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Monday, May 12, 2008

Energy Dispersive XRF vs. Wavelength Dispersive XRF

If you have reviewed the instruments section of the Skyray XRF website you have noticed that we primarily offer Energy Dispersive XRF Instruments (EDXRF). Found in the additional technologies section; however, is a Wavelength Dispersive XRF (WDXRF) system, the WDX-200.
Our product line-up is focused on EDXRF because these models provide versatile options that help laboratories save money, space and sample preparation time. While EDXRF is frequently used in place of WDXRF or as a secondary/back-up testing option; the instruments do utilize slightly different technologies and have different advantages.
Basic principles:
Energy Dispersive XRF excites a sample through an x-ray source (x-ray tube) and collects the resulting excess energy through a detector tube. A more detailed overview can be reviewed here.
Wavelength Dispersive XRF also excites a source through an x-ray tube and collects energies with a detector tube. The difference in a WDXRF system is that a crystal between the tubes diffracts x-rays of a specific wavelength into the detector tube; this means that WDXRF can only read x-rays of a single wavelength (and element).


General technology comparison: 
Detector resolution is important to the range of elements that an instrument can analyze, the higher the resolution (low eV) the better. Of the two technologies WDXRF provides higher resolutions (5eV to 20eV) while EDXRF is generally in the 150eV to 220eV range (however, Skyray is now offering the EDX-6000B System which utilizes a UHRD Detector providing a resolution of 127eV). 
The WDXRF units can only detect one element at a time and therefore are very specific in use (popular for mining, cement and steel applications). EDXRF is designed to detect a group of elements all at once and provides a wider range of applications (RoHS testing, multi-layer coatings, etc).
Both technologies are equally strong in eliminating background radiation which can affect detection limits and repeatability. WDXRF has a natural advantage due to the high detector resolution but with filters and targets EDXRF can reduce background intensities to provide accurate and repeatable results that are comparable with WDXRF.

Since EDXRF does not utilize a diffraction device (crystal) like WDXRF, energy dispersive systems provide greater x-ray source efficiency and subsequently have lower operating cost. In order to achieve similar counts towards the detector a wavelength system needs 100 to 1000 times the direct excitation; which requires more power to produce.


In Summary:
What technology works best for an organization or laboratory really depends on the range of applications that will be tested and the budget that they are working with.   EDXRF offers less up-front and per-use costs, is non-destructive, fast and versatile so many organizations lean towards that technology.

However, both are available through Skyray XRF so please contact us to discuss what your needs are and which method of x-ray fluorescence will best meet them.

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EDXRF WDXRF x-ray fluorescence technology

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