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Smithsonian National Museum of Natural History
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Department of Mineral Sciences

Izalco Volcano
Instrument
  • JEOL 8900 Superprobe

The electron microprobe is mostly used for WDS and EDS quantitative analysis of major and minor elements of minerals and glasses. Volumes as small as 1 micron (10-6 m) diameter can be analyzed. Occasionally museum specimens from other departments or from other museums are analyzed. In the order of 10,000 quantitative analyses are performed per year. A large proportion of the analyses are performed on minerals and glasses from volcanic rocks.

X-ray maps from the WDS and the EDS are used to examine the two-dimensional distribution of elements on a specimen surface. Up to 20 elements can be specified for measurement on each analysis area. Measurement can be made in two modes, stage scanning and beam scanning. A raw-data map of X-ray intensity can be converted into a concentration map using calibration curves. Functions available for two-dimensional data include simple image processing such as various arithmetic operations and smoothing, line profile display, and analytical functions such as distance measurement.

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