OICC Press Journal of Theoretical and Applied Physics 2251-7235 7 1 2023 11 17 Calculation of full-energy peak efficiency of NaI (Tl) detectors by new analytical approach for parallelepiped sources 10.1186/2251-7235-7-52 EN OICC Press Authors Various OICC Press Authors Journal Article 2023 11 17 AbstractA new analytical approach is presented for the calculation of full-energy peak (FEP) efficiency of NaI (Tl) detectors. The self-attenuation of the parallelepiped source matrix, the attenuation by the source container, and the detector housing materials were considered in the mathematical treatment. The efficiency values calculated using the presently suggested analytical approach are compared with those measured values obtained by two different sizes of NaI (Tl) detectors. The calculated and the measured full-energy peak efficiency values were in a good agreement.