Gamma counters
How do Gamma Counters work?
Gamma counters are commonly based on a NaI(Tl) scintillation detector and are usually automated (in that they have a sample changer) and controlled by a computer. The most important parameters the operator needs to input into the computer are the radioisotope being counted (i.e. the energy window that needs to be set) and the length of time for which the instrument should count each sample.
This usually depends on how radioactive the samples are as low activity samples may need to be counted for longer in order to obtain good counting statistics. The samples to be measured are placed in counting tubes in racks which are moved towards the detector where the tubes are taken one by one by the automatic sample changer to be counted.