气体样品核(n,a)反应实验测量方法研究

在课题组多年工作基础上，学习借鉴国际最新研究成果，本项目提出开展气体样品核(n,a)反应测量方法研究。针对气体样品核反应测量中长期存在的壁效应强、样品核数难以准确定量、存在多种本底干扰等问题，提出了新的综合性研究方案。拟依托北京大学4.5MV静电加速器和原子能研究院HI-13串列加速器中子源，以14N(n,a)和20Ne(n,a)两个核反应为测量对象，研究气体样品核反应高精度测量方法，在共振能区获得反应截面随中子能量系统变化的规律，改变长期以来气体样品核反应实验误差大、实验结果稀缺的局面。项目针对气体样品核反应实验难以得到出射粒子方向信息的固有缺点，首次提出在屏栅电离室工作气体中混入少量电负性气体的方法，通过电负性气体对不同出射方向粒子经迹上电子吸附的差异来获得粒子角分布。本项目的开展可有效拓展国际核反应实验研究前沿，填补14MeV以外能区气体样品核反应角分布实验空白。

Based on our long-time research experiences, and inspired by the recent development of international groups, we proposed this project of research on the measurement method for gas sample (n,a) reactions. Aimed at solving the problems (the strong wall effect, the difficulty in the determination of the atom number in the gas sample, and many interfere reaction channels) in the past measurements, new and synthesized research plan is proposed in this project. Two neutron sources based on accelerators (4.5 MV van de Graaff of Peking University, and Beijing HI-13 tandem accelerator) will be used, and the 14N(n,a) and 20Ne(n,a) reactions will be studied inepdth. As a result, precise cross sections of these two reactions are going to be measured systematically in the resonance neutron energy region. Therefore, the present situation of the gas sample reaction measurement (big errors as well as the scarcity of the experiments) can be greatly improved. As it is difficult to measure the angular distributions in previous measurements using gas samples, we proposed for the first time a new method to measure angular distributions by adding small amount of electronegative gas in the ionization chamber for ionization electron attachment. After the implementation of this project, the frontier of the research area of nuclear reaction can be broadened, and angular distributions of the gas sample reactions will be obtained for the first time in the neutron energy region other than 14 MeV.