Accurate bound coherent neutron scattering lengths, bc, of important isotopes

重要同位素的精确束缚相干中子散射长度 bc

• 批准号: 513557453
• 负责人: Professor Dr. Holger Kohlmann
• 金额: --
• 依托单位: Institut für Anorganische Chemie
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/513557453?language=en
• 关键词: Accurate; bound; coherent; neutron; scattering

Neutron scattering lengths b are the measure of the strength of the interaction between neutrons and the nucleus of an atom. They are fundamental properties of matter, and most neutron scattering techniques rely on accurate b values. Surprisingly, neutron scattering lengths are often only known with moderate or poor accuracy or have not been determined experimentally at all. The aim of this research project is to determine bound coherent scattering lengths for thermal neutrons of important stable isotopes with very high accuracy using neutron diffraction. The isotopes and natural isotope mixtures to be examined are: 6Li, 7Li, natLi, 114Cd, natCd, 123Te, natTe, 141Pr (= natPr), 142Nd, 143Nd, 144Nd, 145Nd, 146Nd, 148Nd, 150Nd, natNd, 147Sm, 147Sm , 152Sm, 154Sm, natSm, 151Eu, 153Eu, natEu, 177Hf, natHf, 185Re, 187Re, natRe, 203Tl, 205Tl, natTl. This will provide the user community with fundamental and important data needed for a plethora of neutron experiments in diverse fields ranging from condensed matter to nuclear physics and biology. First, a robust yet accurate method for determining bound coherent neutron scatter lengths by neutron diffraction is developed. Neutron diffraction has the advantage over other (sometimes more accurate) methods of determining the scattering length that it only relies on relative and not on absolute values and is less prone to systematic errors. It is therefore a robust but fairly accurate (< 1%) method and well suited to redetermining the scattering lengths of important isotopes. Suitable materials like LiF, LiBaF3, CdF2, TeO2, LnN and LnOCl (Ln = Pr, Nd, Sm, Eu), ReO3, TlCl are synthesized from isotopically enriched materials. Neutron powder diffraction experiments on these materials are optimized for accurate intensity measurements and diffraction data are analyzed by Rietveld refinement. Statistical and consistency checks complete the neutron scattering length determination. Most neutron experiments are performed at and in collaboration with the Institut Laue-Langevin in Grenoble, France. Additional neutron diffraction data are collected at MLZ, Garching, Munich, Germany, at PSI, Villigen, Switzerland, and at ANSTO, Lucas Heights, Australia. Alternative methods such as single crystal diffraction and neutron interferometry are used for selected compounds such as LiF, LiBaF3 and ReO3.

中子散射长度B是中子与原子核之间相互作用强度的度量。它们是物质的基本特性，大多数中子散射技术都依赖于准确的B值。出乎意料的是，中子散射长度通常仅以中等或差的精度知道，或者根本没有通过实验确定。该研究项目的目的是确定重要稳定同位素的热中微子的结合相干散射长度，使用中子衍射精度很高。要检查的同位素和天然同位素混合物为：6li，7li，natli，114cd，natcd，123te，natte，natte，141pr（= natpr），142nd，143nd，143nd，144nd，145nd，145nd，146nd，146nd，146nd，148nd，148nd，148nd，148nd，148nd，148nd，144nd，144nd，natnd，natnd，natnd，natnd，147.147。 ，152SM，154SM，NATSM，151EU，153EU，NATEU，177HF，NATHF，185RE，187RE，NATRE，NATRE，203TL，205TL，NATTL，NATTL。这将为用户社区提供基本和重要的数据，用于从凝结物质到核物理学和生物学的各种领域中的许多中子实验所需的基本和重要数据。首先，开发了一种可通过中子衍射来确定结合相干的中子散射长度的可靠但准确的方法。中子衍射比其他（有时更准确的）方法具有确定仅依赖相对且不依赖于绝对值的散射长度的方法，并且不容易依靠系统误差。因此，这是一种强大但相当准确的方法（<1％），非常适合重新确定重要同位素的散射长度。合适的材料，例如LIF，LIBAF3，CDF2，TEO2，LNN和LNOCL（LN = PR，ND，SM，EU），REO3，TLCL是从同位素富集的材料中合成的。这些材料上的中子粉末衍射实验已优化，以进行准确的强度测量，并通过Rietveld的细化分析衍射数据。统计和一致性检查完成中子散射长度的确定。大多数中子实验是在法国格勒诺布尔的Laue-Langevin研究所和合作进行的。在MLZ，Garching，慕尼黑，德国，PSI，Villigen，瑞士，瑞士和澳大利亚Lucas Heights的Ansto收集其他中子衍射数据。诸如单晶衍射和中子干涉仪等替代方法用于所选化合物，例如LIF，LIBAF3和REO3。