Calibration of 6Li atomic number of lithium glass detector
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摘要: 在聚变包层中子学性能的实验检验中，造氚率是重要的测量参数之一，探测器中6Li原子数目作为计算造氚率的归一化因子，是决定测量结果精度的关键因素，必须进行精确标定。对6Li原子数标定原理、实验配置及过程、不确定度量化方法进行具体介绍，并首次在中国绵阳研究堆（CMRR）的M5水平孔道以锗单晶单色器获得32.36 meV中子对小型锂玻璃探测器中6Li原子数进行了标定，不确定度为2.62%。Abstract: In experimental validations of fusion blanket neutronics performance, tritium production rate is one of the most crucial measurement parameters. The number of 6Li atoms in the detector, as a normalization factor for calculating the tritium production rate, is a key factor determining the accuracy of measurement results and must be accurately calibrated. This paper specifically introduces the principles of calibrating the number of 6Li, the experimental setup and procedure, and the methods for quantifying uncertainties. For the first time, the number of 6Li atoms in a small lithium glass detector was calibrated using a germanium monocrystal monochromator to obtain 32.36 meV neutrons at the M5 horizontal channel of the China Mianyang Research Reactor (CMRR), with an uncertainty of 2.62%.
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图 2 6Li原子数标定实验测量布局图
Figure 2. Schematic diagram of the measurement layout for calibrating the number of 6Li
图 7 反应堆M5孔道32.36 meV 中子辐照下的脉冲高度谱
Figure 7. Pulse height spectra for the 6Li and 7Li glasses under 32.36 meV neutron irradiation in the M5 channel of the reactor
图 8 源中子谱及对应的6Li (n,α) T反应截面
Figure 8. Source neutron spectrum and corresponding 6Li (n,α) T reaction cross section
表 1 不同散射体对实验的影响
Table 1. Influence of different scatterers on the experiment
No. scatterer 6Li (n,α) T reaction rate 197Au(n,γ) 198Au reaction rate 1 without scatter 5.36×10−23 9.85×10−24 2 cadmium sleeve 5.36×10−23 9.85×10−24 3 cadmium sleeve\sample holder 5.36×10−23 9.85×10−24 4 cadmium sleeve\sample holder\air 4.99×10−23 9.50×10−24 5 cadmium sleeve\sample holder\air\neutron absorbing cavity 4.99×10−23 9.50×10−24 6 cadmium sleeve\sample holder\air\neutron absorbing cavity\3D adjustable platform base 4.99×10−23 9.50×10−24 7 ratio between reaction rates without and with scatterers 93.10% 93.12% 
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表 2 不确定度列表
Table 2. List of uncertainty items
No. item of uncertainty coefficient relative uncertainty/% 1 tritium production reaction rate nt 1.18 0.41 2 the activation reaction rate nnγ 1.18 1.68 3 counting rate of the beam monitor Nm1 1.18 1.00 4 counting rate of the beam monitor Nm2 1.18 0.02 5 microscopic cross-section of 197Au(n,γ) 198Au σnγ 1.18 0.14 6 microscopic cross-section of 6Li(n, T)4He σT 1.00 0.51 7 number of Au atom N197 1.18 0.24 8 detector cross-sectional area S 0.18 1.00 9 neutron beam profile density uniformity k 1.18 0.80
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