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      Influence of geometric factor on detection efficiency in low-background α/β radioactivity measurement


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          Objective To study the influence of the radius of the active zone of the plane source and the horizontal distance between the source center and the center of the detection window on the detection efficiency of low-background α/β measuring instruments.

          Methods The geometric factor was calculated under different conditions in MATLAB, and a traceable plane source was used to test and analyze two commonly used measuring instruments.

          Results With the other parameters unchanged, when the radius of the active zone R1 = 9 mm, the G value was greatest; and when the horizontal distance a = 0 mm, the G value was greatest. According to the calculation formula of the verification regulation, for the 90Sr- 90Y planar source, at the maximum value of a, the detection efficiency of FYFS-400X was 1.2% lower, and that of MPC-9604 was 3.2% lower; for the 241Am planar source, the detection efficiency of MPC-9604 was 1.9% lower at the maximum value of a.

          Conclusion The geometric factor decreases with the increase in the radius of the active zone and the horizontal distance between the source center and the center of the detection window. At the central position, the geometric factor has less influence on the relative standard uncertainty of detection efficiency. When using a standard plane source for counting, measures should be taken to ensure that the plane source is always centrally located in the sample tray.


          摘要: 目的 研究对低本底 α、β 放射性测量仪计量时平面源活性区半径以及其中心与探测窗中心位置水平间距的变 化对探测效率的影响。 方法 基于 MATLAB 对不同条件下的几何因子的数值计算, 采用经溯源的平面源对常用的测 量仪器进行实验分析。 结果 保持其他参数不变, 活性区半径 R1 = 9 mm 时, G 值最大;间距 a = 0 mm 时, G 值最大; 按照检定规程计算公式, 对于 90Sr- 90Y 平面源, a 最大时, FYFS-400X 探测效率偏小 1.2%, MPC-9604 探测效率偏小 3.2%;对于 241Am 平面源, a 最大时 MPC-9604 探测效率偏小 1.9%。 结论 几何因子随着活性区半径、间距的增大而减 小。在居中位置, 几何因子对探测效率相对标准不确定度的影响更小。建议使用标准平面源对仪器计量时应该采取有 效措施确保平面源始终处于样品盘的正中央位置。

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          Author and article information

          Chinese Journal of Radiological Health
          Chinese Preventive Medical Association (Ji’an, China )
          01 April 2024
          01 May 2024
          : 33
          : 2
          : 183-188
          [1] 1Shanghai Insitution of Measurement and Testing Technology, Shanghai 201203 China
          © 2024 Chinese Journal of Radiological Health

          This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 Unported License (CC BY-NC 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. See https://creativecommons.org/licenses/by-nc/4.0/.

          Journal Article

          Medicine,Image processing,Radiology & Imaging,Bioinformatics & Computational biology,Health & Social care,Public health
          Relative standard uncertainty,Solid angle,Detection efficiency,α/β radioactivity,Geometric factor


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