This project involves the construction of a Low Energy Neutron Scattering (LENS) facility at the Indiana University Cyclotron Facility (IUCF). LENS will use the existing linear accelerator at IUCF to produce 11 MeV protons, generating a pulsed neutron beam through (p, n) reactions on a Be target. Not only is LENS a novel and relatively inexpensive pulsed cold neutron source, but also - when completed in 2005 - LENS will enable the design of novel neutron instrumentation for small angle scattering, a broad program of research in materials science and biology, the development of novel neutron sources and moderators, and the education and training of the next generation of neutron scientists in the United States. LENS will also serve as a regional user facility that will be particularly well-suited for high-risk experiments and feasibility studies.
The particular aspects of LENS that are being completed through this project are (1) the construction of neutron guides and (2) the development of a novel Larmor Precession Scattering Instrument (PSI) for spin-echo small-angle neutron scattering (SESANS) experiments. PSI will use polarized neutrons and will be sensitive to structures in the size range from 10 nm to 1000 nm. It can be operated either as a relectometer or as a high-resolution difractometer. In addition, use of coherent neutron waves from pinhole sources, a coded aperture mask, and newly developed phase-contrast imaging will allow imaging of structures from 1 micron to 1cm in size. With conventional small-angle neutron scattering (SANS), the SESANS PSI, and phase-contrast imaging, LENS will enable qualitatively new types of neutron scattering measurements, leading to new science. Among the initial experiments that will be conducted at LENS are studies of heterogeneities in glasses and ceramics, "spintronics" in magnetic semiconductors, hydride formation in alloys and pure metals, polymer networks and blends, nanostructured polymers, RNA helicases and protein:protein complexes, and chlorophyll aggregates.
Small-angle neutron scattering (SANS), using neutrons with relatively low energies (so-called "cold" neutrons), allows scientists to study aspects of materials and biological substances that are not accessible using other types of radiation, such as X-rays. In particular, neutrons are sensitive probes of the structure and dynamics of atoms and molecules. For this reason, they have now become widely used, not only in physics, chemistry, and materials science, but also in biology, earth science, and engineering.
With the completion of the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory in 2006, neutrons promise to be used increasingly as sensitive and versatile scientific probes. However, the relative dearth of neutron sources in the United States up to this time has contributed to the depletion of the ranks of U. S. neutron scientists. The Low Energy Neutron Scattering (LENS) facility at Indiana University will help to correct this situation by providing in a university setting the opportunity for the education and training of the next generation of neutron scientists, including those from fields such as biology that have not traditionally employed neutron scattering techniques to the full extent of their usefulness. In addition, LENS will serve as a regional user facility, enabling investigators from other institutions - including industry - to make use of neutron-scattering methods. LENS will also be used for potentially high-payoff experiments that are too risky to justify time on larger pulsed-neutron sources.
