  Small-Angle Scattering (SAS) investigates structures in samples that
generally range from approximately 0.5 nm to a few 100 nm. This can both be
done for isotropic samples such as blends and liquids, as well as anisotropic
samples such as quasi-crystals. In order to obtain data about that size regime
scattered intensity, mostly of x-rays or neutrons, is investigated at angles
from close to zero, still in the region of the primary beam up to 10\deg ,
depending on the wavelength of the incoming radiation. The two primary sources
for SAS experiments are x-ray (small-angle x-ray scattering, SAXS) sources and
neutron (small-angle neutron scattering, SANS) sources, which shall be the two
cases discussed here. Also scattering with electrons or other particle waves is
possible, but not the main use case for the purpose of this manuscript. For
most small-angle scattering instruments, both SAXS and SANS, the science case
covers the investigation of self-assembled polymeric and biological systems,
multi-scale systems with large size distribution of the contained particles,
solutions of (nano-)particles and soft-matter systems, protein solutions, and
material science investigations. In the case of SANS this is augmented by the
possibility to also investigate the spin state of the sample and hence perform
investigations of the magnetic structure of the sample. In the following
sections the general setup of both SAXS and SANS instruments shall be
discussed, as well as data acquisition and evaluation and preparation of the
sample and the experiment in general. The information contained herein should
provide sufficient information for planning and performing a SAS experiment and
evaluate the gathered data.
