Archive for July, 2012

X-ray Fluorescence: Energy Dispersive v. Wavelength Dispersive

As organizations research analytical equipment to solve particular material analysis needs, they will contact Eastern Applied Research regarding x-ray fluorescence technology.  From time to time, contacts will ask about two difference styles of x-ray technologies – Wavelength Dispersive (WD-XRF) and Energy Dispersive (ED-XRF).  As specialists in ED-XRF analyzers, Eastern Applied has seen improvements in the technology that have resulted in expanded application fields and make it a consideration for applications that used to be solved by WD-XRF.

This article provides a brief comparison of the two technologies
Contact Eastern Applied to discuss further and see if ED-XRF is a fit for your applications.

What is XRF

ED-XRF Structure

Both technologies are based around the principle of using an x-ray source to excite a sample, a detection system to collect fluoresced x-rays, and a software program to process the measurement data.  The difference in a wavelength system is that a crystal between the tubes diffracts x-rays of a specific wavelength into the detector tube.  This added step (and components) results in varying performance capabilities and costs between the technologies.

Two main differences that affect performance:

Energy Resolution
XRF Spectrum ExampleDepending on the instrument specifics, WD-XRF analyzers will provide resolutions of 5eV to 20eV while ED-XRF systems typically offer a range of 120eV to 220eV.  The lower resolutions of WD-XRF will reduce spectral overlaps and provide more efficient characterization of complex samples.

While this difference may benefit wavelength technology for a specific element of interest or application, the optical components required to achieve those resolutions result in a more expensive system – both in the initial cost of acquisition and over the course of its lifespan.  Advancements in ED-XRF detection systems have improved those resolutions greatly and we have seen an increased range of applications solved by ED-XRF due, in part, to those advancements.

Spectral Acquisition
This is a factor that limits wavelength dispersive technology as a spectrum is either made in a point-by-point fashion (very time consuming) or has additional detectors (very costly approach).  Energy dispersive, on the other hand, will acquire an entire spectrum almost simultaneously.  While a user may see a slight reduction in accuracy for one element, the range of elements seen are achieved in a faster, more efficient, approach and result in a broader range of material analysis capabilities.

At Eastern Applied Research, we specialize in the energy dispersive x-ray fluorescence technology.  We have been part of ED-XRF’s evolution over the last twenty years and appreciate the benefits it offers over wavelength, benefits of ED-XRF include:
–  lower cost of acquisition
–  broader, more diverse, analytical scope
–  lower cost of maintenance
–  greater reliability due to less complicated design
–  less electrical power consumption

In addition to those benefits, energy dispersive x-ray fluorescence has seen great improvements over recent years, including the addition of poly-capillary optics (seen in the micro-XRF Hitachi FT-150) and extremely versatile systems like the Hitachi EA6000VX.

If you are considering x-ray fluorescence and would like to learn more about ED-XRF options or the difference between technologies, we encourage you to request a conversation from an Eastern Applied Research XRF specialist.