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RE: [sdpd] Optimal instrument configuration
Hello all,
I have been following this discussion with interest. We have been X'Cellerator users of the first hour and we have only had positive experiences with it. To give you an idea of the gain in speed : we had a program defined for regular use (phase identification) in which we measure a powder specimen from 8° to 100° in 4 hours with 0.04 Sollers (incident and diffracted). Since the arrival of the X'Cellerator, we do our phase identification runs from 5° to 120° in 45 minutes with 0.02 Sollers.
Doing this, not only have we got much better statistics, but the peak shapes are also much easier to fit. Although they are somewhat broader than the peaks obtained with a proportional counter (for the same Soller slits), their shape is much more regular. This results in BETTER determinations of lattice parameters and quantitative analysis, because of an easier peak shape description. To see an example, take a look at http://www3.sckcen.be/microstructure/Infrastructure/Infrastructure_XRD_XPert_Powder_UO2%20lattice%20param.htm. The website is in full development, but it will give you an idea. If there's enough interest, I could provide this forum with some spectra (for instance LaB6) taken in several configurations.
The background is different from what one obtaines with a proportional counter, but smooth and, except for a broad bump at low angles, relatively flat.
We have been using a Ni filter to get rid of the Kb, because there was no back monochromator available yet and we don't have a primary monochromator. In a few weeks, we will also have the new back monochromator available and I'll be able to tell you more on that subject.
We have also done measurements with a capillary spinner and there also, great results were obtained in much shorter times (http://www3.sckcen.be/microstructure/Infrastructure/Infrastructure_XRD_XPert_Capillaries_UO2%2Bx.htm). In the future, we are planning on doing some high temperature diffraction (Buhler furnace), where I expect to see large gains in speed too. Considering the loss of 2 times 15% of the signal because of the Be windows, I think the X'Cellerator will be very useful.
Has anyone ever considered applying signal theory as known in electronics to diffraction patterns ? Because of the recent improvements in resolution in the diffractometers, a lot of effects such as axial divergence have become a rather annoying problem in the description of diffraction peak shapes (at least in my experience). The combination of a high resolution goniometer with a fast, but lower resolution detector may ultimately prove to be the best combination. To demonstrate this, it would be necessary to do the math.
Kind regards,
Sven Van den Berghe
****************************************************************
Dr. Sven Van den Berghe
Microstructure Research
Reactor Materials Research Department (RMO)
Laboratory for High and Medium Activity (LHMA)
Boeretang 200
B-2400 Mol
Belgium
Tel. : +32 14 33 30 64
Fax : +32 14 32 12 16
E-mail : svdbergh...@sckcen.be <mailto:svdbergh...@sckcen.be>
****************************************************************
> -----Original Message-----
> From: Armel Le Bail [mailto:alb...@cristal.org]
> Sent: dinsdag 19 februari 2002 10:12
> To: sdpd...@yahoogroups.com
> Subject: RE: [sdpd] Optimal instrument configuration
>
>
> Hi again,
>
> About the Philips X'celerator. A gain in speed of up to 99 is claimed.
> http://www.analytical.philips.com/products/xrd/xpertpro/x_celerator/
> It is also claimed that the large reduction in data collection
> time can of course also be used to increase the resolution
> of the diffractogram. In order to prove that, the NIST corundum
> plate SRM1976 was measured overnight :
> http://www.analytical.philips.com/news/press/content/file_133.pdf
>
> I should state that we obtain that resolution and statistics quality
> by using a proportional counter in 10 nights, not in 99 nights (but
> not stripping alpha-2 with an incident beam monochromator...).
>
> So, is there not some exaggeration with the X'celerator ?-). Do
> users can confirm ?
>
> I suppose that this new type of detector (Real Time Multiple Strip)
> will be proposed soon by the other manufacturers, or is there
> an exclusive Philips licence ?
>
> ALB
>
>
>
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