XRF contrast imaging: from microscopy to tomography
Diane Eichert (diane.eichert@elettra.eu)
XRF beamline, ELETTRA-Sincrotrone Trieste, Area Science Park, 34149 Basovizza, TS, Italy
X-ray Fluorescence (XRF) is well suited for revealing simultaneously the elemental
distributions in a given sample, qualitatively or quantitatively, and leads to precise and sensitive
elemental co-localisation maps. XRF relying on inherent properties of interaction of X-rays with
matter the achieved elemental contrast is natural (i.e. not dependent on artificial fluorophores); and
the high penetration depth of X-rays allows probing sample thicknesses of tens of microns. XRF
microscopy is now in full expansion, and exists at various degrees of sophistication, ranging from
portable set-ups for field analysis to advanced laboratory apparatus, and is applied to routine
analysis as well as to ambitious in-situ pilot experiments. The instruments themselves can be
designed and optimised for analysing bulk materials (TXRF), or by the mean of focusing optics and
powerful X-ray sources, for analysing, imaging or mapping down to extremely small areas (few tens
of nm), opening the field of micro or nano-XRF.
X-ray imaging, and among which especially X-ray computed tomography take also full
advantage of the X-rays penetration depth. It is an established tool providing images with high
contrast resolution and detailed structural information. Combining X-ray fluorescence and
tomography appears as a natural development in both techniques to access in parallel a wealth of
information about the sample, respectively chemical and morphological.
Coupled with X-ray optics or masks, efficient detectors and powerful sources X-ray
fluorescence imaging is therefore a great tool for in-situ investigations in a countless number of
applications, typically extending from material science to archaeometry, pharmacology to medicine,
chemistry to environmental samples, and opens new fields in micro or nano 2D- and 3D-imaging.
This presentation will underline the fundamentals of X-Ray Fluorescence, from the physic,
i.e. the theory behind the technique, the main developments in instrumentation, the challenges in
elemental analysis (i.e. analytical complexities due to matrix effects, re-absorption, concentrations,
micro-analysis…) and data handling. Supported by examples, each section will pinpoint the strengths
and limitations of the X-Ray fluorescence technique, in 2D and 3D.