Some substances emit scintillations under the effect of radiation. These substances can be used as scintillation detectors. Rutherford was the first to use a scintillation detector to measure alpha radiation. However, scintillation detectors became really important when Zoltan Bay constructed photomultipliers which transform scintilla­tions into electric impulses. As a result of the improvement of scintillator and photomultipliers, scintillation detectors became one of the most important and widely applied tools in radiation measurement.

The advantages of using scintillation methods are as follows:

• The scintillator material is solid or liquid; its density is higher by about three orders of magnitude than the density of the gas in gas-filled detectors. Thus, a significant portion of radiation is converted into light photons. The free path of the light photons can be in the range of 1 m, while the free path of the ions in the gas-filled detectors is only a few centimeters.

• The time of the formation, collection of the light photons, electron conversion and multi­plication, and signal processing is much shorter in scintillation detectors than in gas-filled detectors, so the dead time of scintillation detectors can be as low as about 10_8 s.

• Some scintillator material can be produced as a single crystal. In this case, the intensity of the scintillation is proportional to the energy of the radiation within a wide energy range, so the scintillation detectors are suitable to measure the energy of the radiation.

• The shape of the signals in the scintillation detectors depends on the type of radiation. Thus, it is possible to differentiate between the different types of radiation.

• The scintillation detectors can detect and measure alpha, beta, and gamma radiations. The detectors and the measuring techniques, however, are different for each types of radiation. This will be discussed later.

The scintillation system consists of the following parts:

• The scintillator material converts the radiation into light photons.

• The photomultiplier transforms the light photons into electric impulses.

• The electric processing units amplify, discriminate, process, count, record, the electric impulses.