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

Since most available micro x-ray fluorescence (micro-XRF) spectrometers operate in air, which does not allow the analysis of low-Z elements (Z <or = 14), a special micro-XRF spectrometer has been designed to extend the analytical range down to light elements (Z > or = 6). It offers improved excitation and detection conditions necessary for light element analysis. To eliminate absorption of the exciting and fluorescent radiation, the system operates under vacuum condition. Sample mapping is automated and controlled by specialized computer software developed for this spectrometer. Several different samples were measured to test and characterize the spectrometer. The spot size has been determined by scans across a 10 microm Cu wire which resulted in a full width at half maximum of 31 microm for Mo Kalpha line (17.44 keV) and 44 microm effective beam size for the Cu K edge and 71 microm effective beam size for the Cu L edge. Lower limits of detection in the picogram range for each spot (or microg/cm(2)) were obtained by measuring various thin metal foils under different conditions. Furthermore, detection limits in the parts per million range were found measuring NIST621 standard reference material. Area scans of a microscopic laser print and NaF droplet were performed to show mapping capabilities.