An Overview of the PHITS code and its application to neutron-source design

Sato, Tatsuhiko   ; Niita, Koji*; Matsuda, Norihiro  ; Hashimoto, Shintaro  ; Iwamoto, Yosuke   ; Iwase, Hiroshi*; Nakashima, Hiroshi; Sakamoto, Yukio; Fukahori, Tokio  ; Chiba, Satoshi; Sihver, L.*

PHITS is a general purpose 3-dimensional Monte-Carlo particle transport simulation code developed under collaboration of Japan Atomic Energy Agency (JAEA), Research Organization for Information Science and Technology (RIST), High Energy Accelerator Research Organization (KEK) and a couple of other institutes in Japan and Sweden. In order to apply PHITS to the neutron-source design, several functions specialized for that purpose were implemented in the code. For examples, PHITS has functions to simulate the distortion of neutron trajectory due to the gravity and magnetic fields. For improving the accuracy of neutron-moderator design, PHITS can consider the difference of the neutron scattering cross sections between ortho- and para-hydrogen, using appropriate neutron-scattering libraries. Owing to these functions, PHITS has been successfully used for the neutron-source design in the J-PARC project.