The electron linear accelerator in Hokkaido University Neutron Source (HUNS [1]) was recently upgraded toward HUNS-2 to increase the electron beam current. The HUNS-2 is an accelerator-driven neutron source that is equipped with a cold-, thermal- and fast-neutron type of sources. Experiments such as a small angle neutron scattering [2], neutron transmission imaging [3] and neutron irradiation test have been currently conducted using HUNS-2 for studies of material science and developments of measurement method.

In this work, the neutron beam profile for the HUNS-2 thermal neutron source was calculated with the Monte Carlo simulation code PHITS [4] to improve a target, moderator and reflector assembly (TMRA) of the present thermal neutron source system [5]. The TMRA consists mainly of a neutron production target with a tungsten disc, lead blocks and water channels, a polyethylene moderator and graphite reflectors. Through the simulations, a position and size of TMRA was designed for increasing the intensity of thermal neutron beam.

[1] M. Furusaka, et al., Phys. Proc. 60 (2014) 167. [2] T. Ishida, et al., ISIJ Int. 57 (2017) 1831. [3] K.Y. Hara, et al., EPJ Web Conf. 146 (2017) 03032. [4] T. Sato, et al., J. Nucl. Sci. Technol. 55 (2018) 684. [5] T. Kamiyama, et al., Nuovo Ciemento 38 C (2015) 187.