Dennison Andrew J C, Devishvili Anton, Gutfreund Philipp, Cubitt Robert, Vorobiev Alexei, Zabel Hartmut, Wolff Max
Department of Physics and Astronomy, Uppsala University, P.O. Box 516, 751 20 Uppsala, Sweden.
Institut Laue-Langevin, 71 Rue des Martyrs, Grenoble 38000, France.
Rev Sci Instrum. 2021 Feb 1;92(2):023306. doi: 10.1063/5.0041248.
Graphite intercalation compounds (GICs) are a group of layered materials that are suitable as monochromators for cold neutrons. KC is a particularly interesting compound in this regard as it features a large c-axis lattice spacing of 8.74 Å, high reflectivity, and the possibility to produce large crystals with mosaicity that matches the beam divergence of cold neutron guides. GICs can be synthesized with different levels of intercalation, known as the stage of the compounds. Each stage displays a specific d-spacing. Impure GIC-monochromators containing multiple stages produce mixing of neutron wavelengths, which complicates data analysis on neutron reflectometers. We discuss the implications of GIC crystal purity and stage contamination for neutron reflectometry and show how GIC crystals can be characterized by time-of-flight neutron diffraction providing an efficient and quantifiable measure of the reflected wavelength spectrum. This allows taking into account multiple wavelength contaminations and ascertains the robustness of reflectometry measurements.
石墨插层化合物（GICs）是一类层状材料，适合用作冷中子单色器。在这方面，KC是一种特别有趣的化合物，因为它具有8.74 Å的大c轴晶格间距、高反射率，并且有可能生产出镶嵌性与冷中子导管的束发散度相匹配的大晶体。GICs可以通过不同程度的插层来合成，这被称为化合物的阶段。每个阶段都显示出特定的d间距。含有多个阶段的不纯GIC单色器会产生中子波长的混合，这使中子反射计的数据分析变得复杂。我们讨论了GIC晶体纯度和阶段污染对中子反射测量的影响，并展示了如何通过飞行时间中子衍射对GIC晶体进行表征，从而提供对反射波长谱的有效且可量化的测量。这允许考虑多种波长污染，并确定反射测量的稳健性。
