Author Topic: EPMA Teaching Examples  (Read 816 times)

Probeman

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EPMA Teaching Examples
« on: February 20, 2017, 02:25:02 pm »
I started this topic so we can post interesting examples of EPMA issues for educational purposes...

Here is an example.  I knew that the U Ma peak is close to the Ar absorption edge, but I did not realize that the Cd La peak is also near this absorption edge. 



This is why it is important to scan the region around your analytical peak, to not only avoid interfering secondary emission lines on the off-peak positions, but also to avoid interpolating our background fit across absorption edges from our detectors.
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Probeman

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Re: EPMA Teaching Examples
« Reply #1 on: February 27, 2018, 10:44:27 am »
Here is a microanalysis example I sometimes give my students to make sure they are considering the physics properly.

This example was created using the "demo" EDS simulation mode in Probe for EPMA which utilizes Penepma to generate an EDS spectra in real time. One could also do it on an actual instrument, but I find it useful to have each student download PFE and have them install it on each of their laptops.  That way they can explore the possibilities on their own.

This spectrum is simply an EDS acquisition in PFE on a pure Mo standard at 20 keV.  I ran it for 300 seconds and the spectrum looks quite good.  But just to prove the point I then ran it for 3000 seconds and that what I'll show below, though even a 1 min EDS acquisition makes the point clearly.  Here is the full EDS spectrum "acquired" by Penepma:



We can then zoom in on the Mo La line and see that the KLM markers line up nicely with the L emission family:



Penepma is so cool!    :)

Now we zoom in on the Mo Ka ROI and what do we see?



Nothing!   Now we ask our students: OK, so why don't we see the ~17 keV Mo Ka emission?  Hint: we're using a 20 keV beam energy...  then I ask them to look up the Mo K edge energy...

I'm sure there lots of such entertaining and educational examples for students, so please feel free to share your favorites.
« Last Edit: February 27, 2018, 03:27:35 pm by Probeman »
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Probeman

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Re: EPMA Teaching Examples
« Reply #2 on: March 04, 2018, 11:41:51 am »
Teaching probabilities can be fun.  I just found these old apps I had slapped together for my Weird Science freshman seminar class (for non-science majors) about 5 years ago, so nothing fancy. In fact you can probably find better apps elsewhere on the net.  But they have their appeal.   Also probably good for high school students and science minded middle schoolers even.

Dice.exe is a simple app that allows one to specify the number of dice, and the number of faces for each die.  Default is 2 dice with 6 faces! 



Here's a chart I found that explains what you're seeing with two dice with 6 faces each:



Toss.exe just tracks random coin flips. Run it a few times by clicking the Toss button. You might be surprised.



The exe files are attached below (login to see), along with the MS chart control (MSChrt20.ocx). Just copy the two .exe files and the .ocx file to any folder and they should run fine from there.

If anyone is interested in the source code I'd be happy to share it.
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Probeman

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Re: EPMA Teaching Examples
« Reply #3 on: March 06, 2018, 12:37:22 pm »
This is a very simple app to demonstrate Brownian motion to students.  It is not at all scientific as it's completely schematic, but it does help to illustrate the effects of density and temperature on Brownian motion I think.

The Brownian.exe and the associated color palette files (which can be modified as necessary) are attached below (remember to login to see attachments).

To use the app, copy the exe and the .fc color palette files to any folder, then double-click the Brownian.exe file, and then click the Start menu. There should be no other dependencies on most PCs, but please let me know if you see any problems.

To adjust the temperature (drawing speed), one can use the Options menu or simply tap the up/down cursor keys.  Up for higher temperatures, down for lower temperatures.  To adjust the mean free path (distance), again use the Options menu or simply use the right/left cursor keys. Right to increase mean free path and left to decrease mean free path.

It is not possible to show the temperature effects in a screen shot, but here is the app with a long mean free path (low density):



and here is the app with a short mean free path (high density):



The palette color represents the Z dimension... maybe this app might be useful for middle and high schoolers?
« Last Edit: March 06, 2018, 01:31:16 pm by Probeman »
The only stupid question is the one not asked!