Ultra‐small‐angle neutron scattering with azimuthal asymmetry. Issue 3 (16th May 2016)

• Record Type: Journal Article
• Authors: Gu, X.; Mildner, D. F. R.
• Is Part Of: Journal of applied crystallography. Volume 49:Issue 3(2016)
• Page Start: 934
• Page End: 943
• Publication Date: 2016-05-16
• Subjects: azimuthal asymmetric scattering -- double‐crystal diffractometers -- elliptic scattering contours -- slit‐height smeared scattering -- small‐angle neutron scattering; Crystallography -- Periodicals; 548.05
• DOI: 10.1107/S1600576716005586
• Languages: English
• ISSNs: 0021-8898

Abstract

Abstract : A method is given for converting slit‐smeared azimuthally asymmetric data collected on a double‐crystal diffractometer for concatenation with the usual pinhole‐geometry small‐angle neuton scattering data. Abstract : Small‐angle neutron scattering (SANS) measurements from thin sections of rock samples such as shales demand as great a scattering vector range as possible because the pores cover a wide range of sizes. The limitation of the scattering vector range for pinhole SANS requires slit‐smeared ultra‐SANS (USANS) measurements that need to be converted to pinhole geometry. The desmearing algorithm is only successful for azimuthally symmetric data. Scattering from samples cut parallel to the plane of bedding is symmetric, exhibiting circular contours on a two‐dimensional detector. Samples cut perpendicular to the bedding show elliptically dependent contours with the long axis corresponding to the normal to the bedding plane. A method is given for converting such asymmetric data collected on a double‐crystal diffractometer for concatenation with the usual pinhole‐geometry SANS data. The aspect ratio from the SANS data is used to modify the slit‐smeared USANS data to produce quasi‐symmetric contours. Rotation of the sample about the incident beam may result in symmetric data but cannot extract the same information as obtained from pinhole geometry.