Simultaneous determination of dose and time elapsed since irradiation using CaSO4: Dy thermoluminescent dosimeters

Information about the time which has elapsed since an external radiation exposure is useful in order to determine the time of occurrence of an abnormal exposure in personal and accident dosimetry. This information can be obtained from certain irradiated thermoluminescent dosimeters. A computational method based on decay rates of thermoluminescence glow peaks has been used to estimate a range of suitable values of trap lifetimes of low-temperature glow peaks. This provides the basis to determine not only the absorbed dose from a radiation exposure but also the time elapsed since irradiation. Experimental data on CaSO4: Dy dosimeters agree favourably with theoretical predictions, particularly in the variation of the peak area ratio with elapsed time since an abnormal exposure superimposed on a constant and continuous background exposure. (author)