基于瞬发伽马中子活化分析技术的金属样品检测研究

在合金材料的生产过程中，不同金属元素的含量改变对产品的性能以及可靠性有重要的影响，通过在线检测技术能够对产品中不同元素含量进行实时分析，从而指导其工业生产过程，提高产品质量。目前常规的无损检测方法受限于分析深度，无法对样品内部成分进行分析，从而影响测量结果的准确性。瞬发伽马中子活化分析（PGNAA）技术是一种高灵敏度、多元素同时分析的无损检测技术，可以对大块样品进行快速分析。针对PGNAA技术在大体积金属样品检测的可行性进行研究，通过测量快中子与样品发生非弹性散射反应激发的伽马射线对样品成分进行分析。搭建了一套测量系统，包括D-T中子发生器，中子反射体，中子准直体，高纯锗（HPGe）探测器及探测器屏蔽防护。首先，对Fe，Ti，Cr，Ni和Cu等5种金属元素进行了分析研究。对不同质量下的样品进行测量，通过伽马能谱处理软件GAMMAFIT对HPGe探测器测量到的特征伽马峰进行拟合，获得全能峰的净面积。分析全能峰净面积与样品质量之间的响应，对探测器的探测效率变化造成的非线性响应进行修正，得到不同元素的校准曲线，结果显示各元素修正后的校准曲线均具有良好的线型关系。对不同元素的质量检测限进行分析，不同金属元素的质量检测限分别为Fe（44 g），Ti（25 g），Cr（33 g），Ni（108 g）和Cu（72 g）。利用测量系统对不锈钢合金样品中的Fe和Cr元素含量测量开展了研究，通过测量标准样品建立了Fe和Cr元素的定标曲线，并对未知样品进行了测量分析。同时与X射线荧光光谱（XRF）测量结果进行了对比分析，结果表明两种方法的Fe元素和Cr元素测量值偏差分别为4.08%和2.97%。研究结果表明，利用PGNAA技术可以对多种金属元素和合金样品进行测量分析，为后续其他金属样品的检测奠定了研究基础。

Study on Metallic Samples Determination Based on Prompt Gamma Neutron Activation Analysis Technique

In the productive process of alloy materials, the change of element contents can significantly affect the quality and reliability of the products. The on-line monitoring techniques can determine the element contents of metallic materials in real-time, which can then guide their manufactureing processes and improve their quality and reliability. The normal techniques have limited penetration depth in the sample and are not efficient for volume analysis, which will affect the analytical accuracy. Prompt gamma-ray neutron activation analysis (PGNAA) is a non-destructive, high sensitivity and multi-elemental determination technique and can be used for bulk sample analysis. This work studied the feasibility of determination for metallic materials by using PGNAA. The metallic samples were analyzed by measuring prompt gamma rays produced by inelastic scattering of fast neutrons. A PGNAA system consisting of a D-T neutron generator, neutron reflector, collimator, high-purity germanium (HPGe) detector, and shielding was built and used for analysis of metallic materials. Firstly, Fe, Ti, Cr, Ni and Cu samples with various masses were conducted with the designed system. The prompt gamma rays of the elements were fitted using GAMMAFIT software to obtain the net areas of prompt gamma rays, and the response between sample mass and net peak area was analyzed. The non-linear response caused by variation of detection efficiency was corrected to obtain a calibration curve. A good linear relationship could be observed after correction. The mass detection limit of these elements was calculated, and the values were Fe (44 g), Ti (25 g), Cr (33 g), Ni (108 g) and Cu (72 g), respectively. Secondly, the determination of Fe and Cr of stain steel samples was studied by using the system. The calibration curves of Fe and Cr were obtained with the standard samples. An unknown sample was then measured and analyzed. The results were compared with the X-ray fluorescence (XRF) measurement data. The experimental data showed that the relative deviations of Fe and Cr obtained with the two methods were 4.08% and -2.97%, respectively. The results demonstrated that the PGNAA technique could be applied for determining many metals and alloys, which provides a basis for other metallic samples analyses.