Using Probe for EPMA software in "demonstration mode" to teach EPMA

[John Donovan]

As you know, Probe for EPMA, when run in "demo" mode (the keyword InterfaceType=0 in the probewin.ini file), can simulate both EDS and WDS spectra for performing spectrum simulations for teaching EPMA in the classroom.

The latest version of Probe for EPMA now has a complete set of pure element WDS spectrum simulations at 15 keV from the Penepma Monte Carlo software and is distributed in the Penepma12.zip update which can be downloaded using the Help menu in Probe for EPMA as described here:

http://probesoftware.com/smf/index.php?topic=366.msg1936#msg1936

These pure element spectra are utilized to synthesize WDS spectra for simulation of wavescans on compounds.  I am currently running simulations also at 5, 10, 20 and 25 keV and many of these are already in the Penepma12.zip distributions though they are not 100% complete.
john

Hi John,

I'm struggling to figure out how to get compound spectra - I have Si element but the wavescan is just for Si Metal. Standards added are plagioclase, hornblende etc

Thanks

Ben

Hi Ben,
I really should add a special "pop up list" for the user to select which compound they want the wavescan or unknown sample to be based on!   But I haven't been able to think of a "sexy" way to do it yet!

The idea is that for standard samples, the program knows exactly what the composition should be, but that is not the case for unknowns and wavescans.   So what I do currently is assume the composition of the last standard for the next wavescan or unknown.  And if that's not available, just calculate a random composition based on the currently analyzed elements.

The only caveat, is that if the unknown or wavescan doesn't have *exactly* the same elements (analyzed *and* specified) as the previous standard composition, the program will generate a random composition for the subsequent unknown or wavescan.

The easiest way to do that is to just assign to the unknown (or wavescan) sample all the elements present in the standard composition (that are not being analyzed for), as specified (not analyzed) elements using the Elements/Cations dialog.

Frankly it's more about the issue of the aesthetics of a "pop up" asking the user for the sample composition, that would only occur for these simulation modes, that is stopping me.  Let me think a bit more about it...
john

[Ben Buse]

Hi John,

Thanks matching elements to standard did it. Looks good.

In an earlier post you mention two uses
(1) Train people to use software
(2) Help assign background positions - when creating analytical setup.

I wonder if for (2) it would be better not to have it in the demonstration mode. Using an unknown setup and selecting a standard - a wavescan could be generated instantly without waiting for it to virtual flip crystal, run wavescan etc - (in demo mode when changing beam current this changes noise?). The wavescan could be created in the live version of the program alllowing background selection then analyse?

Ben

[John Donovan]

In an earlier post you mention two uses
(1) Train people to use software
(2) Help assign background positions - when creating analytical setup.

I wonder if for (2) it would be better not to have it in the demonstration mode. Using an unknown setup and selecting a standard - a wavescan could be generated instantly without waiting for it to virtual flip crystal, run wavescan etc - (in demo mode when changing beam current this changes noise?). The wavescan could be created in the live version of the program allowing background selection then analyse?

Hi Ben,
What an excellent idea!

Actually, this has sort of already been done using Sandrin Feig's EPMA method development tool:

http://probesoftware.com/smf/index.php?topic=743.0

But if I can think of a simple way to do it for "on-line" probe runs, it would be cool... 
john

[John Donovan]

As you know, Probe for EPMA, when run in "demo" mode (the keyword InterfaceType=0 in the probewin.ini file), can simulate both EDS and WDS spectra for performing spectrum simulations for teaching EPMA in the classroom.

The latest version of Probe for EPMA now has a complete set of pure element WDS spectrum simulations at 15 keV from the Penepma Monte Carlo software and is distributed in the Penepma12.zip update which can be downloaded using the Help menu in Probe for EPMA as described here:

http://probesoftware.com/smf/index.php?topic=366.msg1936#msg1936

These pure element spectra are utilized to synthesize WDS spectra for simulation of wavescans on compounds.  I am currently running simulations also at 5, 10, 20 and 25 keV and many of these are already in the Penepma12.zip distributions though they are not 100% complete.
john

Hi John,

I'm struggling to figure out how to get compound spectra - I have Si element but the wavescan is just for Si Metal. Standards added are plagioclase, hornblende etc

Thanks

Ben

Hi Ben,
I really should add a special "pop up list" for the user to select which compound they want the wavescan or unknown sample to be based on!   But I haven't been able to think of a "sexy" way to do it yet!

The idea is that for standard samples, the program knows exactly what the composition should be, but that is not the case for unknowns and wavescans.   So what I do currently is assume the composition of the last standard for the next wavescan or unknown.  And if that's not available, just calculate a random composition based on the currently analyzed elements.

The only caveat, is that if the unknown or wavescan doesn't have *exactly* the same elements (analyzed *and* specified) as the previous standard composition, the program will generate a random composition for the subsequent unknown or wavescan.

The easiest way to do that is to just assign to the unknown (or wavescan) sample all the elements present in the standard composition (that are not being analyzed for), as specified (not analyzed) elements using the Elements/Cations dialog.

Frankly it's more about the issue of the aesthetics of a "pop up" asking the user for the sample composition, that would only occur for these simulation modes, that is stopping me.  Let me think a bit more about it...
john

Hi Ben,
Ok, there is no caveat now with the latest version of PFE.

The simulation mode will now always use the composition of the last standard for subsequent unknowns or wavescans, as long as the takeoff, keV and analyzed elements do not change.

If the conditions change and a standard has not been simulated, the program will simulate a random unknown or wavescan composition until a standard has been simulated using the new conditions.

I think this makes it much more intuitive now, try it out please and let me know what you think. And thanks for your help.
john

[Ben Buse]

Hi John,

Thanks that makes it easier.

Also I've found out what I was doing wrong. I created the standard - but did not acquire any counts on the standard. For it to work you have to create the standard and click 'start standard or unknown acquisition' to acquire counts. Before doing the wavescan.

All working & looks good thanks

Ben

[Ben Buse]

I ran the simulation on a zircon - for a sample I already had an actual wavescan for at 17kV.

It does a very good job, shows the effect of absorption edge, and allows correct background selection - or use of Mb line. Plus when compare to xeno counter spec 4 see difference

Simulation green. Actual wavescan blue



At 25kV - see simulation includes Zr La 5 order, for like wavelength tables, the reflectivity of crystals for high orders not none

[John Donovan]

Hi Ben,
Cool.

I do add a correction in for higher orders, but I can't say I "tuned" it much. 

One could spend a life time adjusting these parameters!  Since it's only intended for teaching it's probably OK for now.

I hope you find the new simulation code easier to use now...
john

[John Donovan]

Also I've found out what I was doing wrong. I created the standard - but did not acquire any counts on the standard. For it to work you have to create the standard and click 'start standard or unknown acquisition' to acquire counts. Before doing the wavescan.

Hi Ben,
Yes, one has to let it calculate the simulated standard intensities first. That is you don't need to actually finish acquiring the standard data point, but you do need to let it run at least until it starts counting- then you could click cancel. That way the simulated standard intensities are calculated and stored for the next point or unknown or wavescan sample.
john

[John Donovan]

I ran the simulation on a zircon - for a sample I already had an actual wavescan for at 17kV.

It does a very good job, shows the effect of absorption edge, and allows correct background selection - or use of Mb line. Plus when compare to xeno counter spec 4 see difference

Simulation green. Actual wavescan blue



At 25kV - see simulation includes Zr La 5 order, for like wavelength tables, the reflectivity of crystals for high orders not none

Here is a comparison I did of higher order reflections.  It does appear I could decrease their simulated intensity a bit:

http://probesoftware.com/smf/index.php?topic=837.msg5477#msg5477

john

[John Donovan]

I ran the simulation on a zircon - for a sample I already had an actual wavescan for at 17kV.

It does a very good job, shows the effect of absorption edge, and allows correct background selection - or use of Mb line. Plus when compare to xeno counter spec 4 see difference

Simulation green. Actual wavescan blue

Hi Ben,
I worked a bit on the higher order Bragg reflection code and here is a simulated scan of U ma ROI on PET for a zircon composition (at 25 keV):



I think this looks better. 

By the way I also happened to also run a simulation of the Hf La region and here is a teaching opportunity to demonstrate to students why in zircon we prefer the Hf Ma line:



In addition I ran a full spectrometer range simulation on the K-411 glass here (at 15 keV):



and here is an experimental scan from my SX100:



Not too bad I think.  Good enough for teaching in the classroom I think.

The cool thing about this improved simulation mode in the latest PFE is that the students learn not only the theory and practice of EPMA without wasting time on the instrument, but also learn the actual software that they will be utilizing, for when they do get on the instrument!

I'll be uploading this improved simulation version tonight.
john

[Ben Buse]

Hi John,

Looks very good and I think in most cases could be used to select backgrounds -removing the need the timely wavescans.

Obviously the confidence will be less around high order interferences - where a real wavescan could be done if required - high order interferences cahnge from machine to machine - In the case of Fe La & Lb - have Fe 9th order - clearly visible on the cameca but not visible on the Jeol. I'm guessing (but haven't looked carefully) this is because Jeol sets Fe La to 4 volts, whereas on the Cameca Fe La will be set to 1-2 volts - so the 9th order remains in the spectra.

OOPS - I was wrong above - The difference between the Jeol and Cameca observed - was that the Jeol was running in differential mode with a fully open window (0.5-9.5volts; in which 9th order excluded) - which for some reason is not the same as running the Jeol in integral mode (in which 9th order occurs). The Cameca was in integral mode. The same may apply to Zr Ka V?

Any plans to include the distinction between L and H type?

Here are wavescans on Monazite



Which give LIFL 9.4 eV FWHM for Ce Lb and Nd La



And LIFH 17.71 ev FWHM


(peak fit using Fityk)

[John Donovan]

Hi John,

Looks very good and I think in most cases could be used to select backgrounds -removing the need the timely wavescans.

Obviously the confidence will be less around high order interferences - where a real wavescan could be done if required - high order interferences change from machine to machine - In the case of Fe La & Lb - have Fe 9th order - clearly visible on the Cameca but not visible on the Jeol. I'm guessing (but haven't looked carefully) this is because Jeol sets Fe La to 4 volts, whereas on the Cameca Fe La will be set to 1-2 volts - so the 9th order remains in the spectra.

Any plans to include the distinction between L and H type?

Hi Ben,
The difference in PHA voltage range between JEOL and Cameca is just a difference in gain (multiplication) convention so far as I know (that is, multiply a Cameca PHA scan by a factor of two and one should have a JEOL PHA scan).  I also haven't looked at any differences between the higher order sensitivities between JEOL and Cameca either, but since you have both instruments, you are in an ideal position to do so!

What aspect of L and H type crystals(?) are you thinking of?
john

[John Donovan]

Hi John,
Here are wavescans on Monazite

What are these two scans being compared?

[Ben Buse]

Sorry did I forget to say. Its REE in Monazite. LIFL in pink, LIFH in blue

Ben

[Ben Buse]

What aspect of L and H type crystals(?) are you thinking of?
john

Hi John

So the H crystals have poorer resolution compared to the L crystals - due to the smaller rowland circle. Therefore they ideally would be given different energy resolutions

Ben