Organic scintillators doped with capture agents provide a detectable signal for neutrons over a broad energy range. This work characterizes the fast and slow neutron response of EJ-254, an organic plastic scintillator with 5% natural boron loading by weight. For fast neutrons, the primary mechanism for light generation in organic scintillators is n-p elastic scattering. To study the fast neutron response, the proton light yield of EJ-254 was measured at the 88-Inch Cyclotron at Lawrence Berkeley National Laboratory. Using a broadspectrum neutron source and a double time-of-flight technique, the EJ-254 proton light yield was obtained over the energy range of approximately 270 keV to 4.5 MeV and determined to be in agreement with other plastic scintillators comprised of the same polymer base. To isolate the slow neutron response, an AmBe source with polyethylene moderator was made incident on the EJ-254 scintillator surrounded by an array of EJ-309 observation detectors. Events in the EJ-254 target coincident with the signature 477.6 keV γ ray (resulting from deexcitation of the residual 7Li nucleus following boron neutron capture) were identified. Pulse shape discrimination was used to evaluate the temporal differences in the response of EJ-254 scintillation signals arising from γ-ray and fast/slow neutron interactions. Clear separation between γ-ray and fast neutron signals was not achieved and the neutron-capture feature was observed to overlap both the γ-ray and fast neutron bands. Taking into account the electron light nonproportionality, the neutron-capture light yield in EJ-254 was determined to be 89.4 ± 1.1 keVee.

中文翻译：

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EJ-254 载硼塑料闪烁体的中子响应


掺杂有捕获剂的有机闪烁体在较宽的能量范围内提供可检测的中子信号。这项工作表征了 EJ-254 的快中子响应和慢中子响应，EJ-254 是一种有机塑料闪烁体，天然硼负载量按重量计为 5%。对于快中子，有机闪烁体中发光的主要机制是 np 弹性散射。为了研究快中子响应，在劳伦斯伯克利国家实验室的 88 英寸回旋加速器上测量了 EJ-254 的质子光产额。使用广谱中子源和双飞行时间技术，在大约 270 keV 至 4.5 MeV 的能量范围内获得 EJ-254 质子光产额，并确定与由相同聚合物组成的其他塑料闪烁体一致根据。为了隔离慢中子响应，将带有聚乙烯慢化剂的 AmBe 源入射到由 EJ-309 观测探测器阵列包围的 EJ-254 闪烁体上。确定了 EJ-254 靶中与 477.6 keV γ 射线特征一致的事件（由硼中子捕获后残留 7Li 核去激发引起）。脉冲形状辨别用于评估由 γ 射线和快/慢中子相互作用引起的 EJ-254 闪烁信号响应的时间差异。 γ 射线和快中子信号之间没有实现清晰的分离，并且观察到中子俘获特征与 γ 射线和快中子带重叠。考虑到电子光非比例性，EJ-254 的中子捕获光产额确定为 89.4 ± 1.1 keVee。