Matthew, I think Klug & Alexander (1974) give a good explanation about the origin of the term "parafocusing": 2nd edition, section "parafocusing methods", page 222 ff.
Cheers, Arnt From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf Of Eduard E. Levin Sent: Montag, 2. Mai 2016 13:21 To: Cline, James Dr. (Fed); Matthew Rowles Cc: rietveld_l@ill.fr Subject: RE: Parafocussing definition? Dear James, For me too, please, if it would not be much of a trouble. Thank you in advance! Eduard On Mon, 2 May 2016 11:09:31 +0000, Cline, James Dr. (Fed) wrote > Bob Cheary and I developed and presented a workshop several times in the > 1990's that included a discussion of this issue. I can send you the notes > for it if you would like them. > > Jim > > > James P. Cline > Materials Measurement Science Division > National Institute of Standards and Technology > 100 Bureau Dr. stop 8520 [ B113 / Bldg 217 ] > Gaithersburg, MD 20899-8523 USA > jcl...@nist.gov<mailto:jcl...@nist.gov> > (301) 975 5793 > FAX (301) 975 5334 > > From: rietveld_l-requ...@ill.fr [mailto:rietveld_l-requ...@ill.fr] On Behalf > Of Matthew Rowles > Sent: Monday, May 02, 2016 1:53 AM > To: RIETVELD_L Distribution List <rietveld_l@ill.fr> > Subject: Parafocussing definition? > > > Hi all > > > > I've been trying to find a good explanation of what parafocussing (wrt > Bragg-Brentato geometry) actually is, but haven't been able to find one. > > > > Klug and Alexander just reference Brentano's papers. > > > > "The Basics of Crystallography and Diffraction" 2nd ed say that B-B geometry > is "semi-focussing" because the sample is flat, and not curved to follow the > focussing circle (this doesn't sound right to me) > > > > Brentano, J Appl. Phys. 17, 420 (1946) says that a ray reflecting off the arc > defined by ACB where A is the source, C is the centre of the gonio, and B is > the detector (ie the focussing circle) is automatically parafocussing, > because you only can establish the location of the crystallites, not their > orientation, but then goes on to say that you can actually find the > orientation, as the lattice plane normal bisects the angle ACB. > > > > I also haven't been able to find a use of the word "parafocus" outside of the > diffraction literature, so I can't see how the word is used elsewhere. > > > > Any ideas? > > > > > > Matthew -- Open WebMail Project (http://openwebmail.org<http://openwebmail.org/>)
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
