Electron microprobe

This enables the abundances of elements present within small sample volumes (typically 10-30 cubic micrometers or less) to be determined,[2] when a conventional accelerating voltage of 15-20 kV is used.

Electron energy loss spectroscopy is very good for light element analysis and they obtained spectra of C-Kα, N-Kα and O-Kα radiation.

In 1947, Hiller patented the concept of using an electron beam to produce analytical X-rays, but never constructed a working model.

His design proposed using Bragg diffraction from a flat crystal to select specific X-ray wavelengths and a photographic plate as a detector.

However, the Geiger counter could not distinguish X-rays produced from specific elements and in 1950, Castaing added a quartz crystal between the sample and the detector to permit wavelength discrimination.

Peter Duncumb combined all three technologies and developed a scanning electron X-ray microanalyzer for his PhD thesis (1957), which was commercialized as the Cambridge MicroScan.

During the late 1950s and early 1960s there were over a dozen other laboratories in North America, the United Kingdom, Europe, Japan and the USSR developing electron beam X-ray microanalyzers.

Significant subsequent improvements and modifications to microprobes included scanning the electron beam to make X-ray maps (1960), the addition of solid state EDS detectors (1968) and the development of synthetic multilayer diffracting crystals for analysis of light elements (1984).

Several advances in CAMECA instruments in recent decades expanded the range of applications on metallurgy, electronics, geology, mineralogy, nuclear plants, trace elements, and dentistry.

As the innermost shells are involved, the X-ray line energies are generally not affected by chemical effects produced by bonding between elements in compounds except in low atomic number (Z) elements ( B, C, N, O and F for Kalpha and Al to Cl for Kbeta) where line energies may be shifted as a result of the involvement of the electron shell from which vacancies are filled in chemical bonding.

WDS utilizes Bragg diffraction from crystals to select X-ray wavelengths of interest and direct them to gas-flow or sealed proportional detectors.

Counts from the sample must be corrected for matrix effects (depth of production of the X-rays,[16][17] absorption and secondary fluorescence[18][19]) to yield quantitative chemical compositions.

This information may illuminate geologic processes such as crystallization, lithification, volcanism, metamorphism, orogenic events (mountain building), and plate tectonics.

This technique is also used for the study of extraterrestrial rocks (meteorites), and provides chemical data which is vital to understanding the evolution of the planets, asteroids, and comets.

The change in elemental composition from the center (also known as core) to the edge (or rim) of a mineral can yield information about the history of the crystal's formation, including the temperature, pressure, and chemistry of the surrounding medium.