Research on Monte Carlo Methods for Particle Transport in Media with Continuously Varying Cross-Sections

In the traditional Monte Carlo method,the cross-sections are assumed to be constant,but this Monte Carlo technique is no longer applicable in continuous materials where the material cross-sections vary over the particle flight paths.Three Monte Carlo methods are developed to solve this kind of problem in this paper,namely Sub-stepping method,Delta-tracking method and Direct Numerical method.Based on the results from different methods to calculate the particle transport in media with continuously varying cross-sections,the comparison of three methods is made and Delta-tracking method is used as the main method to solve this kind of problem.And also an improved Delta-tracking method is posted in this paper to make this method more powerful in solving problems where the material cross-sections vary sharply over the particle flight paths.