An inclined detector geometry for improved X-ray total scattering measurements.

An inclined geometry is investigated for X-ray total scattering measurements using a digital flat-panel area detector. The inclined geometry enables acquisition of higher quality data for simultaneous Rietveld refinement and total scattering studies, yielding structural information on the short-, medium- and long-range orders from one single measurement. X-ray total scattering measurements are implemented using a digital flat-panel area detector in an inclined geometry and compared with the traditional geometry. The traditional geometry is defined here by the incident X-ray beam impinging on and normal to the center-most pixel of a detector. The inclined geometry is defined here by a detector at a pitch angle α, set to 15° in this case, bisected by the vertical scattering plane. The detector is positioned such that the incident X-ray beam strikes the pixels along the bottom edge and 90° scattered X-rays impinge on the pixels along the top edge. The geometric attributes of the inclined geometry translate into multiple benefits, such as an extension of the measurable scattering range to 90°, a 47% increase in the accessible magnitudes of the reciprocal-space vector Q and a leveling of the dynamic range in the measured total scattering pattern. As a result, a sixfold improvement in signal-to-noise ratios is observed at higher scattering angles, enabling up to a 36-fold reduction in acquisition time. Additionally, the extent of applied modification functions is reduced, decreasing the magnitude of termination ripples and improving the real-space resolution of the pair distribution function G(r). Taken all together, these factors indicate that the inclined geometry produces higher quality data than the traditional geometry, usable for simultaneous Rietveld refinement and total scattering studies.

使用数字平板面探测器对一种倾斜几何结构进行了X射线全散射测量研究。倾斜几何结构能够获取更高质量的数据，以便同时进行里特韦尔德精修和全散射研究，从单次测量中得出短程、中程和长程有序的结构信息。 在倾斜几何结构下使用数字平板面探测器进行X射线全散射测量，并与传统几何结构进行比较。这里传统几何结构定义为入射X射线束垂直入射到探测器最中心的像素上。这里倾斜几何结构定义为探测器倾斜角α（在本案例中设为15°），且被垂直散射平面平分。探测器的放置方式是使入射X射线束撞击底部边缘的像素，而90°散射的X射线撞击顶部边缘的像素。倾斜几何结构的几何特性带来了诸多益处，例如可测量的散射范围扩展到90°，倒易空间矢量Q的可获取量值增加了47%，测量的全散射图谱中的动态范围变得更均匀。结果是，在较高散射角处观察到信噪比提高了6倍，采集时间可减少多达36倍。此外，所应用的修正函数的范围减小，降低了截断涟漪的幅度，提高了对分布函数G(r)的实空间分辨率。综上所述，这些因素表明倾斜几何结构比传统几何结构能产生更高质量的数据，可用于同时进行里特韦尔德精修和全散射研究。