4.3 Classification of radiation detectors
Radiation detectors can be classified following several principles. Some detectors are exposed to radiation during a long period of time (usually several days) in order to produce a significant effect, and the interpretation of this effect requires of additional processing. Since the recorded effect of radiation is cumulative, the measurement results are usually considered ‘passive’. When the measurements are carried during shorter periods of time (from a few seconds to hours) and the interpretation is instantaneous, the detectors are considered as ‘active’. Detectors can also be classified based on the effect produced in the detector material (see section 2.10) or in the type of response signal (counting or spectrometry).
The table below summarizes the main characteristics of different types of detectors.
| Detector denomination | Sensor material | Energy resolution | Active / Passive | Effect used for detection |
|---|---|---|---|---|
| Track edge | Film Photographic Emulsion | None | Passive | Alpha particles produce damage (tracks) |
| Film dosimeter | Film Photographic Emulsion | None | Passive | Chemical interaction (darkening) |
| Luminescence dosimeters | Special crystals / mineral | None | Passive | Electrons in the crystal's atoms are driven to higher energy states. Later luminescence is excited by either thermal (TLD) or optical stimulation (OSLD) |
| Ionization chambers | Gas | None | Active | Ionization of the gas and collection of charge from produced discharges |
| Geiger Müller counters | Gas | None | Active | Ionization of the gas and collection of charge from produced discharges |
| Proportional counters | Gas | Poor | Active | High voltage is limited as to have an intensity of the sparks proportional to the incident energy |
| Scintillators | Special crystals | Moderate | Active | Photons produce the emission of light in the crystal, which is then sensed by an additional device |
| Semiconductor | Semiconductor with different conductivity arrangements | High | Active | Pulses of charge are collected after the ionization of the semiconductor material |