Resolution, truncation and smearing of the one-dimensional spin echo small-angle scattering instrument

The resolution of the spin echo small-angle neutron scattering (SESANS) instrument is limited by the precession Larmor fields and by the wavelength of the neutrons. It can reach to about a micrometer with thermal neutrons and to a few tens of micrometers with cold neutrons. Since a SESANS instrument will have a limited coverage in scattering angles or in neutron momentum transfers, there will be truncation errors in the measured correlation functions. These truncation errors increase with smaller scattering particles and they limit the smallest particle that can be effectively studied by the instrument. The off-plane scatterings in one-dimensional SESANS as well as the inhomogeneity of the precession fields cause smearing effects in the correlation functions. Desmearing procedures developed for the traditional small-angle scattering instruments can be used to restore the true parameters of the scattering particle.