X射线荧光成像是一种可无损获得样品内部元素空间分布信息的实验技术, 可分为荧光mapping扫描成像与荧光CT成像, 其空间分辨率由X射线聚焦束斑的大小决定。 上海光源成像线站已建立X射线荧光成像系统并对用户开放, 在多个领域取得较好的研究成果, 该系统基于狭缝限束获取微束X射线, 束斑为150 μm, 限制了该方法的广泛应用。 椭球聚焦镜是反射面为椭球面的单次反射单毛细管光学元件, 基于全反射原理, 具有反射效率高、 工作距离长、 接收角宽、 适用X射线能量范围宽、 体积小等优点, 已应用到X射线聚焦、 全场纳米成像等领域。 由于对面型精度的要求较高, 制备椭球聚焦镜难度较大。 为满足广大用户对微束荧光成像的需求, 自行设计并成功研制了针对微束荧光成像系统的单毛细管椭球镜, 并对其进行了X射线聚焦性能检测, 结果显示可获得14 μm聚焦光斑, 焦点处增益可达255倍。 基于自主研制的椭球镜, 在上海光源BL13W搭建微束X射线荧光成像系统, 并开展了微束荧光mapping成像与微束荧光CT实验研究: (1)对中风鼠脑切片的荧光mapping扫描成像, 得到中风鼠脑中微量元素铜、 铁、 钙与锌的元素分布荧光光谱图； (2)对鼠脑及毛细管中浓度为0.5 mg·L-1的标准砷溶液进行同步辐射微束X射线荧光CT成像, 利用OSEM重构算法重构投影数据, 获得了鼠脑中铜元素和毛细管中砷元素二维分布的切片图。 两组实验表明, 基于自行设计与研制的单毛细管椭球镜的微束X射线荧光成像系统, 样品处的光通量密度增加, 空间分辨率得到提高, 单张荧光光谱的获取时间显著减少, 同时也提高了系统的元素探测限。

Micro X-ray fluorescence (μXRF) imaging is powerful non-destructive technique for imaging distributions of nonradioactive elements within the body, including scanning X-ray fluorescence and X-ray fluorescence computed tomography. The spatial resolution is determined by the size of the X-ray focused beam spot. The μXRF instrumentation, which uses a simple pinhole aperture to restrict the incident beam size on the sample surface, has been established and opened to users at SSRF X-ray imaging beamline (BL13W). It has a typical spatial resolution ranging in diameter from 200 micrometers up toseveral millimeters. Ellipsoidal shaped single-bounce glass capillaries have been used as achromatic X-ray focusing optics for various applications at synchrotron beamlines, which can provide efficient and high demagnification focusing with large numerical apertures, large Working distance, the wide energy range of x-rays, small volume and so on. The support a wide range of applications, including Micro X-ray fluorescence, full-field transmission X-ray microscopy (TXM), etc. But the challenge is to make an accurate profile with small slope errors. In order to meet the requirements of users for μXRF imaging, the single bounce ellipsoidal glass mono-capillary was designed and fabricated and its performance was measured by an X-ray test. The focus spot and the gain of this mono-capillary were 14μm and 255 at 8 keV, respectively. The images of focal spot by detector showed that this fabricated mono-capillary had high quality and satisfied the requirement of the designed data for μXRF. The μXRF instrumentation has been established, based on ellipsoidal mono-capillary designed and fabricated by ourselves, andcarried out scanning X-ray fluorescence and X-ray fluorescence computed tomography experimental research at SSRF X-ray imaging beamline (BL13W). Firstly, the fluorescence spectrum of the trace elements copper, iron, calcium and zinc in the stroke rat brain by scanning X-ray fluorescence. Secondly, the Arsenic of standard solution and the rat brain were subjected to microX-ray fluorescence computed tomography. Two-dimensional slices of Arsenic element in solution and copper element in the rat brain by OSEM algorithm to reconstructed. This study demonstrates that the μXRF instrumentation is a powerful X-ray analytical microscope with the high resolution and high sensitivity μXRF capabilities available.