基于核四极矩共振原理的炸药探测方法研究与实验

介绍了一种基于核四极矩共振（Nuclear Quadrupole Resonance, NQR）原理的炸药探测方法及其基本原理和其用于炸药探测的依据,提出了一种可行的基于核四极矩共振原理的炸药检测系统,描述了其结构组成、工作原理及实验方法,并给出了对黑索金（RDX）、梯恩梯（TNT）、奥克托今（HMX）、太恩（PETN）和特屈儿（TETRYL）炸药的测试实验结果. 实验表明该方法可行,能实现对以上炸药的探测.     

PETN炸药NQR信号处理方法

利用核四极共振(Nuclear Quadrupole Resonance, NQR)原理探测隐藏炸药,具有准确率高、误报率低、无放射性沾染和防护问题等优点. 但NQR信号十分微弱,湮没在噪声中,检测困难,这成为制约NQR技术发展的一项瓶颈. 为提升NQR信号信噪比,根据NQR信号的特点,提出了一种基于改进阈值函数小波变换的NQR信号去噪方法. 计算表明该方法可以有效消除外界噪声对信号的干扰,提高探测的准确性.      

特殊炸药的爆轰参数计算

 针对BKW（Becker-Kistiakowsky-Wilson）状态方程,编写了爆炸参数计算程序。该程序除了可以计算常规含C、H、O、N元素炸药的爆轰参数,还能计算含有其它金属元素炸药的爆轰参数。通过对含Fe、Mn元素的乳化炸药以及含Al元素的水胶炸药的爆轰参数计算表明,该计算程序得到的计算结果与实验结果基本一致,相对误差不超过1%。采用该程序计算爆轰参数时,只需输入炸药的化学式、常温常压密度和生成焓即可。     

NQR炸药探测系统中射频线圈的设计研究

基于核四极矩共振(Nuclear Quadrupole Resonance, NQR)炸药探测原理,对探测系统中拾取信号的关键部件射频线圈进行了优化设计,并确定了小型螺线管型线圈的直径、长度和匝数. 试验测试表明,此线圈射频场均匀性好、信噪比大、灵敏度高,可以快速准确探测到NQR信号,验证了线圈设计理论的有效性和制作方法的可行性. 该设计方法对提高隐藏炸药探测的准确率以及不同试验条件下射频线圈的设计具有重要意义.     

基于Apollo信号控制台的NQR炸药探测方法

介绍了一种基于Apollo信号控制台的核四极矩共振（NQR）炸药探测方法，描述了系统的结构组成、工作原理和实现方法，并给出了对RDX的测试试验结果. 试验表明该方法可实现对RDX信号的探测.     

用PVDF压力计研究未反应JB-9014钝感炸药的Grüneisen参数北大核心CSCD

为了获得未反应JB-9014炸药的Grüneisen参数Γ,在火炮加载平台上对JB-9014炸药进行一维平面冲击实验。实验中,将炸药样品安装于两个铜板之间,两个PVDF压力计分别安装在炸药样品前表面和中部,记录两个位置处的压力随时间的变化历程;将圆形铜板作为飞片安装于弹托前表面,利用火炮加速弹托,使飞片以一定速度撞击样品装置前铜板,前铜板中产生右行冲击波对炸药样品形成一次压缩;随后冲击波在炸药样品/后铜板交界面发生反射,产生左行冲击波对炸药样品形成二次压缩。假设炸药样品的Grüneisen参数Γ为常数,计算不同Γ值下炸药样品前表面和中部压力随时间的变化历程,将不同Γ下的计算值与实验值进行对比,获得了JB-9014钝感炸药Grüneisen参数的最优值,为1.7。     

主动法探测炸药的实验

在核弹头核查中非核组件尤其是炸药难以探测。针对炸药的特点，开展了以下工作：(1)从理论上分析了主动法探测炸药的原理，并分析了在实际时影响测量结果的因素(屏蔽体的影响、自然本底的影响和反应截面)。(2)利用^252Cf中子源辐照模拟炸药半球(质量分别为10．4kg和15．8kg)，采用高纯锗γ探测器探测由中子与^1H，^12C，^16O，^14N核素发生俘获反应(n，γ)产生的γ射线。在实验中通过改变模拟炸药的质量、中子源与模拟炸药球心之间的距离和增减中子源和模拟炸药半球之间的慢化剂，进行了多种模型的实验研究。     

未反应炸药冲击绝热线的近似计算

 综合考虑了炸药作为一类多组分和疏松材料的特点,在已知炸药各组分冲击绝热参数的条件下,利用叠加原理和疏松材料冲击绝热线的计算方法,对未反应炸药的冲击绝热线进行了计算。计算结果与实验数据符合较好。     

高聚物黏结炸药的分子模拟进展

回顾了近年来在高聚物黏结炸药(PBX)原子和分子尺度数值模拟方面取得的进展,主要研究领域包括以下6个方面:炸药分子力场、热力学参数计算、耗散/输运性能、相图/相变动力学、动力学响应行为和热点形成机制。针对当前研究现状,介绍了各领域的代表性工作和主要研究成果。目前对PBX炸药的结构和静力学性能已有较充分的认识,但对炸药的动力学响应行为和细观起爆机制尚缺少系统的科学认识,存在一系列挑战性问题,如结构缺陷在爆轰反应后期的形态和表征,以及初始缺陷对爆轰波波形畸变的影响机制。需要将理论计算与实验相结合,以解决爆轰物理领域中的难点问题。     

主动法探测炸药成分实验

军控核查中，炸药的探测难度较大。在实验中利用^252Cf中子源辐照不同质量件和不同组合的模拟炸药半球（图1），采用高纯锗γ探测器探测由中子与^1H，^12C，^16O和^14N核素发生（n，γ）俘获反应产生的γ射线来探测炸药成分。     

Feedback optimization of pulse width in the SORC sequence.

A method for increasing the signal-to-noise ratio (SNR) of nuclear quadrupole resonance (NQR) measurements by automatically adjusting a pulse parameter in real-time is presented. This approach is useful in situations where the optimal pulse parameters cannot be chosen beforehand due to lack of knowledge regarding the system. For example, NQR provides a means for detecting explosives by revealing the presence of (14)N. In this particular application, the distance between the search coil and the explosive, as well as the temperature of the explosive, is unknown. As a result, a fixed set of pulse parameters will not yield the largest SNR for all possible search applications. This paper describes a feedback algorithm that uses measurements of the NQR signal to automatically adjust the pulse width in the strong off-resonant comb sequence to maximize the SNR of the NQR measurement. Experimental results obtained using a sample of sodium nitrite are presented.     

利用核四极矩共振技术探测炸药

介绍了用核四极矩共振的原理进行爆炸危险物品检测的方法及实验测试系统. 该系统运用特殊的激励信号来激发被检测样品中所含的特殊元素¹⁴N（炸药的主要成分）,使其产生核四极矩共振,并产生辐射,从而达到检测的目的. 由于该辐射信号的能量非常小(10 nV量级）,在通常的环境中很难检测该信号, 这就对此弱信号的检测和提取提出了很高的要求. 本测试系统使用了一系列有效的组合激励信号及弱信号采集、处理技术,在通常环境中成功地检测到了RDX（黑索金）信号.     

NQR Characteristics of an RDX Plastic Explosives Simulant

For reliable detection of explosives, a combination of methods integrated within a single measurement platform may increase detection performance. However, the efficient field testing of such measurement platforms requires the use of inexplosive simulants that are detectable by a wide range of methods. Physical parameters such as simulant density, elemental composition and crystalline structure must closely match those of the target explosive. The highly discriminating bulk detection characteristics of nuclear quadrupole resonance (NQR) especially constrain simulant design. This paper describes the development of an inexplosive RDX simulant suited to a wide range of measurement methods, including NQR. Measurements are presented that confirm an RDX NQR response from the simulant. The potential use of the simulant for field testing a prototype handheld NQR-based RDX detector is analyzed. Only modest changes in prototype operation during field testing would be required to account for the use of simulant rather than real explosive.     

Detection of plastic explosives in luggage with14N nuclear quadrupole resonance spectroscopy

Nuclear quadrupole resonance (NQR) of¹⁴N nuclei has many advantages as a method for detecting nitrogen-containing explosives, the most important are very high chemical specificity, true noninvasive operation and detection of bulk explosive in situ only (no vapor or particular capture needed). One of the most high explosives is hexogen (RDX) often used by terrorists in plasticized forms. The ring nitrogen nuclei in an RDX molecule generate three sets of NQR frequencies corresponding to three physically nonequivalent positions of the molecule in the crystal lattice. The prototype device we have constructed is intended for inspection of suitcases for the presence of plastic explosives containing RDX or octogen by¹⁴N quadrupole resonance. It is essentially a fully automated PC-controlled pulsed FT NQR spectrometer equipped with a large volume (70 1) radio-frequency (RF) sample coil to accommodate a typical suitcase. The device consists of a measure chamber with an RF coil, tuning and matching box, an RF pulse transmitter and a control PC with dedicated cards like digital receiver, frequency synthesizer, pulse programmer and probe-tuning controller. The control software finds the NQR lines and measures their frequencies. An alarm is produced if any of these frequencies matches the characteristic NQR frequency of the explosive and the signal-tonoise ratio exceeds the preset threshold. Multipulse sequences of the type SORC (strong off-resonance comb) or SLSE (spin-locked spin echo) were used in order to increase the allowed data acquisition rate. We could detect 230 g of PMW-8, a plastic explosive (containing 81% of RDX) in 10 s or 100 g in 30 s. Detection probability was not less than 90%.     

<Superscript>14</Superscript>N Nuclear Quadrupole Resonance Study of Polymorphism in Trinitrotoluene Samples Obtained from Old Ordnances

The field application of a ¹⁴N nuclear quadrupole resonance (NQR) detector needed for the detection of different explosives, including trinitrotoluene (TNT), requires the examination of the distribution of ¹⁴N NQR lines stemming from the monoclinic and/or orthorhombic modifications of TNT, as well as from a mixture of both. In this work, 30 different TNT samples up to 70 years old were measured. The main result of this study is that the measured ¹⁴N NQR spectrum is strongly influenced by the environmental conditions to which the explosive was subject during its history.     

Some Aspects of the Effective Detection of Ammonium Nitrate-Based Explosives by Pulsed NQR Method

The nuclear quadrupole resonance (NQR) method has been applied to ammonium nitrate (AN)-based explosives, ANFO and REOGEL+, to find an optimized multi-pulse technique for effective detection. The relaxation parameters and signal intensities for nitrogen-14 lines of these substances were measured. The experimental results of applying the proposed multi-pulse technique in these samples are presented and convincingly demonstrate a path toward efficient detection. A detection using sequences of this character could be achieved over real-world scan volumes for screening of goods. It was proven that the cross-polarization technique can significantly enhance the NQR signal for AN-based explosives.     

爆炸物检测中NQR信号的处理及判识

介绍了基于核四极矩技术的爆炸物检测原理及信号处理方法.系统分析了NQR信号检测中主要误差来源,提出多种方法消除NQR信号处理中检测误差,主要包括相关累加消除随机噪声;单通道自适应消除振铃影响;相关性检测抑制同频干扰.实验表明相关检测可有效提高NQR信号信噪比,提高微弱NQR信号检测的准确性.