Author Topic: JEOL Diffractors  (Read 3310 times)

SteveSeddio

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JEOL Diffractors
« on: March 15, 2016, 01:24:39 PM »
Does anyone know the dimensions of JEOL diffractors? The best dimensions I can find are 10x30 mm.

Also, I apologize if this is obvious, but what is the difference between a J-type crystal and a generic crystal (e.g., PET vs. PETJ) beyond the J type being of "high reflectivity."

Thanks!
-Steve
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Malcolm Roberts

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Re: JEOL Diffractors
« Reply #1 on: March 15, 2016, 06:01:54 PM »
Hi Steve
I think 'high reflectivity" is a buzz word so skate over that bit. As far as I am aware J-type and H-type relate to the curvature of the crystal which has to fit with the dimensions of the Rowland circle.  L-type are a the new larger area one's but crystal dimensions and size of the Rowland circle I do not have on hand. The H and J-type are about 10 by 30 as you say.
Cheers,
Malc.

Probeman

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Re: JEOL Diffractors
« Reply #2 on: March 15, 2016, 10:17:40 PM »
I think 'high reflectivity" is a buzz word so skate over that bit.

I don't know any details, but I seem to remember that John Armstrong while at Cal Tech found that many of the "high reflectivity" crystals supplied by JEOL had problems with asymmetrical diffraction, which led to issues with the effective takeoff angle for several spectrometers.

Hence the "simultaneous k-ratio" test described here:

http://probesoftware.com/smf/index.php?topic=369.msg1948#msg1948
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Ben Buse

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Re: JEOL Diffractors
« Reply #3 on: March 17, 2016, 09:49:19 AM »
J and L type go on 140 mm Rowland circle, H type on 100 mm Rowland circle

Ben

SteveSeddio

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Re: JEOL Diffractors
« Reply #4 on: March 17, 2016, 10:33:49 AM »
Thanks everyone!
Now to learn the dimensions of the L-type diffractors...
Your friendly, neighborhood, EPMA-minded EDS guy.
stephen.seddio@thermofisher.com

Probeman

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Re: JEOL Diffractors
« Reply #5 on: September 23, 2020, 12:31:53 PM »
Radoslaw Michallik at the Geological Survey of Finland asked about JEOL TAP vs TAPJ crystals on the JEOL list server, and Cyril (Mr "T") responded there as follows:

Quote
An old probe service guy here.
Julian and Stewart are correct.
Johan crystals (TAPJ) vs Johansson crystals (TAP)
See the article from Microscopy and Microanalysis

The link to the Wittry paper to Fournelle's server is here:

http://www.geoscience.wisc.edu/~johnf/g777/MM/Wittry.pdf

and I attached the pdf below.   Thank-you Cyril.
« Last Edit: September 23, 2020, 12:44:10 PM by Probeman »
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Anette von der Handt

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Re: JEOL Diffractors
« Reply #6 on: September 23, 2020, 05:16:54 PM »
Thanks, very useful. According to the Wittry-Paper attached to the previous post:

The JEOL H-type spectrometer (focal circle radius of 100 mm) uses 31.5 × 14.7 mm crystals and the regular JEOL spectrometer (140 mm radius) uses 25 × 12 mm crystals.

I have some info material from Cameca that shows that their standard crystals are 22x32 mm and the large high-sensitivity crystals are 22x60 mm.

I am also leaving a link to a different discussion on the forum about Johann versus Johansson crystals: https://probesoftware.com/smf/index.php?topic=848.0
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