SANS polarization analysis with nuclear-spin-polarized He-3

A neutron spin filter based on transmission through nuclear-spin-polarized He-3 gas has been applied to polarization analysis of small angle neutron s cattering (SANS). Such spin filters, which are based on the large spin depe ndence of the absorption of neutrons by He-3, make SANS polarization analys is possible because of their large angular acceptance. In the present exper iment, a He-3-based analyzer was employed to separate nuclear scattering in to its coherent and spin-incoherent components. Polarized He-3 analyzers we re prepared by two different optical pumping methods and installed on the N G3 SANS instrument at the NIST Center for Neutron Research (NCNR). Measurem ents were taken on cellophane tape and silica gel, for which the scattering is almost completely incoherent and coherent, respectively, and on a combi ned sample. For the combined sample, separation of the coherent part from t he incoherent part was successfully demonstrated using polarization analysi s.