Scintillation detectors typically identify gamma radiation sources. The detection is based on using a scintillation crystal, which is a material that when it is excited by ionizing radiation, it re-emits the absorbed energy in the form of light. For operation, this light is then sent to a photomultiplier tube and detector to multiply and detect the light. The photon produced is proportional to the gamma ray absorbed. The most common scintillation detector types are NaI and LaBr3.