摘要
γ全吸收型探测装置由40个BaF_(2)探测单元组成,用于在线测量中子辐射俘获反应截面数据,填补国内实验数据的空白.实验本底的一个重要来源是BaF_(2)晶体自身包含的α粒子.为扣除α粒子本底,数据获取系统采用全波形采集的方式,在线实验存储的数据量为118 MB/s,产生了较长的死时间.利用BaF_(2)探测单元测量3种放射源(^(22)Na,^(137)Cs及^(60)Co)的实验数据,确定了信号波形的积分长度为2000 ns时,能够达到最佳能量分辨率;使用快总成分比、脉冲宽度和时间衰减常数3种方法进行α粒子和γ射线的鉴别,计算得到快总成分比(快成分5 ns总成分200 ns)方法的品质因子为1.19-1.41,脉冲宽度(10%峰值)方法的品质因子为0.94—1.04,时间衰减常数方法的品质因子为0.93-1.07.通过品质因子的定量分析和能谱的比较,确定快总成分比鉴别方法效果最好,能够有效去除α粒子本底,为下一步升级数据获取系统,减少实验数据量,降低截面数据不确定度奠定基础.
The gamma-ray total absorption facility(GTAF)composed of 40 BaF_(2)detection units is designed to measure the cross section data of neutron radiation capture reaction online,in order to comply with the experimental nuclear data sheet.Since 2019,several daunting experiment results have been analyzed and published,and we have found that one of the most important sources of experimental background is the initial a particles emitted by the BaF_(2)crystal,which is the core component of GTAF detection unit.Considering the current industrial manufacturing process capabilities,the impurities of Ra and its compounds cannot be completely removed from the BaF_(2).Developing data analysis algorithms to eliminate the influence of alpha particles in experimental data has become a key aspect.In this work,in order to meet the needs of data acquisition,online measurement and analysis of neutron radiation cross section,the GTAF data acquisition system adopts a full waveform acquisition method,which results in a large number of data recorded,transmitted,and stored during experiment,which also affects the uncertainty of the cross-section data.The number of data stored in the online experiment is about 118 MB/s,resulting in a long dead time.Based on the signal waveform characteristics of the BaF_(2)detection unit,in order to solve the aforementioned problems,three methods,namely the ratio of fast component to total component,pulse width,and time decay constant,are used to identify and distinguish a particles and g rays.The quality factor FOM is utilized as an evaluation value and several experiments are conducted using three radioactive sources(^(22)Na,^(137)C,^(60)Co)for verification.Due to the slow components of BaF_(2)light decay time being about 620 ns,the waveform pulse should essentially return to baseline at approximately 1900 ns to 2000 ns,allowing for the complete waveform of theγrays signal to be captured at that moment,which may provide the best energy resolution.Therefore,in the online experiment,the integration length for the energy spectrum is chosen to be 2000 ns in this work.The quality factor is 1.19–1.41 from the fast total component ratio(fast component 5 ns,total component 200 ns)method,0.94–1.04 from the pulse width(10%peak)method,and 0.93–1.07 from the time attenuation constant method.Through the quantitative analysis of quality factor and the comparison of energy spectrum,it is determined that the fast total component ratio method has the best effect and can effectively remove the background of a particles.The next step is to upgrade the online experimental data acquisition system to reduce the quantity of experimental data and the uncertainty of cross section data.The experimental data that need to be recorded should be the crossing threshold time(for the time-of-flight method)and the amplitude integration values of 5 ns after the threshold(for the fast component),200 ns after the threshold(for the total component),and 2000 ns(for the energy)for each signal waveform,as well as the number of related detection units.The above information should be sufficient to complete online processing of experimental data,including the processing of the a particle background and(n,γ)reaction data.It is estimated that the data acquisition rate of the upgraded system will decrease from 118 MB/s to 24 MB/s,which can significantly reduce the dead time of the data acquisition system,thereby improving the accuracy of cross section data.
作者
邹翀
张奇玮
栾广源
吴鸿毅
罗淏天
陈玄博
王晓宇
贺国珠
任杰
黄翰雄
阮锡超
鲍杰
朱兴华
ZOU Chong;ZHANG Qiwei;LUAN Guangyuan;WU Hongyi;LUO Haotian;CHEN Xuanbo;WANG Xiaoyu;HE Guozhu;REN Jie;HUANG Hanxiong;RUAN Xichao;BAO Jie;ZHU Xinghua(Key Laboratory of Nuclear Data,China Institute of Atomic Energy,Beijing 102413,China;China Shipbuilding Trading Co.,Ltd.,Beijing 100044,China;Huaneng Shandong Shidao Bay Nuclear Power Co.,Ltd.,Rongcheng 264312,China)
出处
《物理学报》
北大核心
2025年第10期76-84,共9页
Acta Physica Sinica
基金
国家自然科学基金(批准号:11975317,12275363)
核数据重点实验室基金(批准号:JCKY2022201C158)
稳定支持基础科研计划(批准号:BJ010261223282)
中核集团集中研发项目(批准号:FD010241222552)资助的课题。
关键词
能量分辨率
快总成分比
脉冲宽度
时间衰减常数
energy resolution
ratio of fast to total component
pulse width
time decay constant
