Micro X-ray Fluorescence of Particles Using a Laboratory X-ray Source and Capillary Optics

Abstract Micro X-ray fluorescence (micro-XRF) is a useful nondestructive technique for multielement analysis of samples from a few hundred to a few micrometers in size. Micro-XRF is usually performed at synchrotron sources where element sensitivities are not compromised by micrometer spatial collimation of high flux beams. Ideally, micro-XRF would not have the burden of transporting samples to a synchrotron facility, but could be performed on a laboratory or portable scale. At the National Institute of Standards and Technology we are developing a micro-XRF system that combines a polycapillary optic with a standalone X-ray tube. This optic not only transmits the X-ray beam over 80 mm, but also focuses the beam to an area smaller than the unfocused beam size. The fine resolution combined with a high intensity produces a tool for laboratory scale micro-XRF analyses. The X-ray focusing optic is a tapered, glass polycapillary optic. This optic, contained in an approximately 5 × 70 mm steel cylinder, transmits and focuses incoming X-rays to a spot 9.5 mm from the optic exit.