X‐ray fluorescence analysis with sample excitation using radiation from a secondary target

This paper presents a scheme of an x-ray spectrometer with exchangeable secondary targets and investigation of its characteristics. A high-voltage power source with a voltage up to 75 kV and x-ray tubes with power up to 2.5 kW were used in the spectrometer to generate the primary x-ray radiation. The exchangeable secondary targets made it possible to get monochromatic radiation with a rather high degree of the spectral contrast. The use of tubes with different anodes materials (chromium, tungsten and rhodium) and different secondary targets provides efficient performance for the analysis of a range of concentrations of elements with atomic numbers 13 < Z < 92. In this case, it was possible to optimize the sample analysis for definite groups of elements, reaching detection limits (DL) of 10 - 6 g/g in aqueous solutions. According to the sensitivity (DL), this device can act as a spectrometer with total external reflection of the primary beam (TXRF spectrometer). However, its design is simpler, it has better optical efficiency, its adjustment is simple and convenient and it has a high operating efficiency. Besides, the design of the device makes it possible to perform simultaneously, if necessary, x-ray fluorescence and x-ray absorption analyses of a sample. Examples of the application of the device for the determination of heavy-metal content in the aqueous solutions and measurement of thickness of films are presented in this paper.