Research On Explosive Identification Simulation Device Based On PGNAA Technology

With the rapid development of human society,a variety of high-performance explosives emerge in endlessly,which has brought many negative effects to the world and deeply affected the social security and stability.How to quickly identify explosives is an urgent problem to be solved.It is found that explosives（such as TNT,C₇H₅N₃O₆）are mainly composed of C,H,O,N and other elements.It is expected that the rapid identification of explosives can be carried out by analyzing the proportion of elements.The prompt gamma neutron activation analysis（PGNAA）technology uses the gamma rays emitted by the reaction between neutrons and material elements for qualitative and quantitative analysis,which is expected to build a non-destructive and penetrating detection technology,so as to realize the rapid identification of explosives.In this paper,based on PGNAA technology,a set of explosive identification simulation device using pulsed D-T neutron tube as neutron source is designed.The simulation device model is established by MCNP software based on Monte Carlo method,and the numerical calculation is carried out.By simulating and optimizing the materials and sizes of moderators,reflectors and multilayer shields,it is expected that the fast neutron and thermal neutron fluxes can be optimized under the condition of reducing gamma ray interference,and the material selection scheme for improving neutron utilization is given;The influence of the relative position of the sample and neutron source and the distance between the sample and the model on the detection results is explored.On the premise of ensuring the neutron flux,these two factors have little influence on the detection within a certain range.In addition,the sample density has an effect on the characteristic gamma peak count of elements,but the influence trend of different elements is different.According to the characteristics of periodic emission of neutrons by pulsed neutron source,using the time difference of gamma rays produced by inelastic scattering and radiation capture reaction,the optimal acquisition time is proposed to distinguish the characteristic gamma rays of different elements.Based on the above devices and method,the response of the device to different concentrations of C,H,Oand N was simulated according to the element composition of TNT and glucose simulants,it is found that there was a good linear relationship between the Gammat characteristic peak area and the corresponding element concentration,and the linear correlation coefficien twas all above0.99.The simulation results show that the relative error of C,H,O and N can reach less than 4%,.Judging by the C/Oand N/Ovalues,the explosive identification device has a good recognition effect on the explosive simulation..To sum up,this paper established a set of explosive identification simulation device model based on PGNAA technology.Through different acquisition time to distinguish the characteristic gamma rays of elements,the element quantitative analysis was carried out.The simulation results show that the model can identify explosives.This paper provides data support for the quantitative analysis of these elements,and has certain guiding significance for the identification of explosives.