Explosives detection using photoneutrons produced by X-rays
Explosives detection using photoneutrons produced by X-rays
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DOI：
10.1016/j.nima.2007.04.087
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发表时间：
2007-08
影响因子：
1.4
通讯作者：
Yigang Yang;Yuanjing Li;Haidong Wang;Tiezhu Li;Bin. Wu
中科院分区：
文献类型：
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作者：
Yigang Yang;Yuanjing Li;Haidong Wang;Tiezhu Li;Bin. Wu
在最近的恐怖袭击之后，爆炸物的探测已成为一个关键问题。本文介绍了利用光中子探测器中的光中子探测爆炸物的研究，光中子探测器由20公斤重水组成，铝容器的形状经过优化，以最有效地将X射线转换为光中子。X射线由9 MeV电子加速器产生，平均电子流为100μA，光中子产额> 10 ~（11）n/s。蒙特-卡罗模拟表明，辐射场由X射线脉冲、快中子脉冲和热中子组成。X射线和快中子脉冲的宽度均为5μs，重复频率为300 Hz。热中子通量大于104 n/cm ~ 2/s，基本上是时不变的。研制了一种时间屏蔽电路，用于在强X射线脉冲作用下暂停光谱仪的采样过程。采用石蜡、碳化硼和铅保护探测器，使其免受光中子引起的系统材料中的X射线、快中子、热中子和本底γ射线的干扰。选用5″×5″ NaI（Tl）闪烁器作为探测器，对被检炸药模拟物中的光中子感生γ射线进行了探测。用一个探测器探测了氮（6.01cps）10.828MeV γ射线，探测器前60 cm处放置了一个50 kg的尿素块。用准直器减少来自空气中氮气的10.828MeV γ射线的本底，使信噪比从0.136提高到1.81。用7个5″×5″ NaI（Tl）探测器组成的探测器阵列测量了样品中N和H的二维分布。光中子分析和X射线成像的结合显示出提高爆炸物探测能力的希望。
The detection of explosives has become a critical issue after recent terrorist attacks. This paper describes research on explosives detection using photoneutrons from a photoneutron convertor that consists of 20kg heavy water in an aluminum container whose shape was optimized to most effectively convert X-rays to photoneutrons. The X-rays were produced by a 9MeV electron accelerator with an average electron current of 100μA, resulted in a photoneutron yield of >1011n/s. Monte-Carlo simulations show that the radiation field is composed of X-ray pulses, fast neutron pulses and thermal neutrons. Both the X-ray and fast neutron pulses are 5μs wide with a 300Hz repetition frequency. The thermal neutron flux, which is higher than 104n/cm2/s, is essentially time invariant. A time shielding circuit was developed for the spectrometry system to halt the sampling process during the intense X-ray pulses. Paraffin, boron carbide and lead were used to protect the detector from interference from the X-rays, fast neutrons, thermal neutrons and background γ-rays coming from the system materials induced by photoneutrons. 5″×5″ NaI (Tl) scintillators were chosen as the detectors to detect the photoneutrons induced γ-rays from the inspected explosive simulant. Nitrogen (6.01cps) 10.828MeV γ-rays were detected with one detector from a 50kg carbamide block placed 60cm in front of the detector. A collimator was used to reduce the number of background 10.828MeV γ-rays coming from the nitrogen in the air to improve the signal to background ratio from 0.136 to 1.81. A detector array of seven 5″×5″ NaI (Tl) detectors was used to measure the 2-D distributions of N and H in the sample. The combination of photoneutron analysis and X-ray imaging shows promise for enhancing explosives detection capabilities.