Certain materials, when subjected to ionizing radiation, will undergo an internal alteration in their crystal structure which will store a certain amount of that energy. When these materials are heated they release that stored energy as visible or ultraviolet light. A photomultiplier tube observing the sample will then generate an electrical signal whose magnitude can be related to the amount of radiation dose that the sample received. Thermoluminescence dosimetry has a very wide range of dose in which the response of the detectors can be made linear.