Polarization analysis for small-angle neutron scattering with a 3He spin filter at a pulsed neutron source
Polarization analysis for small-angle neutron scattering with a 3He spin filter at a pulsed neutron source
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在脉冲中子源上使用 3He 自旋滤波器进行小角度中子散射的偏振分析
DOI：
10.1107/s1600576721001643
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发表时间：
2021
影响因子：
6.1
通讯作者：
Iwase Hiroki
中科院分区：
文献类型：
--
作者：
Okudaira Takuya;Ueda Yuki;Hiroi Kosuke;Motokawa Ryuhei;Inamura Yasuhiro;Takata Shin-ichi;Oku Takayuki;Suzuki Jun-ichi;Takahashi Shingo;Endo Hitoshi;Iwase Hiroki
通过应用 3He 自旋过滤器作为样品散射中子的自旋分析器，成功实现了使用脉冲中子源进行小角中子散射 (SANS) 实验的中子偏振分析 (NPA)。 3He 旋转过滤器的单元具有微弱的小角度散射强度（背景），并覆盖足够的立体角以进行 SANS 实验。 3He极化的弛豫时间足以连续使用大约2天，从而达到整套SANS实验所需的典型持续时间。尽管使用基于样品元素组成的计算来准确评估非相干中子散射（主要归因于样品中氢原子的极大非相干散射截面）是困难的，但开发的NPA方法考虑了多重中子散射的影响，能够将SANS强度分布可靠地分解为相干和非相干散射分量。迄今为止，NPA 尚未成为日本质子加速器研究中心 (J-PARC) 和美国散裂中子源等脉冲中子源 SANS 实验的标准技术。预计这项工作将大大有助于准确确定 J-PARC SANS 实验中各种类型有机样品系统中散射体的相干中子散射分量，特别是涉及相干和非相干散射强度之间竞争的系统。
Neutron polarization analysis (NPA) for small-angle neutron scattering (SANS) experiments using a pulsed neutron source was successfully achieved by applying a 3He spin filter as a spin analyzer for the neutrons scattered from the sample. The cell of the 3He spin filter gives a weak small-angle scattering intensity (background) and covers a sufficient solid angle for performing SANS experiments. The relaxation time of the 3He polarization is sufficient for continuous use for approximately 2 days, thus reaching the typical duration required for a complete set of SANS experiments. Although accurate evaluation of the incoherent neutron scattering, which is predominantly attributable to the extremely large incoherent scattering cross section of hydrogen atoms in samples, is difficult using calculations based on the sample elemental composition, the developed NPA approach with consideration of the influence of multiple neutron scattering enabled reliable decomposition of the SANS intensity distribution into the coherent and incoherent scattering components. To date, NPA has not been well established as a standard technique for SANS experiments at pulsed neutron sources such as the Japan Proton Accelerator Research Complex (J-PARC) and the US Spallation Neutron Source. It is anticipated that this work will contribute significantly to the accurate determination of the coherent neutron scattering component for scatterers in various types of organic sample systems in SANS experiments at J-PARC, particularly for systems involving competition between the coherent and incoherent scattering intensity.