Development of a Low Energy Neutron Scattering Facility

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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) modifications and upgrades of the linear accelerator, including a beam-switching system and a transfer beam line; (2) construction of the target, moderator, and neutron reflector; (3) construction of a conventional small-angle neutron scattering (SANS) instrument; and (4) development of cold neutron moderators. The flux of cold neutrons that will be produced when LENS is completed will be comparable to that of the Intense Pulsed Neutron Source (IPNS) currently in operation at Argonne National Laboratory. With the high-powered Spallation Neutron Source (SNS) at Oak Ridge National Laboratory scheduled for completion in 2006, the construction of LENS is particularly timely. 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), 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 serve as the only U. S. testbed for the development of cold neutron moderators - the devices that slow down the neutrons to the low energies needed for materials investigations and biological studies and which are thus key parts of any neutron-scattering facility - and for potentially high-payoff experiments that are too risky to justify time on larger pulsed-neutron sources.