Low activities of radionuclides in environmental and occupational samples demand for the lower detection limits of the measuring system, which can be achieved by minimizing the source-to-detector distance. Analytical technique to calculate full-energy peak efficiency and total efficiency, self-absorption of sources and a coincidence factor of the NaI cubic scintillation detector with rectangular cavity for rectangular source have been derived. The photon path length of the volumetric sources calculated and determined source self-absorption. The photon attention by rectangular sources and detector cap materials is also calculated. In the experiments gamma aqueous source containing Eu-152 radionuclide covering range from 121 to 1408 keV was used. By comparison analytical method for calculating the full energy peak efficiency and the corrected experimental efficiency values are in good a agreement.

中文翻译：

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NaI立方探测器全能峰值效率，包括使用分析方法对矩形源的重合和自吸收校正

环境和职业样品中放射性核素的低活度要求测量系统具有较低的检测限，这可以通过最小化源到探测器的距离来实现。推导出了计算矩形源矩形腔NaI立方闪烁探测器全能峰值效率和总效率、源自吸收和符合因子的解析技术。体积源的光子路径长度计算并确定源自吸收。还计算了矩形光源和探测器帽材料的光子注意力。在实验中，使用了包含 Eu-152 放射性核素的伽马水源，覆盖范围从 121 到 1408 keV。