Electron Probe Microanalysis

What is an EPMA (Electron Probe Micro Analyzer)? It is an SEM (scanning electron microscopy) but was designed to primarily perform quantitative X-ray microanalysis using both wavelength dispersive (WDS) and energy dispersive spectrometers (EDS). A basic SEM will have an EDS that will often, and incorrectly, be referred to as an EPMA.

The advantages of WDS are significant when performing quantitative analyses. Compared to EDS, the sensitivity (or lowest concentration detectable) is about 100 times lower (typically 10 to 50ppm), the spectral resolution is from 4 to 60eV (EDS is about 150eV), the peak to background ratio is as much as 100X greater and >100,000 count per second count rates are possible. These properties result in a much more direct measurement of the x-ray intensities which translates into higher precision and accuracy. Most often no peak deconvolutions are needed, just simple peak height and background measurements. Peak overlaps are rare and superior x-ray images are obtainable faster due to the very high peak to background ratios and the count rates.

Our JEOL JXA-8600 electron probe microanalyzer has five WDS as well as an EDS. It is fully automated with our own computer control system, dQant32 and dSspec. The automation provides the ability to acquire large amounts of data in a short time periods, thereby minimizing the cost of the analysis.What is an EPMA (Electron Probe Micro Analyzer)? It is an SEM (scanning electron microscopy) but was designed to primarily perform quantitative X-ray microanalysis using both wavelength dispersive (WDS) and energy dispersive spectrometers (EDS). A basic SEM will have an EDS that will often, and incorrectly, be referred to as an EPMA.

The advantages of WDS are significant when performing quantitative analyses. Compared to EDS, the sensitivity (or lowest concentration detectable) is about 100 times lower (typically 10 to 50ppm), the spectral resolution is from 4 to 60eV (EDS is about 150eV), the peak to background ratio is as much as 100X greater and >100,000 count per second count rates are possible. These properties result in a much more direct measurement of the x-ray intensities which translates into higher precision and accuracy. Most often no peak deconvolutions are needed, just simple peak height and background measurements. Peak overlaps are rare and superior x-ray images are obtainable faster due to the very high peak to background ratios and the count rates.

Our JEOL JXA-8600 electron probe microanalyzer has five WDS as well as an EDS. It is fully automated with our own computer control system, dQant32 and dSspec. The automation provides the ability to acquire large amounts of data in a short time periods, thereby minimizing the cost of the analysis.

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