Comparison and assessment of electron cross sections for Monte Carlo track structure codes.
Comparison and assessment of electron cross sections for Monte Carlo track structure codes.
复制标题
蒙特卡罗轨道结构规范的电子横截面的比较和评估。
作者：
S. Uehara;H. Nikjoo;D. Goodhead
本研究的目的是对电子径迹结构程序中的水中电子截面进行比较和评价。本研究旨在阐明输入数据与物理和化学假设之间的差异在多大程度上影响辐射效应生物物理建模的结果。用各种理论计算了二次电子的电离截面和电离能谱。对水蒸气截面进行了分析，因为这些截面更丰富，更容易获得。所有合适的已发表的实验总电离截面由适当的函数拟合，并用于产生电子轨道。三组汇编的数据用于比较总激发截面和平均激发能量。由蒙特卡罗轨道代码生成的轨道，使用各种组合的横截面，相互作用和点核的径向分布进行了比较。由电离过程发射的二次电子的光谱被认为是对这些量影响最大的因素。一组不同的激发和弹性散射的横截面没有影响电子轨道结构尽可能多的电离截面。它的结论是，所有的代码，使用不同的横截面和在不同的阶段，目前用于生物物理建模表现出密切的相似性，在较大尺寸的目标，而观察到的B-DNA大小的目标的能量沉积。我们建议所有可用的合适的实验数据的总电离和弹性截面的拟合函数。我们的结论是，大多数代码产生的轨道在合理的协议与宏观量，如总阻止能力和总产量的链断裂。然而，我们预测的不同模型的轨道中的聚类频率的差异。
The purpose of this study was to make an intercomparison and assessment of cross sections for electrons in water used in electron track structure codes. This study is intended to shed light on the extent to which the differences between the input data and physical and chemical assumptions influence the outcome in biophysical modeling of radiation effects. Ionization cross sections and spectra of secondary electrons were calculated by various theories. The analyses were carried out for water vapor cross sections, as these are more abundant and readily available. All suitable published experimental total ionization cross sections were fitted by an appropriate function and used for generation of electron tracks. Three sets of compiled data were used for comparison of total excitation cross sections and mean excitation energy. The tracks generated by a Monte Carlo track code, using various combinations of cross sections, were compared in terms of radial distributions of interactions and point kernels. The spectrum of secondary electrons emitted by the ionization process was found to be the factor that has the most influence on these quantities. A different set of cross sections for excitation and elastic scattering did not affect the electron track structure as much as did ionization cross sections. It is concluded that all codes, using different cross sections and in different phase, currently used for biophysical modeling exhibit close similarities for energy deposition in larger size targets while appreciable differences are observed in B-DNA-size targets. We recommend fitted functions to all available suitable experimental data for the total ionization and elastic cross sections. We conclude that most codes produce tracks in reasonable agreement with the macroscopic quantities such as total stopping power and total yield of strand breaks. However, we predict differences in frequencies of clustering in tracks from the different models.