Influence of gamma rays on measurement of neutrons spectrawith spherical proportional counter of recoil protons
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摘要: 通过蒙特卡罗模拟和实验测量相结合的方法,获得从50 keV~10 MeV区间射线在直径为30 mm内充1.013 25 MPa氢气的球形含氢正比计数管上的能量响应,结果显示,射线在该计数管中的能量沉积主要集中在100 keV附近及以下。Am-Be中子源和137Cs源的实验测量结果显示,强137Cs源的射线会严重影响含氢正比计数管对Am-Be中子源100 keV以下能谱的测量,这表明,裂变材料介质内的强射线同样会影响到介质内100 keV以下中子能谱的测量。根据计数管对反冲质子和电子电离信号的收集特性,采用上升时间法甄别掉本底射线是可行的。Abstract: The energy responses of gamma rays from 50 keV to 10 MeV of a spherical counter filled with 1 MPa hydrogen and with a 30 mm diameter have been obtained by experimental measurement and Monte Carlo simulation. It shows that the energy deposited in the counter is focused near 100 keV and below. An experiment with Am-Be source and 137Cs source indicates that intense gamma rays of the 137Cs source have made great influence on the measurement of the neutrons spectra below 100 keV from Am-Be source. It can be concluded that the measurement of neutron spectra below 100 keV from fissionable materials would be affected by the intense gamma rays. According to the collective features of recoil protons and electrons ionization in the counter, it is feasible to discriminate the gamma rays from the neutrons by rise-time method.
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