Chuong Huynh Dinh, Ngoc Trang Le Thi, Nguyen Vo Hoang, Thanh Tran Thien
Nuclear Technique Laboratory, University of Science, Ho Chi Minh City, Viet Nam; Vietnam National University, Ho Chi Minh City, Viet Nam.
Department of Nuclear Physics, Physics and Engineering Physics, University of Science, Ho Chi Minh City, Viet Nam; Vietnam National University, Ho Chi Minh City, Viet Nam.
Appl Radiat Isot. 2020 Aug;162:109179. doi: 10.1016/j.apradiso.2020.109179. Epub 2020 Apr 10.
In present work, the validity of the virtual point detector (VPD) model for the NaI(Tl) detectors is studied and confirmed in the photon energy range of 60-1408 keV. The full energy peak efficiency (FEPE) of two NaI(Tl) detectors, which have scintillation crystal dimensions of 5.08 × 5.08 cm and 7.62 × 7.62 cm respectively, is measured for "point-like" radioactive sources on the symmetry axis with source-to-detector distances in the range of 2-40 cm. It is found that the VPD model is valid to fit too well to the experimental FEPE for the two surveyed NaI(Tl) detectors. The dependence of the VPD position on the incident photon energy for the NaI(Tl) detectors with different scintillation crystal dimensions is shown based on experimental data. A semi-empirical equation involving incident photon energy and source-to-detector distance is proposed to calculate the FEPE for the NaI(Tl) detectors. The calculated results for the two surveyed NaI(Tl) detectors by this equation are in a good agreement with experimental results for photon energies in the range of 344-1408 keV. However, the difference between experimental and calculated results is quite significant for source-to-detector close geometries for photon energies lower than 344 keV.
在本工作中，研究并证实了虚拟点探测器（VPD）模型对碘化钠（铊）探测器在60 - 1408 keV光子能量范围内的有效性。对于两个碘化钠（铊）探测器，其闪烁晶体尺寸分别为5.08×5.08 cm和7.62×7.62 cm，在对称轴上对“点状”放射源进行测量，源到探测器的距离范围为2 - 40 cm，测量了它们的全能峰效率（FEPE）。结果发现，VPD模型对于所研究的两个碘化钠（铊）探测器的实验FEPE拟合得非常好。基于实验数据，给出了不同闪烁晶体尺寸的碘化钠（铊）探测器的VPD位置与入射光子能量的关系。提出了一个涉及入射光子能量和源到探测器距离的半经验方程来计算碘化钠（铊）探测器的FEPE。对于344 - 1408 keV光子能量范围内，用该方程对所研究的两个碘化钠（铊）探测器的计算结果与实验结果吻合良好。然而，对于低于344 keV的光子能量，当源到探测器的几何距离较近时，实验结果与计算结果之间的差异相当显著。
