快中子硼-10三体造氚核反应实验方法研究

As one of the most important nuclear meterials, Boron-10 is widely used in reactor control, neutron detection and radiation protection. The accurate cross section date for fast neutron induced tritium production reaction n+10B- - >t+a+a with triple particle emission are indispensable for the calculation of the tritium production in the nuclear reactor,and they are also important for the improvment of the model calculations for light nuclei reactions. However, there are not enough experimental data exist up to now on this reaction, and large discrepancies exist between the results measured with different experimential methods, with big uncertainties. In this project, cross sections of this reaction at neutron energies between 1- - 7 MeV will be measured systematically on the 4.5 MeV Van de Graaff accelerator of Peking University. Two kinds of samples, gaseous sample and solid sample with thin backing, will be used. The charged particle detector is the gridded ionization chamber (GIC) and the event pulse will be recorded by data acquisition system based on wave form digitizers. Through the Q value of different nuclear reactions the expected event can be selected and the background can be reduced by the coincidences of different signals from the GIC.The large discrepancy between existed experimential results measured by different groups will be cleared and accurate cross section data can be obtained. This project is important for the improvment of our ability in nuclear reaction measurment and the perfection of theoretical calculation of light nuclei reactions, and the results can be used for safe operation of the nuclear reactor and radiation protection.

硼-10是重要的核材料，在反应堆控制和中子的探测与防护中有广泛的应用。快中子引起的硼-10三体造氚反应n+10B- - >t+a+a 截面，是准确计算反应堆内的产氚量所必需的，同时对改进轻核反应模型理论计算具有重要作用。然而，迄今该反应截面实验数据缺乏，不仅误差大，而且不同实验方法的测量结果之间存在很大分歧。本项目拟依托北京大学4.5 MV静电加速器单能中子源，采用气体样品和薄衬固体样品两种实验方法，利用屏栅电离室作为带电粒子探测器，用数据采集卡记录脉冲波形、实现符合，扣除本底，通过不同的核反应Q值选择待测事件；在1- - 7MeV能区对该反应截面进行系统的实验测量。探求不同作者采用气体样品实验结果存在严重分歧的根源，结合理论分析得到该反应截面的准确结果。本项目的研究对于提高我国核反应实验测量水平、改进核反应理论计算具有重要意义，研究成果对于反应堆安全运行和辐射防护具有重要的应用价值。

硼-10是重要的核材料，在反应堆控制和中子的探测与防护中有广泛的应用。快中子引起的硼-10三体造氚反应n+10B-->t+a+a 截面，是准确计算反应堆内产氚量所必需的，同时对改进轻核反应模型理论计算有重要作用。然而，该反应截面实验数据缺乏，不仅误差大，而且不同实验方法的测量结果间存在很大分歧。本项目研制了薄衬B-10样品，依托北京大学4.5 MV静电加速器中子源，利用屏栅电离室作带电粒子探测器，用数据采集卡记录脉冲波形，通过将实验测量与理论分析、模拟计算相结合，在MeV能区得到了准确的反应截面数据，澄清了不同作者实验结果存在严重分歧的根源。本项目的开展使我们从原来的两体核反应研究拓展到了三体核反应研究，提高了核反应实验测量水平，研究成果对反应堆安全运行和辐射防护都具有应用价值。