Harti Ralph P, Kottler Christian, Valsecchi Jacopo, Jefimovs Konstantins, Kagias Matias, Strobl Markus, Grünzweig Christian
Opt Express. 2017 Jan 23;25(2):1019-1029. doi: 10.1364/OE.25.001019.
The performance of X-ray and neutron grating interferometers is characterised by their visibility, which is a measure for the maximum achievable contrast. In this study we show how the real grating geometry in a grating interferometer with three gratings impacts the interference and self projection that leads to visibility in the first place. We quantify the individual contributions of wavelength distributions and grating shapes in terms of visibility reduction by determining the absolute as well as relative effect of each contribution. The understanding of the impact of changed geometry and wavelength distributions on the interference of neutrons/X-rays allows us to present the first fully quantitative model of a grating interferometer setup. We demonstrate the capability of the simulation framework by building a model of the neutron grating interferometer at the ICON beamline and directly comparing simulated and measured visibility values. The general nature of the model makes it possible to extend it to any given grating interferometer for both X-rays and neutrons.
X射线和中子光栅干涉仪的性能由其可见度来表征，可见度是衡量可实现的最大对比度的指标。在本研究中，我们展示了具有三个光栅的光栅干涉仪中的实际光栅几何结构如何影响干涉和自投影，而正是这些导致了可见度的产生。我们通过确定每种贡献的绝对以及相对效应，从可见度降低的角度量化波长分布和光栅形状的个体贡献。对几何结构变化和波长分布对中子/X射线干涉的影响的理解，使我们能够提出光栅干涉仪装置的首个完全定量模型。我们通过构建ICON光束线处中子光栅干涉仪的模型，并直接比较模拟和测量的可见度值，展示了模拟框架的能力。该模型的通用性使其有可能扩展到任何给定的X射线和中子光栅干涉仪。
