Harald Schneider

A tunable focusing monochromator for total reflection x-ray fluorescence spectrometers

The application of curved multilayer mirrors as monochromatizing and focusing elements to the primary beam of total reflection x-ray (TXRF) spectrometers is shown to be subjected to constraints which arise mainly as a result of the extended nature of the x-ray source and the low angular spread of the incident beam permissible at the target surface. If, in addition, tunability of the monochromator is required over a broad range of energy, the design of the mirrors becomes even more critical. A ray-tracing program has been developed for the optimization of the relevant parameters, such as the materials and d-spacing of the multilayer mirrors and their curvature, which takes into consideration all relevant distances and angles important for the operation of TXRF instruments. The influence of the various design parameters on the intensity at the sample spot and on the detection limits was calculated and experiments with a prototype instrument were performed in order to compare the predicted intensities and detection limits with experimental data. Copyright