Light transport modelling of pulse shape discrimination within plastic scintillators
Light transport modelling of pulse shape discrimination within plastic scintillators
复制标题
塑料闪烁体中脉冲形状辨别的光传输建模
DOI：
10.15126/thesis.00857773
复制
发表时间：
2020
影响因子：
2.8
通讯作者：
M. Hubbard
中科院分区：
文献类型：
--
作者：
M. Hubbard
塑料散热器用于需要伽马射线识别的场景，并且可以扩展到大尺寸，用于粒子物理和核安全等应用。特别是，现代塑料材料具有通过脉冲形状识别（PSD）检测中子的能力，为该领域的研究提供了令人兴奋的新途径。这些材料的脉冲形状具有基于引起闪烁发射的辐射相互作用的特征衰减时间常数。材料在几立方厘米的体积下表现出这种能力，但是当缩放到更大的体积时，PSD性能降低。通过识别这种恶化的原因，可以确定和实施方法来提高PSD性能。
通过所报告的工作过程，确定了提高性能的方法。在一个实例中，应基于应用选择检测器配置。应根据配置和应用环境选择随附的PSD算法，以实现最佳性能。在设计探测器配置时，应使用模拟作为工具，以帮助最大限度地提高性能。在这篇论文中提出的模拟已经确定，脉冲形状的变化基于闪烁系统的许多方面。通过对光传输进行建模，已经发现闪烁光的发射方向改变脉冲形状衰减时间。光基于方向性以不同的分布到达。此外，这些分布基于反射器类型、反射率百分比和闪烁发射的位置而改变。PSD依赖于脉冲形状衰减时间常数的差异。所概述的这些因素导致与脉冲形状卷积的附加时间常数。这在算法中计算的PSD参数中产生变化。这种变化随着闪烁体体积的增加而增加，并且是大尺寸塑料闪烁器性能降低的原因。
Plastic scintillators are used in scenarios where gamma-ray identification is necessary and can be scaled to large sizes for use in applications such as particle physics and nuclear security. In particular, modern plastic materials with the ability to detect neutrons via Pulse Shape Discrimination (PSD) are providing exciting new avenues of research for the field. The pulse shapes for these materials have characteristic decay time constants based on the radiation interaction causing scintillation emission. The materials exhibit this capability with volumes of a few cubic centimetres, but when scaled to larger volumes, the PSD performance diminishes. By identifying the cause of this deterioration, methods can be determined and implemented to increase PSD performance.
Through the course of the work reported on, methods for increasing the performance are identified. In one instance, the detector configuration should be chosen based upon the application. The accompanying PSD algorithm should be selected based on the configuration and application environment to achieve maximum performance. When designing the detector configuration, simulations should be used as a tool to help maximise performance. The simulations presented in this thesis have identified that pulse shapes change based on many aspects of the scintillation system. By modelling the light transport, it has been found that the emission direction of scintillation light alters the pulse shape decay times. The light arrives in different distributions based on the directionality. Moreover, these distributions change based on reflector type, the percentage reflectivity and location of the scintillation emission. PSD relies on differences in the decay time constants of pulse shapes. These factors outlined lead to additional time constants being convolved with the pulse shape. This creates variation in the PSD parameter calculated in the algorithms. This variation increases with the scintillator volume and is the cause of reduced performance with large-sized plastic scintillators.