一种高精度的核密度计设计与实现

Design and Implementation of a High-precision Nuclear Density Gauge

为改善传统核密度计标定过程中,被测介质密度与探测器测量强度之间的线性关系,设计了一种双探测器模型的核密度计。首先基于γ射线指数衰减理论、能量较低的光子向前与向后散射概率相当的假设以及Klein-Nishina公式推导出被测物质密度计算的理论公式,建立对应的密度理论方程。然后利用蒙特卡罗软件MCNP5对双探测器模型进行仿真计算,验证上述三种理论方程的合理性。研究表明双探测器模型对改善核密度计标定方程的线性关系是有效的,其拟合系数相比于传统的核密度计而言,提升了2.4%,从而提高了核密度计的测量精度。

In order to improve the linear relationship between the density of the measured medium and the measurement intensity of the detector during the calibration process of traditional nuclear density gauge,a dual detector model nuclear density gauge was designed.Three methods which are used to establish the theoretical formula for calculating the density of the measured substance,which are that the theoretical formula for calculating the density of matter are based on the exponential decay theory when gamma ray penetrated through the matter;The probability of forward scattering and backward scattering is equivalent when compton scattering occurs for the lower energy photons and the Klein-Nishina formula.Then the corresponding density equation was established.And then,Monte Carlo software MCNP5 was used to simulate the dual detector model and verify the rationality of the three theoretical equations mentioned above.Research has shown that the dual detector model is effective in improving the linear relationship of the calibration equation of nuclear density gauge.It's fitting coefficient has increased by 2.4%compared to traditional nuclear density gauge,which improves the measurement accuracy of nuclear density gauge.