面向PGNAA技术的碘化钠探测器MCNP模拟计算

MCNP Simulation of NaI Detector for PGNAA Technology

碘化钠(NaI)探测器因其优秀的探测效率和相对较低的成本在瞬发γ射线中子活化分析技术(prompt gamma-ray neutron activation analysis,PGNAA)中具有广泛应用。为了获取PGNAA测量过程中探测器对γ射线的响应,针对NaI探测器建立了蒙特卡罗模型,基于该模型对中子以及γ射线输运过程进行模拟计算。对^(60)Co、^(137)Cs、^(152)Eu、^(133)Ba和^(241)Am标准点源以及^(137)Cs水体源进行了测量分析,并与MCNP模拟计算进行对比,结果显示两者吻合。之后结合D-D中子发生器对水溶液进行测量,并分析H元素辐射俘获反应产生的2.223 MeV特征γ射线。研究结果表明,MCNP模拟计算的H元素特征峰计数与测量的结果偏差为13%,证明了MCNP建立的NaI测量系统模型能够实现对γ和中子混合输运过程的模拟仿真,可为后续系统优化工作的开展奠定基础。

Sodium iodide(NaI) detector has wide applications in Prompt Gamma-ray Neutron Activation Analysis(PGNAA) due to its excellent detection efficiency and relatively low cost.In order to obtain the response of the detector to gamma-rays during PGNAA measurement process,a Monte Carlo model was established for the NaI detector to simulate the transport processes of neutrons and gamma-rays.Measurements and analyses were conducted on standard point sources of ^(60)Co,^(137)Cs,^(152)Eu,^(133)Ba,and ^(241)Am,as well as a waterborne source of ^(137)Cs.These measurements were compared with MCNP simulation calculations,and the results demonstrated agreement between the two methodologies.Then,measurements were conducted on aqueous solutions using a D-D neutron generator,and the 2.223 MeV characteristic gamma-ray produced by the H element radiative capture reaction was analyzed.The research results show that the deviations between MCNP simulation calculations of characteristic peaks for the H element and experimental measurements were consistently within 13%,demonstrating that the NaI measurement system model established by MCNP can simulate the transport processes of gamma and neutrons,laying a foundation for the subsequent optimization of the system and other related work.