3.2.3 Types of x-ray detectors and main applications

Different detectors can be used for measuring x-rays, and are usually classified in the following types:

• Gas detectors
  • Ionization chambers
  • Proportional counters
  • Geiger Müller tubes
• Scintillation counters
  • NaI(Tl)
  • Plastic
• Solid state detectors
  • Intrinsic semiconductor
  • P-I-N junctions
  • Silicon drift
• Charge coupled device detectors
  • Indirect
  • Direct coupled

The purpose of the detection and the principle of work of the spectrometer rule the selection of a suitable detector. The energy resolution capability is an important feature for XRS.

In WDXRF the radiation reaching the detector has been already separated by wavelength by using a high resolution analysing crystal, thus there is no need to use a high energy resolution detector. However, detectors need to have enough pulse amplitude as to allow filtering-out of the background noise and spurious photons from the primary beam or from analysing crystal fluorescence. Gas flow proportional detectors or scintillators are normally used.

EDXRF requires using the highest possible energy resolving detector, and semiconductor detectors are a must. The more commonly used detectors in the past were the intrinsic semiconductor Si(Li). With the development of new technologies, Ge, PIN and SDD detectors have become more and more used.