毛细管X光透镜三维共聚焦微束X射线荧光技术在岩矿样品分析中的应用

利用毛细管X光透镜搭建了三维共聚焦微束X射线荧光谱仪，处在激发道的多毛细管X射线会聚透镜和处在探测道的多毛细管X射线平行束透镜处于共聚焦状态，该共聚焦结构降低了X射线荧光光谱的背底，从而有利于降低的X射线荧光分析技术的探测极限。在上述共聚焦结构中，多毛细管X射线会聚透镜和多毛细管X射线平行束透镜的焦斑重合形成共聚焦微元，探测器只能探测到来自该共聚焦微元内的X射线荧光信号，当该共聚焦微元在样品移动时，就可利用该共聚焦技术原位无损得到样品内部的三维X射线荧光信息。该共聚焦技术使用的多毛细管X射线会聚透镜具有103量级的功率放大倍数，从而降低了该共聚焦技术对高功率X射线源的依赖程度，即利用低功率普通X射线源就可以设计毛细管X光透镜共聚焦X射线荧光技术。利用上述共聚焦微束X射线荧光谱仪对两种岩矿样品进行三维无损分析，在其中一种岩石中发现：Fe浓度大的区域Cu的浓度也大，这在一定程度上反映了岩矿自然生长的机理。实验结果证明：该共聚焦X射线荧光技术可以在不破坏样品情况下分析岩矿样品中元素成分组成和元素三维分布情况。该共聚焦三维微束X射线荧光技术在矿石勘察、玉器选材和鉴别、石质食用器皿、“赌石”和家用石质地板检测等领域具有潜在的应用。

Application of Three Dimensional Confocal Micro X-Ray Fluorescence Technology Based on Polycapillary X-Ray Lens in Analysis of Rock and Mineral Samples

Confocal three dimensional (3D) micro X-ray fluorescence (XRF) spectrometer based on a polycapillary focusing X-ray lens (PFXRL) in the excitation channel and a polycapillary parallel X-ray lens (PPXRL) in the detection channel was developed. The PFXRL and PPXRL were placed in a confocal configuration. This was helpful in improving the signal-to-noise ratio of the XRF spectra, and accordingly lowered the detection limitation of the XRF technology. The confocal configuration ensured that only the XRF signal from the confocal micro-volume overlapped by the output focal spot of the PFXRL and the input focal spot of the PPXRL could be detected by the detector. Therefore, the point-to-point information of XRF for samples could be obtained non-destructively by moving the sample located at the confocal position. The magnitude of the gain in power density of the PFXRL was 103. This let the low power conventional X-ray source be used in this confocal XRF, and, accordingly, decreased the requirement of high power X-ray source for the confocal XRF based on polycapillary X-ray optics. In this paper, we used the confocal 3D micro X-ray fluorescence spectrometer to non-destructively analyzed mineral samples and to carry out a 3D point-to-point elemental mapping scanning, which demonstrated the capabilities of confocal 3D micro XRF technology for non-destructive analysis elements composition and distribution for mineral samples. For one mineral sample, the experimental results showed that the area with high density of element of iron had high density of copper. To some extent, this reflected the growth mechanisms of the mineral sample. The confocal 3D micro XRF technology has potential applications in such fields like the analysis identification of ore, jade, lithoid utensils, “gamble stone” and lithoid flooring.