Characterization of SANS Facility at Necsa and SANS Application to the Study of Wool Fibres

Abstract

A short-version ( 10 m) Small Angle Neutron Scattering (SANS) beam line facility was installed at the South African Nuclear Energy Corporation (Necsa)'s SAFARI-1 Research Reactor. This was in a way to prepare for a practical low signal-to-noise ratio SANS at Necsa, although there is no cold source nor available tangential beam channel, the beam line has been installed on a radial beam channel. A low signal-to-noise ratio SANS is possible by using curved neutron guides and a long scattering chamber to observe a broad momentum transfer range with minimal use of radiation shielding. In this work, Silver Behenate (AgC22H43O2) was used as a standard sample for calibrating the small-angle scattering instruments to calibrate the shortversion SANS facility. The results were compared with those from a similar facility at the Budapest Neutron Centre (BNC) in Hungary. Using the BNC SANS facility, a study of wool and mohair bre properties during the wetting process was also performed. The process has been exploited by di erent techniques, especially Small Angle X-ray Scattering (SAXS). Although the macroscopic wetting process is well understood, observation of the exact location of the water accumulation has not been con- rmed, or observed dynamically, and furthermore has not been studied using SANS, especially with the use of D2O (contrast variation method) as a wetting agent. The use of D2O provides for improved contrast so as to understand, in detail, the absorption process that these di erent types of bres undergo when dry and wet. An outline of a long version of the SANS facility at Necsa is also discussed. Modelling and implementation of this version is also presented. This completed facility will be used to study various characteristics of nano materials, amongst others, to determine the conformation of polymers, the molecular constituents of biological molecules, the critical opalescence at second order phase transformations, etc. These very di erent examples demonstrate the broad eld of applications using SANS technique.