JEOL H type spectrometers with TAP crystals

[Probeman]

I've heard various interesting effects for JEOL H type spectrometers (100 mm FC) with the TAP crystal.  Would someone be willing to post some scans of say Al Ka and Kb on say Al2O3?  A scan that includes both the Al Ka and Al Kb would be most interesting.  I obtain these L-units for the two lines so a single scan that includes both emission lines would be ideal.

al ka on TAP (140 mm), is 90.90472 (with refractive index correction, k= 0.00218)
al kb on TAP (140 mm), is 87.0001 (with refractive index correction, k= 0.00218)

These lines should both be above the lower limit on these spectrometers.   And if possible a comparison with the normal 140mm spectrometer TAP crystal for Al Ka/Kb also.

Thanks!
john

[Jason in Singapore]

Our TAPH only just barely reaches out to Al Kb, but here are some wavescans for Al in corundum and Mg in periclase.

What are these effects? If I know what to look for I can scale the wavescans accordingly.

[Probeman]

Our TAPH only just barely reaches out to Al Kb, but here are some wavescans for Al in corundum and Mg in periclase.

What are these effects? If I know what to look for I can scale the wavescans accordingly.

Hi Jason,
These are wonderful.  I wanted to compare the LTAP and TAP peak shapes.  The TAP is from a 140mm FC spectrometer and the LTAP from an 80mm FC spectrometer, correct?

Can you post the MDB file so I can overlay them in PFE?
john

[Probeman]

The TAP is from a 140mm FC spectrometer and the LTAP from an 80mm FC spectrometer, correct?

Hi John

Assuming you're referring to Rowland circle diameter, for JEOL spectros:

TAP, TAPL = 140mm RC
TAPH = 100mm RC

In general, "regular" or L-type = 140mm, H-type = 100mm. Don't think JEOL makes an 80mm.

Hope this helps,
OKN

Yes, I meant a 100mm Rowland circle.

Can you provide an MDB file with both a TAP and a TAPH scan on Al Ka/Kb?
john

[Probeman]

Can you provide an MDB file with both a TAP and a TAPH scan on AL Ka/Kb?
john

Wish I could - I can get you one on a regular TAP, but no TAPH or TAPL on our probe, unfortunately.

Sorry,
OKN

Guess I'll have to wait for Jason then.

[Jason in Singapore]

Here it is. Spectrometer 3 (100mm) is our TAPH. Spectrometer 1 is 140mm with a regular crystal.

[Probeman]

John Armstrong gave me permission to post his list server reply to Axel's question:

I agree with John D.  We  have both TAPH and TAPL crystals on our new 8530F and we had to replace the TAPH's (under warranty) over six times because of their initially having or building up cracks.  Cracks add a significant Lorentzian tail to the peaks.  If you're looking at trace elements, L-lines of the first row transition elements or cases, where there's a nearby peak this can be a big deal.  We're not able to obtain the same k-ratio's for measurements of the Cu L lines in copper metal vs copper-gold alloys on our TAPH spectrometer (with its cracked crystals) as we did with our TAPL spectrometers.  We ran into similar problems with measuring 2nd order Si (can't do 1st order Si on the TAPH) in the Ni-rich silicates and silicides.  I'm going to be presenting some of this data at the MAS EPMA workshop in Madison this spring.

(Because of the basic extreme bending of the TAPH crystal with its reduced Rowland circle diameter, we decided to return the spectrometer and get an L-type spectrometer instead.  If I were going to keep the spectrometer, I'd make sure not to use the TAPH crystal for any critical trace element or high accuracy quantitative analysis work.  One of our other spectrometers is an H-type with PET and LiF crystals.  They are able to bend to the appropriate degree without cracking and work fine.)

If your cracked crystal is an L-type, it just depends on how bad the crack is.  A good test of how bad the peak shapes are being affected is to take wavelength scans with your good and cracked crystals over a good intensity peak and then plot them with log(intensity) vs L-value.  The degree of Lorentzian tailing will be really obvious.