符合测量法选择核素全能峰的Geant4模拟

发布时间：2018-08-25 07:37

【摘要】：在热中子活化中,活化能谱的探测和能谱分析非常重要。但是统计涨落和本底会对中子活化的γ能谱分析造成影响。所以,减少统计涨落和本底的影响有利于提高中子活化能谱分析的准确性。能谱探测方法的不同会对获取的能谱造成很大的影响,采用合适的探测技术有利于获取自己需要的活化能谱。目前符合测量法在核物理实验中已经成为多参数测量的重要实验方法。热中子活化会产生放射性核素,放射性核素衰变产生的γ射线存在时间上的关联关系,是实现符合测量的重要前提。本文的工作就是利用符合测量技术对热中子活化能谱进行全能峰筛选。首先利用热中子轰击材料产生放射性核素,然后利用探测器对活化能谱进行探测。具体的工作内容有:(1)利用Geant4软件对衰变核素产生的特征γ射线进行记录,将获得的特征射线的能量和强度与NNDC和PGAA数据库进行对比;(2)利用NaI(Tl)探测器对中子活化能谱进行探测,并运用傅里叶变换法对中子活化能谱进行处理;(3)利用γ-γ单峰级联符合法对中子活化能谱进行全能峰筛选,通过单特征峰筛选出级联的射线,从而实现能谱简化,凸显核素特征峰。(4)γ-γ双峰求和符合选择简化能谱,通过将级联射线求和的能量作为门信号进行特征峰选择,达到去除本底,凸显全能峰的目的。符合测量技术能够很好的将能谱简化,降低统计涨落和本底计数的影响,凸显全能峰,有利于提高中子活化能谱分析的准确性。
[Abstract]:The detection and analysis of activation energy spectrum are very important in thermal neutron activation. However, statistical fluctuations and background will have an effect on the neutron activated 纬-ray spectrum analysis. Therefore, reducing the effect of statistical fluctuations and background is helpful to improve the accuracy of neutron activation energy spectrum analysis. The difference of energy spectrum detection method will have a great influence on the energy spectrum obtained, and it is advantageous to obtain the activation energy spectrum by adopting the appropriate detection technology. At present, coincidence measurement has become an important experimental method in nuclear physics experiments. Radionuclides can be produced by thermal neutron activation, and the correlation of the existence time of 纬 -rays produced by radionuclides decay is an important prerequisite for the realization of coincidence measurement. The work of this paper is to screen the thermal neutron activation energy spectrum by coincidence measurement. First, radionuclides are produced by bombarding materials with thermal neutrons, and then the activation energy spectra are detected by detectors. The specific contents of the work are as follows: (1) the characteristic 纬 rays produced by decay nuclides are recorded by Geant4 software, and the energy and intensity of the obtained characteristic rays are compared with those of NNDC and PGAA databases; (2) the neutron activation energy spectrum is detected by NaI (Tl) detector. The neutron activation energy spectrum is processed by Fourier transform method. (3) the 纬-纬 single peak concatenated coincidence method is used to screen the universal peak of the neutron activation energy spectrum, and the single characteristic peak is used to screen out the cascaded rays, so as to simplify the energy spectrum. (4) the summation of 纬-纬 double peaks coincides with the selection of simplified energy spectrum. By using the energy of cascade ray summation as the gate signal, the characteristic peak is selected to remove the background and highlight the omnipotent peak. The coincidence measurement technique can simplify the energy spectrum, reduce the influence of statistical fluctuation and background counting, highlight the omnipotent peak, and improve the accuracy of neutron activation energy spectrum analysis.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O571.5

【参考文献】