Abstract
In recent years many nuclear microprobes have developed to sophisticated tools for elemental analysis with high resolutions down to about 1xa0;μm micron. The application to trace element analysis is mainly in the field of biological and medical research. Numerous successful studies on microscopic scale structures, e.g. cells, lead to the demand for higher spatial resolution or lower detection limits. Therefore, several labs started new efforts for sub-micron resolutions, sometimes intending 100xa0;nm. The Leipzig microprobe laboratory \LIPSION\ has recently improved its analytical capabilities. We are now able to perform quantitative trace element analysis with sub-micron spatial resolution (beam diameter 0.5xa0;μm at 120xa0;pA). As an example we give the trace element distribution in neuromelanin (intracellular pigment of neurons). Furthermore, when the scan size is reduced from cellular level, i.e. about 50xa0;μm, to sub-cellular level of about 10xa0;μm, the beam diameter can further be reduced by choosing smaller object diaphragms. The unavoidable reduction in beam current will not affect the mapping sensitivity unless the accumulated charge per spatial resolution is not decreased. The smallest beam diameter with analytical capabilities for elemental analysis we achieved thus far was about 300xa0;nm in diameter. It enables an outstanding microPIXE resolution. However, some difficulties appeared in high-resolution work, which limited the acquisition time to less than 30xa0;min.
