Ishikawa Akihisa, Segawa Mariko, Toh Yosuke, Watanabe Kenichi, Masuda Akihiko, Matsumoto Tetsuro, Yamazaki Atsushi, Yoshihashi Sachiko, Uritani Akira, Harano Hideki
Research Group for Nuclear Sensing, Nuclear Science and Engineering Center, Japan Atomic Energy Agency, 2-4 Shirakata, Tokai-mura, Ibaraki 319-1195, Japan.
Department of Applied Quantum Physics and Nuclear Engineering, Kyushu University, 744, Motooka, Nishi-ku, Fukuoka 819-0395, Japan.
J Radiat Res. 2025 Sep 23;66(5):563-569. doi: 10.1093/jrr/rraf048.
An optical fiber-based neutron detector is a real-time neutron monitor for an intense neutron field. A small piece of neutron scintillator, such as Ce-doped lithium glass (Li-glass), used in the detector has a random shape with a grain size of 200-400 μm. This causes shape-dependent effects on the detector response. However, it is difficult to control or determine its shape due to its small size. Here we propose a technique to characterize the fine structure of a small piece of scintillator using a microcomputed tomography (CT) system. To verify accuracy, the mass calculated based on the density of Li-glass and the volume extracted from the obtained CT image was compared to the mass measured in advance using an electronic balance. In the obtained CT images, the fine shape of the small piece of Li-glass was clearly visible, and no false signals from the surrounding components were observed. The calculated mass was in good agreement with the measured value, however, when the total number of projection images was 2000, a slight underestimation was observed. This was mitigated by increasing the number of projection images, and the difference between the calculated and measured mass was 1.6% when the number of the projection images was 3141. This was equivalent to the uncertainty of the measured mass. The proposed technique will be useful when high accuracy is needed, such as for medical applications.
基于光纤的中子探测器是一种用于强中子场的实时中子监测器。该探测器中使用的一小片中子闪烁体，如掺铈锂玻璃（Li-玻璃），形状不规则，晶粒尺寸为200 - 400μm。这会对探测器响应产生形状相关的影响。然而，由于其尺寸小，很难控制或确定其形状。在此，我们提出一种使用微型计算机断层扫描（CT）系统来表征一小片闪烁体精细结构的技术。为验证准确性，将基于Li-玻璃密度计算出的质量与从获得的CT图像中提取的体积计算出的质量，与预先使用电子天平测量的质量进行比较。在所获得的CT图像中，小片Li-玻璃的精细形状清晰可见，未观察到来自周围组件的虚假信号。计算出的质量与测量值吻合良好，然而，当投影图像总数为2000时，观察到轻微低估。通过增加投影图像数量可减轻这种情况，当投影图像数量为3141时，计算质量与测量质量之间的差异为1.6%。这与测量质量的不确定度相当。当需要高精度时，如在医疗应用中，所提出的技术将很有用。
