Validation of the event generator mode in the PHITS code and its application

Abstract

The Generator has been introduced into the PHITS code in the treatment of low energy transport phenomena. In this mode, the evaluated nuclear data for neutrons and a special evaporation model are combined so as to trace all correlations of ejectiles keeping the energy and the momentum conservation in a collision. We have calculated the double differential cross section, the kerma coefficient and the displacement cross section by the event generator mode of PHITS, and compared them with the evaluated nuclear data for the validation of the mode in neutron-induced reactions under 30MeV. As results, all calculated results by the event generator mode reproduce the evaluated nuclear data well below 20MeV. As an application of this mode, we indicate a new approach to the deposit energy distribution for the thermal neutron transport and the averaged quality factor for neutrons. The concept of the event generator is rather popular with the Monte Carlo simulation code for high energy particles. In the event generator mode, the conservation law on the energy and the momentum is sustained in each event. Recently, the correlated quantities such as event-by-event distribution of deposit energy even in low energy fields are often required for microdosimetric estimations of irradiation effects in biol- ogy and semiconductors. For these requirements, the Generator has been introduced into the PHITS code (1) in the transport of low energy neutrons. In this mode, the evaluated nuclear data for neutrons and a special evaporation model are combined so as to trace all correlations of ejectiles keeping the energy and the momentum conservation in a collision. This mode enables us to calculate the correlated quantities mentioned above, and also to estimate the kerma coefficient and the displacement cross section data without additional evaluated cross section libraries. In this work, we have calculated particle production cross sections, the kerma coefficient and the displacement cross section by the event generator mode of PHITS, and compared them with the evaluated nuclear data for the validation of the mode in neutron-induced reactions under 30MeV. As an ap- plication of this mode, we will suggest a new approach to the deposit energy distribution for the thermal neutron transport and the averaged quality factor for radiation protection against low energy neutron exposure. 2 Method of calculations A brief flowchart of the Event Generator Mode is shown in figure 1. A detail is presented in the other paper of these proceedings (2). The evaluated neutron data of the total cross section, the channel cross section, i.e., capture, elastic and (n,n � ), (n,Nn) cross section are used for branching the