Williamson J F, Deibel F C, Morin R L
Phys Med Biol. 1984 Sep;29(9):1063-73. doi: 10.1088/0031-9155/29/9/003.
Many Monte Carlo simulations ignore coherent scattering events and utilise the Klein-Nishina free electron distribution, rather than the incoherent differential cross-section, for choosing the trajectories of incoherently scattered photons. We assess the accuracy of this model by comparing its results with those of the complete bound electron model (form factor approach), which simulates coherent scattering events, and uses the appropriate bound electron angular scattering distributions. Both analytic and Monte Carlo calculations demonstrate that use of the free electron scattering distributions significantly underestimates the angular distribution of scattered photon energy resulting from low and medium energy photons incident upon carbon, iron, and platinum barriers. In using the free electron approximations to calculate barrier transmission, significant errors occur only for primary photon energies below 100 keV. Implementation of the complete bound electron model reduces the computational efficiency of our Monte Carlo code by only 10-25%.
许多蒙特卡罗模拟忽略了相干散射事件，并利用克莱因-仁科自由电子分布，而不是非相干微分截面，来选择非相干散射光子的轨迹。我们通过将该模型的结果与完整束缚电子模型（形状因子方法）的结果进行比较，来评估该模型的准确性。完整束缚电子模型模拟相干散射事件，并使用适当的束缚电子角散射分布。解析计算和蒙特卡罗计算均表明，使用自由电子散射分布会显著低估低能和中能光子入射到碳、铁和铂屏障时产生的散射光子能量的角分布。在使用自由电子近似来计算屏障透射率时，仅在初级光子能量低于100 keV时才会出现显著误差。完整束缚电子模型的实现仅使我们的蒙特卡罗代码的计算效率降低了10%-25%。
