基于电子加速器的核共振荧光无损探测模拟计算

Simulation of Nondestructive Inspection of Nuclear Resonance Fluorescence Based on Electron Accelerator

核共振荧光(nuclear resonance fluorescence,NRF)是一种新兴的无损探测技术,通过分析伽马能谱中的特征能量来识别特定同位素,在含未知爆炸物小型箱体的扫描检查中发挥重要作用。本研究利用电子加速器韧致辐射产生的X射线为射线源,通过蒙特卡罗模拟程序Geant4优化设计NRF背散射探测方案。结果表明,优化后的X射线泄漏率降低了386倍,束流不对称度低于2%,束流均匀度高于70%。基于HPGe探测器获得石墨样品、硝酸铵样品的NRF特征能谱验证了设计方案的可行性,利用重要性抽样法将石墨样品模拟计算效率提高了72.23倍。该设计方案和计算结果可为基于NRF的无损核探测系统研发提供技术支撑。

Nuclear resonance fluorescence(NRF)is an emerging nondestructive active inspection technology.Specific isotopes can be identified by analyzing the characteristic energy recorded in the gamma spectrum.This technology plays an important role in the scanning inspection of small containers containing unknown explosives.In this paper,an NRF backscatter inspection scheme is optimized using Monte Carlo simulation program based on the X-ray source generated by electron accelerator bremsstrahlung radiation.After optimized design,X-ray leakage rate is reduced by 386 times,the beam asymmetry is less than 2%,the beam uniformity is more than 70%.The NRF characteristic energy spectrum of graphite samples and ammonium nitrate sample obtained by HPGe detector verifies the feasibility of the design scheme.The innovative application of importance sampling technique improves the simulation calculation efficiency of graphite sample by 72.23 times.The design scheme and calculation results provide technical support for the research and development of NRF based non-destructive nuclear detection system.