Confocal micro-x-ray fluorescence spectrometer for light element analysis

Abstract

An existing micro-x-ray fluorescence (micro-XRF) spectrometer designed for light element analysis (6 ≤ Z ≤ 14) has been extended to confocal geometry: a second polycapillary x-ray optic has been introduced in front of the energy dispersive x-ray detector. New piezo positioners for optimum alignment of both optics have been installed inside the vacuum chamber. The spectrometer offers now the possibility of true 3D elemental analysis in the micrometer regime. Depth resolution varies between 100 μm at 1 keV fluorescence energy (Na-Kα) and 30 μm for 17.5 keV (Mo). To further extend analytical capabilities a second x-ray tube with a Rh anode has been acquired to supplement to existing Mo anode tube. Lower limits of detection have been determined to be in the ppm region for confocal geometry. The spectrometer has been characterized and tested using different samples. Furthermore, results have been compared with SR micro-XRF to show the capabilities and limitations of this spectrometer.

Simulation of layer measurement with confocal micro-XRF

“…[13] For the experiment, thin (4 μm) and quasi-infinite thick (for the simulation, 200 μm was chosen) Ni layers were probed. In Fig.…”

“…For the comparison with real data, we use a confocal micro-XRF setup that is installed at the Atominstitut in Vienna. [13] Simulation model In this simulation model, only isotropic mixtures of materials are considered for each layer. We only use the cross section area of the overlap of the polycapillaries instead of the measuring volume as a further simplification.…”

Three dimensional subsurface elemental identification of minerals using confocal micro-X-ray fluorescence and micro-X-ray computed tomography

“…This is achieved by moving the region of interest of a sample into the confocal excitation/detection volume using a set of lateral XY stages and a vertical Z stage. The confocal geometry creates a spatially constricted ellipsoidal [11] or spherical [12] X-ray excitation/detection volume, which allows for the nondestructive elemental analysis of surface and subsurface regions of interest, such as stratified layers [8], paint layers [13], embedded metal-doped polymer layers [14,15], and lithium-ion battery cathodes. [16] However, one drawback of confocal MXRF is the time required to obtain full 3D elemental maps, which can vary from days to weeks, depending on the energy of the Xray source, sample composition, sample size, desired horizontal and vertical resolutions, and dwell time needed to obtain an appropriate signal-to-noise ratio.…”

Laboratory-based micro-X-ray fluorescence setup using a von Hamos crystal spectrometer and a focused beam X-ray tube

“…39 Typical application domains for polycapillary optics are μ-XRF, absorption, or diffraction experiments with the aim to realize spatially resolved measurements, to increase the detection efficiency, 35,36,40,41 or to optimize the background conditions by shielding the detector from scattered particles or X-ray radiation. 37,40 Arranged in the confocal geometry, [42][43][44][45][46][47][48] 3D-measurements with micrometer resolution can also be realized. In general, the advantages offered by polycapillary optics are the compact size, the spatial acceptance of the incoming X-ray beam, and a broad usable energy range.…”