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

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.