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首页> 外文学位 >Gamma-ray and neutron radiography for a pulsed fast-neutron analysis cargo inspection system.
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Gamma-ray and neutron radiography for a pulsed fast-neutron analysis cargo inspection system.

机译：用于脉冲中子分析货物检查系统的伽马射线和中子射线照相。

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This dissertation presents the design, optimization, and characterization of a gamma-ray and neutron radiographic subsystem that was developed for the Pulsed Fast Neutron Analysis (PFNA) cargo inspection system. The PFNA inspection system uses nanosecond pulsed neutrons to produce three-dimensional elemental density images of cargo. Contraband in the cargo can be detected by its elemental content. The PFNA neutron source produces gamma rays as well as neutrons. The radiographic subsystem measures these radiations in an array of plastic scintillators to produce gamma-ray and neutron transmission images of the cargo simultaneously with the PFNA measurement.; Although the radiographic subsystem improves PFNA performance in many forms of contraband detection, it was specifically designed to detect Special Nuclear Material (SNM) in cargo containers and trucks. A feasibility study, including experiments and modeling, was performed to determine the usefulness of gamma-ray radiography in this application. The study assumed a baseline configuration of the PFNA source, a relatively small rectangular radiation beam, and a plastic detector with a 5.1 cm diameter and a 7.6 cm length. The study showed that the baseline configuration was useful in cargoes up to 144 g/cm2 thick. At this thickness, a signal-to-noise ratio of three was obtainable per pixel. The maximum cargo thickness was later increased to 180 g/cm2 by increasing the detector length to 17.0 cm and by changing the source beam stop from gold to copper.; An experiment was then performed that determined a 3.5 cm radiographic resolution was adequate for SNM detection. The detector configuration and the source motion were optimized to obtain a resolution of approximately 3.5 cm using the minimal number of detectors and the maximum detector diameter. The source is moved up and down as the cargo is pulled through the system to irradiate the entire surface of the cargo with the radiation beam. The final design consisted of 128 radiographic detectors each with a 5.1 cm diameter. A prototype of the final design was built, installed, and tested, and is currently in use at the PFNA test facility.
机译：本文介绍了为脉冲快速中子分析（PFNA）货物检查系统开发的伽马射线和中子射线照相子系统的设计，优化和特性。 PFNA检查系统使用纳秒脉冲中子产生货物的三维元素密度图像。货物中的违禁品可以通过其元素含量进行检测。 PFNA中子源产生伽玛射线以及中子。射线照相子系统在一系列塑料闪烁体中测量这些辐射，以在进行PFNA测量的同时产生货物的伽马射线和中子透射图像。尽管射线照相子系统可以在许多形式的违禁品检测中提高PFNA的性能，但它是专门为检测货柜和卡车中的特殊核材料（SNM）而设计的。进行了包括实验和建模在内的可行性研究，以确定该应用中的伽玛射线照相术的实用性。这项研究假设PFNA源的基线配置，相对较小的矩形辐射束以及直径为5.1厘米，长度为7.6厘米的塑料探测器。研究表明，基线构造可用于厚度最大为144 g / cm 2 的货物。在该厚度下，每个像素可获得三的信噪比。通过将检测器的长度增加到17.0 cm并将源束的光阑从金变成铜，最大货物厚度随后增加到180 g / cm 2 。然后进行了一项实验，确定3.5厘米的射线照相分辨率足以进行SNM检测。使用最少数量的探测器和最大的探测器直径，可以优化探测器的配置和源运动，以获得大约3.5厘米的分辨率。当货物被拉动通过系统时，光源将上下移动，以用辐射束照射货物的整个表面。最终设计包括128个射线照相探测器，每个探测器的直径为5.1厘米。最终设计的原型已构建，安装和测试，并且目前正在PFNA测试设施中使用。

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