Performance of voxel and mesh phantoms in PHITS

Furuta, Takuya   

Recently polygon phantoms with tetrahedral-mesh became treatable in PHITS by implementation of a new function. Using this function, radiation transport simulation of external radiation exposure of the new ICRP mesh-type reference computational phantoms becomes possible. The function was introduced together with an original algorithm to limit number of elements and surfaces in search during the transport calculation to reduce the computational cost. Owing to this algorithm, efficient transport calculation in tetrahedral-mesh geometries was realized as good as in voxel-mesh geometries with the same number of meshes. The tetrahedral-mesh can represent complex structures such as human phantoms with a much smaller number of meshes compared to the voxel representation and thus the computational speeds of radiation transport simulation using human phantoms can be faster with tetrahedral-mesh representation. The performance of PHITS was demonstrated by a comparison of the computational time between the voxel and tetrahedral-mesh for radiation transport calculations in water and human phantoms. Benchmark studies using the ICRP mesh-type reference computational phantoms in comparison with other Monte Carlo codes such as MCNP and Geant4 were also performed.