Author Topic: Oxford WDS spectrometers  (Read 1131 times)

Probeman

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Oxford WDS spectrometers
« on: April 18, 2023, 01:30:05 PM »
Here's an interesting blog post by Rosie Jones at Oxford comparing various WDS geometries:

https://www.oxinst.com/blogs/why-do-all-wd-spectrometers-not-give-the-same-results?business=nanoanalysis&sbms=nanoanalysis

Most surprising is that Oxford comes out on top...    :D
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sem-geologist

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Re: Oxford WDS spectrometers
« Reply #1 on: April 19, 2023, 11:18:49 AM »
Here's an interesting blog post by Rosie Jones at Oxford comparing various WDS geometries:

https://www.oxinst.com/blogs/why-do-all-wd-spectrometers-not-give-the-same-results?business=nanoanalysis&sbms=nanoanalysis

Most surprising is that Oxford comes out on top...    :D

Interesting design of spectrometer. Is there a collimator attached to the counter (looks a bit like that, but I could be wrong, it however would make sense for higher resolution)? SX detectors has resolution in between those presented curves. Too bad there is no intensity scale on the side of that comparison graph... so what is the price of that higher resolution is not very clear. I would not be surprised if there was quite different analytical conditions utilized to hide higher noise for better resolution if run at same conditions.

BTW, Oxford is well known to have problems with peak-overlaps and thus due to that needs better resolution spectrometers. That is then their R&D clearly had not looked to any other software outside their Oxford software. I had recently been forced to read some quite recent paper (one of authors of paper was from Oxford instruments) there they present WDS (Oxford) as solution to EDS (Oxford, yes Oxford engineer was discrediting EDS of own company to promote other detector of same company) overlapping peaks (oxford software problem to be exact). Ironically that problem is no problem in NIST DTSA-II, which is capable to deal with those situation for already a decade. IMO WDS for SEM is absolute overkill - there are dozen other things which EPMA takes care, which are not on any SEM, and WDS as the sole solution for resolution is to little gain for that price. Inclined WDS (SEM-like) is not very brightest thing too.

... If I would have access to SEM only, I would, indeed, add WDS for different reason - low energy X-rays of light elements (Be, B, C, N, O, F) there that would bring some real difference to EDS.
« Last Edit: April 19, 2023, 11:29:03 AM by sem-geologist »

sem-geologist

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Re: Oxford WDS spectrometers
« Reply #2 on: April 19, 2023, 11:45:29 AM »
... But indeed these spectrometers are really interesting, I just put there some interesting highlight from their site:
Quote
....
* Bent and ground crystals and a motorised counter entrance slit further optimises resolution and peak to background for every X-ray line
Ha, I had right gut feeling where that improved resolution comes from
Quote
* Fully separate the most closely spaced X-ray lines that cannot be achieved with other techniques – for example, the Ti Kβ/V Kα overlap can only be fully resolved with Wave
Now this is interesting, I really would like to see if higher resolution can separete V Ka from TiKb satelite lines and absorbtion edge.
Quote
* Unique dual counters in series using Ar-CH4 for optimised light element and Xe for optimised high energy collection
Oh, this is like the tandem discussed in this forum for adding PIN detector behind, except without the downsides of semiconductor detectors; That now explains what we see in that photograph and animated sketch.

Indeed, the design of that spectrometer is very interesting and looks quite promising! Now if only few of such detectors could be attached vertically to some probe...
« Last Edit: April 19, 2023, 12:37:51 PM by sem-geologist »

Probeman

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Re: Oxford WDS spectrometers
« Reply #3 on: June 17, 2023, 08:26:20 AM »
Quote
* Fully separate the most closely spaced X-ray lines that cannot be achieved with other techniques – for example, the Ti Kβ/V Kα overlap can only be fully resolved with Wave

Now this is interesting, I really would like to see if higher resolution can separete V Ka from TiKb satelite lines and absorbtion edge.

I too would really like to see this demonstrated... because WDS "tails" are extended.

I guess it depends on what one means by "fully resolved" since due to polygonization thermal cycling defects during manufacturing, there is always a greater than zero level detection of x-rays from other angles as described here:

https://probesoftware.com/smf/index.php?topic=79.msg7818#msg7818
« Last Edit: June 17, 2023, 04:27:58 PM by Probeman »
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