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中国物理学会期刊
CSTR: 32037.14.aps.73.20231957
CSTR: 32037.14.aps.73.20231957
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  • 中子辐射俘获反应在反应堆运行、核装置设计及核天体物理研究中起重要的作用. 4π BaF2探测装置有着高时间分辨能力、低中子灵敏度、高探测效率等优点, 适合开展中子辐射俘获反应截面数据的测量. 中国原子能科学研究院核数据重点实验室建立了伽马全吸收装置(Gamma total absorption facility, GTAF), 该装置用28块六棱BaF2晶体和12块五棱BaF2晶体构成了外径25 cm, 内径10 cm的球壳, 覆盖了95.2%的立体角. 利用GTAF在中国散裂中子源Back-n束线上, 测量了197Au(n, γ)的反应截面数据. 测量数据通过能量筛选、PSD方法、晶体多重性筛选进行了初步本底扣除, 随后结合对natC及空样品的测量数据对本底进行了分析及扣除, 获得了197Au俘获反应的产额, 利用SAMMY程序拟合得到了197Au在1—100 eV的共振能量、中子共振宽度和伽马共振宽度参数. 实验测量结果与ENDF/B-VIII.0数据库符合良好, 其共振参数存在一定差异, 分析原因可能与GTAF能量分辨率、Back-n的中子能谱测量精度、以及实验本底扣除方法相关, 这也是下一步工作的重点.

     

    Neutron capture reaction is one of the neutron reactions and plays an important role in using reactor control rods and shell materials, designing nuclear device structures, and studying nuclear astrophysics S processes and element origins. The 4π BaF2 detection device has advantages such as high time resolution, low neutron sensitivity, and high detection efficiency, thus making it suitable for measuring neutron radiation capture reaction cross-section data. In order to fill the gap in our neutron capture reaction data in the keV energy range and improve their accuracy, the Key Laboratory of Nuclear Data at the Chinese Institute of Atomic Energy (CIAE) has established a Gamma Total Absorption Facility (GTAF), which consists of 28 hexagonal BaF2 crystals and 12 pentagonal BaF2 crystals to form a spherical shell with an external diameter of 25 cm and an internal diameter of 10 cm, covering 95.2% of the solid angles. The Back-n beam line of the Chinese Spallation Neutron Source (CSNS) is a back-streaming white beam line that covers neutron energy ranging from a few eV to several hundred MeV, making it suitable for measuring neutron capture cross-sections. The reaction cross-section data of 197Au is measured by using GTAF on the Back-n beam line. The measurement data are preliminarily background deducted through energy screening, PSD method, and crystal multiplicity screening. Subsequently, the background is analyzed and deducted based on the measurement data of natC and empty samples, and the yield of 197Au capture reaction is obtained. Resonance parameters are a set of parameters extracted from experimental data to describe the resonance curve, which can eliminate the influence of experimental conditions on resonance data and are more important than the cross-section obtained from experiments. The resonance energy, neutron resonance width, and gamma resonance width parameters of 197Au at 1–100 eV are fitted by using the SAMMY program. From the comparison between the resonance curves obtained from experimental measurements and the resonance parameters obtained from fitting with the ENDF/B-VIII.0 database, it can follow that the experimental measurement results are in good agreement with the database, nevertheless, there exist some differences in the resonance parameter, which may be due to the GTAF energy resolution, Back-n neutron spectrum measurement accuracy, and the experimental background deduction method. Our next work is to identify the sources of difference.

     

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