Superconducting Wollaston Prism for Spin Echo Scattering Angle Measurement

Small Angle Neutron Scattering (SANS) has been an extremely productive materials science probe for several decades and is used extensively by researchers studying a wide range of subjects, including polymers, ceramics, metals and biological macromolecules and functions. However, it is limited to length scales from 1 to 100 nm and requires highly collimated and relatively monochromatic neutron beams, reducing its ability to study dilute systems. Ultra- SANS increases the achievable length scale, but at the cost of reduced signal. Spin Echo Scattering Angle Measurement (SESAME) has been developed to visualize larger structures and permit broader bandwidth and divergence of the neutron beam, increasing signal. To fully capitalize on this method hardware with much improved performance is required. The proposed neutron spin interferometer uses matched pairs of magnetic Wollaston prisms to provide the precisely cancelling neutron spin precession needed for spin echo angle encoding. A novel design using superconducting coils and Meissner screens is proposed to achieve high magnetic fields and the dimensional precision that is required for accurate structural measurements over a range of length scales extending from a few nanometers to several mircons. The resultant device does not require careful cancelling of background magnetic fields and will greatly extend the measurement capabilities of neutron scattering in the area of nanoscience. The end product is a more compact, lower-cost instrument capable of measuring a wider range of structures with increased signal. Commercial Applications and Other Benefits: By extending the range of structural objects that can be studied, the proposed instrument will open new fields of material science studies. Possibilities include visualizing the later stages of precipitate coarsening in metal alloys, cavity growth in fatigued metals and ceramics as well as many aggregation and self-assembly phenomena. Applications are in petrochemicals (colloidal and aggregate dynamics), biotechnology and medicine (membranes, macromolecules), and industry (metallurgy, ceramics, polymers, electrolytes in fuel cells, magnetic sensors and memory). Given the lower cost and size of this system along with the continuing development of more powerful neutron generators, the proposed instrument should be suitable for neutron studies at weak neutrons sources installed at smaller laboratories, such as at universities.