Recent improvements of the particle and heavy ion transport code system - PHITS version 3.33

The Particle and Heavy Ion Transport code System (PHITS) is a general-purpose Monte Carlo radiation transport code that can simulate the behavior of most particle species with energies up to 1 TeV (per nucleon for ions). Its new version, PHITS3.33, was recently developed and released to the public. In the new version, the compatibility with nuclear data libraries and the algorithm of the track-structure modes have been improved, and they are recommended to be used for certain simulation conditions. Some utility functions and software have been developed and integrated into the new PHITS package, such as PHITS Interactive Geometry viewer in 3D (PHIG-3D) and RadioTherapy packaged based on PHITS (RT-PHITS). With these upgraded features, PHITS can be applied in a wide diversity of fields - beyond traditional nuclear engineering domains - including cosmic-ray, environmental, medical, life, and material sciences. In this paper, we summarize the upgraded features of PHITS3.33 with respect to the physics models, utility functions, and application software introduced since the release of PHITS3.02 in 2017.