Most of the XRF instruments in use today fall into two categories: energy-dispersive (ED) and wavelength-dispersive (WD) spectrometers. Within these two categories is a tremendous variety of differing configurations, X-ray sources and optics, and detector technologies. This paper will cover the most common types of instruments, with forays into the more advanced or specialized components where they are of interest.
A diagram of a WD system is shown in Figure 2. The instrument operates based on the principle of Bragg diffraction of a collimated X-ray beam, in this case the beam emanating from the sample. A detector is angularly scanned relative to the analyzing crystal, registering the spectrum.