Three-dimensional reconstruction of a small piece of Ce-doped lithium glass scintillator of an optical fiber-based neutron detector using microcomputed tomography technique.

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.