Development of a Low Energy Neutron Scattering Facility

该项目涉及在印第安纳大学回旋加速器设施(IUCF)建造一个低能中子散射(LENS)设施。LENS将利用IUCF现有的直线加速器产生11 MeV质子，通过Be靶上的(p，n)反应产生脉冲中子束。透镜不仅是一种新颖且相对便宜的脉冲冷中子源，而且在2005年建成后，还将使设计用于小角散射的新型中子仪器、材料科学和生物学的广泛研究计划、新型中子源和慢化剂的开发以及美国下一代中子科学家的教育和培训成为可能。Lens还将作为一个地区性用户设施，特别适合高风险实验和可行性研究。通过该项目完成的透镜的具体方面是：(1)对直线加速器的修改和升级，包括束流切换系统和转移束线；(2)靶、慢化器和中子反射器的建造；(3)传统小角中子散射(SANS)仪器的建造；以及(4)冷中子慢化器的开发。透镜完成后产生的冷中子通量将与目前在阿贡国家实验室运行的强流脉冲中子源(IPNS)相当。随着橡树岭国家实验室的高功率散裂中子源(SNS)计划于2006年完工，透镜的建设尤为及时。小角中子散射(SANS)利用能量相对较低的中子(所谓的“冷”中子)，使科学家能够研究使用其他类型的辐射(如X射线)无法获得的材料和生物物质的方面。特别是，中子是原子和分子的结构和动力学的灵敏探测器。由于这个原因，它们现在得到了广泛的应用，不仅在物理、化学和材料科学中，而且在生物学、地球科学和工程学中。随着散裂中子源(SNS)的建成，中子有望越来越多地被用作灵敏和多功能的科学探测器。然而，到目前为止，美国相对稀缺的中子源导致了美国中子科学家队伍的枯竭。印第安纳大学的低能中子散射(LENS)设施将帮助纠正这种情况，它将在大学环境中为下一代中子科学家提供教育和培训的机会，包括那些传统上没有充分利用中子散射技术的生物等领域的科学家。此外，Lens将作为一个地区性用户设施，使来自其他机构--包括工业--的调查人员能够使用中子散射方法。Lens还将作为美国唯一的冷中子慢化器开发试验台，用于将中子减慢到材料研究和生物研究所需的低能量，因此是任何中子散射设施的关键部件-以及潜在的高回报实验，这些实验风险太大，不足以证明在较大的脉冲中子源上花费时间是合理的。

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.