New Features of the Particle and Heavy Ion Transport Code System; PHITS

We present recent developments of the PHITS code concerned with the event generator mode for low energy neutron transport, the function for correlated sources and micro-dosimetric treatment of the deposit energy.One of the recent important issues which general-purpose transport codes such as PHITS should treat is "correlations".We have therefore developed a new treatment of radiation behaviour for the low energy neutron transport by introducing an event generator model, in which we have combined the nuclear data and a theoretical model so as to trace all correlations among ejectiles keeping the energy and momentum conservation in a collision.In addition to the event generator mode, we discuss a role of the correlated source, which is newly introduced in PHITS, for the correlated observables in event-by-event.We also present a new tally function SED (Specific Energy Distribution), which enables us to estimate the deposit energy distribution in a micro-dosimetric region such as a cell or DNA..