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Radiation Detectors


High Energy Physics

Radiation Detectors

Several quite different radiation detectors are used in the various projects in the nuclear physics laboratory. Which detector is used depends on the type of radiation being detected, its energy and what energy resolution is required.

Canberra is one major manufacturer of modern radiation detectors. General information about radiation detectors may be found on their web site.

Detector types

  • Solid state detectors
    • Surface Barrier detectors. These are modern solid state semiconductor devices. We use them mainly for the detection of alpha and beta radiation. A brief description of such a detector can be found here. Such detectors are used in the alpha particle scattering and the alpha particle spectroscopy project.
    • Cooled Germanium detectors. This type of detector is used for the detection of gamma-rays and offers very high spectral resolution. Such a detector is used in the High Resolution Gamma-ray Spectroscopy project. Information on germanium detectors can be found here.
  • Gas filled detectors
    • Geiger counters. These are gas filled counting devices that, unlike gas filled proportional chambers, provide no spectral resolution. They are used mainly for particle detection and are used in the High Energy Electron spectrometer project.
    • Photomultiplier tubes (PMTs). An incoming photon knocks an electron out of the photocathode, which is then multiplied by a dynode chain to generate a readable current at the anode. These sorts of detector are often used with a scintillator in particle physics experiments, such as in the Muon Physics project. To see a pictorial representation of a PMT in action click here.
  • Scintillators
    • Inorganic scintillators. The most common scintillation crystal used as a radiation detector is NaI(Tl). They are used for the detection of x-ray and gamma-ray radiation with medium resolution. Photoelectric absorption or Compton scattering in the crystal leads to scintillation light that is usually converted to an electrical pulse by a photomultiplier tube.
    • Organic (plastic) scintillators. These low mass detectors are used for the detection of many types of radiation with generally low energy resolution. They are often used in coincidence systems where a particle or gamma-ray loses a small part of its energy to the detector. The scintillation light is usually converted to an electrical pulse by a photomultiplier tube. Such detectors are used in the Muon Physics project.