Development of high-energy X-ray fluorescence analysis and application to the study of origin of earth and planetary materials

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Traditionally, the X-ray fluorescence (XRF) analysis of heavy elements is based on their L-series spectral lines. This is because the K-lines of these elements are difficult to excite by commercially available XRF spectrometers. A typical energy dispersive X-ray fluorescence spectrum of a multi-component material in energy regions of less than 20 keV is usually crowded with an overlap of the K, L, and M emission lines of the component elements. In contrast, the XRF spectrum above 20keV contains only K lines, and the spectrum becomes simple. Therefore, the use of the K-lines is ideal for the analysis of heavy elements of atomic number Z ≧45 (=Rh Kα_1=20.12 KeV). We have developed for the first time high energy XRF analysis utilizing 116keV X-rays from synchrotron radiation source of Spring-8 and found that this technique enables us to determine all heavy elements with sufficient sensitivity. The minimum detection limit was at a sub-ppm level. This technique has been successfully applied to two-dimensional analysis of zoning of heavy elements in garnet, forensic identification of automobile paints, provenance analysis of old-china wares from Kutani and Arita and the potential advantages of this technique have been elucidated. High-energy XRF analyses will become a powerful tool for analyzing environmental samples, archaeological samples, forensic samples, geochemical samples, and high-tech materials containing heavy elements such as rare earth elements. It is expected that the utilization of high-energy X-rays will open new application fields for X-ray fluorescence analyses