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Moderator: Ellery Frahm, [log in to unmask], Electron Microprobe Lab, University of Minnesota
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AECL-OFFICIAL USE ONLY
Hello Alfred and Jim:
I use a LDE1 xtal which is actually from Osmic Inc. (probably used to be Ovonics ..Ovonyx or is now) for O2 quantitative measurement with fairly good success for minute concentration changes in Oxygen content. The xtal is multiplayer WSi with a wavelength of 23.62 d-spacing of 29.70A and thus it is called an OVO 60A10 multi-layered xtal . I have determined optimum operating conditions in order to obtain the best analysis results. This company that supplied the xtal charged around $3000.00 for it in 1999...so hopefully this helps in your possible purchase..
Pam
-----Original Message-----
From: JEOL-Focused Probe Users List [mailto:[log in to unmask]]On Behalf Of McGee, James
Sent: September 15, 2008 6:16 PM
To: [log in to unmask]
Subject: Re: [PROBE-USERS] multi-layer crystals
Alfred,
I use LDE2 when it is most efficient and the LDE1-crystal/spectrometer is not available or over-allocated, and when the O measurement is not super-critical (trace O measurement is difficult on any crystal, but it would be better done on the LDE1). You can get numbers out of anything of course, but to make the measurements as useful as possible, just be careful about positioning background offsets so as to stay away from overlaps as much as possible. On the low side of an LDE2, you have about 8 - 9mm offset before the lower spectrometer limit is reached. The crystal gets good count rates, certainly better to use than a TAP for O and better than I remember the old PbSd crystals with similar 2d spacing. Calculated detection levels are down in the 100s Backgrounds and overlap effects can also be handled by some good software routines (to correct for the overlaps for example, and to measure backgrounds by the mean atomic number method)- nothing new here, just some general guidelines as you will have to try to make the O measurements yourself before saying they are useless.
Owen, there used to be a company in Michigan called Ovonics (part of Energy Conversion Devices) that made these crystals; they called them LSM (layered synthetic multicrystals)- I had one of theirs with a 2d spacing of ~160 on a JEOL 8900 (for B analysis) and it worked well. Another possible source for pricing.
Jim
************************************
James J. McGee
Materials Engineer, Test Operations
Lockheed Martin, KAPL, Inc.
Mail Bin 149
PO Box 1072
Schenectady, NY 12301-1072
Tel: 518-395-4612
Fax: 518-395-4340
email: [log in to unmask]
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_____
From: JEOL-Focused Probe Users List [mailto:[log in to unmask]] On Behalf Of Alfred Kracher
Sent: Friday, September 12, 2008 10:12 AM
To: [log in to unmask]
Subject: [PROBE-USERS] multi-layer crystals
JEOL Probe Users Listserver
Moderator: Ellery Frahm, [log in to unmask], Electron Microprobe Lab, University of Minnesota
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* Hello Jim,
Yes. On the JEOL it is called the LDE2 crystal, 2d spacing of ~97
angstroms. The Oxygen measurement on this is near the low end of the
spectrometer, so backgrounds get a bit high, but it works.
Do you actually use it for O? I thought it was pretty useless, but if you have a way to get O numbers out of LDE2 I would appreciate learning your technique (off-list unless you think it's interesting for other JEOL owners, too). We only have 2 light elements spectrometers on our 8200, and it would be useful.
Alfred
Alfred Kracher
Ames Laboratory (USDOE)
Iowa State University
227 Wilhelm Hall
Ames, IA 50011-3020
Tel.: 515 294 7097
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