Author Topic: can you explain this... or is it a bug  (Read 844 times)

Ben Buse

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can you explain this... or is it a bug
« on: May 21, 2018, 07:54:09 am »
Hi,

I simulated an inclusion of pyrope in rutile at 20kV

Emission plots are intergrated over interaction volume (i.e. you see x vs z, intergrated over y). But oxygen and Ti L look strange (assymetric). Ti K line makes sense the darker square is the inclusion in the middle of the interaction volume (for its intergrated over y).

config


Thanks

Ben

JonF

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Re: can you explain this... or is it a bug
« Reply #1 on: May 22, 2018, 11:54:51 pm »
When DTSA-II models a detector with take off angle etc, does it say where the detector is on those plots?

A detector top left and large absorption of the soft O Ka1 and Ti La1 in the pyrope phase could do that?

Ben Buse

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Re: can you explain this... or is it a bug
« Reply #2 on: May 23, 2018, 07:41:05 am »
I'm liking that idea, I will spin the detector round and post the results

Ben

Ben Buse

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Re: can you explain this... or is it a bug
« Reply #3 on: May 23, 2018, 07:55:40 am »
Hi Jon,

Just look at this, your right! Now detector azimuth is 180 (previously 0)



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Ben

Probeman

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Re: can you explain this... or is it a bug
« Reply #4 on: May 23, 2018, 11:09:02 am »
This is very cool. 

Because Penepma defaults to an annular detector (for better statistics), one wouldn't see this detector artifact unless one selects one of the "cardinal" direction detector geometries as seen here in the Standard.exe GUI for Penepma:



as discussed here:

http://probesoftware.com/smf/index.php?topic=58.msg1611#msg1611
The only stupid question is the one not asked!

JonF

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Re: can you explain this... or is it a bug
« Reply #5 on: May 23, 2018, 01:46:52 pm »
Wouldn't defaulting to a 360 degree annular detector for boundary fluorescence corrections actually both over and under estimate the effect of the boundary fluorescence, dependent on the real world geometry and measurement? Assuming you actually managed to convince the user that this is a problem (...) and were attempting to subtract the fluorescence from real data.

For example, assuming a boundary fluorescence issue rather than an inclusion, the Ti La and O Ka measured X-ray intensity would vary dependent on whether the generated X-rays pass through the rutile or the pyrope on their way to the detector, which is dependent on the geometry of the boundary and azimuth of the detector used.

And then if you were measuring traces on multiple detectors and summing the counts... argh!

An interesting thought experiment, but would you be able to put specific elements on specific simulated detectors (or multiple) and get PENEPMA to work out whether it would travel through a particular phase?
I guess this is only going to become more of a problem as we work towards lower accelerating voltages and consequently lower energy emission lines.   

Probeman

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Re: can you explain this... or is it a bug
« Reply #6 on: May 23, 2018, 02:04:00 pm »
Wouldn't defaulting to a 360 degree annular detector for boundary fluorescence corrections actually both over and under estimate the effect of the boundary fluorescence, dependent on the real world geometry and measurement? Assuming you actually managed to convince the user that this is a problem (...) and were attempting to subtract the fluorescence from real data.

Absolutely!   The annular detector geometry is only utilized to improve calculation statistics and really intended for bulk samples only.  I just wanted to point that out in case anyone is interested in modeling these boundary effects using the Penepma GUI in Standard.exe (CalcZAF).

The effect of detector orientation at phase boundaries is discussed in our recent paper (and in several other publications by Llovet):

http://probesoftware.com/smf/index.php?topic=58.msg7189#msg7189

And to your subsequent points, yes.  This gets complicated...
The only stupid question is the one not asked!