The Excitation of Low Z Elements by Means of a Cylindrical Graded Multilayer as a High Energy Cut-Off in Edxrf Analysis

Abstract

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.