An
electron microprobe (EMP), also known as an
electron probe microanalyzer (EPMA) or
electron micro probe analyzer (EMPA), is an analytical tool used to non-destructively determine the chemical composition of small volumes of solid materials. It works similarly to a
scanning electron microscope: the sample is bombarded with an
electron beam, emitting x-rays at wavelengths characteristic to the elements being analyzed. This enables the abundances of elements present within small sample volumes (typically 10-30 cubic
micrometers or less) to be determined. The concentrations of elements from
beryllium to
plutonium can be measured at levels as low as 100
parts per million (ppm). Recent models of EPMAs can accurately measure elemental concentrations of approximately 10 ppm.