AI 中文总结
本研究针对JUNO校准系统的放射性本底展开全面分析，通过材料测量、模拟及原位数据验证，确认其总贡献小于76 mHz，满足设计要求，对反应堆反中微子测量无显著影响。
AI 中文摘要
江门地下中微子天文台（JUNO）实验是一个采用20千吨超纯液体闪烁体的反应堆反中微子探测器，用于确定中微子质量顺序并精确测量振荡参数。在用于反应堆中微子分析的 fiducial 体积内，0.7-12 MeV 能量范围内，来自放射性的总单事例本底率需低于10 Hz。校准系统旨在表征探测器的能量和位置响应，但其多个组件靠近靶区，可能会对本底预算产生贡献。因此，需要进行广泛的材料筛选和选择，以构建低本底校准系统，并确保其贡献保持在设计要求内。本研究对校准系统诱导的放射性本底进行了全面研究，包括采用高纯度锗探测器的材料放射性测量、中子活化分析技术，用于评估本底的详细蒙特卡罗模拟，以及与原位探测器数据的比较以验证预测。在数据分析中，开发了专用的空间选择方法，以分离校准相关贡献并抑制液体闪烁体本底。校准系统的总放射性贡献估计小于76 mHz，满足200 mHz（总本底预算的2%）的要求。原位数据的结果与基于材料分析和模拟的预期在不确定度范围内一致。这些结果表明，校准诱导的本底已得到充分理解，数据与模拟一致，对JUNO中的反应堆反中微子测量可忽略不计。
英文摘要
The Jiangmen Underground Neutrino Observatory (JUNO) experiment is a reactor antineutrino detector employing 20 kton of ultra-pure liquid scintillator to determine the neutrino mass ordering and to precisely measure oscillation parameters. The total singles background rate from radioactivity is required to be below 10 Hz in the energy range of 0.7-12 MeV within the fiducial volume for reactor neutrino analysis. The calibration system is designed to characterize the detector energy and position responses, while several of its components are located close to the target and may contribute to the background budget. Therefore, extensive material screening and selection are required to construct a low-background calibration system and to ensure that its contribution remains within the design requirements. In this work, a comprehensive study of the radioactive background induced by the calibration system is presented, including material radioactivity measurements using high-purity germanium detectors and neutron activation analysis techniques, detailed Monte Carlo simulations to evaluate the background, and comparisons with in-situ detector data to validate the predictions. In this data analysis, dedicated spatial selection methods are developed to isolate calibration-related contributions and to suppress the liquid scintillator background. The total radioactivity contribution from the calibration system is estimated to be less than 76 mHz, which satisfies the requirement of 200 mHz (2% of the total background budget). The results from in-situ data are found to be consistent with the expectations based on material assay and simulation within uncertainties. These results demonstrate that the calibration-induced background is well understood, in agreement between data and simulation, and negligible for reactor antineutrino measurements in JUNO.
Comments18 page, 9 figures, 5 tables
