Mitigating background caused by extraneous scattering in small-angle neutron scattering instrument design.

Measurements, calculations and design ideas to mitigate background caused by extraneous scattering in small-angle neutron scattering (SANS) instruments are presented. Scattering includes processes such as incoherent scattering, inelastic scattering and Bragg diffraction. Three primary sources of this type of background are investigated: the beam stop located in front of the detector, the inside lining of the detector vessel and the environment surrounding the sample.

Effects of multiple scattering encountered for various small-angle scattering model functions.

In small-angle scattering theory and data modeling, it is generally assumed that each scattered ray - photon or neutron - is only scattered once on its path through the sample. This assumption greatly simplifies the interpretation of the data and is valid in many cases. However, it breaks down under conditions of high scattering power, increasing with sample concentration, scattering contrast, sample path length and ray wavelength.