AI 中文总结
本文测量了JUNO两种20英寸PMT的长延迟后脉冲，发现其成分依赖于PMT倍增结构，产额与初级光强线性相关，为中微子实验的本底建模提供关键输入。
AI 中文摘要
在江门地下中微子观测站（JUNO）这类大型液体闪烁体探测器中，宇宙缪子等高强度事例会引发光电倍增管（PMT）后脉冲，可能干扰延迟物理信号的分析。为系统评估这类仪器本底，本文专门测量了JUNO两种20英寸PMT的长延迟后脉冲：一种是基于打拿极的PMT，另一种是微通道板（MCP）PMT。后脉冲时间轮廓先在1.8ms的直接波形窗口内表征，再通过滑动窗口读出策略扩展至20ms。观测到不同的长延迟成分，其强烈依赖于PMT的倍增结构：打拿极PMT呈现一个峰值约260μs的宽后脉冲成分；MCP-PMT则有一个约90μs的明显峰值、一个约550μs的额外成分，以及一个小得多、分布较宽的毫秒级成分。对于微秒级成分，所选延迟窗口内每个初级光电子的后脉冲产额处于10⁻³量级，且随初级光强近似线性增加。因此，高强度事例后累积的延迟活性可能不可忽略。这些定量结果为PMT响应表征以及高精度中微子实验中延迟关联本底的精确建模提供了关键输入。
英文摘要
In large-scale liquid scintillator detectors such as the Jiangmen Underground Neutrino Observatory (JUNO), high-intensity events like cosmic muons induce photomultiplier tube (PMT) afterpulses that can interfere with the analysis of delayed physics signals. To systematically evaluate this instrumental background, we present a dedicated measurement of long-delayed afterpulses in two types of JUNO 20-inch PMTs: a dynode-based PMT and a microchannel-plate (MCP) PMT. The afterpulse time profiles were first characterized within a direct 1.8~ms waveform window and were further extended to 20~ms using a sliding-window readout strategy. Distinct long-delayed components are observed, revealing a strong dependence on the PMT multiplication structure. The dynode PMT exhibits a broad afterpulse component peaking at approximately 260~$μ$s, whereas the MCP-PMT shows a pronounced peak around 90~$μ$s, an additional component around 550~$μ$s, and a much smaller, broadly distributed millisecond-scale component. For the microsecond-scale components, the afterpulse yield per primary photoelectron is at the $10^{-3}$ level in the selected delayed windows and increases approximately linearly with the primary light intensity. The accumulated delayed activity can therefore become non-negligible following high-intensity events. These quantitative findings provide critical inputs for PMT response characterization and for the accurate modeling of delayed correlated backgrounds in high-precision neutrino experiments.
Comments15 pages, 9 figures. Submitted to JINST
