Shielded field emission EPMA for microanalysis of radioactive materials

摘要

A standard Jeol 8500F electron probe microanalyzer (EPMA) with field emission gun (FEG) has been installed in a lead shielded cabin of the laboratory and customized for remote control. The wavelength-dispersive X-ray spectrometers (WDS) have been additionally shielded against β,γ-radiation with tungsten alloy modules. These measures have proven to be very effective for the examination of specimens with an activity of less than 20 GBq ~(137)Cs. The background intensity is dependent on crystal type, spectrometer and sample position. The efficiency of the spectrometer with Xe-sealed counter is higher but also its sensitivity to the specimen's γ-radiation than the Ar/CH_4 flow counter. The possibility of applying high beam currents increases the peak-to-background ratio for the analysis of low concentrations in the active sample. The high electron beam density of the FE-gun allows for the recording of high resolution elemental X-ray maps in the range of a few tenths of a micrometre at even medium acceleration voltage and thus short acquisition time. It is thus a valuable instrument in post irradiation examinations of spent fuel rods and materials irradiated by other sources.