球床式高温气冷堆球流CT探测器辐照光输出稳定性研究

针对长时间实验过程中CsI(Tl)闪烁体探测器的辐照光输出会不断变化的问题，在实现探测器输出暗场的稳定性控制后，对按实际堆芯5∶1比例缩小设计的球流检测系统进行了长达48 h的空载γ射线辐照，并记录了暗场稳定性的控制结果及探测器的辐照光输出。结果表明：各闪烁体探测单元受γ辐照后，辐照光输出先不断上升，达到最大值后再线性下降。分析探测器辐照光输出发现，几何尺寸和物理成分相同的各探测单元彼此间的辐照光输出上升幅度比与辐照损伤均存在差异，但辐照光输出达到最大时对应的累计剂量基本相同，且与初始辐照光输出大小无关。最后提出了对系统辐照光输出的上升和下降阶段分别采用指数校正和线性校正的思路，为球床式高温气冷堆球流检测系统图像重建过程中投影数据的校正提供解决方案。

Study on Irradiation Light Output Stability of PB-HTGR Pebble Flow CT Detector

Aiming at the problem that the irradiation light output of CsI(Tl) scintillator detector changes constantly during the long time experiment, with the stability control of dark field signal, a pebble flow detection system with a 5∶1 ratio reduction of the actual core was irradiated for 48 h with no-load γ ray. Besides, the controlled result of dark field stability and the irradiation light output of the detector were recorded. Experiment results show that after the γ irradiation, the irradiation light output of the scintillator detector increases firstly, and then decreases linearly after it reaches a maximum value. After the analysis of irradiation light output, it is found that the irradiation light output rise ratio and the corresponding irradiation damage between detectors are different despite of the same geometric and physical component. However, the cumulative dose corresponded to the maximum irradiation light output is basically the same, and it has little relevance with the size of the initial irradiation light output. Based on above, a corresponded exponential method and a linearity method were proposed respectively for the correction of the rising and falling stages of the irradiation light output, and it provides a solution for the correction of the projection data during the process of image reconstruction in PB-HTGR pebble flow detection system.