Resonant Larmor precession for three-dimensional polarisation analysis in diffraction and reflectometry in the presence of a field

A new application of Larmor precession will be described that can be applied in various neutron techniques. The use of resonant spin-flippers enables one to change the precession phase from the time to the space domain and reverse. This transformation property is essential for resonant field precession. In this paper this transformation property is used to present the polarisation vector in a space with field in a well-defined direction over the whole space at one single moment. This enables one to study the change of polarisation during scattering in a magnetic sample without hindrance of change in polarisation direction by the Larmor precession in that sample. The time analysis of the precession enables one to scan the different orientations of the polarisation vector in that space during the scattering and the polarisation change by the scattering.