Hi, Wouldn't a change of Ni filter for a thicker one at least reduce significantly the problem. It would absorb mostly below the edge but still will absorb a significant amount of all the radiation that goes through reducing the tails? Or a monochromator is the only solution? Would a tube replacement reduce some of the problem? Thanks, Leo
2013/9/16 Alan Coelho <[email protected]> > Matt > > >I am not sure I understand how you would account for the additional > >wavelengths in the beam. > > Tube tails is spectrally independent and its aberration shape is 2Th > independent. Its realized in TOPAS by a convolution called stacked_hats > which, as its name suggests, convolutes a series of stacked impulse > functions. An intense narrow hat represents the beam and wider hats the > penetration of the electrons in the tube. > > Cheers > Alan > > -----Original Message----- > From: Matt Beekman [mailto:[email protected]] > Sent: Tuesday, 17 September 2013 2:08 AM > To: Peter Y. Zavalij; Alan Coelho; [email protected]; > [email protected] > Subject: RE: Instrumental resolution function > > Alan, Peter, > > Would you mind briefly elaborating on the procedure used to "fit tube > tails?" I personally have only used GSAS for Rietveld refinement, and other > than adding another phase(s) with slightly different lattice parameter(s) I > am not sure I understand how you would account for the additional > wavelengths in the beam. > > Many thanks in advance! > > Matt > > -- > Matt Beekman, Ph.D. > Assistant Professor of Physics > Department of Natural Sciences > Oregon Institute of Technology > 3201 Campus Drive > Klamath Falls, OR 97601 > Tel: 541-885-1940 > Fax: 541-885-1849 > Email: [email protected] > Web: > http://www.oit.edu/faculty-staff/home-pages/natural-science/matt-beekman > > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf > Of Peter Y. Zavalij > Sent: Monday, September 16, 2013 6:11 AM > To: Alan Coelho; [email protected]; [email protected] > Subject: RE: Instrumental resolution function > > I do exactly the same - fit tube tails using LaB6 standard and use the > parameters (usually w/o fitting) in all other refinements. Although tube > tails fitting helps a lot it's not perfect. > Peter Zavalij > > -----Original Message----- > From: Alan Coelho [mailto:[email protected]] > Sent: Sunday, September 15, 2013 10:05 PM > To: Peter Y. Zavalij; [email protected]; [email protected] > Subject: RE: Instrumental resolution function > > Hi Peter, Mario > > I happen to have a Ni filter, Cu, LaB6 pattern that has a very similar > look > to the one sent by Mario. Probably best to look at the 21.35 degrees 2Th > peak. The Ni filter cut-off occurs at 20.6 degrees 2Th, the satellite group > is hard to see due to the low angle and hence compression of the emission > profile. What made sense in the pattern was to fit Tube tails. Across the > whole patter the Rwp was reduced by 2.1% where Tube tails was considered > and > the fit at the shoulders was good. > > Cheers > Alan > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf > Of Peter Y. Zavalij > Sent: Monday, 16 September 2013 10:55 AM > To: [email protected]; [email protected] > Subject: RE: Instrumental resolution function > > Hi Mario, > The shoulder you observe is what's left from "white" after it is cut off by > beta-filer. You could check the absorption edge of Ni and it is right at > the > shoulder you observe. > Peter > > __________________________________ > Peter Zavalij > X-ray Crystallographic Center > University of Maryland > College Park, MD 20742 > Phone/Fax: (301)405-1861 > http:/www.chem.umd.edu/crystallography > > > > -----Original Message----- > From: [email protected] [mailto:[email protected]] On > Behalf > Of [email protected] > Sent: Sunday, September 15, 2013 6:08 PM > To: [email protected] > Subject: Instrumental resolution function > > Dear All, > > I am calculating the corresponding instrumental resolution function of our > Bruker diffractometer which is operating in Bragg-Brentano geometry with Cu > radiation, using a nickel filter and LynxEye detector. > > The calculation is carried out by the Rietveld analysis of the LaB6 (660b) > NIST-standard. We observed the Kbeta peaks, but also some shoulders in the > left part of the peaks. We have some ideas about this but taking into > account that I'm not an actual expert, your comments will be very important > to me. > > In the attached file, I send an image to make a better illustration of my > doubts. > > Thanks in advance for your help. > Best Regards, > > Mario A. Macías > Universidad Industrial de Santander > Bucaramanga-Colombia. > > > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > Please do NOT attach files to the whole list <[email protected] > > > Send commands to <[email protected]> eg: HELP as the subject with no body > text > The Rietveld_L list archive is on > http://www.mail-archive.com/[email protected]/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > -- Dr. Leopoldo Suescun Prof. Agr (Assoc. Prof.) de Física Tel: (+598) 29290648/29249859 Cryssmat-Lab./DETEMA Fax: (+598) 29241906 Facultad de Quimica, Universidad de la Republica ,_. | \ | v- ,' \ | ( \__Montevideo, Uruguay
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <[email protected]> Send commands to <[email protected]> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/[email protected]/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
