Three Dimensional Synchrotron Radiation Confocal X-ray Method And Its Applications

Confocal micro-X-ray method is a sensitive tool for analysis of threedimensional (3D) elemental composition and chemical species, and has manyimportant applications in the research fields such as geology, archaeology,environment, biology and materials science. At SSRF insert device beamlines,confocal Micro-X-ray methods，with high detection sensitivity and high spatialresolution，were established. Applied this methods the multilayer structures of anarchaeological sample was studied in order to reveal the raw materials and theproduction process.At the undulator beamline BL15U, confocal X-ray method was constructed bythe combination of the KB mirror and a polycapillary half-lens. The KB mirror wasused for the focusing of the incident X-ray and the polycapillary half-lens was usedfor the collection of the X-ray fluorescence. Horizontal and vertical spatial resolutiondepends on the incoming beam size, while the depth spatial resolution depends on thefoci size of the polycapillary half lens which is defined by the optical parameters andis a function of the X-ray energy. This confocal X-ray system has a depth spatialresolution of31.5m at8.04keV(Cu-K）. With the undulator source, the confocalX-ray method has a higher spatial resolution and better detection limit, therefore,could be used for three-dimensional nondestructive imaging （confocal Micro-XRF)，and three-dimensional chemical imaging（confocal Micro-XANES).At the wiggler beamline BL14W1，confocal X-ray method was constructed bythe combination of two polycapillary half lens. One polycapillary half lens wasarranged after the secondary source point to refocus the incident X-ray. And the otherwas placed in front of the detector to collect the X-ray fluorescence. This systemcould be used for3D nondestructive element distribution imaging with spatialresolution about several tens to one hundred micrometers. And it also could be used tofor3D nondestructive fine structure analysis by confocal Micro-EXAFS. Thetransmission efficiency and the focus properties of the polycapillary half lens werestudied. Si diode detector was used as the incident beam detector, and test results revealed that the ratio of signal to noise (S/N) of the EXAFS spectrum is better whenSi diode detector is positioned just before the sample.Using the confocal X-ray method, the unique production process of Doucaiporcelain in Pavilion of Delight of the Imperial Palace was studied. By analysis of theelements depth profile, a typical structure of Doucai with three glaze layers has beendisclosed. From the ratio of Fe/Co and Mn/Co, a conclusion could be reached that theraw materials of the white and blue glaze was from domestic. Confocal Micro-X-raymethod was used as a nondestructive "slicing" tool to probe the layer structure of aDoucai imperial porcelain through the analysis of elements mapping in a virtualsection plane under the sample surface. A special layer structure has been detectedthat the glaze layer with Co and Fe is on top of the glaze layer with Pb, which seemsto be conflicted with the knowledge of production procedure for this kind of porcelain.Further study is needed in order to clarify the “abnormal” structure.All of the studies show that the confocal X-ray methods based on differentsources have their own characteristic respectively, and proved to be a powerfulnondestructive method for analysis of3D elements and its chemical state inheterogeneous samples.