Performances of capillary X-ray optics for confocal three-dimensional micro-X-ray fluorescence technology

The performances of capillary X-ray optics (CXRO) for confocal three-dimensional micro-X-ray fluorescence (3D Micro-XRF) technology are presented. In particular, the energy dependence of the collecting angle and input focal spot size of the polycapillary parallel X-ray lens (PPXRL), and the energy dependence of spatial resolution of the confocal 3D Micro-XRF spectrometer based on the CXRO are reported. In order to obtain the input focal spot size of the PPXRL, the source scan method was used. The size of the input focal spot of the PPXRL was 25.5 μm at 13 keV, and it was close to that of the output focal spot of a polycapillary focusing X-ray lens (PFXRL) at the same energy. The collecting angle of the PPXRL was 110 mrad at 10 keV, and it decreased with the increasing energies. The depth spatial resolution of the confocal 3D Micro-XRF spectrometer based on the CXRO was 29.3 μm at 17 keV, and it decreased with the increasing energies. The minimal detection limit of this confocal 3D Micro-XRF spectrometer was 101 ppm for the Ti-Kα, when the operating voltage and current of the Mo X-ray tube were 36.0 kV and 800.0 μA, respectively.