How do you define signal to noise in powder diffraction? I have seen this term used several times, but I have not found a definition so far with regard to powder diffraction per se. I have just done two runs on a Panalytical one with 0.04 soller slits and one with 0.02 (both with a CuKa1 premonochromator) both for about 9 hours. The strongest peak for the 0.02 case is 2700 counts, half width 0.08 degrees and a background of 25 counts. The same peak with the 0.04 slits has 70000 counts, half width 0.11 degrees and a background of 700 counts.
Mike Glazer -----Original Message----- From: Van der Lee [mailto:[EMAIL PROTECTED] Sent: 18 February 2008 16:36 To: rietveld_l@ill.fr Subject: Re: advice on new powder diffractometer Leonid Solovyov wrote the following on 18/02/2008 16:27: >> Yes it is mainly down to the Soller slits, there was a very large >> thread on soller slits somewhere in the Rietveld archives about this >> discussion. I think the down side of changing the soller slits is a >> move away from the optimum FWHM that can be obtained? > > Changing sollers from 0.04 rad to 0.02 or 0.01 reduces the asymmetry, > the FWHM and the intensity, so the peak shape and the resolution > become more optimal but the intensity is sacrificed. > > However, the signal to noise ratio becomes better with 0.02/0.01 rad sollers compared to 0.04 rad Arie -- *************************************************************************** A. van der Lee Institut Européen des Membranes CNRS - UMR 5635 Université de Montpellier II - Case Courrier 047 Place E. Bataillon 34095 MONTPELLIER Cedex 5 - FRANCE Tel : 33 (0) 4 67 14 91 35 Fax : 33 (0) 4 67 14 91 19 Website X-ray scattering facility ICG/IEM: http://www.iemm.univ-montp2.fr/xrayweb/main_uk.html ****************************************************************************
