基于EJ299-33A探测器的核材料时间关联测量系统的时间分辨

n-γ的时间关联测量可提取核材料的质量、增殖因数，其中时间分辨是表征关联精度的1个重要指标。本文基于数字化数据获取与处理方法，对具有n-γ甄别能力的塑料闪烁体EJ299-33A探测器组成的核材料时间关联测量系统的时间分辨进行研究，采用⁶⁰Co与²²Na γ源进行了对比测量，分析了源对本征时间分辨的影响，进一步通过离线的条件加载反演，给出时间分辨的等效电子能量阈值依赖关系。通过对²⁵²Cf自发裂变时间关联谱的测量和解耦，讨论了时间分辨对不同符合事件的影响。结果表明：系统时间分辨随阈值增加而减少，在阈值为230 keVee时采用⁶⁰Co测量的结果约为560 ps，可满足核材料快时间符合测量的精度要求，而在相同条件下，由于正电子湮没位置的不确定性和延迟符合的影响，²²Na源测量的时间分辨展宽至816 ps；裂变事件时间关联测量中n-n符合受时间分辨的相对影响小于γ-γ符合。

Time Resolution of Nuclear Material Time Cross-correlation Measurement System Based on EJ299-33A Detector

The neutron and gamma time cross-correlation measurement could extract mass and multiplication coefficient of nuclear material, in which time resolution is an important parameter to characterize the correlation precision. Based on the means of digital data acquisition and processing, the time resolution was assessed for nuclear material time cross-correlation measurement system, which consisted of two novel plastic scintillator EJ299-33A detectors with particle discrimination capability, and the effect of the source was analyzed by comparing the ⁶⁰Co and ²²Na measurements. Furthermore, the equivalent electron energy threshold dependence of time resolution was given by off-line inversion, and the influences on different coincidence events were discussed by decoupling of the time correlated spectrum of ²⁵²Cf. The results show that the time resolution of system decreases with the increase of equivalent threshold, and the time resolution of 560 ps was obtained at the threshold of 230 keVee by ⁶⁰Co measurement, which could meet the accuracy requirement of the nuclear material time cross-correlation measurements. Nevertheless, the result acquired by ²²Na measurement is widened to about 816 ps at the same threshold due to the uncertainty of positron annihilation position and the delayed coincidence. In the fission events correlated measurement, the relative influence of time resolution on n-n coincidences is smaller than that on γ-γ coincidences.