Other radiation detectors

The ionization chambers previously described may be used to detect and measure both photons and charged particles, provided that the radiation can penetrate the wall or entrance window of the device and also that the ionization current is sufficiently large as to be measurable. Where the radiation intensity is too low for ionization chambers to work satisfactorily, such as in detecting and measuring radiation emitted from a small radioactive source, other more sensitive instruments must be used. The most sensitive devices are ‘event counters’, able to detect and record individual photon interactions or the passage of individual charged particles. Each interactions results in an electrical pulse which is counted either to give a total number of interactions recorded or the number recorded per unit interval of time to provide a ‘count rate’. The decay of a radioactive material may be measured for example by monitoring the fall in count rate with time.

Common types of device that are used in the detection and measurement of low intensity radiation use gas amplification (Geiger-muller counters and proportional counters) and scintillation detectors.

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