Monday, July 28, 2008

X-RayFluorescence Detection Systems Overview

In the XRF Technology section, we provide a brief overview of energy dispersive x-ray fluorescence technology and its process. We also offer a brief overview of the major components involved in this non-destructive material analysis equipment; including the role of the detector tube. This XRF-Blog acts as a supplement to the technology section and focuses on the various detection systems available in Skyray XRF Analyzers.

XRF Detector Tubes Image
The detection system of an x-ray fluorescence instrument collects the energy that results from displaced electrons in the form of an x-ray. The peak intensities of emitted x-rays are characteristic of the elements contained in the sample and provide information about the elements concentrations. When comparing detection systems, the energy resolution (measured as eV) is frequently considered because the smaller the eV represents the more clearly the detector identifies elements.

Various detection systems include:

SiLi Detectors: Developed in the 1960’s in the United States and until recently these have provided the best resolution. However, to obtain sufficiently low conductivity these systems must be cooled using Liquid Nitrogen (LN2). Because of the costs and hassle involved with LN2, many organizations prefer to avoid systems using SiLi Detectors and they are featured less in new units because of the advancements in detector technology.
Best Energy Resolution: 129eV / Typical Resolution: 148eV
Skyray XRF instruments obtain better resolution without using SiLi detection systems

Si-PIN Detectors: In the early 1990’s, a United States organization developed the silicon pin semiconductor detector. This detector features an ultra thin window design and the model Skyray XRF utilizes features a signal-to-noise enhancer (SNE) for increased accuracy of the instrument. Si-PIN detectors are electronically refrigerated so that LN2 is not required and instruments can be utilized at normal room temperatures without additional accessories or procedures.
Best: 149eV / Typical: 160eV
Skyray XRF features this detector system in the EDX-2800, EDX-3000, EDX3600B, etc

SDD; silicon-drift detector: Developed in Germany in the early 2000’s; this system is electrically cooled, uses an ultra thin beryllium window and can be kept at normal temperatures providing high-efficiency and excellent results for light elements.
Best: 128eV / Typical: 139eV
Skyray XRF utilizes SDD in several units throughout the 6000+ and 3600+ line

Ultra-High Resolution Detectors: The newest detection system available was just recently developed by Skyray Instrument Inc. The UHRD provides the best resolution available, is electronically cooled and offers the best counts per second (number of photons received per second).
     Best: 125eV / Typical: 135eV
     Very new, the UHRD is currently available in the EDX-6000B but others soon

Proportional Counter Systems: These detector tubes use photo-ionization gases within the counter to detect emitted x-rays. They are most commonly utilized in systems that provide PCB Quality Control and Plating Thickness Measurements. They have poor resolution compared to other systems but are inexpensive and provide good performance for specific tasks.
Skyray XRF features a proportional counter system in the low-cost EDX-600

Feel free to contact Skyray XRF for more information on what detection system and XRF analyzer is best for your testing need(s).