中国散裂中子源反角白光中子束流参数的初步测量

Experimental result of back-streaming white neutron beam characterization at Chinese spallation neutron source

中国散裂中子源(CSNS)已于2018年5月建设完工,随后进行了试运行.其中的反角白光中子束线(Back-n)可用于中子核数据测量、中子物理研究和核技术应用等多方面的实验.本文报道对该中子束的品质参数测量实验过程以及最终实验结果.实验主要采用中子飞行时间法,利用^(235)U,^(238)U裂变室和~6Li-Si探测器测量了中子能谱和中子注量率,又利用闪烁体-互补金属氧化物半导体探测系统测量了中子束斑的剖面,得到了该束线的初步实验测量结果.其中白光中子的全能谱测量范围eV—100 MeV,给出了不确定度分析;给出了中子注量率两个实验厅位置的满功率值;给出了白光中子在直径60 mm情况下的全能区束斑.通过与模拟结果的比较探讨了以上结果的合理性,并提出了改进计划.这些实验结果为以后该束线的核数据测量和探测器标定实验奠定了基础.

The Chinese spallation neutron source was completed in May 2018 and then subsequently commissioned.The Back-streaming white neutron beam line can be used in neutron nuclear data measurement,neutron physics research,and nuclear technology.In these experiments,it is necessary to know the neutron energy spectrum,the neutron flux,and the neutron beam profile of the neutron beam.In this paper,we present the preliminary measurements of these parameters.The neutron energy spectrum and neutron flux are measured by the time-of-flight method with a fission chamber equipped with 235 U and 238 U samples and a 6 Li-Si detector.The neutron beam profile is measured by a scintillator-CMOS detection system.The preliminary experimental measurements of the beam line are obtained.Among them,the energy spectrum measurement range of white neutrons is from eV to more than 100 MeV,which also gives an uncertainty analysis;the neutron fluence rate gives the full power value of the two experimental halls;the collimated white neutron beam spot is given under a diameter of 60 mm.The future plan is also given.The results of these experimental parameters can serve as the foundation for the future nuclear data measurement and detector calibration experiments of the beam line.