This work illustrates the development of X-ray fluorescence tomography and polycapillary based confocal imaging towards a three-dimensional (3D), quantitative analytical method with lateral resolution levels down to the 2-20 μm scale. Detailed analytical characterization is given for polycapillary based confocal XRF imaging, which is a new variant of the 3D micro-XRF technique. Applications for 2D/3D micro-XRF are illustrated for the analysis of biological (zooplankton) and geological samples (microscopic inclusions in natural diamonds and fluid inclusions in quartz). Based on confocal imaging, fully three-dimensional distributions of trace elements could be obtained, representing a significant generalization of the regular 2D scanning technique for micro-XRF spectroscopy. The experimental work described in this paper has been carried out at the ESRF ID18F microfluorescence end-station and at HASYLAB Beam Line L.
The intensity distributions of the coherent and partially coherent x-rays passed through a poly-capillary lens have been computed at the focal plane. The computations showed that at the appropriate experimental conditions the interference phenomenon does affect the intensity distribution. In the case of the coherent input radiation with the photon energy of 0.1 keV, the interference fringes were observed, while the non-coherent x-ray radiation produced no interference-like intensity distributions.
This work focuses on the investigation of the distribution of contaminants in individual sediment particles from the New York/New Jersey Harbor. Knowledge of the spatial distribution of the contaminants within the particles is needed to enable (1) more sophisticated approaches to the understanding of the fate and transport of the contaminants in the environment and (2) more refined methods for cleaning the sediments. The size of the investigated particles ranges from 30-80 microns. Due to the low concentration of the elements of interest and the microscopic size of the environmental particles in these measurements, the small size and high intensity of the analyzing X-ray beam was critical. The high photon flux at the ESRF Microfocus beam line (ID13) was used as the basis for fluorescence tomography to investigate whether the inorganic compounds are taken upon the surface organic coating or whether they are distributed through the volume of the grains being analyzed. The experiments were done using a 13 keV monochromatic beam of approximately 2 micrometers in size having an intensity of 1010 ph/s, allowing absolute detection limits on the 0.04-1 fg level for Ti, Cr, Mn, Fe, Ni, and Zn.
KEYWORDS: Tomography, Monte Carlo methods, X-ray fluorescence spectroscopy, Scattering, X-rays, Compton scattering, Rayleigh scattering, Photons, Sensors, Chemical elements
Experimental data and results from a detailed Monte Carlo (MC) simulation of X-ray Fluorescence, Compton and Rayleigh scattering tomography are presented. The MC model was developed by the authors for aiding the optimization and evaluation of synchrotron radiation induced X-ray fluorescence (SRXRF) experiments. The code simulates complete X-ray fluorescence spectra in the incident energy range of 1 - 100 keV, including K,L fluorescent lines and Compton, Rayleigh scattering contributions. This generalized simulation model describes the interactions between X-ray photons and heterogenous samples. The MC code was evaluated by comparisons of simulated and experimental X-ray fluorescent and scattering tomography data. These data were collected at HASYLAB, beamline L (polychromatic setup) and BW5 (monochromatic setup). Good agreement was found between experimental and simulated results.
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