Wavelength dispersive X-ray spectroscopy

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The Wavelength dispersive X-ray spectroscopy (WDXRF or WDS) is a method used to determine the energy spectrum of an X-ray radiation. It is mainly used in chemical analysis, in an X-ray fluorescence spectrometer, or in an electron microprobe (Castaing probe).

[edit] Explanation

The X-rays emitted by the analysed object are collimated by parallel copper blades (called collimator or Soller slits), and irradiate a known single crystal. The single crystal diffracts the photons (Bragg's law) which are collected by a detector, usually a scintillation counter or a proportional counter.

The single crystal and the detector are mounted on a goniometer which is a device similar to a traditional X-ray diffractometer. It is usually operated under vacuum to reduce the absorption of soft radiation (low-energy photons) by the air and thus increase the sensitivity for the detection and quantitation of light elements (between boron and oxygen).

Modern systems contain a number of crystals of known but differing properties, with automated changing of the crystal depending on the energy range being analysed, enabling a wide range of energies to be analysed.