Neutron adiabaticity and its impact on data analysis, illustrated for polarized GISANS

The significance of neutron spin adiabaticity in the data analysis of polarized Grazing Incidence Small Angle Neutron Scattering (GISANS) is discussed, with the aim of minimizing the number of simulation parameters of complex magnetic models within the neutron scattering cross-section. We illustrate how an estimate of the neutron polarization direction and adiabaticity can be obtained by magnetic field and neutron ray-tracing simulations and compare the results with measurements of the magnetic field map for the beamline used in the GISANS experiment. We show how small deviations from the neutron polarization direction with respect to the magnetic field vector at the sample position significantly affect the data analysis, and how this can be considered within the magnetic model of the scattering cross section using the Distorted Wave Born Approximation.