An atomic beam source for actinides. Conception, construction, and mode of operation

For ultratrace analysis as well as for studies of the physical properties of actinide elements by means of resonance ionization mass spectroscopy (RIMS) suitable beam sources are required delivering a stable atomic beam of the element of interest with a high yield. This can be accomplished using sandwich filaments with tantalum as the backing material and titanium as a covering layer. The evaporation kinetics, the desorption and the diffusion as well as the surface ionization and the associative desorption are considered. Furthermore the requirements for an atomic actinide beam source are described with respect to the evaporation behaviour of the actinide elements and their oxides. Results are presented on the desorption and adsorption of actinides on Ti- and Ta surfaces and the influence of various parameters. Data on the reproducibility of the evaporation of Ti-actinide-Ta-filaments obtained with RIMS are given together with some applications. (author) 24 figs., 11 tabs., 67 refs