中文摘要：

在中低密度样品中，γ射线的线衰减系数主要由γ射线能量和样品密度决定，采用MCNP（Monte Carlo N Particle Transport Code）程序模拟计算了多种γ射线能量和多种样品密度条件下的线衰减系数，对线衰减系数模拟值进行多元非线性回归，确定了以Y射线能量和样品密度为因变量的线衰减系数函数及参数。实验测定了三种能量γ射线在6种不同密度样品中的线衰减系数值，并与模拟所得函数值进行比较分析。结果表明，所得函数值与实验值的相对误差均在7％以内，蒙特卡罗程序计算所得函数值与实验测量值较为吻合，所采用的函数模型准确验证了线衰减系数与γ射线能量、样品密度之间的关系特征。

英文摘要：

Background： With low and intermediate level density sample, linear attenuation coefficient is mainly determined by gamma ray energy and material density. Purpose： The aim is to determine the relationships and effect of gamma ray energy and material density to linear attenuation coefficient. Methods： This work has constructed different samples with different densities from 0.3 g.cm^-3 to 3.0 g·cm^-3 by using Monte Carlo N Particle Transport Code （MCNP）. Linear attenuation coefficients are obtained for gamma ray energies from 100 keV to 1 500 keV. Relationships and effect of gamma ray energy and material density to linear attenuation coefficient are determined by using a function model. Through experimental measurement of 137Cs and 60Co, linear attenuation coefficients are obtained for gamma ray energies 661.661 keV, 1 173.238 keV, 1 332.513 keV in different samples with densities from 1.0 g.cm^-3 to 2.7 g·cm^3. Results： Relative deviations of linear attenuation coefficients between experimental and MCNP simulation results are less than 7%. Conclusion： Simulation results are in good agreement with experimental measurement data. Linear attenuation coefficient function accurately reveals relationships and effect of gamma ray energy and material density to linear attenuation coefficient.