in general, I made the observation that intensity may drop more than expected from theory due to alignment problems. Alignment becomes increasingly critical for smaller divergences as we normally have to sintonize 2 slits, one in the incident and one in the diffracted beam. With low divergences, a small twist of the soller axis around theta or the X-ray beam may cut an important portion of intensity.
BTW, in our old Philips with 2 Soller 0.04 rad slits and sec beam graphite monochromator, using 1º div slits and a 0.2 mm receiving slit gives 12550 cps and FWHM=0.119º (including alpha2 which is visible as a shoulder) for the 2th=26.6º quartz peak and ~15 cps for the background (zero bk Si sample holder) below this peak. miguel On 19 Feb 2008 at 8:29, Michael Glazer wrote: > > Leonid > I don't know why we have such a large difference, but for some reason we > do. I will send you privately the two diagrams. > Mike > > -----Original Message----- > From: Leonid Solovyov [mailto:[EMAIL PROTECTED] > Sent: 19 February 2008 03:56 > To: rietveld_l@ill.fr > Subject: RE: advice on new powder diffractometer > > Dear Mike, > > Normally, changing sollers must not influence the signal/background > ratio. Wider sollers, however, make the primary beam wider and if the > sample diameter is small then a parasitic scattering from the sample > holder edges may appear. > > I am really surprised that moving from 0.04 Soller slits to 0.02 you got > 25 times intensity reduction. When I change the primary soller from > 0.04 to 0.02 the intensity drops ~2 times, so if you changed both the > primary and the secondary sollers the intensity should decrease ~4 > times, but not 25 times. > > Leonid Solovyov > -- Miguel Gregorkiewitz Dip Scienze della Terra, Università via Laterina 8, I-53100 Siena, Europe fon +39'0577'233810 fax 233938 email [EMAIL PROTECTED]
