8b-4935-a427-7affce7e9ffd]
________________________________
From: PyMca general purpose mailing list. <pym...@li...>
Sent: May 13, 2022 9:00 AM
To: pym...@li... <pym...@li...>
Subject: Re: [PyMca] coherent scatter from mono-energetic excitation

Hi David,

If your beam is monochromatic, there should not be any difference compared to using synchrotron radiation as excitation source. In the BEAM tab of the fit configuration window you enter 17.5 as energy with weight 1 and make sure the magenta checkbox is selected.

You will then have the scatter peak area as Scatter Peak000.

See you,

Armando

On 12/05/2022 18:44, PyMca general purpose mailing list. wrote:
Hi Everyone,

We have been using PyMca for years for fitting spectra from both synchrotron applications and from applications with a small lab-based portable XRF system.

For the portable system, we are currently interested in quantifying the coherent scatter peak area. The excitation source for this system is a mono-energetic beam resulting from the K alpha energy of a molybdenum target x-ray tube (so the resulting coherent scatter energy is at approximately 17.5 keV).

To this point, the best way we have come up with to quantify this peak area is to enter an artificially high excitation energy for the system (for example, 20 keV) and then simply fit the coherent scatter peak at 17.5 keV as resulting from Mo K alpha characteristic X-ray emissions. An example of the coherent peak fitting from this approach is shown in the attached picture file.

We have two questions: 1) Does our approach make sense? 2) Is there a better way to do it?

Many thanks,
David Fleming





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Re: [PyMca] coherent scatter from mono-energetic excitation

[PyMca g. p. m. list. <pym...@li...>]

On 16/05/2022 22:04, PyMca general purpose mailing list. wrote:
> Thank you, Armando. This makes sense. Using this approach with our 
> system, while we get a decent fit to the coherent peak, the Compton 
> peak fit is too narrow compared with the observed data. In the example 
> shown below, the coherent peak fit is decent but is probably too large 
> in area - a result that in turn is likely linked to the shape of the 
> fit provided for the Compton peak.
>
> I'm wondering if we would do better if we provided more information 
> about the XRF system under the tabs such as Attenuators. We do not 
> know much about the properties of the system itself, so have not 
> entered anything under that particular tab. Likewise, there may be 
> other pieces of useful information about the system that we simply do 
> not have.
>

As you have noticed, the problem of that approach is that the Compton 
peak is not properly described in PyMca. It is not a problem of the 
description of your setup.


https://www.silx.org/doc/PyMca/dev/faq.html#the-description-of-the-scattering-peaks-is-very-poor-why


What PyMca offers in that case would only serve for some qualitative 
work  (ex. if all your spectra are fitted the same way, the fitted areas 
and ratios with the scatter peak will provide you information about 
relative average Z and sample density). However, if you restrict the 
fitting region to just that region, the bad fit of the Compton peak will 
distort your overall fit as you can observe.


You can also perform a) a Simple Fit of just the scatter peak or b) just 
use a ROI if it is so well separated.


Armando

Re: [PyMca] coherent scatter from mono-energetic excitation

[PyMca g. p. m. list. <pym...@li...>]

Dear Armando,

Thanks very much for the additional thoughts given below. We would be interested in the best possible fit to the coherent peak for quantitative work. Therefore, we will pursue the options you noted for fitting the coherent scatter peak of A) Simple Fit; and B) ROI.

Just to make sure I am understanding the Simple Fit and ROI options correctly, is there a tutorial or overview of these two options you would recommend?

Best wishes,
David

________________________________
From: PyMca general purpose mailing list. <pym...@li...>
Sent: May 17, 2022 9:35 AM
To: pym...@li... <pym...@li...>
Subject: Re: [PyMca] coherent scatter from mono-energetic excitation

On 16/05/2022 22:04, PyMca general purpose mailing list. wrote:
Thank you, Armando. This makes sense. Using this approach with our system, while we get a decent fit to the coherent peak, the Compton peak fit is too narrow compared with the observed data. In the example shown below, the coherent peak fit is decent but is probably too large in area - a result that in turn is likely linked to the shape of the fit provided for the Compton peak.

I'm wondering if we would do better if we provided more information about the XRF system under the tabs such as Attenuators. We do not know much about the properties of the system itself, so have not entered anything under that particular tab. Likewise, there may be other pieces of useful information about the system that we simply do not have.



As you have noticed, the problem of that approach is that the Compton peak is not properly described in PyMca. It is not a problem of the description of your setup.


https://www.silx.org/doc/PyMca/dev/faq.html#the-description-of-the-scattering-peaks-is-very-poor-why


What PyMca offers in that case would only serve for some qualitative work  (ex. if all your spectra are fitted the same way, the fitted areas and ratios with the scatter peak will provide you information about relative average Z and sample density). However, if you restrict the fitting region to just that region, the bad fit of the Compton peak will distort your overall fit as you can observe.


You can also perform a) a Simple Fit of just the scatter peak or b) just use a ROI if it is so well separated.


Armando

Re: [PyMca] coherent scatter from mono-energetic excitation

[PyMca g. p. m. list. <pym...@li...>]

Sehr geehrte Damen und Herren, bis zum 30.05.2022 bin ich nicht erreichbar. Emails werden schnellstmöglich beantwortet.
Mit freundlichen Grüßen, Carsten Wintermann
 
To whom it may concern, I am offline until 30th Mai 2022. I will answer your messages as soon as possible.
Sincerely, Carsten Wintermann

Am 19.05.2022 um 21:02 schrieb PyMca general purpose mailing list. <pym...@li...>:

> Dear Armando,
> 
> Thanks very much for the additional thoughts given below. We would be interested in the best possible fit to the coherent peak for quantitative work. Therefore, we will pursue the options you noted for fitting the coherent scatter peak of A) Simple Fit; and B) ROI. 
> 
> Just to make sure I am understanding the Simple Fit and ROI options correctly, is there a tutorial or overview of these two options you would recommend?
> 
> Best wishes,
> David
> 
> 
> From: PyMca general purpose mailing list. <pym...@li...>
> Sent: May 17, 2022 9:35 AM
> To: pym...@li... <pym...@li...>
> Subject: Re: [PyMca] coherent scatter from mono-energetic excitation
>  
> On 16/05/2022 22:04, PyMca general purpose mailing list. wrote:
> Thank you, Armando. This makes sense. Using this approach with our system, while we get a decent fit to the coherent peak, the Compton peak fit is too narrow compared with the observed data. In the example shown below, the coherent peak fit is decent but is probably too large in area - a result that in turn is likely linked to the shape of the fit provided for the Compton peak.
> 
> I'm wondering if we would do better if we provided more information about the XRF system under the tabs such as Attenuators. We do not know much about the properties of the system itself, so have not entered anything under that particular tab. Likewise, there may be other pieces of useful information about the system that we simply do not have.
> 
> 
> 
> As you have noticed, the problem of that approach is that the Compton peak is not properly described in PyMca. It is not a problem of the description of your setup.
> 
> 
> https://www.silx.org/doc/PyMca/dev/faq.html#the-description-of-the-scattering-peaks-is-very-poor-why
> 
> 
> 
> What PyMca offers in that case would only serve for some qualitative work  (ex. if all your spectra are fitted the same way, the fitted areas and ratios with the scatter peak will provide you information about relative average Z and sample density). However, if you restrict the fitting region to just that region, the bad fit of the Compton peak will distort your overall fit as you can observe.
> 
> 
> You can also perform a) a Simple Fit of just the scatter peak or b) just use a ROI if it is so well separated.
> 
> 
> 
> Armando
> 
> 
> 
> _______________________________________________
> PyMca-users mailing list
> PyM...@li...
> https://lists.sourceforge.net/lists/listinfo/pymca-users

Re: [PyMca] coherent scatter from mono-energetic excitation

[PyMca g. p. m. list. <pym...@li...>]

On 19/05/2022 21:02, PyMca general purpose mailing list. wrote:
> Just to make sure I am understanding the Simple Fit and ROI options 
> correctly, is there a tutorial or overview of these two options you 
> would recommend?
>

For the simple fit there is no official tutorial. If I remember well 
some users had prepared tutorials for their needs (FTIR, XEOL, ...) 
Perhaps they would like to share them with you.


For the ROIs, you can take a look at the kinetics tutorial in


http://ftp.esrf.fr/pub/scisoft/pymca/kineticstutorial.htm


It makes use of ROIs in a batch mode over multiple spectra.

Re: [PyMca] coherent scatter from mono-energetic excitation

[PyMca g. p. m. list. <pym...@li...>]

Dear David,


I confirm that you can find a video presenting the main utilities of 
PyMca< ROI Imaging here <https://youtu.be/1wdt6VhK28Y>.


Best regards,


Marine

On 20/05/2022 13:52, PyMca general purpose mailing list. wrote:
> On 19/05/2022 21:02, PyMca general purpose mailing list. wrote:
>> Just to make sure I am understanding the Simple Fit and ROI options 
>> correctly, is there a tutorial or overview of these two options you 
>> would recommend?
>>
>
> For the simple fit there is no official tutorial. If I remember well 
> some users had prepared tutorials for their needs (FTIR, XEOL, ...) 
> Perhaps they would like to share them with you.
>
>
> For the ROIs, you can take a look at the kinetics tutorial in
>
>
> http://ftp.esrf.fr/pub/scisoft/pymca/kineticstutorial.htm
>
>
> It makes use of ROIs in a batch mode over multiple spectra.
>
>
>
>
> _______________________________________________
> PyMca-users mailing list
> PyM...@li...
> https://lists.sourceforge.net/lists/listinfo/pymca-users