Paper detail

An ultra compact on-beam 3He polarizer for separation of incoherent background in high Q-range SANS

Incoherent background can create an intrinsic problem for standard small angle neutron scattering measurements. Biological samples contain hydrogen which is a strong incoherent scatterer thus creating an intrinsic source of background that makes determination of the coherent scattering parameters difficult in special situations. This can especially be true for the Q-range from around 0.1-0.5 Å-1 where improper knowledge of the background level can lead to ambiguity in determination of the samples structure parameters. Polarization analysis is a way of removing this ambiguity by allowing one to distinguish the coherent from incoherent scattering, even when the coherent scattering is only a small fraction of the total scattered intensity. 3He spin filters are ideal for accomplishing this task because they permit the analysis of large area and large divergence scattered neutron beams without adding to detector background or changing the prorogation of the scatter neutron beam. This rapid note describes a design for a new ultra compact SEOP based 3He polarized that can be used for this application. This is a work in progress, the magnetic system has been completed and tested. We are in the process of constructing the mechanical components for online polarization, such as a compact laser system and the oven described in this intermediate document.