Study on the Effect of Boron-coated Thickness of Boron-coated Proportional Counter Tube on the Detection Efficiency
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摘要: 涂硼正比计数管是可用于反应堆压力容器外对中子注量率进行监测的关键设备，涂硼正比计数管的涂硼厚度对自身的本征探测效率有影响。仿真不同厚度硼层中10B(n,α)7Li生成的7Li和α粒子的输运过程，计算硼层界面位置离子整体射出率并给出涂硼正比计数管本征探测效率的计算方法。仿真与计算结果表明：单位核反应率下硼层界面处离子整体射出率在涂硼厚度小于1.5 μm时与硼层厚度近似呈正线性相关，在涂硼厚度大于1.5 μm后随涂硼厚度增大而增速变缓，在涂硼厚度为3.6 μm时达最大为1.3×10−4 (cm2·s)−1。基于离子整体射出率的结果进一步计算得到涂硼正比计数管本征探测效率与涂硼厚度之间关系曲线，该关系曲线可以为涂硼正比计数管研制中选择合适涂硼厚度、确定最佳的探测效率提供参考。Abstract: The boron-coated proportional tube is a key device for monitoring the neutron fluence outside the reactor pressure vessel. The boron-coated thickness of the boron-coated proportional tube affects its intrinsic detection efficiency. Simulating the transport process of the 7Li and α generated by 10B(n,α)7Li in the boron layer with different thicknesses, and calculating the overall ion emission rate on boron layer interface and further the calculation method of the intrinsic detection efficiency of the boron-coated proportional counting tube is proposed. The results of simulation and calculation show that: when 10B(n,α)7Li is under unit nuclear reaction rate, the overall ion emission rate on boron layer interface is positively linearly correlated with the thickness of the boron layer when it is less than 1.5 μm, and increases more slowly with the increase of the thickness of the boron coating when it is greater than 1.5 um, finally the overall ion emission rate on boron layer interface reaches the maximum─1.3×10−4(cm2·s)−1 when the thickness of the boron coating is 3.6 μm. Based on the results of the overall ion emission rate, the relationship curve between the boron coating thickness and the intrinsic detection efficiency of the boron-coated proportional counting tube was further calculated, which can provide reference value for selecting an appropriate thickness of boron coating to define the best detection efficiency in the manufacturing of the boron-coated proportional tube.
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图 1 硼层对7Li和α粒子的阻止本领及7Li和α粒子在硼层中射程
Figure 1. Stopping Power of Boron Layer to 7Li and α and Range of 7Li and α in Boron Layer
图 4 射出率与硼层厚度关系
Figure 4. Relationship between Emission Rate and Thickness of Boron Layer
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