To measure X-ray fluorescence radiation of low Z elements especially requires a very high excitation intensity with an energy as close as possible to the absorption edges. Furthermore, a monochromatization of the excitation radiation and a cut-off of higher energies is desirable in order to reduce the background in the spectral region of interest.
A cylindrical graded multilayer was designed and tested to concentrate and to monochromatize the radiation of a thin window Mo fine focus tube. The variation of the dspacing is tuned to reflect the Mo La-radiation of the fine focus tube. The physical dimensions of the cylindrical shape are optimized for concentrating the Mo La tube radiation onto the specimen with a spot size of about 3 mm. This corresponds to the size of the specimens from a time dependent personal aerosol sampler used.
The multilayer is characterized with respect to its reflecting, focusing, and monochromatizing properties. Two examples of low Z element analysis are given.