Use of polygon geometry in PHITS

Furuta, Takuya   

It was difficult to construct complex three-dimensional (3D) geometries with original version of PHITS because 3D geometries in PHITS are defined by combinations of objects enclosed by simple surfaces planes, spheres, cylinders and so on. There are many requests from users to have a function which enables to import general polygon geometries into PHITS. We thus introduce a function to treat tetrahedral-mesh geometries, which is a type of polygon-mesh geometries, in PHITS. Being one of the simplest, the tetrahedral-mesh geometry is sufficiently flexible to construct complex geometries. It is also compatible with other polygon-mesh geometries by format conversions. In addition, we have developed an algorithm to reduce computational time required by the transport process in tetrahedral geometries. Owing to this algorithm, transport calculation in tetrahedral-mesh geometry can be as fast as that for the geometry in voxel-mesh with the same number of meshes.