JEOL Diffractors

[SteveSeddio]

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

[Malcolm Roberts]

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]

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

[Ben Buse]

J and L type go on 140 mm Rowland circle, H type on 100 mm Rowland circle

Ben

[SteveSeddio]

Thanks everyone!
Now to learn the dimensions of the L-type diffractors...

[Probeman]

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:

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.

[Anette von der Handt]

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

[jlmaner87]

Does anyone have any experience (or data) with H-type vs L-type PET and LiF crystals? In particular, Peak-to-background and intensities. Thanks.

[Probeman]

Does anyone have any experience (or data) with H-type vs L-type PET and LiF crystals? In particular, Peak-to-background and intensities. Thanks.

I would say that in general one should avoid the H type crystals as they are highly curved and tend to crack over time making them unsuitable for quantitative work. They also have a much smaller focal circle which lowers the spectral resolution. The L types are larger and therefore have more intensity and utilize the same focal circle (I think) as the normal crystals.

[Anette von der Handt]

Here is a comparison of LIF vs LIFH vs PETJ for Ti ka on Ti metal from my old JEOL JXA-8900R at the University of Minnesota. I see if I can add the data for the L-variants as well.

[Anette von der Handt]

I would say that in general one should avoid the H type crystals as they are highly curved and tend to crack over time making them unsuitable for quantitative work. They also have a much smaller focal circle which lowers the spectral resolution. The L types are larger and therefore have more intensity and utilize the same focal circle (I think) as the normal crystals.

I would agree as far as regarding the TAPH crystal but I have not heard of cracking of PETH and LIFH crystals (anyone has stories?). I personally think the L-type versions are the best of both worlds with great intensities at comparable spectral resolution to the regular-sized crystals but the H-type spectrometers are still widely popular in Europe (and probably beyond). The significant price difference between an H-type spectrometer and the same configuration with L-type crystals is probably the main reason behind this.

[Anette von der Handt]

Does anyone have any experience (or data) with H-type vs L-type PET and LiF crystals? In particular, Peak-to-background and intensities. Thanks.

I think this is what you are looking for: A comparison of JEOL monochromator performance